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Coordination in animals

Interneurones (relay or intermediate (a) Axons of some neurones are covered
neurones) by myelin sheath which offers
These are neurones which are found protection and insulation to the cell.
exclusively in the central nervous system (b) The myelin sheath also facilitates rapid
(brain and spinal cord). They are also called transmission of impulses.
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connector neurones. They are much smaller (c) Neurones have Schwann cells that
nerve cells with many interconnections. secrete myelin sheath.
Unlike sensory neurones, these neurones (d) A neurone is provided with many
have short dendrites and short or long axon dendrites which provide large surface
as shown in Figure 2.6. They connect the area for transmission of impulses
sensory neurones and motor neurones
thus, facilitating the transmission of nerve (e) These neurones are distributed in all
impulse between sensory and motor parts of the body of living organism
neurones. The terminal part of a dendron in order to facilitate effective
of the interneurone receives impulses from transmission of impulses from one
the terminal part of the axon of the sensory part of the body to the other.
neurone. Impulses from the axon of the (f) Some neurones have elongated axons
interneurone are passed to the dendrites of so that they can carry information in
the motor neurone. the body over long distances.
(g) Presence of tiny branches, the
Adaptation of a neurone to its function dendrites at the end of each neurone
There are several features which enables facilitates it to receive nerve impulse
neurones to carry out their functions from other neurones.
efficiently.

Dendrites

Nucleus Cell body

Axon

Synaptic ending

Figure 2.6: Structure of interneurone

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