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Parasympathetic Nervous System

The part of the nervous system that slows the heart, dilates blood vessels, decreases pupil size, increases digestive juices, and relaxes muscles in the gastrointestinal tract.

PubMed Health Glossary
(Source: NIH - National Cancer Institute)

About the Parasympathetic Nervous System

The sympathetic and parasympathetic nervous systems usually do opposite things in the body. The sympathetic nervous system prepares your body for physical and mental activity. It makes your heart beat faster and stronger, opens your airways so you can breathe more easily, and inhibits digestion.

The parasympathetic nervous system is responsible for bodily functions when we are at rest: it stimulates digestion, activates various metabolic processes and helps us to relax. But the sympathetic and parasympathetic nervous systems do not always work in opposite directions; they sometimes complement each other too. Institute for Quality and Efficiency in Heath Care

Terms to know

Autonomic Nervous System (Involuntary Nervous System)
The part of the nervous system that controls muscles of internal organs (such as the heart) and glands. One part of the autonomic nervous system helps the body rest, relax, and digest food and another part helps a person fight or take flight in an emergency.
Axons
Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.
Cell Body
The bulbous end of a neuron, containing the cell nucleus.
Dendrites
A long, branching outgrowth or extension from a neuron, that carries electrical signals from synapses to the cell body.
Myelin Sheath
A fatty covering that forms a protective sheath around nerve fibers and dramatically speeds the transmission of nerve signals.
Neurons (Nerve Cells)
A type of cell that receives and sends messages from the body to the brain and back to the body. The messages are sent by a weak electrical current. Also called nerve cell.
Neurotransmitters
A chemical that is made by nerve cells and used to communicate with other cells, including other nerve cells and muscle cells.
Oligodendrocyte
A cell that forms the myelin sheath (a layer that covers and protects nerve cells) in the brain and spinal cord.
Postsynaptic Membrane
Cell membranes associated with synapses.
Receptors
A molecule inside or on the surface of a cell that binds to a specific substance and causes a specific effect in the cell.
Sympathetic Nervous System
The part of the nervous system that increases heart rate, blood pressure, breathing rate, and pupil size. It also causes blood vessels to narrow and decreases digestive juices.
Synapses
The space between the end of a nerve cell and another cell. Nerve impulses are usually carried to the neighboring cell by chemicals called neurotransmitters, which are released by the nerve cell and are taken up by another cell on the other side of the synapse.
Synaptic Terminals (Axon Terminals)
An area at the end of an axon that contains neurotransmitters.

Terms to know

Autonomic Nervous System (Involuntary Nervous System)
The part of the nervous system that controls muscles of internal organs (such as the heart) and glands. One p...
Axons
Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body....
Cell Body
The bulbous end of a neuron, containing the cell nucleus....
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