The Peripheral nervous system is composed by the nerves that forms the nervous system. It is divided into two categories: Somatic System and Autonomic System
Somatic System
The somatic system is related to voluntary control, it includes 12 pairs of cranial nerves and 31 pairs of spinal nerves. These nerves send information from and to the CNS to and from the body related to voluntary movements -- for example, when we are done reading a page of a book and we plan to turn to the next page, our somatic system is being used in this situation.
Autonomic System
The autonomic system is responsible for the involuntary control. It helps to maintain homeostatic by adjusting the body to variations in the external and internal environments. There are two divisions for the autonomic system:
- Sympathetic Nervous System: This system is used in stressful situations and is often referred as "fight-or-flight" response. When activated it decreases the energy consume of other system that are not going to be used in a stressful situation, for example the digestion. Blood pressure and heart beat increase.
- Parasympathetic Nervous System: System that is activated when the body is calm and at rest. Restores energy. Referred as rest-and-digest response. Slows heart rate, reduces blood pressure, promotes the digestion of food. It is also responsible for stimulating genital organs.
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