Nervous System-Brain and Spinal cord -All Information-Human Organ System

 Human Organ System:

 Human organ system cooperate and work together to maintain life. eg: Excretory  system, Respiratory system, Digestive system, Circulatory system and Nervous system. Nervous system controls and coordinates all other system of the body. Excretory system regulates the chemical composition of body fluids by removing wastes.                                                                                       

  

Introduction to Nervous System:                                           

    What is a nervous system? Do we sleep every day?  Yes, we do, unless we have an important event or   examination coming up ,we take a sound sleep. But how do we fall asleep? Does our brain shut     down once we are asleep?                                                                                                                          

  How are we able to react as soon as we dip our fingers into a hot cup of tea? how are we able to change  paths while walking, when we hear a car honk?  your answer to all these question is that we have a system  which is responsible for all these sudden response. These series of  actions are controlled and coordinated  by a system in our body called the Nervous system .                                                                                                                                                                                                      Living organisms adapt to their positions and move as an attempt in response to the changes in the environment for their advantage or protection. Any change in the environment, that causes an organism to react is called Stimulus, and the reaction or action of the organisms in reply to the stimulus is known as a  response.Some familiar stimuli are light, sound, heat, taste, smell, water, gravity and air.                                                                                                                                                                                                                                                                                                                   Receptor   cells are present in the sense organs that are sensitive to specific stimuli. receptor includes ears, eyes, nose,tongue, skin etc. whereas effectors   respond to a stimulus according to the instructions given from the nervous system.                                                                             

           The muscles and glands are effectors. We  are going to learn more about them in this blog.                                                                                                                                                                                    The brain and the spinal cord make up what is called the central nervous system or CNS. The rest of the nerves together are  called the peripheral nervous system or PNS.    

                                                                                            

  Central Nervous System:                                                                 

                                                                                                                The central nervous system consists of the brain the spinal cord.The brain is protected inside the skull and the spinal cord is protected inside vertebrae or the backbone.Both the brain and the spinal cord are wrapped in three layers of connective tissue known as Meninges. A human brain can be divided into three parts: forebrain, midbrain and hindbrain.                                                                                                                                                                                                                                                                   

The fore Brain:  

Cerebrum of  the brain is made up of two cerebral hemispheres. The Hemispheresare the largest part in the brain. They are concerned With intelligence,learning,memory,emotions and overall controll of all the voluntary actions. The surface of the human brain is further enlarged by the presence of many grooves in the cerebral hemisphere.

The Mid Brain:

The mid brain lies between fore brain and hind brain and connects the two. It acts as a railway station between fore brain and hind brain. It is connected with the movements of eyeballs.

The Hind Brain:

The hind brain includes cerebellum,pons and medulla oblongota. Cerebellum is situated under the cerebrum.  It controls balance and muscle contraction. Pons is a small lobe like structure. It functions with the medulla to regulate breathing rate.Medulla oblongata lies below the cerebrum. Its posterior end narrows down gradually into the spinal cord.It controls heartbeat,circulation of blood and respiration etc.                                                                                                                                                                                                                                                                                                                              

Spinal Cord:                                                              

The spinal cord is an oval shaped hollow cylinder. It extends from the brain to  the end of the vertebral column which protects it. Like the brain,the spinal cord consists of the both grey and white matter. The gray matter is surrounded by white matter on the outside. The outer region is light in the color. The inner region is butterfly shaped and darker in color.                                                 There is a narrow central canal which contains cerebrospinal fluid.  

                                                                                                                 

 

Functions of Spinal Cord:                                                                                                     

(a) It is the link between brain and different parts.                                                                                        (b) The spinal cord carries out reflex action.

(c) It serves to transmit impulses from receptor to the brain.

(d) It serves to transmit impulses from brain to effectors. 

(e) The spinal cord performs  some involuntary actions e.g.,contraction of urinary bladder.

Peripheral Nervous system:                                    

The peripheral nervous system includes nerves arising from the brain and spinal cord.

Cranial Nerves There are twelve pairs of cranial nerves arising from the brain. The cranial  nerves are sensory nerve, motor nerve or a mixed  nerve. Each  cranial nerve has a specific function. 

Spinal Nerves. These emerge at intervals along the length of spinal cord. There are thirty-one pairs of spinal nerves in a man.These nerves pass between the vertebrae.  They all carry both sensory and motor nerves and are described as mixed nerves. They carry impulses to all part of the body and also bring impulses from all parts of the body to the spinal cord.

Division of peripheral Nervous system:                                                                                

There are the two divisions of peripheral nervous system:Autonomic Nervous System and  Somatic Nervous system.                                                                                                                                                      (a)The somatic Nervous sytem is the part of peripheral nervous sysem associated with the voluntary control of the body movements via skeletal muscles.

(b) The autonomic nervous system is a component of peripheral nervous system that  that regulates involuntary physiological processes including heart rate, blood pressure, respiration, digestion, and other drives.