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Coordination in animals

the brain, such as kicking a football. The unconscious activities in the body, such as
involuntary nervous system is composed of the heartbeat, peristalsis and sweating. The
sensory and motor neurones that link the peripheral nervous system is summarized
central nervous system and smooth muscles in Figure 2.10.
of the internal organs. It is concerned with
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Peripheral nervous system

Involuntary nervous system Voluntary nervous system
(autonomic) (somatic)

Sympathetic nervous system Parasympathetic nervous system

Spinal nerves Spinal nerves Cranial nerves Spinal nerves Cranial nerves

Figure 2.10: Peripheral nervous system

The peripheral nervous system also The autonomic nervous system controls
comprises of cranial and spinal nerves. the involuntary actions of smooth muscles
The cranial nerves arise from the brain and certain glands. It is divided further into
and they form receptors and effectors in the sympathetic nervous system which has
the head. Generally, the function of these mainly excitatory effect on the body, and
nerves is to transmit impulses from the the parasympathetic nervous system which
sensory organ to the brain for interpretation. has mainly calming influence. The two
The spinal nerves arise from the spinal cord systems oppose each other in action. For
through the inter-vertebral foramen of the example, if the sympathetic system causes
vertebrae. The spinal nerves occur in pairs the muscles to contract, the parasympathetic
and each with two roots namely dorsal and system causes the muscles to relax. Also,
ventral root. These two roots join together if the sympathetic system constricts the
before they pass through the inter-vertebral arteries, the parasympathetic system dilates
foramen. The dorsal root is made up of the arteries. Other examples are shown in
sensory nerve fibres whereas ventral root Figure 2.11.
is made up of motor nerve fibres.

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