Structure of neuron
Neuron : It is the structural and functional unit of nervous system.
Parts of Neuron :
(a) Dendrite : Acquires information.
(b) Cell body : Acquired information travels as an electrical impulse.
(c) Axon: Longest fibre on the cell body is called axon. It transmits electrical
impulse from cell body to dendrite of next neuron.
Synapse : It is the gap between the nerve ending of one neuron and dendrite of
the other neuron. Here electrical signal is converted into chemical signal for
Reflex action is quick, sudden and immediate response of the body to a stimulus.
E.g., Knee jerk, withdrawal of hand on touching hot object.
Control And Coordination
Reflex arc : The pathway through which nerve impulses pass during reflex
action is called reflex arc.
Response : Responses are of three main types :
(a) Voluntary : Controlled by fore brain. £.g., talking, writing.
(b) Involuntary : Controlled by mid and hindbrain. E.g., heart beat, vomiting,
(c) Reflex action : Controlled by spinal cord. E.g., withdrawal of hand on
touching a hot object.
Need of Reflex Actions : In some situations such as touching a hot object,
pinching etc. we need to act quickly, otherwise our body would be harmed.
Here response is generated from spinal cord instead of brain.