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Coordination and Response

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(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.
  Parts of mammalian brain
 1 cerebrum
  •  intelligence
  • memory
  • voluntary actions
  • sensations
 2 hypothalamus
  •  regulation of body temperature and blood osmotic pressure
  • appetite
  • emotions
 3 pituitary gland
  •  secretes a number of hormones
 4 optic lobes
  •  sight and movement of eyeball
 5 cerebellum
  •  muscular coordination
  • body balance
 6 medulla oblongata
  •  involuntary actions, eg:
    • heartbeat
    • respiratory movements
    • peristalsis

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.