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| The Peripheral Nervous System |
The Peripheral Nervous System
The peripheral nervous system is a network of sensory neurons that branch out from the spinal cord to reach every nook and cranny of your body. One set of sensory neurons transmits signals towards the central nervous system and then on to your brain, and another set of motor neurons transmits signals in the opposite direction to activate both the voluntary and involuntary action of muscles.
The peripheral system has a right-left symmetry with forty-three pairs of major nerve fibres. Ten of these pairs emerge from the underside of your skull to serve your head, and the other thirty-three pairs emerge at different points along your spine to serve the rest of your body.
The peripheral nervous system can be further divided into the somatic nervous system and the autonomic nervous system.
The somatic nerves serve activities that are under your conscious control. They collect information from sensory organs and transmit signals to muscles to initiate voluntary movement.
The autonomic nervous system controls short-term actions and systems that function without conscious control. Some autonomic neurons (sympathetic) are dedicated to stimulating organs and muscle action, and other autonomic neurons (parasympathetic) are dedicated to inhibiting the action of muscles and organs. The autonomic system can transmit signals to alter the size of your pupils in response to light, change your rate of breathing, alter your heart rate, stimulate muscular contractions in your stomach and intestines, and cause the hairs on your skin to stand on end.
The autonomic system can also transmit signals to generate a co-ordinated set of activities such as a response to perceived danger. The danger response includes an increase in respiration and heart rate, the dilatation of air passages, the diversion of blood from the skin and internal organs to muscles, and the release of extra sugar from the liver into the bloodstream.
The peripheral nervous system is a network of sensory neurons that branch out from the spinal cord to reach every nook and cranny of your body. One set of sensory neurons transmits signals towards the central nervous system and then on to your brain, and another set of motor neurons transmits signals in the opposite direction to activate both the voluntary and involuntary action of muscles.
The peripheral system has a right-left symmetry with forty-three pairs of major nerve fibres. Ten of these pairs emerge from the underside of your skull to serve your head, and the other thirty-three pairs emerge at different points along your spine to serve the rest of your body.
The peripheral nervous system can be further divided into the somatic nervous system and the autonomic nervous system.
The somatic nerves serve activities that are under your conscious control. They collect information from sensory organs and transmit signals to muscles to initiate voluntary movement.
The autonomic nervous system controls short-term actions and systems that function without conscious control. Some autonomic neurons (sympathetic) are dedicated to stimulating organs and muscle action, and other autonomic neurons (parasympathetic) are dedicated to inhibiting the action of muscles and organs. The autonomic system can transmit signals to alter the size of your pupils in response to light, change your rate of breathing, alter your heart rate, stimulate muscular contractions in your stomach and intestines, and cause the hairs on your skin to stand on end.
The autonomic system can also transmit signals to generate a co-ordinated set of activities such as a response to perceived danger. The danger response includes an increase in respiration and heart rate, the dilatation of air passages, the diversion of blood from the skin and internal organs to muscles, and the release of extra sugar from the liver into the bloodstream.
