The nervous system
The nervous system is a two-way communication system. It responds to internal and external stimuli via electrical messages that flow between the central nervous system and body to produce a variety of responses.
The nervous system is composed of three parts:
- The central nervous system
- The peripheral nervous system
- The autonomic nervous system
The central nervous system
This is made up of:
- The brain – a communication centre that interprets incoming sensory impulses and triggers a motor response (e.g a muscle movement)
- The spinal cord – relays electrical impulses to and from the brain and is the centre of reflex actions
The peripheral nervous system
This links the central nervous system to the rest of the body via:
- Twelve pairs of cranial nerves. These supply the head and face and include olfactory, optic, oculomotor, trochlear, trigeminal, facial, auditory, glossopharyngeal, vagus, accessory and hypoglossal nerves
- Thirty-one pairs of spinal nerves. These receive electrical sensory impulses from the body and send motor signals to different parts of the body. Include cervical, thoracic, lumbar, sacral and coccygeal nerves
- Motor nerves (efferent nerves), which send messages from the brain to the spinal cord and skeletal muscles, glands and involuntary muscular tissue
- Sensory nerves (afferent nerves), which send messages from the sensory nerve endings in glands to the brain and spinal cord
- Mixed nerves, which contain both sensory and motor nerves
The autonomic nervous system
This controls the parts of the body not under our conscious control – involuntary and cardiac muscle, etc. It is composed of two parts – the sympathetic system and the parasympathetic system.
The sympathetic system is composed of a network of nerve plexuses located on either side of the anterior surface of the spinal column. There it prepares the body for activity, increasing its energy output by accelerating its involuntary activities, eg increasing the heartbeat and blood supply.
The parasympathetic system deals mainly with the vagus nerve and cranial nerves. It slows down the body’s activities creating a balancing effect on the sympathetic nervous system inducing relaxation and rest within the body.
Nervous system presentation.