Note on Nervous System

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Nervous system


with the development of higher organism in natire complexity .in the body structure aslo increased the complexity in stuructre need a system ,that can regulate and control all other parts of the body in higher animals. there 2 system to coordinate the functioning of the body the nervous system and endocrine system the nervous system consistis of, large number of specailly cells called neurons . it condcuts the impulses in diffrent part of the body in form of electrcical signals .these signals are called "nerve impulese". their actions are rapid and localized the endocirine system consists of glandular cells, that secrets chemical substance called hormones.

fig nervous system



Function of nervous system

1 reception of stimulus from the enviroment and covey towards sensory nerves or affector nerves.

2 sensory nerves carry stimulus towards brains or spinal cords which acting as modulator or cenverter.

3 brains or spinal cords converts stimulates into message.

4 transmission of message by motor nerve or effector nerve towards the effective region.

5 help to control various activites of the body.

6 only this system help to react immediately to out side stimulates by animals which is absent in plants.

this chapter deals with the react immediatly with the nervous system. the main parts of the nervous system are brain the spinal cords and peropheral nerves .The units of the nervous system are called "neurons" which are interconnected with each other throughout the body . conventionally nervous system are three types:-

1 Central nervous system

2 peripheral nervous system

3 autonomic nervous system

here are two they of nervous system ANS and CNS.

Autonomic nervous system

these are responsible for you involuntary control.such as reflex to sudden exposure to heat or temperature. there is no any function of brain never reaches to spinal cords only .

Central nervous system

these are voluntary movement in which brain function takes place.

Brain and its Amatomy/ structure along with its function -

- is the situated in the cranial cavity of the skull .The cranial bones protect it from meachnical injury . brain is the cranial portion of the central nervous system, the weight of the brain and spinal cord is about 1300 to 1400gm of which 2% is the cord the cerebrum represents about 2%is the cord. the cerebrum represent about 85% of the weight of the brain .

the brain soft whitish somewhat fattened organ. it is composed of neurons and neuolgi a or supporting cell .Grey matter is composed principally of nerve bodies and is concentrated in the cerebral cortex and the nuclei and basal ganglia.White matter is composed nerve cell processes which from tract connecting various parts of the brain with other.

morphologically brain is divisible into three main region I,E, forebrain , midbrain and hingbrain brain has frntal , parietal occipital temporal and insula lobes.

Fore brain

– consists of cerebrum and diencephalon .
Cerebral hemisphere from the largest pasrt of brain consisting two hemisphere .Separated by depp longitudinal fissure
the hemishphere are united by three commissars. the corpus callsum and tha anterior and posterior hippocampal commisure , the surface of each hemisphere is thrown into numerous folds or convolution called "gyri or Sulci" cerebru develop from the telencephalon .The most anterior portion of the prosencephalone or forebrain , Each cerebral hemisphere conists of 3 primary portion :-
1 rhinencephalone
2 Corpus stratium
4 cerebral cortex

with in the cerebrum are 2 cavities the lateral ventrical and the rostral portion of the 3rd ventrical .
ventrical – the cavities of the brain are the 1st and 2nd lateral ventrical ,which lies in the cerebral hemisphere , the third ventrical of the diencephalone and the 4th ventricle of meduula . First and second communicate with the third by interventricular foramen the 3rds with 4ith by cerebral cannal .The 4th with the subarchnoid space by 2 foramina of luschke and the formena of megendie.

Diencephalon- It encloses a slit like cavity the 3rd ventricle. The thin roof of this cavity is kniw as "epithelamus". The thick right and left side as the thalmi floor as the hypothalamus .Thalami act as relay station for sensory impulses .
Midbrain is significantly small it consists the 2 heavy fibre tract called "cerebral pedencles "on the ventral side and two sweeliing tremed superior and inferior colliculi of each side are refered to ,as corpora bigemina and of both side as corpora Quardigemina . The superior colliculi control reflex of iris and eyelied. The inferior colliculi receives sensory information from the ear and relay it to cerebrum.

hibdbrain – the hindbrain consists of cerebellum , pons varolli and medluua oblongata.

Cerebeluum -
it lies below the posterior portion of the cerebral hemisphere and bove the medulla. It consists of pair of large pasrt the cerebellar hemishphere and a small median portion the vermis .the cerebellum is involved in synergic control of skleletal system and plays an important role in the coordination as weel .the cerebellum controls the property of movement such as speed acceleration and trajectory.

pons varolii

- it is rounded eminence on the ventral surface of brain . it lies between the medulla and cerebral penduncles and appears externally as a board band of transverse fibres. It is connected to the cerebellum by the mid cerebellar pendencles or brachium points. the origin of abducens facial trigeminal and cochlear division of the 8 th neavr are at the boarder of the pons and gray matter.In the pons controls some aspects of repiration white matter tract in the pons form a two way conduction system ,that connects higher brain centre with the spinal cords .

tranismition nerve impulse takes place by following ways
fig A.N.S

Action potential is generated and the neuro transmiteer asires the 'pre synatic ganglions' towards the 'post synaptic ganglions'. And those neuro transmitter are released by the process of 'synapses’ as shown in the figure.


Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069

Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.

Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.

  1. reception of stimulus from the enviroment and covey towards sensory nerves or affector nerves

  2.  sensory nerves carry stimulus towards brains or spinal cords which acting as modulator or cenverter

  3.  brains or spinal cords converts stimulates into message

  4. Action potential is generated and the neuro transmiteer asires the pre synatic ganglions towards the post synaptic ganglions. 

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