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24 September 2014
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Nervous system - Peripheral Nervous System

Function: To relay information to and from your central nervous system

Actions: Your peripheral nerves transmit voluntary and involuntary actions

Sympathetic nervous system: Fight or flight

Parasympathetic nervous system: Rest and digest

Network outside your central nervous system

All the nerves and nerve cells outside your central nervous system make up your peripheral nervous system. Its task is to relay information from your brain and spinal cord to the rest of your body and from your body to your brain and spinal cord.

Your peripheral nervous system consists of 12 pairs of cranial nerves, which emerge from your brain and mainly serve your head and neck. It also contains 31 pairs of spinal nerves, which branch off from your spinal cord and supply the rest of your body.

Voluntary and involuntary actions

With the help of your peripheral nerves, you are able to carry out voluntary and involuntary actions.

If you pick up a mug, clap your hands or lift weights in the gym, you are performing voluntary actions. You are conscious of what you're doing. Your brain receives nerve impulses and analyses them before you decide what to do next.

In contrast, your heart beats and your intestines digest without your conscious control. Involuntary actions such as these are regulated by your autonomic nervous system. The autonomic part of your peripheral nervous system ensures that all your internal organs and glands function smoothly.

Your autonomic nervous system has two parts: the sympathetic and the parasympathetic. Both supply essentially the same organs but cause opposite effects. This is because their activating chemicals, or neurotransmitters, are different.

Fight or flight

Often referred to as your 'fight-or-flight' system, your sympathetic nervous system prepares your body for emergencies. It shunts your blood to your muscles and increases your blood pressure, heart rate and breathing rate, enabling you to cope with stressful situations.

Rest and digest

Your parasympathetic nervous system maintains and restores your energy. It directs blood to your digestive tract and makes sure you actively digest food. It also maintains your blood pressure, heart rate and breathing rate at a low level. That's why it is sometimes called your 'rest and digest' system.

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