chapter 7 control & coordination class 10 science.

Nervous system in Human Beings

All the parts of the nervous system are structurally connected with one another and functionally integrated, but for sake of our convenience they can be divided into the following three parts:

(i) Central Nervous system

 It consists of two parts:

  1. Brain

  2. Spinal

1. Brain

     Brain is enclosed and well protected in the cranial cavity or brain box of skull. 

The brain is surrounded by three membranes called meneings.

This fluid protects brain from external shocks and mechanical injury.

Structure of brain

    Human brain is a whitish, symmetrical structure that weighs about 1200-1400g and forms about 80% of central nervous system.

  It is divisible into three regions:

(A) Fore Brain

     It is the largest part of human brain that forms 4/5th of the brain. It is divided into three parts:

(a) olfactory lobes :  These are a pair of poorly developed, club-shaped, widely separated bodies which are visible from the ventral surface only.

They are concerned with the sense of smell.

(b) Cerebrum : It is the largest part of brain and consists of two lobes called cerebral hemispheres. They lie side by side and cover all parts of the brain.

The two cerebral hemispheres are seperated from each other by a cerebral fissure. 

Each cerebral hemisphere is divided into four lobes called frontal lobe, parietal lobe, occipital lobe and temporal lobe.

 Functions : 

   • It is the seat of memory, will power, thinking, emotions, experiences, reasoning, learning, etc.

  • controls the movement of striped muscles.

  • controls the sensation.

  • perceives the sensory impulses such as pain, temptation, touch, taste, smell, hearing,sight, etc.

(c) Diencephalon : It is a small rhombodial lobe completely covered by large cerebrum. 

 Functions : 

  • It has many centres called nuclei 

which control water balance, fat metabolism, eating, blood pressure, body temperature, sleep, thirst, etc.

 • acts as relay centre for various senses except smell.

(B) Mid- Brain

     Mid- Brain of human brain is small, about 2 cm long thick stalk. It connects the forebrain with cerebellum and pons of hind- brain. 

The mid brain is differentiated into upper corpora quadrigemina on the upper side and crura cerebri on the lower side.

 Functions :

  • It connects the hind brain with forebrain and convey impulses.

  • It controls the sight.

  • It controls the auditory impulses.

(C) Hind-Brain 

      It is the posterior small part of the brain. It is differentiated into three parts:

(a) pons : It is thick, white structure dorsally covered by the cerebellum and ventrally made up of transverse fibres. 

It Carrie's impulses from medulla to fore brain and one lobe of cerebral to another lobe.

(b) cerebellum  : It is the largest part of the hind-brain present below the cerebrum and above the medulla. It Consists of two large lobes called cerebellar

Functions

   • The Cerebellum helps to maintain the posture, balance or equilibrium during movements.

  • It controls and coordinates the movements of various groups of muscles 

(c) Medulla : It is about 2.5 cm long structure that extends from pons to spinal Cord. It is triangular in shape. It is hollow inside.

Function

  Most of the involuntary activities of body viscera are controlled by different areas of medulla. It controls breathing, swallowing, heart beats, vomiting,sneezing,etc.