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Students can Download Chapter 10 Neural Control and Coordination Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 10 Neural Control and Coordination

What is coordination?
Coordination is the process through which two or more organs interact and complement the functions of one another.

Neural System
The neural system of all animals is composed neurons that receive and transmit different kinds of stimuli.

Neural system in lower forms

• The neural organisation is very simple in lower invertebrates.
• For example, in Hydra it is composed of a network of neurons.
• The neural system is better organised in insects, where a brain is present.

The vertebrates have a more developed neural system.

Human Neural System
The human neural system is divided into two parts:

(i) Central neural system (CNS) (ii) Peripheral neural system (PNS)

• The CNS includes the brain and the spinal cord and is the site of information processing and control.
• The PNS comprises of all the nerves of the body associated with the CNS.

The nerve fibres of the PNS are of two types:

(a) afferent fibres (b) efferent fibres

Function of afferent efferent of nerve fibres:
The afferent nerve fibres transmit impulses from tissues/organs to the CNS. The efferent fibres transmit regulatory impulses from the CNS to the peripheral tissues/organs.
The PNS is divided into two divisions

1. Somatic neural system
2. Autonomic neural system.

Function:
The somatic neural system relays impulses from the CNS to skeletal muscles. The autonomic neural system transmits impulses from the CNS to the involuntary organs and smooth muscles of the body.
The autonomic neural system is classified into

1. sympathetic neural system
2. parasympathetic neural system.

Neuron As Structural And Functional Unit Of Neural System
A neuron is composed of three major parts,

1. cell body 2. dendrites and 3. axon

1. The cell body contains cytoplasm with cell organelles and certain granular bodies called Nissl’s granules.

2. Repeated branches project out of the cell body are called dendrites.

3. The axon is a long fibre, the distal end of which is branched. Each branch terminates as a bulb-like structure called synaptic knob which possess synaptic vesicles containing chemicals called neurotransmitters. Based on the number of axon and dendrites, the neurons are divided into three types,

• multipolar (with one axon and two or more dendrites; found in the cerebral cortex)
• bipolar (with one axon and one dendrite, found in the retina of eye)
• unipolar (cell body with one axon only found usually in the embryonic stage).

4. The myelinated nerve fibres are enveloped with Schwann cells, which form a myelin sheath around the axon.

5. The gaps between two adjacent myelin sheaths are called nodes of Ranvier.

6. Myelinated nerve fibres are found in spinal and cranial nerves.

8. Non-myelinated nerve fibre is enclosed by a Schwann cell that does not form a myelin sheath around the axon, and is commonly found in autonomous and the somatic neural systems.

Generation and Conduction of Nerve Impulse
Neurons are excitable cells because their membranes are in a polarized state.
In resting state of neuron:
The axonal membrane is more permeable to potassium ions (K⁺) and impermeable to sodium ions (Na⁺) and negatively charged proteins present in the axoplasm. The fluid outside the axon contains a low concentration of K⁺, a high concentration of Na⁺ and thus form a concentration gradient.

These ionic gradients are maintained by the active transport of ions by the sodium-potassium pump which transports 3 Na⁺ outwards for 2 K⁺ into the cell.

As a result, the outer surface of the axonal membrane possesses a positive charge while its inner surface becomes negatively charged and therefore is polarised. The electrical potential difference across the resting plasma membrane is called as the resting potential.

When a stimulus is applied at a site on the polarised membrane:
The membrane freely permeable to Na and influx of Na⁺ followed by the reversal of the polarity at that site, i.e., the outer surface of the membrane becomes negatively charged and the inner side becomes positively charged.

This is called depolarized state. The electrical potential difference across the plasma membrane is called the action potential At sites immediately ahead, the axon membrane has a positive charge on the outer surface and a negative charge on its inner surface. As a result, a current flows on the inner surface from site A to site B.

On the outer surface current flows from site B to site A to complete the circuit of current flow. Hence, the polarity at the site is reversed, and an action potential is generated at site B. Thus, the impulse (action potential) generated at site A arrives at site B. The sequence is repeated along the length of the axon and consequently the impulse is conducted.

Transmission of Impulses
A nerve impulse is transmitted from one neuron to another through junctions called synapses. The junction between pre-synaptic neuron and a post-synaptic neuron is called synaptic cleft. There are two types of synapses, namely

1. Electrical synapses and 2. Chemical synapses

At electrical synapses, erlectrical current flowdirectly from one neuron into the other across these synapses. It is very similar to impulse conduction along a single axon, impulse transmission across an electrical synapse is always faster than that across a chemical synapse.

At a chemical synapse, the membranes ofthepre-and post-synaptic neurons are separated by a fluid-filled space called synaptic cleft Chemicals called neurotransmitters are involved in the transmission of impulses at these synapses.

The released neurotransmitters bind to the specific receptors, present on the post-synaptic membrane. This binding opens ion channels allowing the entry of ions which can generate a new potential in the post- synaptic neuron.

Central Neural System
It controls the voluntary movements such as balance of the body, functioning of vital involuntary organs (e.g., lungs, heart, kidneys, etc.), thermoregulation, hunger and thirst, circadian (24-hour) rhythms of our body, activities of several endocrine glands and human behaviour.

It is also the site for processing of vision, hearing, speech, memory, intelligence, emotions and thoughts. The human brain is well protected by the skull. Inside the skull, the brain is covered by cranial meninges consisting of an outer layer called dura mater, a very thin middle layer called arachnoid and an inner layer called pia mater.

The brain is divided into three major parts:

• forebrain
• midbrain
• hindbrain

Forebrain
The forebrain consists of cerebrum, thalamus and hypothalamus. Cerebrum forms the major part of the human brain. Cerebrum divided longitudinally into two halves the left and right cerebral hemispheres. The hemispheres are connected by nerve fibres called corpus callosum.

The layer of cells which covers the cerebral hemisphere is called cerebral cortex. The cerebral cortex is referred to as the grey matter .The cerebral cortex contains motor areas, sensory areas and large regions These regions called as the association areas.They are responsible functions like memory and communication.

The inner part of cerebral hemisphere gives white appearance to the layer and called as the white matter. Hypothalamus lies at the base of the thalamus contains a number of centres which control body temperature, urge for eating and drinking. Hypothalamus secrete hormones called hypothalamic hormones.

he inner parts of cerebral hemispheres and a group of associated deep structures like amygdala, hippocampus, etc., form a complex structure called the limbic lobe or limbic system. Along with the hypothalamus,

it is involved in the regulation of sexual behaviour, expression of emotional reactions (eg: excitement, pleasure, rage and fear), and motivation

Midbrain
The midbrain is located between the thalamus/hypothalamus of the forebrain and pons of the hindbrain. A canal called the cerebral aqueduct passess through the midbrain.

The dorsal portion of the midbrain consists mainly of four round swellings (lobes) called corpora quadrigemina. Midbrain and hindbrain form the brain stem..

Hindbrain
The hindbrain comprises pons, cerebellum and medulla (also called the medulla oblongata). Pons consists of fibre tracts that interconnect different regions of the brain. Cerebellum provide the additional space for many more neurons.

The medulla of the brain is connected to the spinal cord. The medulla contains centres which control respiration, cardiovascular reflexes and gastric secretions.

Reflex Action And Reflex Arc
It involves the sudden withdrawal of a body part which comes in contact with objects that are extremely hot, cold pointed or animals that are poisonous. The reflex pathway consists of one afferent neuron (receptor) and one efferent (effector or excitor) neuron arranged in a series.

The afferent neuron receives signal from a sensory organ and transmits the impulse via a dorsal nerve root into the CNS (at the level of spinal cord). The efferent nueuron carries signals from CNS to the effector. The stimulus and response thus forms a reflex arc in the knee jerk reflex.

Sensory Reception And Processing
The sensory organs detect all types of changes in the environment and sent to different parts/centres of the brain. The sense organs are the eye (sensory organ for vision) and the ear (sensory organ for hearing).

Eye
Our paired eyes are located in sockets of the skull called orbits.

Parts of an eye
The wall of the eye ball is composed of three layers. External layer is composed of a dense connective tissue and is called the sclera. Anterior portion of this layer is called the cornea. Middle layer, choroid, contains many blood vessels and looks bluish in colour.

The choroid layer is thin over the posterior part of eye ball, but it becomes thick in the anterior part to form the ciliary body. The ciliary continues forward to form a pigmented and opaque structure called the iris which is the visible coloured portion ofthe eye.

1. The eye ball contains lens which is held in place by ligaments attached to the ciliary body. In front of the lens, the aperture surrounded by the iris is called the pupil.
2. The inner layer is the retina contains three layers of cells – from inside to outside.
3. Ganglion cells, bipolar cells and photoreceptor cells.
4. There are two typ es of photoreceptor cells, namely, rods and cones
5. The daylight (photopic) vision and colour vision are functions of cones
6. The twilight (scotopic) vision is the function of the rods.
7. The rods contain a purplish-red protein called the rhodopsin which contains a derivative of Vitamin A. In the human eye, there are three types of cones that respond to red, green and blue lights.

What is blind spot?
The optic nerves and the retinal blood vessels enter above the posterior pole of the eye ball. Photoreceptor cells are not present in that region and hence it is called the blind spot.

What is macula lutea?
At the posterior pole of the eye lateral to the blind spot, there is a yellowish pigmented spot called macula lutea with a central pit called the fovea where only the cones are densely packed. It is the point where the visual acuity (resolution) is the greatest.

The space between the cornea and the lens is called the aqueous chamber and contains fluid called aqueous humor. The space between the lens and the retina is called the vitreous chamber and contains fluid called vitreous humor.

Mechanism of Vision
The light rays falls on the retina through cornea and lens generate impulses in rods and cones. The photosensitive compounds (photopigments) in the human eyes is composed of opsin (a protein) and retinal (an aldehyde of vitamin A). Light induces the changes in the structure of the opsin.

This causes membrane permeability changes. As a result, potential differences are generated in the photoreceptor cells. This produces a signal that generates action potentials in the ganglion cells through the bipolar cells.

These action potentials are transmitted by the optic nerves to the visual cortex area of the brain, where the neural impulses are analysed and the image formed on the retina is recognised based on earlier memory and experience.

The Ear
The ear is divided into three major sections called the outer ear, the middle ear and the inner ear. The outer ear consists of the pinna and external auditory meatus (canal).The pinna collects the vibrations of sound. The external auditory meatus leads inwards and extends up to the tympanic membrane (the ear drum).

There are wax-secreting sebaceous glands in the skin of the pinna and the meatus. The middle ear contains three ossicles called malleus, incus and stapes which are attached to one another in a chain-like fashion.

The malleus is attached to the tympanic membrane and the stapes is attached to the oval window. of the cochlea. The ear ossicles increase the efficiency of transmission of sound waves to the inner ear.

An Eustachian tube connects the middle ear cavity with the pharynx. The Eustachian tube helps in equalising the pressures on either sides of the eardrum. The fluid-filled inner ear called labyrinth consists of two parts, the bony and the membranous labyrinths.

The bony labyrinth is connected with membranous labyrinth, which is surrounded by a fluid called perilymph. The membranous labyrinth is filled with a fluid called endolymph. The coiled portion of the labyrinth is called cochlea.

The membranes constituting cochlea, the reissner’s and basilar, divide the surounding perilymph filled bony labyrinth into an upper scala vestibuli and a lower scala tympani. The space within cochlea called scala media is filled with endolymph.

At the base of the cochlea, the scala vestibuli ends at the oval window The organ of corti is a structure located on the basilar membrane which contains hair cells that act as auditory receptors. The hair cells are present in rows on the internal side of the organ of corti.

The basal end of the hair cell is in close contact with the afferent nerve fibres. A large number of processes called stereo cilia are projected from the apical part of each hair cell. Above the rows of the hair cells is a thin elastic membrane called tectorial membrane. The inner ear also contains vestibular apparatus, located above the cochlea.

The vestibular apparatus is composed of three semi-circular canals and the otolith organ consisting of the saccule and utricle. The membranous canals are suspended in the perilymph of the bony canals. The base of canals is swollen and is called ampulla, which contains a projecting ridge called crista ampullaris which has hair cells.

The saccule and utricle contain a projecting ridge called macula. The crista and macula are the specific receptors of the vestibular apparatus responsible for maintenance of balance of the body and posture.

Mechanism of Hearing
How does ear convert sound waves into neural impulses, which are sensed and processed by the brain enabling us to recognise a sound?
The external ear receives sound waves and directs them to the ear drum.The ear drum vibrates in response to the sound waves and these vibrations are transmitted through the ear ossicles (malleus, incus and stapes) to the oval window.

The vibrations are passed through the oval window on to the fluid of the cochlea, where they generate waves in the lymphs. The waves in the lymphs induce a ripple in the basilar membrane. These movements of the basilar membrane bend the hair ceils, pressing them against the tectorial membrane.

As a result, nerve impulses are generated in the associated afferent neurons. These impulses are transmitted by the afferent fibres via auditory nerves to the auditory cortex of the brain, where the impulses are analysed and the sound is recognized.

The vibrations are passed through the oval window on to the fluid of the cochlea, where they generate waves in the lymphs. The waves in the lymphs induce a ripple in the basilar membrane. These movements of the basilar membrane bend the hair cells, pressing them against the tectorial membrane.

As a result, nerve impulses are generated in the associated afferent neurons. These impulses are transmitted by the afferent fibres via auditory nerves to the auditory cortex of the brain, where the impulses are analysed and the sound is recognized.

NCERT SUPPLEMENTARY SYLLABUS
Sense organs:
The environmental changes (both internal and external) called stimuli detected by the special sensory cells, are conveyed to the brain in the form of nerve impulses. The response for each stimulus from brain is sent to the various body parts for its well being. There are five senses: touch, vision, hearing, smell and taste.

While touch is a complex general sense, the other four are special senses. The general sensory receptors are simple receptors that are present in the skin, mucous membranes, connective tissues and muscles.

These sense the information such as tactile sensation (a mix of touch, pressure, stretch and vibration), heat, cold, pain and muscle sense.

Special sensory receptors are present in the head especially sensory organs like eyes and ears and tissues of the taste buds and olfactory epithelium. These sensory organs and tissues of eye and ear are photoreceptors and the auditory receptors respectively.

The chemical senses: the taste and smell:
The receptors fortaste and smell are called as chemoreceptors found as film of liquid coating in the membranes of the receptor cells. The taste receptors are specialized cells that detect chemicals present in the mouth while smell receptors are modified sensory neurons in the nasal passage which detect the volatile chemicals.

These two types of receptors complement each other and often respond to the same stimulus. The smell receptors are 3,400 times more sensitive than the taste receptors.

Sense of smell (olfaction):
Nose contains the receptors of smell, in the mucous coated thin, yellowish patch (about 5 cm2) of modified pseudo stratified epithelium called olfactory epithelium. It is located at the roof of the nasal cavity on either sides of the nasal septum.

The olfactory epithelium contains three types of cells:

• millions of olfactory receptor cells
• columnar supportive cells
• short basal cells.

Olfactory receptors bear a cluster of about 20 modified cilia which function as receptor sites. These cilia extend from the olfactory epithelium into the thin coat of nasal mucous secreted by the supportive cells and olfactory glands. This mucous dissolves the airborne odour molecules.

Once dissolved, the chemicals bind to the specific receptors on the cilia stimulating the receptor cells. This causes depolarization then action potential in the receptor cell.

The axons of the olfactory receptors unite to form the olfactory nerve which transmits the information directly to olfactory bulb, a relay station in the brain. The nasal cavity contains pain receptors that respond to irritants such as ammonia, vinegar or hot chilly pepper.

Impulses from these pain receptors reach the brain. The brain combines these sensations with those of smell to identify the odours Humans can detect about 10,000 different odours but the olfactory capability of fish and mammals such as a dog is high.

Sense of taste (gustation):
The receptor cells fortaste are located in taste buds. Humans have about 10,000 taste buds are located in pockets around the papillae on the surface and sides of the tongue, but some on the surface of the pharynx and the larynx.

Each taste bud contains about 40 specialized receptor cells or gustatory cells, that helps to replace the worn out cells of the taste buds. The receptor cells for taste are not neurons, but they are microvilli .The microvilli protrude into the surrounding fluids through a narrow opening called the taste pore.

Dissolved chemicals contacting the microvilli bind to specific receptor proteins on the microvilli, thereby depolarizing the cell,it releases neurotransmitter which leads to the generation of an action potential in the associated sensory neuron.

Each dendrite receives signals from several receptor cells within the taste bud pass to the brain stem. From here the nerve impulse is relayed to the taste centre in the cerebral cortex of the brain that perceives the taste sensation.
In humans there are four basic taste senses:

sweet, sour, salt, and bitter. It is located in different parts of the tongue sweet and salty on the front, bitter on the back, and sour on the sides.

Sense of touch:
Skin is the largest sense organ. These sensations of touch come from millions of microscopic simple sensory receptors located all over the skin and associated with the general sensations of contact or pressure, heat, cold, and pain. Some parts of the body have a large number of these such as the fingertips.

Structurally, these touch receptors are either free dendritic endings or encapsulated dendritic endings present in the skin (and other parts of the body). Free or bare dendritic nerve endings are present throughout the epidermis in “zigzag” form .These respond chiefly to pain and temperature but some respond to pressure as well.

Meissner’s corpuscles are small receptors are surrounded by specialized capsule (Schawann) cells. These are found just beneath the skin epidermis in dermal papillae and abundant in finger tips and soles of the feet. These are light pressure receptors. Pacinian corpuscles are the large egg shaped bodies surrounded by multilayers of capsule cells. These are scattered deep in the dermis and in the subcutaneous tissue of the skin .These are stimulated by deep pressure.(box)

Whenever one or more of these sensory receptors are stimulated (by heat, cold, vibrations, pressure or pain) an impulse or action potential is generated. This impulse is then taken to the spinal cord and from there to the brain which analyses the stimulus and then generates appropriate response.

Students can Download Chapter 7 Bill of Exchange Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 7 Bill of Exchange

Summary:
Bill of Exchange:
A bill of exchange is an acknowledgement of debt given by one person to another, incorporating all the terms and conditions of payment.

Features and advantages of a bill:
A bill is a written unconditional order, it is signed by the creditor and accepted by the debtor, the amount of the bill is payable either on demand or at a fixed period.

Parties to a bill of Exchange:
There are three parties, ie., drawer, drawee and payee.

Promissory Note:
A promissory note is an undertaking in writting given by the debtor to the creditor to pay the latter a certain sum of money in accordance with the conditions stated therein. There are two parties to a promissory note, the promissor and the promisee.

Maturity of Bill:
The term maturity refers to the date on which a bill or promissory note becomes due for payment. In arriving at the maturity date three days known as “days of grace” must be added to the date on which the period of credit expires instrument is payable.

Endorsement:
An endorsement is a written order on the back of the instrument by the payee or the holder for transferring his right to another person.

Accounting treatment:
A bill can be treated in the following four ways by its receiver.

Dishonour of a bill:
A bill is said to have been dishonoured when the drawee fails to make the payment on the date of maturity. In this situation, liability of the acceptor is restored. Therefore, the entries made on the receipt of the bill should be reserved. The entries of dishonour of bill as follows
(i) When the bill was kept by drawer till maturity.

Noting Charges:
When a bill is dishonoured due to non-payment, it is usual to get it ‘noted’, to establish the matter of dishonour. The noting is done by “Notary Public.” Noting authenticates the fact of dishonour. For providing this service, a fees is charged by the Notary Public which is called Noting Charges. The following facts are generally noted by the Notary;

• Date, fact and reasons of dishonour;
• If the bill is not expressly dishonoured, the reasons why he treats it as dishonoured and;
• The amount of noting charges.

The entries recorded for noting charges in the drawers book are as follows:
When Drawer himself pays:

Where endorsee pays:

When the bank pays on discounted bill:

When the bank pays in the event of sending the bill for collection to the bank:

The entry recorded for noting charges in the book of drawee as follows:
For recording noting charges the drawee opens “Noting ChargesAccount”.

Renewal of the bill:
Sometimes the acceptor of the bill foresees that it may be difficult to meet the obligation of the bill on maturity and may, therefore approach the drawer with the request for extension of time for payment.

If it is so, the old bill is cancelled and . the fresh bill with new terms of payment is drawn and duly accepted and delivered. This is called renewal of the bill. The drawee may have to pay interest to the drawer for the extended period of credit.
Following journal entries are recorded in the case of renewal of the bill.

Retiring of the Bill:
Making payment of the bill of exchange before the due date is called retiring of the bill. To encourage the retirement of the bill, the holder allows some discount called “Rebate on bill” for the period between date of retirement and maturity. The rebate is calculated at a certain rate of interest.

The following journal entries are recorded:
(i) In the book of drawer:
On retiring the acceptance, rebate allowed.

(ii) In the book of drawee:

Students can Download Chapter 9 Locomotion and Movement Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 9 Locomotion and Movement

What is locomotion?
The movements result in a change of place or location. Such voluntary movements are called locomotion. Walking, running, climbing, flying, swimming are all some forms of locomotory movements.

Locomotory Movements In Lower Organisms

1. Paramoecium, cilia helps in the movement of food through cytopharynx and locomotion.
2. Hydra use its tentacles for capturing its prey and also use them for locomotion.

All locomotions are movements but all movements are not locomotions.

Types Of Movement
The three main types of movements of cells of the human body are

• Amoeboid
• Ciliary
• Muscular.

Amoeboid movement: 1. Macrophages and leucocytes in blood exhibit amoeboid movement 2. pseudopodia formed by the streaming of protoplasm (as in Amoeba). 3. Cytoskeletal elements like microfiiaments exhibit amoeboid movement

Ciliary movement: 1. Internal tubular organs which are lined by ciliated epithelium. 2. The coordinated movements of cilia in the trachea help us in removing dust particles and foreign Substances 3. Passage of ova through the female reproductive tract.is also facilitated by the ciliary movement.

Muscular movement: 1. Movement of our limbs, jaws, tongue, etc, require muscular movement. 2. The muscles are used for locomotion. Locomotion requires a coordinated activity of muscular, skeletal and neural systems.

Muscle
About 40-50 perent of the body weight of a human adult is contributed by muscles. Muscles are classified based on their location, three types of muscles are identified.

1. Skeletal
2. Visceral
3. Cardiac.

1. Skeletal muscles:
They have a striped appearance and called as striated muscles. They are voluntary muscles because their activities are under the voluntary control of the nervous system. They are involved in locomotory actions and changes of body postures.

2. Visceral muscles:

• They are located in the innerwalls alimentary canal, reproductive tract, etc. They are called smooth muscles (non striated muscle).
• Their activities are not underthe voluntary controlcalled as involuntary muscles.
• They helps in transportation of food through the digestive tract and gametes through the genital tract.

3. Cardiac muscles:

• They are found in the muscles of heart. Based on appearance, cardiac muscles are striated and involuntary.
• Skeletal muscle is made of a number of muscle bundles or fascicles held together by a common collagenous connective tissue layer called fascia
• Each muscle bundle contains a number of muscle fibres. Each muscle fibre is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm.
• Muscle fibre is a syncitium because it contains many nuclei.
• The endoplasmic reticulum, i.e., sarcoplasmic reticulum of the muscle fibres is the store house of calcium ions.

The muscle fibre consists of parallelly arranged filaments in the sarcoplasm called myofilaments or myofibrils. Each myofibril has alternate dark and light bands on it. The striated appearance is due to two important proteins – Actin and Myosin. The light bands contain actin and is called l-band or Isotropic band, whereas the dark band called A’ or Anisotropic band contains myosin. The A and T bands are arranged alternately. Actin filaments are thinner as compared to the myosin filaments.In the centre of each T band is an elastic fibre called ‘Z’ line which bisects it. The thin filaments are firmly attached to the Z line. The thick filaments in the ‘A’ band are attached in the middle of this band by a thin fibrous membrane called ‘M’ line. The myofibril between two successive ‘Z’ lines is the functional unit of contraction and is called a sarcomere In a resting state, the edges of thin filaments on either side of the thick filaments partially overlap the free ends of the thick filaments. The central part of thick filament, not overlapped by thin filaments is called the ‘H’ zone.

Structure of Contractile Proteins
Each actin filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins. Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length.

Acomplex protein Troponin is distributed at regular intervals on the tropomyosin. In the resting state a subunit of troponin masks the active binding sites for myosin on the actin filaments.

Monomeric proteins called Meromyosins forms one thick filament. Each meromyosin has two important parts, a globular head with a short arm and a tail, the former being called the heavy meromyosin (HMM) and the latter, the light meromyosin (LMM). The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin.

Mechanism of Muscle Contraction
The sliding filament theory which states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments.
Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron. The junction between a motor neuron and the sarcolemma of the muscle fibre is called the neuromuscular junction or motor-end plate.

1. In the junction, the neurotransmitter (Acetyl choline) is released which generates an action potential in the sarcolemma. This spreads and release of calcium ions into the sarcoplasm.
2. Increase in Ca⁺⁺ level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin.
3. The energy from ATP hydrolysis is used to bind the myosin head with exposed active sites on actin to form a cross bridge.
4. This pulls the attached actin filaments towards the centre of ‘A’ band. The Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e. contraction.
5. During shortening of the muscle the T bands get reduced, whereas the ‘A’ bands retain the length The myosin, releasing the ADP and P1 goes back to its relaxed state.
6. The ATP is again hydrolysed by the myosin head and the cycle of cross bridge formation and breakage is repeated causing further sliding.
7. The process continues till the Ca⁺⁺ ions are pumped back to the sarcoplasmic cisternae resulting in the masking of actin filaments.

This causes the return of ‘Z’ lines back to their original position, i.e., relaxation.

What is muscle fatigue?
Repeated activation of the muscles can lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen causing fatigue. Muscle contains a red coloured oxygen storing pigment called myoglobin. These muscles contain plenty of mitochondria which helps in ATP production.

Hence they are called aerobic muscles. Some of the muscles possess very less quantity of myoglobin and gives whitish appearance . These are the White fibres. Number of mitochondria are also few in them. They depend on anaerobic process for energy.

Seletal System
1. Skeletal system consists of a framework of bones and a few cartilages.

2. Bone and cartilage are specialised connective tissues.

3. The former has a very hard matrix due to calcium salts in it and the latter has slightly pliable matrix due to chondroitin salts. In human beings, this system is made up of 206 bones and a few cartilages. It is grouped into two divisions.

Axial skeleton:

1. It comprises 80 bones distributed along the main axis of the body.
2. The skull, vertebral column, sternum and ribs constitute axial skeleton.

The skull is composed of two sets of bones – Cranial bones are 8 in number. The facial region is made up of 14 skeletal elements which form the front part of the skull.

Diagrammatic view of human skull:
A single U-shaped bone called hyoid is present at the base of the buccal cavity and it is also included in the skull.

What is ear ossicles ?
Each middle ear contains three tiny bones – Malleus, Incus and Stapes, collectively called Ear Ossicles.

Vertebral column:
It is formed by 26 serially arranged units called vertebrae and is dorsally placed. Each vertebra has a central hollow portion (neural canal) through which the spinal cord passes. First vertebra is the atlas and it articulates with the occipital condyles. The vertebral column is differentiated into cervical (7), thoracic (12), lumbar (5), sacral (1-fused)and coccygeal (1-fused) regions starting from the skull.

Vertebral column (right lateral view) Ribs and rib cage. The vertebral column protects the spinal cord, supports the head and serves as the point of attachment for the ribs and musculature of the back.

Sternum:
It is a flat bone on the ventral midline of thorax.
There are 12 pairs of ribs.
1. First seven pairs of ribs are called true ribs. Dorsaily, they are attached to the thoracic vertebrae and ventrally connected to the sternum with the help of hyaline cartilage.

2. The 8^th, 9^th and 10^th pairs of ribs do not articulate directly with the sternum but join the seventh rib with the help of hyaline cartilage. These are called vertebrochondral (false) ribs.

3. Last 2 pairs (11^th and 12^th) of ribs are not connected ventrally and are called floating ribs. Thoracic vertebrae, ribs and sternum together form the rib cage.

Appendicular skeleton:
It includes bones of the limbs alongwith their girdles Each limb is made of 30 bones. The bones of the hand (fore limb) are humerus, radius and ulna, carpals (wrist bones-8 in number), metacarpals (palm bones – 5 in number) and phalanges (digits – 14 in number) Femur (thigh bone – the longest bone), tibia and fibula, tarsals (ankle bones – 7 in number), metatarsals (5 in number) and phalanges (digits -14 in number) are the bones of the legs (hind limb).

A cup shaped bone called patella cover the knee ventrally (knee cap). Pectoral and Pelvic girdle bones help in the articulation of the upper and the lower limbs respectively with the axial skeleton.

Each half of pectoral girdle consists of a clavicle and a scapula. Scapula is a large triangular flat bone situated in the dorsal part of the thorax between the second and the seventh ribs. The dorsal, flat, triangular body of scapula has a slightly elevated ridge called the spine which projects as a flat, expanded process called the acromion.

Below the acromion is a depression called the glenoid cavity which articulates with the head of the humerus to form the shoulder joint. Each clavicle is a long slender bone with two curvatures. This bone is commonly called the collar bone. Pelvic girdle consists of two coxal bones Each coxal bone is formed by the fusion of three bones

1. ilium
2. ischium
3. pubis.

Joints
Joints are points of contact between bones, or between bones and cartilages. The movability of joints vary depending on different factors.
Joints are classified into three,

1. Fibrous joints This type of joint is found in the flat skull bones which fuse end-to-end with the help of dense fibrous connective tissues in the form of sutures, to form the cranium. They do not allow any movement. 2. Cartilaginous joints The bones are joined together with the help of cartilages. It allows limited movements. 3. Synovial joints It has fluid filled synovial cavity between the articulating surfaces of the two bones. These joints help in locomotion and many other movements.(box)

Ball and socket joint (between humerus and pectoral girdle), Hinge joint (knee joint), Pivot joint (between atlas and axis), Gliding joint (between the carpals) and Saddle joint (between carpal and metacarpal of thumb) are some examples.

Disorders Of Muscular And Skeletal System
Myasthenia gravis:
Auto immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.

Muscular dystrophy:
Progressive degeneration of skeletal muscle mostly due to genetic disorder.

Tetany:
Rapid spasms (wild contractions) in muscle due to low Ca⁺⁺ in body fluid.

Arthritis:
Inflammation of joints.

Osteoporosis:
Age-related disorder characterised by decreased bone mass and increased chances of fractures. Decreased levels of estrogen is a common cause.

Gout:
Inflammation of joints due to accumulation of uric acid crystals.

NCERT SUPPLEMENTARY SYLLABUS
Types of movements: Flagellar movement
The three main types of movements shown by the cells of the human body are amoeboid, ciliary and muscular. Human sperms shows type of movement called the flagellar movement. The flagellum is the propulsion equipment (due to whip like movement of the tail and the middle piece of the sperm) forthe movement of sperm towards the ovum.

Students can Download Chapter 11 Chemical Coordination and Integration Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 11 Chemical Coordination and Integration

What is neural system?
The neural system and the endocrine system coordinate and regulate the physiological functions in the body.

Endocrine Glands And Hormones:
Endocrine glands lack ducts and are called ductless glands. Their secretions are called hormones.

Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts

Human Endocrine System
The endocrine glands are located in different parts of our body constitute the endocrine system. Pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus and gonads (testis in males and ovary in females) are the organised endocrine bodies in our body.

In addition to these, some other organs, eg: gastrointestinal tract, liver, kidney, heart also produce hormones.

The Hypothalamus:
The hypothalamus is the basal part of diencephalon, forebrain and it regulates body functions. The hormones produced by hypothalamus are of two types

1. The releasing hormones (which stimulate secretion of pituitary hormones)
2. The inhibiting hormones (which inhibit secretions of pituitary hormones).

For example,

Hypothalamic hormone called Gonadotrophin releasing hormone (GnRH) stimulates the pituitary synthesis and release of gonadotrophins.

Somatostatin from the hypothalamus inhibits the release of growth hormone from the pituitary.

These hormones originating in the hypothlamic neurons, pass through axons and are released from their nerve endings reach the pituitary gland through a portal circulatory system and regulate the functions of the anterior pituitary. The posterior pituitary is under the direct neural regulation of the hypothalamus.

The Pituitary Gland:
The pituitary gland is located in a bony cavity called sella tursica. It is divided into an adenohypophysis and a neurohypophysis.

Adenohypophysis:
It consists of two portions, pars distalis and pars intermedia. The pars distalis region of pituitary, commonly called anterior pituitary, produces growth hormone (GH), prolactin (PRL), thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), luteinizing hormone (LH) and follicle stimulating hormone (FSH).

Pars intermedia secretes only one hormone called melanocyte stimulating hormone (MSH). Pars intermedia is almost merged with pars distalis.

Neurohvpophysis:
It is also known as posterior pituitary, stores and releases two hormones called

1. Oxytocin
2. vasopressin

Function:
These are synthesised by the hypothalamus and are transported to neurohypophysis.

Growth hormone:
Over-secretion of GH stimulates abnormal growth of the body leading to gigantism and low secretion of GH results in stunted growth resulting in pituitary dwarfism. Prolactin regulates the growth of the mammary glands and formation of milk in them.

TSH stimulates the synthesis arid secretion of thyroid hormones from the thyroid gland. ACTH stimulates the synthesis and secretion of steroid hormones called glucocorticoids from the adrenal cortex. LH and FSH stimulate gonadal activity and called as gonadotrophins.

Activity of LH and FSH in males and females:
In males, LH stimulates the synthesis and secretion of hormones called androgens from testis. In males, FSH and androgens regulate spermatogenesis. In females, LH induces ovulation of fully mature follicles (graafian follicles) and maintains the corpus luteum, formed from the graafian follicles after ovulation.

In females FSH stimulates growth and development of the ovarian follicles. MSH acts on the melanocytes (melanin containing cells) and regulates pigmentation of the skin. Oxytocin stimulates a vigorous contraction of uterus at the time of child birth, and milk ejection from the mammary gland.

Hormone in water reabsorption:
Vasopressin acts on kidney and stimulates resorption of water and electrolytes by the distal tubules and thereby reduces loss of water through urine (diuresis). Hence, it is also called as anti-diuretic hormone (ADH).

The Pineal Gland:
The pineal gland is located on the dorsal side of forebrain. It secretes a hormone called melatonin. It regulates 24-hour (diurnal) rhythm of our body. For example, it helps in maintaining sleep-wake cycle, body temperature, metabolism, pigmentation, the menstrual cycle as well as our defense capability.

Thyroid Gland:
It is composed of two lobes which are located on either side of the trachea. The thyroid gland is composed of follicles and stromal tissues. The follicular cells synthesise two hormones, tetraiodothyronine or thyroxine (T4) and triiodothyronine (T3). Deficiency of iodine in our diet results in hypothyroidism and enlargement of the thyroid gland called goitre.

Hypothyroidism during pregnancy causes defective development and maturation of the growing baby leading to stunted growth (cretinism), mental retardation, low intelligence quotient, abnormal skin, deaf-mutism, etc.

In adult women, hypothyroidism cause the occurrence of irregular menstrual cycle. Due to cancer of the thyroid gland the synthesis and secretion of the thyroid hormones is increased to abnormal high levels leading to a condition called hyperthyroidism.

Parathyroid Gland:
It is present on the back side of the thyroid gland and secrete a peptide hormone called parathyroid hormone (PTH).

Parathyroid hormone (PTH) increases the Ca2+ levels in the blood. It acts on bones and stimulates the process of bone resorption (dissolution/demineralisation).

PTH also stimulates reabsorption of Ca²⁺ by the renal tubules and increases Ca²⁺ absorption from the digested food. Hence PTH is a hypercalcemic hormone i.e., it increases the blood Ca²⁺ levels. Along with TCT, it plays a significant role in calcium balance in the body.

Thymus:
The thymus gland is located on the dorsal side of the heart and the aorta and plays a major role in the development of the immune system.

This gland secretes the peptide hormones called thymosins which is involved in the differentiation of T-lymphocytes and provides cell-mediated immunity.

Thymosins also promote production of antibodies to provide humoral immunity. Thymus is degenerated in old individuals and the immune responses of old persons become weak.

Adrenal Gland:
It is located at the anterior part of each kidney. The gland is composed of inner adrenal medulla, and outside the adrenal cortex.

Adrenal medulla:

It secretes two hormones called adrenaline or epinephrine and noradrenaline or norepinephrine. These are commonly called as catecholamines

Adrenaline and noradrenaline are secreted during emergency situations and are called emergency hormones or hormones of Fight or Flight. These hormones increase alertness, pupilary dilation, piloerection (raising of hairs), sweating, etc.

These hormones increase the heart beat, the strength of heart contraction and the rate of respiration. Catecholamines stimulate the breakdown of glycogen resulting in an increased concentration of glucose in blood. They also stimulate the breakdown of lipids and proteins.

Adrenal cortex:
It is divided into three layers, called

1. zona reticularis (inner layer)
2. zonafasciculata (middle layer)
3. zona glomerulosa (outer layer).

The secretory hormones are commonly called as corticoids. They are involved in carbohydrate metabolism called as glucocorticoids. eg: Cortisol.

Function:
It maintains the cardio-vascular system as well as the kidney functions, suppresses the immune response and stimulates the RBC production. Corticoids, which regulate the balance of water and electrolytes in our body are called mineralocorticoids. eg: Aldosterone.

Glucocorticoids stimulate, gluconeogenesis, lipolysis and proteolysis and inhibit cellular uptake and utilisation of amino acids. Aldosterone stimulates the reabsorption of Na⁺ and water and excretion of K⁺ and phosphate ions.

Hence it helps in the maintenance of electrolytes, body fluid volume, osmotic pressure and blood pressure. Androgenic steroids secreted by the adrenal cortex which play a role in the growth of axial hair, pubic hair and facial hair during puberty.

Pancreas:
It acts as both exocrine and endocrine gland. The endocrine consists of ‘Islets of Langerhans’.

The two main types of cells in the Islet of Langerhans are called alpha cells and beta -cells. The alpha cells secrete a hormone called glucagon, while the beta cells secrete insulin

Glucagon is a peptide hormone maintains the normal blood glucose levels, stimulates glycogenolysis – increased blood sugar (hyperglycemia),stimulates the process of gluconeogenesis – contributes to hyperglycemia. Insulin is a peptide hormone, which enhances cellular glucose uptake and utilisation.

As a result, there is a rapid movement of glucose from blood to hepatocytes and adipocytes resulting in decreased blood glucose levels (hypoglycemia). Insulin also stimulates conversion of glucose to glycogen (glycogenesis) in the target cells.

Prolonged hyperglycemia leads to a complex disorder called diabetes mellitus which is associated with loss of glucose through urine and formation of harmful compounds known as ketone bodies.

Testis:
A pair of testis is present in the scrotal sac of male individuals Testis performs dual functions as a primary sex organ as well as an endocrine gland. Testis is composed of seminiferous tubules and stromal or interstitial tissue. The Leydig cells or interstitial cells, which produce a group of hormones called androgens mainly testosterone.

Androgens regulate the development, maturation and functions of the male accessory sex organs like epididymis, vas deferens, seminal vesicles, prostate gland, urethra etc.

Androgens also stimulate muscular growth, growth of facial and axillary hair, aggressiveness, low pitch of voice, spermatogenesis (formation of spermatozoa), influence the male sexual behaviour (libido).

These hormones produce anabolic (synthetic) effects on protein and carbohydrate metabolism.

Ovary:
It is the primary female sex organ which produces one ovum during each menstrual cycle. Ovary produces two groups of steroid hormones called estrogen and progesterone. The estrogen is are secreted by the growing ovarian follicles. After ovulation, the ruptured follicle is converted to a structure called corpus luteum, which secretes progesterone.

Estrogens involved in stimulation of growth and activities of female secondary sex organs, development of growing ovarian follicles, appearance of female secondary sex characters (e.g., high pitch of voice, etc.), mammary gland development, regulate female sexual behaviour.

Progesterone supports pregnancy, stimulates the formation of alveoli (sac-like structures which store milk) and milk secretion.

Hormones Of Heart Kidney And Gastrointestinal Tract:
The atrial wall of our heart secretes a very important peptide hormone called atrial natriuretic factor (ANF), which decreases blood pressure. When blood pressure is increased, ANF is secreted which causes dilation of the blood vessels. This reduces the blood pressure.

The juxtaglomerular cells of kidney produce a peptide hormone called erythropoietin which stimulates erythropoiesis (formation of RBC). The gastro-intestinal tract secrete four major peptide hormones, namely gastrin, secretin, cholecystokinin (CCK) and gastric inhibitory peptide (GIP).

Gastrin stimulates the secretion of hydrochloric acid and pepsinogen. Secretin stimulates secretion of water and bicarbonate ions. CCK acts on both pancreas and gall bladder and stimulates the secretion of pancreatic enzymes and bile juice, respectively. GIP inhibits gastric secretion and motility.

Mechanism Of Hormone Action:
Hormones bind to specific proteins called hormone receptors Hormone receptors present on the cell membrane of the target cells are called membrane-bound receptors and the receptors present inside the target cell are called intracellular receptors.

Binding of a hormone to its receptor leads to the formation of a hormone-receptor complex. Hormone- Receptor complex formation leads to certain biochemical changes in the target tissue. On the basis of their chemical nature, hormones can be divided into groups.

1. peptide,
2. polypeptide,
3. protein hormones (eg: insulin, glucagon, pituitary hormones, hypothalamic hormones, etc.)
   • steroids (eg: cortisol, testosterone, estradiol and progesterone)
   • iodothyronines (thyroid hormones)
   • amino-acid derivatives (eg: epinephrine).

Hormones which interact with membrane-bound receptors do not enter the target cell, but generate second messengers (eg: cyclic AMP, IP3, Ca^++, etc) which in turn regulate cellular metabolism. Hormones which interact with intracellular receptors (eg: steroid hormones, iodothyronines, etc.) regulate gene expression or chromosome function.

Exophthalmic goitre, also called Grave’s disease:
This occurs due to hyperthyroidism i.e the excessive secretion of thyroxine hormone is accompanied by the enlargement of the thyroid glands. It is an autoimmune disease where patients produce antibodies that act on the thyroid glands to increase thyroxine hormone production and thyroid size. eg: Patients suffering from cancerof thyroid glands.

The symptoms are elevated metabolic rate, sweating, rapid and irregular heartbeat, weight loss despite increased appetite, frequent bowel movement and nervousness. Some patients may also experience exophthalmos (or protrusion of the eyeballs). Thus this condition is also known as exophthalmic goitre.

Addison’s’ disease:
The hyposecretory disorder of the adrenal cortex or destruction of adrenal cortex in diseases such as tuberculosis leads to deficit of both glucocorticoids and mineralocorticoids. This condition is known as Addison’s disease. The symptoms are loose weight, their blood glucose and sodium levels drop and potassium levels rise.

NCERT SUPPLEMENTARY SYLLABUS
Exophthalmic goitre, also called Grave’s disease:
This occurs due to hyperthyroidism i.e the excessive secretion of thyroxine hormone is accompanied by the enlargement of the thyroid glands.

It is an autoimmune disease where patients produce antibodies that act on the thyroid glands to increase thyroxine hormone production and thyroid size. eg: Patients suffering from cancer of thyroid glands.

The symptoms are elevated metabolic rate, sweating, rapid and irregular heartbeat, weight loss despite increased appetite, frequent bowel movement and nervousness. Some patients may also experience exophthalmos (or protrusion of the eye balls). This condition is also known as exophthalmic goitre.

Addison’s’ disease:
The hyposecretory disorder of the adrenal cortex or destruction of adrenal cortex in diseases such as tuberculosis leads to deficit of both glucocorticoids and mineralocorticoids.

This condition is known as Addison’s disease. The symptoms are weight loss, blood glucose and sodium levels drop and potassium levels rise.

Students can Download Chapter 5 Trial Balance and Rectification of Errors Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 5 Trial Balance and Rectification of Errors

Summary:
Meaning of trial balance:
A statement showing the abstract of the balance (debit/credit) of various accounts in the ledger.

Objectives of trial balance:
The main objectives of preparing the trial balance are:

• To ascertain the arithmetical accuracy of the ledger accounts;
• To help in locating errors; and
• To help in the preparation of the final accounts.

Preparation of trial balance by the balance method:
In this method, the trial balance has three columns. The first column is for the head of the account, the second column for writing the debit balance and the third for the credit balance of each account in the ledger.

Format of a Trial balance
Trial Balance of ………………… as on March 31.2005

It is normally prepared at the end of an accounting year. However, an organisation may prepare a trial balance at the end of any chosen period, which may be monthly, quarterly, half yearly or annually depending upon its requirements.
In order to prepare a trial balance following steps are taken:

• Ascertain the balances of each account in the ledger.
• List each account and place its balance in the debit or credit column as the case may be. (If an account has a zero balance, it may be included in the trial balance with zero in the column for its normal balance).
• Compute the total of debit balances column.
• Compute the total of the credit balances column.
• Verify that the sum of the debit balances equal the sum of credit balances. If they do not tally, it indicates that there are some errors. So one must check the correctness of the balances of all accounts.

It may be noted that all assets expenses and receivables account shall have debit balances whereas all liabilities, revenues and payables accounts shall have credit balances.

Illustrative Trial Balance

Various types of errors:
1. Errors of commission:
Errors caused due to wrong recording of a transaction, wrong totalling, wrong casting, wrong balancing, etc.

2. Errors of omission:
Errors caused due to omission of recording a transaction entirely or partly in the books of account.

3. Errors of principle:
Errors arising due to wrong classification of receipts and payments between revenue and capital receipts and revenue and capital expenditure.

4. Compensating errors:
Two or more errors committed in such a way that they nullify the effect of each other on the debits and credits.

Rectification of errors:
Errors affecting only one account can be rectified by giving an explanatory note or by passing a journal entry. Errors which affect two or more accounts are rectified by passing a journal entry.

Meaning and utility of suspense account:
An account in which the difference in the trial balance is put till such time that errors are located and rectified. It facilitates the preparation of financial statements even when the trial balance does not tally.

Disposal of suspense account:
When all the errors are located and rectified the suspense account stands disposed off.

Students can Download Chapter 4 Bank Reconciliation Statement Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 4 Bank Reconciliation Statement

Summary
Bank Reconciliation Satement
A statement prepared to reconcile the bank balance as per cash book with the balance as per passbook or bank statement, by showing the items of difference between the two accounts.

Causes of difference
Timing of recording the transaction Errors made by business or by the bank.

Need for Reconciliation
It is generally experienced that when a comparison is made between the bank balance as shown in the firm’s cash book, the two balances do not tally. Hence, we have to first ascertain the causes of difference thereof and then reflect them in a statement called Bank Reconciliation Statement to reconcile (tally) the two balances.

In order to prepare a bank reconciliation statement we need to have a bank balance as per the cash book and a bank statement as on a particular day along with details of both the books.

If the two balances differ, the entries in both the books are compared and the items on account of which the difference has arisen are ascertained with the respective amounts involved so that the bank reconciliation statement may be prepared.

Proforma of bank reconciliation statement

It can also be prepared with two amount columns one showing additions (+ column) and another showing deduction (- column).

Proforma of bank reconciliation statement (table form)

Correct cash balance
It may happens that some of the receipts or payments are missing from either of the books and errors, if any, need to be rectified. This arises the need to look at the entries/errors recorded in both statements and other information available and compute the correct cash balance before reconciling the statements.

Students can Download Chapter 3 Recording of Transactions – I & II Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 3 Recording of Transactions – I & II

Summary:
Meaning of source documents:
Various business documents such as invoice, bills, cash memos, vouchers, which form the basis and evidence of a business transaction recorded in the books of account are called source documents.

Meaning of accounting equation:
A statement of equality between debits and credits signifying that the assets of a business are always equal to the total liabilities and capital.

Rules of debit and credit:
An account is divided into two sides. The left side of an account is known as debit and the credit. The rules of debit and credit depend on the nature of an account. Debit and Credit both represent either increase or decrease, depending on the nature of an account.

These rules are summarised as follows:

Books of original entry:
The transactions are first recorded in these books in a chronological order. Journal is one of the books of original entry. The process of recording entries in the journal is called journalising.

Format of Journal

Ledger:
A book containing all accounts to which entries are transferred from the books of original entry. Posting is process of transferring entries from books of original entry to the ledger.

Format of a Ledger

Special Journals:
Special journals are also called day books or subsidiary books. Transactions that cannot be recorded in any special journal are recorded in journal is called the “Journal Proper.”

The special-purpose journals are:

• Cash Book
• Petty Cash Book
• Purchase Book
• Purchase Return Book
• Sales Book
• Sales Return Book
• Journal Proper

(a) Cash Book
A book used to record all cash receipts and payments. Cash book may be single column cash book, doulbe column cash book and three column cash book.

Single Column Cash book
This is cash book containing only one column for cash and prepared as cash account in ledger.

Format of Single Column Cash Book

Double Column Cash book:
This is cash book containing one more column for bank along with the cash column, it serves the purpose of cash and bank account.

Format of Double Column Cash Book

(b) Petty Cash Book:
A book used to record small cash payments

(c) Purchase Book / Purchase Journal:
A special journal in which only credit purchases are recorded.

Format of Purchase Day Book

(d) Purchase Return Book:
A book in which return of purchased goods on credit is recorded.

Format of Purchase Return Book

(e) Sales Book / Sales Journal:
A special journal in which only credit sales are recorded.

Format of Sales Day Book

(f) Sales Return Book:
A special book in which return of goods sold on credit is recorded.

Format of Sale Return Book

Balancing the Accounts:
Accounts in the ledger are periodically balanced, generally at the end of the accounting period with the object of ascertaining the net position of each amount.

Balancing of an account means that the two sides are totaled and the difference between them is shown on the side which is shorter in order to make their totals equal. The words ‘balance carried down (c/d)’ are written against the amount of the difference between the two sides.

The amount of balance is brought down (b/d) in the next accounting period indicating that it is a continuing account until finally settled or closed. In case the debit side exceeds the credit side.

The difference is written on the side, if the credit side exceeds the debit side, the difference between the two appears on the debit side and is called debit and credit balance respectively. The accounts of expenses losses, gains and revenues are not balanced but are closed by transferring to trading and profit and loss account.

Students can Download Chapter 2 Theory Base of Accounting Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 2 Theory Base of Accounting

Summary:
Generally accepted Accounting Principles (GAAP):
GAAP refers to the rules or guidelines adopted for recording and reporting to business transactions in order to bring uniformity in the preparation and presentation of financial statements. These principles are also referred to as concepts and conventions.

From the practicality viewpoint, the various terms such as principles, conventions, modifying principles, assumptions, etc., have been used interchangeably and are referred to as basic accounting concepts.

Systems of Accounting:
There are two systems of recording business transactions, i.e., double entry system and single entry system.

Basis of Accounting:
There are two broad approach of accounting are cash basis and accural basis. Under cash basis transactions are recorded only when cash are received or paid, where as under accural basis, revenue or costs are recognises when they Occur rather than when they are paid.

Accounting Standards:
Accounting standards are written statement of uniform accounting rules and guidelines in practice for preparing the uniform and consistent financial statements.

Students can Download Chapter 1 Introduction to Accounting Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 1 Introduction to Accounting

Summary
Meaning of Accounting:
Accounting is a process of identifying, measuring, recording the business transactions and communicating thereof the required information to the interested users.

Accounting as a source of information:
Accounting as a source of information system is the process of identifying, measuring, recording and communicating the economic events of an organization to interested users of the information.

Users of accounting information:
Accounting plays a significant role in society by providing information to management at all levels and to those having a direct financial interest in the enterprise, such as present and potential investors and creditors.

Accounting information is also important to those having an indirect financial interests, such as regulatory agencies, tax authorities, customers, labour unions, trade associations, stock exchanges, and others.

Qualitative characteristics of Accounting:
To make accounting information decision-useful, it should possess the following qualitative characteristics.

• Reliability
• Understandability
• Relevance
• Comparability

The objective of accounting:
The primary objectives of accounting are to:

• Maintain records of business;
• Calculate profit or loss;
• Depict the financial position: and
• Make information available to various groups and users.

Role of accounting:
Accounting is not an end in itself. It is a means to an end. It plays the role of a:

• Language of a business
• Historical record
• Current economic reality
• Information system
• Service to users

Students can Download Chapter 8 Excretory Products and their Elimination Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 8 Excretory Products and their Elimination

What is excretion?
Excretion is the elimination common nitrogenous wastes. Ammonia, urea and uric acid are the major forms of nitrogenous wastes excreted by the animals.

Ammonotelic.ureotelic and urecotelic animals and their excretion:
1. The process of excreting ammonia is Ammonotelism. eg: Many bony fishes, aquatic amphibians and aquatic insects are ammonotelic.

2. Mammals, many terrestrial amphibians and marine fishes mainly excrete urea and are called ureotelic animals.

3. Reptiles, birds, land snails and insects excrete nitrogenous wastes as uric acid in the form of pellet or paste with a minimum loss of water and are called uricotelic animals.

Where is urea produced?
Ammonia produced by metabolism is converted into urea in the liver and released into the blood which is filtered and excreted out by the kidneys.

Excretion in lower organisms:

Protonephridia or flame cells are the excretory structures in Platyhelminthes (Flatworms, eg: Planaria), rotifers, some annelids and the cephalochordate – Amphioxus. Nephridia are the tubular excretory structures of earthworms and other annelids Malpighian tubules are the excretory structures of most of the insects including cockroaches. Antennal glands or green glands perform the excretory function in crustaceans like prawns.

Human Excretory System
In humans, the excretory system consists of

1. A pair of kidneys
2. One pair of ureters
3. A urinary bladder
4. A urethra.

Each kidney of an adult human measures 10 – 12 cm in length, 5 – 7 cm in width, 2 – 3 cm in thickness with an average weight of 120 – 170 g.

1. Centre of the inner concave surface of the kidney is a notch called hilum through which ureter, blood vessels and nerves enter.

2. Innerto the hilum is a broad funnel shaped space called the renal pelvis with projections called calyces.

3. Inside the kidney, there are two zones, an outer cortex and an inner medulla.

4. The medulla is divided medullary pyramids projecting into the calyces.

5. The cortex extends in between the medullary pyramids as renal columns called Columns of Bertini.

6. Each kidney has nearly one million complex tubular structures called nephrons, which are the functional units. A diagrammatic representation of a nephron showing blood vessels, duct and tubule Each nephron has two parts -1 The glomerulus & 2 Renal tubule.

7. Glomerulus is a tuft of capillaries formed by the afferent arteriole – a fine branch of renal artery.

8. Blood from the glomerulus is carried away by an efferent arteriole.

9. The renal tubule begins with a double walled cup-like structure calle Bowman’s capsule, which encloses the glomerulus.

10. Glomerulus alongwith Bowman’s capsule, is called the malpighian body or renal corpuscle

11. The tubule continues further to form a highly coiled network proximal convoluted tubule (PCT).

12. A hairpin shaped Henle’s loop is the next part of the tubule which has a descending and an ascending limb.

13. The ascending limb continues as another highly coiled tubular region called distal convoluted tubule (DCT).

14. The DCTs open into a straight tube called collecting duct, many of which open into the renal pelvis through medullary pyramids in the calyces.

15. The Malpighian corpuscle, PCT and DCT of the nephron are situated in the cortical region of the kidney whereas the loop of Henle dips into the medulla.

Types of Nephrons:
1. In majority of nephrons, the loop of Henle is too short and extends only very little into the medulla. Such nephrons are called cortical nephrons.

2. In some of the nephrons, the loop of Henle is very long and runs deep into the medulla.These nephrons are called juxta medullary nephrons. A minute vessel of capillary network runs parallel to the Henle’s loop forming a ‘LT shaped vasa recta. Vasa recta is absent or highly reduced in cortical nephrons.

Urine Formation
1. It involves three main processes namely, glomerular filtration, reabsorption and secretion

2. The first step in urine formation is the filtration of blood, which is carried out by the glomerulus and is called glomerular filtration.

3. 1100 – 1200 ml of blood is filtered by the kidneys per minute. The glomerular capillary blood pressure causes filtration of blood through 3 layers,

(a) Endothelium of glomerular blood vessels (b) Epithelium of Bowman’s capsule and (c) Basement membrane between these two layers.

4. The epithelial cells of Bowman’s capsule called podocytes which possess minute spaces called filtration slits.

5. Blood is filtered through these membranes, that almost all the constituents of the plasma except the proteins pass onto the lumen of the Bowman’s capsule. It is the process of ultra filtration.

Glomerular filtration in a healthy individual is approximately 125 ml/minute, i.e., 180 litres per day

6. The kidneys have efficient mechanism for the regulation of glomerular filtration rate. It is carried out by juxta glomerular apparatus (JGA).JGA is found in the distal convoluted tubule .

7. A fall in GFR can activate the JG cells to release renin which can stimulate the glomerular blood flow and thereby the GFR back to normal.

8. Nearly 99 percent of the filtrate is reabsorbed by the renal tubules. This process is called reabsorption.

9. For example, substances like glucose, amino acids, Na⁺, etc., in the filtrate are reabsorbed actively whereas the nitrogenous wastes and water are absorbed by passive transport.

10. During urine formation, the tubular cells secrete substances like H⁺, K⁺ and ammonia into the filtrate.

11. Tubular secretion is helpful in the maintenance of ionic and acid-base balance of body fluids.

Function Of The Tubules
Proximal Convoluted Ttubule (PCT):
1. PCT consists of simple cuboidal brush border epithelium which increases the surface area for reabsorption.

2. All essential nutrients, and 70 – 80 per cent of electrolytes and water are reabsorbed by this segment.

3. PCT also helps to maintain the pH and ionic balance of the body fluids. It occurs through selective secretion of hydrogen ions, ammonia and potassium ions into the filtrate and by absorption of HCO₃^– from it.

Henle’s Loop
Function:
It helps to maintain high osmolarity of medullary interstitial fluid. The descending limb of loop of Henle is permeable to water but impermeable to electrolytes. This concentrates the filtrate as it moves down.

The ascending limb is impermeable to water but allows transport of electrolytes actively or passively. Therefore, as the concentrated filtrate pass upward, it gets diluted due to the passage of electrolytes to the medullary fluid.

Distal Convoluted Tubule (DCT):
The reabsorption of Na⁺, HCO₃^– and water takes place in this segment. In this segment selective secretion of hydrogen and potassium ions and NH₃ to maintain the pH and sodium-potassium balance in blood.

Collecting Duct:
It extends from the cortex of the kidney to the inner parts of the medulla. Large amounts of water is reabsorbed from this region to produce a concentrated urine. This part maintains pH and ionic balance of blood by the selective secretion of H⁺ and K⁺ ions.

Mechanism Of Concentration Of The Filtrate
The flow of filtrate in the two limbs of Henle’s loop is in opposite directions and thus forms a counter current. The flow of blood through the two limbs of vasa recta is also in a counter current pattern.

The proximity between the Henle’s loop and vasa recta, as well as the counter current in them help in maintaining an increasing osmolarity towards the inner medullary interstitium, i.e. from 300 mOsmolL^-1 in the cortex to about 1200 mOsmolL^-1 in the inner medulla. This gradient is mainly caused by NaCl and urea.

NaCl is transported by the ascending limb of Henle’s loop which is exchanged with the descending limb of vasa recta. NaCl is returned to the interstitium by the ascending portion of vasa recta. Similarly, small amounts of urea enterthe thin segment of the ascending limb of Henle’s loop which is transported back to the interstitium by the collecting tubule.

This transport is facilitated by the counter current mechanism This mechanism helps to maintain a concentration gradient in the medullary interstitium. Presence of such interstitial gradient helps in an easy passage of water from the collecting tubule thereby concentrating the filtrate (urine).

Regulation Of Kidney Function
The functioning of the kidneys is influenced by hypothalamus, JGA and to a certain extent, the heart in the body are activated by changes in blood volume.

How can diuresis is prevented in body?
The decrease of fluid from the body can activate these Osmoreceptors which stimulate the hypothalamus to release antidiuretic hormone (ADH) or vasopressin from the neurohypophysis. ADH facilitates water reabsorption Hence it prevents diuresis.

An increase in body fluid volume switch off the osmoreceptors and suppress the ADH release. ADH can also affect the kidney function by its constrictory effects on blood vessels. This causes an increase in blood pressure. An increase in blood pressure increase the glomerular blood flow and the GFR.

A fall in glomerular blood flow/glomerular blood pressure/GFR can activate the JG cells to release renin which converts angiotensinogen in blood to angiotensin I and further to angiotensin II. Angiotensin II, increases the glomerular blood pressure and thereby GFR. Angiotensin II also activates the adrenal cortex to release Aldosterone. Aldosterone causes reabsorption of Na+ and water from the distal parts of the tubule. This also leads to an increase in blood pressure and GFR. This is known as the Renin-Angiotensin mechanism.

An increase in blood flow to the atria of the heart can cause the release of Atrial Natriuretic Factor (ANF). ANF can cause vasodilation (dilation of blood vessels) and thereby decrease the blood pressure. ANF mechanism acts as a check on the renin-angiotensin mechanism.

Micturition
It is the voluntary signal from the central nervous system (CNS). This signal is initiated by the stretching of the urinary bladder in response to the stretch receptors on the walls of the bladder.

The process of release of urine is called micturition and the neural mechanisms causing it is called the micturition reflex. An adult human excretes 1 to 1.5 litres of urine per day.

The urine is slightly acidic (pH – 6.0) and has a characterestic odour. 25 – 30 gm of urea is excreted out per day. Analysis of urine helps to know malfunctioning of the kidney.

For example, presence of glucose (Glycosuria) and ketone bodies (Ketonuria) in urine are indicative of diabetes mellitus.

Role Of Other Organs In Excretion
Lungs remove large amounts of CO₂ (18 litres/day) and water every day. Liver secretes bile-containing substances like bilirubin, biliverdin, cholesterol, degraded steroid hormones, vitamins and drugs.

The sweat and sebaceous glands in the skin eliminates watery fluid containing NaCl, small amounts of urea, lactic acid, etc. Sebaceous glands eliminates sterols, hydrocarbons and waxes through sebum. This secretion provides a protective oily covering for the skin.

Disorders Of The Excretory System
Uemia:
It leads to the accumulation of urea in blood. It lead to kidney failure. In such patients, urea can be removed by a process called hemodialysis.

Procedure of Dialysis:
Blood drained from a artery is pumped into a dialysing unit after adding an anticoagulant like heparin.The unit contains a coiled cellophane tube surrounded by a fluid (dialysing fluid).

The porous cellophane membrance allows the passage of molecules based on concentration gradient.
As nitrogenous wastes are absent in the dialysing fluid, the cleared blood is pumped back to the body through a vein after adding anti-heparin to it.

Remedy for kidney damage:
Kidney transplantation is the ultimate method in the correction of acute renal failures (kidney failure). A functioning kidney is used in transplantation from a donor to minimise its chances of rejection by the immune system of the host.

Renal calculi:
Stone or insoluble mass of crystallised salts (oxalates, etc.) formed within the kidney.

Glomerulonephritis:
Inflammation of glomeruli of kidney

NCERT SUPPLEMENTARY SYLLABUS
Diabetes Insipidus:
Antidiuretic hormone (ADH) is released from the posterior pituitary, prevents dehydration. It helps in the reabsorption of water by the distal parts of the kidney tubules and prevents diuresis. Deficiency of ADH leads to diabetes insipedus, that means huge amounts of dilute urine is formed followed by intense thirst.

The name itself (diabetes = overflow; insipidus = tasteless) distinguishes it from diabetes .mellitus (mel = honey), in which insulin deficiency causes large amounts of blood sugar to be lost in the urine

Artificial kidney:
Hemodialysis machine is known as the artificial kidney. Hemodialysis is an artificial process of removing toxic substances from the blood in patients of kidney failure.