In animals control and co ordination is done by the nervous system
and endocrine system.
The nervous system consists of the brain, spinal cord and nerves.
a) Receptors :- are the sense organs which receive the stimuli and
pass the message to the brain or spinal cord through the sensory
Eg :-Photoreceptorsin the eyes to detect light.
Phonoreceptorsin the ears to detect sound.
Olfactory receptors in the nose to detect smell.
Gustatory receptorsin the tongue to detect taste.
Tangoreceptorsin the skin to detect touch.
b) Effectors :- are the muscles and glands which respond to the
information from the brain and spinal cord through the motor nerves.
c) Sensory nerves :- are nerves which carry information from the
receptors (sense organs) to the brain and spinal cord.
d) Motor nerves :- are nerves which carry information from the brain
and spinal cord to the effectors (muscles and glands).
3) Human nervous system :-
a) Parts of the nervous system :-
The human nervous system consists of the Central Nervous System
and Peripheral Nervous System.
i) The central nervous system :- consists of the brain, and spinal
ii) The peripheral nervous system:- consists of cranial nerves
arising from the brain and spinal nerves arising from the spinal cord.
Spinal cord :-
Reflex action :-
Reflex actionis a sudden, unconcious and involuntary response of the effectors to a stimulus.
Eg :- We suddenly withdraw our hand if we suddenly touch a hot object.
In this reflex action, the nerves in the skin (receptor) detects the heat and passes the message through the sensory nerves to the spinal cord. Then the information passes through the motor nerves to the muscles (effector) of the hand and we withdraw our hand.
Reflex arc :-
The pathway of a reflex action is called reflex arc. In a reflex arc the stimulus is received by the receptors (sense organs) and it passes through the sensory nerves to the spinal cord. From the spinal cord the information passes through the motor nerves to the effectors (muscles/glands) for the response.