2.2.2 Types of Neurone


Types of Neurone
There are three types of neurone:
(a)  Sensory neurone
(b)  Relay neurone (intermediate neurone)
(c) Motor neurone






Characteristics
Sensory neurone
Relay neurone
Motor neurone
Position in the body
Present in all parts of the body
Present in the brain and the spinal cord only
Present in all parts of the body
Position of cell body
In the middle of neurone
At the centre of neurone
At the end of neurone
Length of axon
Short
Very short
Long
Function
Transmits impulses from a receptor to the central nervous system
Transmits impulses from a sensory neurone to a motor neurone
Transmits impulses from the central nervous system to the effector



2.2.1 Neurone

Neurone

  Structure of a neurone

  1. The basic unit of the nervous system is neurone.
  2. The function of neurone is to carry impulses.
  3. Each part of s neurone plays an important role in the transmission of nervous impulses.

Neurone Part
Function
Cell body
Controls all activities of the neurone
Dendron
Transmits impulses towards a cell body
Dendrite
Receives impulse from other neurone and transmits them to cell body
Axon
Transmits impulses out of cell body
Myelin sheath

Speed up the transmission of impulses.
Insulator that prevents the leakage of impulses.
 

 
 
 
 

2.2 Human Nervous System


Human Nervous System
 
1. The human nervous system is divided into
(a) Central nervous system (or CNS) – consists of the brain and spinal cord.
(b) Peripheral nervous system (or PNS) – consists of the spinal nerves and cranial nerves.
 
 
Chart showing the classification of human nervous system
 
 



Human nervous system
 

Central Nervous System
  1. The central nervous system is the control centre of the body.
  2. This system consists of the brain and the spinal cord.
  3. The brain controls all voluntary actions of the body like walking and talking.
  4. The spinal cord controls the reflex actions such as sneezing.

Peripheral nervous system
  1. The peripheral nervous system consists of all the nerves which connect the central nervous system to the receptor and effector located at other parts of the body.
  2. The function of the peripheral nervous system is to transmit impulses from the sensory organ through central nervous system to the effector to respond accordingly.