Coordination and Response
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(Credits to Mustafa Asif)
Notes
The Nervous System
The nervous system of a mammal consists of:
The central nervous system (CNS) comprising the brain and the spinal cord.
The peripheral nervous system (PNS) comprising the cranial nerves, spinal nerves and sense organs.
Neurone
A neurone is a nerve cell.
A nerve fibre is a long protoplasmic extensions of the cell body of a neurone. It serves to transmit impulses.
A nerve is a collection of nerve fibres.
Types of neurons
Sensory neurones:
a receptor neurone,
transmits impulses from the sense organ (receptor) to the CNS.
Motor neurone:
an effector neurone.
transmits impulses from the CNS to the effectors.
Relay neurone:
connects sensory neurones to motor neurones.
Synapse
A synapse is a junction between two neurones.
A dendron transmits impulses towards the cell body of a neurone.
An axon transmits impulses away from the cell body of a neurone.
Reflex Actions
Reflex actions involve messages being transmitted from the sensory neurone to the motor neurone without involving the conscious part of the brain.
A reflex arc is the shortest pathway by which impulses travel from the receptor to the effector in a reflex action.