Sanyam Jain, Academic Content Creator at Edumarz
In animal bodies, control and coordination are the responsibility of the nervous system which comprises nerves, spinal cord and brain.
The nervous system of all animals is composed of neurons whose functions are to send and receive signals.
General scheme of nerve impulse transmission in the body-
Stimulus from the environment is received by the neurons at the dendrites
A chemical reaction generates an electrical impulse that travels down the axon to its end.
The impulse causes the release of chemical messengers from nerve endings which cross the gap between the two neurons (synapse).
These messengers start a similar chemical reaction in the next neuron producing another electrical impulse.
The impulse at the last neuron generates the response by releasing chemicals that act on the target organ (muscle/gland).
The brain is the main centre of coordination in the human body. Together with the spinal cord, it comprises the central nervous system (CNS).
Parts of the brain-
The forebrain is the main thinking part of the brain which is majorly constituted by the cerebrum. It is the site where sensory information from various organs is put together, interpreted and a final decision is made which is passed onto the target motor organ.
The midbrain is mainly involved in vision and hearing.
The hindbrain comprises the cerebellum, pons and medulla which controls involuntary actions. The medulla is responsible for controlling BP, vomiting and salivation. The cerebellum is also responsible for the precision of voluntary actions and maintaining body posture and balance.
The brain is protected inside a bony box called cranium with three membranes known as meninges filled with cerebrospinal fluid.
The medulla of the hindbrain continues to form the spinal cord which is protected inside the vertebral column along the back.
The CNS communicates with the rest of the body with cranial and spinal nerves forming the peripheral nervous system.
Reflex action is an involuntary, instantaneous response to a stimulus mediated by the central nervous system. Reflex arc refers to the path followed by electrical impulse during the reflex action.
Reflex actions evolve due to avoid the time required in interpreting the stimuli. It simply involves detecting and responding to the stimulus, thereby preventing any possible harm due to late response.
In the reflex action-
Information is brought to the CNS by sensory neurons from the receptor
Decision is carried to the effector organ by motor neurons from the CNS
In spinal reflexes, even the information is not brought to the brain but a message reaches there.
