Coordination and Response


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Coordination and Response

(Credits to Mustafa Asif)


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.


    • 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

    1. Sensory neurones:

      • a receptor neurone,

      • transmits impulses from the sense organ (receptor) to the CNS.

    2. Motor neurone:

      • an effector neurone.

      • transmits impulses from the CNS to the effectors.

    3. Relay neurone:

      • connects sensory neurones to motor neurones.


    • 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.