Nervous System Nervous System

      The nervous system is our processing system which keeps us in contact with the outer world. Or,The nervous system is the part of human body that coordinates the voluntary action to transmit signals between the different parts of bodyOur Nervous system is made up of different nerve cells. The number of these nerve cell in a human nervous system has been estimated at 100 to 200 billion. They are basically alike in structure but appear in different lengths, sizes and shapes designed for specialized functions.

The Nervous System is divided into 2 parts-
1.The Central Nervous System (CNS)2.Peripheral Nervous System (PNS).1.The Central Nervous System (CNS)-

The CNS is a central part of Nervous system, which consists Brain and Spinal cord. Lies in well protected in bony case of Skull and spine,CNS comprises 2% of body weight (3–4 pounds).Receives 15% of blood supply

Human Brain is the Master Tissue of the Body. It is located within the skull. Brain is the largest and important aspects  and center of  Nervous system.

Human Brain weights almost 3 pounds(1.36 Kg) ,which is quite big and weighty compared to other animals except Elephant and Whale.

•Brain uses 20% of oxygen consumed by body at res

•Brain uses 50% of glucose consumed by body at rest

Or, we can call Brain as the  control room of the huge complicated telephone system of the body .It is composed of three main divisions:

                 1.The forebrain2.Mid Brain and
Hind Brain

1.The Forebrain – It is at the Very top of the Brain. Its important structures are :

vThe Thalamus

vHypothalamus

vThe Cerebrum 

a.The Thalamus- It consists two egg shape structures situated in central core of fore brain just over the brainstem. Little role in reflex action.

ØAll Sensory impulses except Smell pass through it to the higher centers. Therefore it is known as relay station. (It receives input from all incoming fibers as seeing,hearing,pressure,pain,temperature,body position, and test ,except Olfaction(Smell)

ØIt is also known as sensory switch Board because it transforms and modify the inputs before sending to other parts.

ØPlays role in Alertness and reaction. 

The Hind Brain is situated behind and under the fore brain. It connects the upper part of spinal cord with the lowest part of the brain.

It is composed of three structures.

ØMedulla

ØPons

ØCerebellum 

1.Medulla –Medulla is the bulb like structure of hind brain which is near spinal cord. It controls many important Reflex and complex process like:

Respiration, Digestion and Circulation which are necessary for the preservation of life.

Ø It controls blood pressure, heart rate, digestion, vomiting & Breathing

ØIt relays incoming information to other brain centers and outgoing message to spinal cord.

.The Pons – It connects the cerebellum at the top of the brain.

It assists the breathing, transmitting impulses from the cerebellum to the higher brain regions and coordinatinating the activities of both sides of the brain.

ØIt plays important role in arousal and sleep.

ØIt consists of respiratory centers that play role in regulating respiration .

ØIt controls salivation. 

3.The cerebellum – It is composed of two circular hemispheres . It helps in performing many bodily functions.

It is responsible for body balance and the coordination of body movements.

ØIt is responsible for body movements.

Øit co-ordinates muscles so that movement is smooth.

ØIt plays vital role in normal speech.

ØIt plays important role in learning motor skills.

ØMovements in playing basketball, football, dancing, typing and playing the piano etc are controlled by cerebellum.