Central Nervous System

It is divided into 2 parts : (1.1) Brain and (1.2) spinal cord.

(1.1)         Brain:-Also called Encephalon.

The study of brain in all aspects is called Encephalology. It is situated in cranial cavity of skull. It has about 100 billion neurons.  Brain is soft, whitish organ. Brain has 3 divisions.

(1)   Forebrain (mesencephalon)

(2)   Midbrain (mesencephalon)

(3)   Hindbrain (rhombencephalon)

(1)   Forebrain:-large part of brain and had 3 regions

(A)  Olfactory lobes :- these are a pair of small, solid & cup shaped bodes and are fully covered by cerebral hemisphere. Visible only in ventral view.

(B)  Cerebral hemisphere (cerebrum ) :- They are two, lie side by side. A thin line that separates these 2 hemisphere from middle is called cerebral fissure . the surface of hemisphere is made up of grey matter which has many layers of nerve cells. & this surface is called gyri and depressions between these folds are called sulci. Deep sulci called fissure, divide each hemisphere into 4 lobes.

Frontal lobe, parietal lobe, occipital and temporal lobe.                   

Frontal lobe

(1)Thought & action (2) creative ideas (3) learning (4)memory (5) reasoning (6)decision making (7) muscular movements (8) speech (9) smell.  

Parietal lobe

(1) pain (2) touch (3) temperature sensation  (4)speech(5) smell

Temporal lobe

(1) hearing  (2) speech (3) smell  (4)emotions

Occipital love

(1)center of sight  (2) gearing.


(C)  Diencephalon:-it has a cavity whose floor is called hypothalamus and its roof is called hypothalamus and the cavity itself is called third ventricle.

(1)   Hypothalamus:-A region of forebrain located below the floor of the diencephalon, it regulates body temp., some metabolic process and contacts the ANS autonomic nervous system. It has a grayish outgrowth called infundibulum sounded body pituitary is attached to infundibulum.

(2)   Epitheliums:-the posterior segment of the diencephalon. It connects limbic system to other parts of brain , also secrete melatonin by pineal gland and regulation of emotions.

Cerebellum (little brain)

Medulla oblongata

Pons  varolii

It is very large & well developed part. it is solid. It lies below cerebral  hemispheres  and above medulla.  

It is lowermost part of brain. It encloses a cavity called forth ventricle. It is thin. 

It is oval shaped body that lies above medulla oblongata as Pons means bridge that why it interconnects the 2 hemispheres and also join medulla with higher brain centre. 

(3)   Third Ventricle :- Also called Rhombencephalon, it has 3 parts cerebellum, Pons varolii and medulla oblongata .             


Brain stem:-medulla, Pons, midbrain & diencephalon together forms brain stem.

Cerebrospinal fluid:- All ventricles have a lymph like fluid (colorless) called cerebrospinal fluid (c.s.p). it is alkaline.

(1)   It protects the brain & spinal cord from shots by acting as shock-proof cushion.

(2)   It keeps them waist, & forms a medium for exchange of food materials, waste products, respiratory gases & other substance between neurons.

Protective coat of brain

It is called Meringues is composed of 3 coats.  


Pia mater

Arachnoid mater

Aura mater

(1)It is inner coat of meninges .

(2)Thin & highly muscular

(1)It is middle coat of meninges .

(2)Thin & non-muscular

(1)It is outer coat of meninges .

(2)Thick, tough and lines the cranial cavity.


Gray matter and white matter :- Brain is composed of 2 types of nervous tissue.

Gray matter

White matter

It contains nerve cell with their dendrites and axons.

It contain modulated nerve fibres.


Functions of Brain :-

(1)   It has olfactory lobes that receives information about smell.

(2)   Its medulla oblongata has cardiac centre that controls rate of heart beat, respiratory centre controls breathing movement, reflex centre control swallowing, sharing, vomiting, urinating etc.

(3)   Cerebrum is seat of memory, thanking ,emotions, learning etc.

(4)   Cerebellum maintains muscle control & also control the voluntary movements.

(5)   Pons varolii transfer the impulse from one side of cerebellum.

(6)   Diencephalon part of brain controls sensation of heat, cold & pain itc.

(7)   Hypothalamus maintains body temperature, blood pressure, water balance, hunger, thirst, feeling of pain, anger, fear, etc.

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