Definition

1. Noun:
   • A division of the autonomic nervous system: The parasympathetic nervous system is one of the two main divisions of the autonomic nervous system, which controls involuntary bodily functions.
   • Promotes "rest and digest" activities: It generally conserves energy and supports bodily maintenance functions such as digestion, salivation, and slowing the heart rate.
   • Anatomically distinct: Its nerve fibers originate in the brain stem and the sacral region (lower part) of the spinal cord.

Usage

The term is used in medical, biological, and physiological contexts to describe the part of the nervous system responsible for calming the body and promoting routine maintenance. It is often discussed in contrast to the sympathetic nervous system, which prepares the body for "fight or flight" responses. - It is typically used as a singular noun phrase. - It can be abbreviated as PNS, though this can be confused with the peripheral nervous system.

Examples

• Noun:
  • The parasympathetic nervous system is activated after a meal to stimulate digestion.
  • Deep breathing exercises help to engage the parasympathetic nervous system, promoting relaxation.
  • A key function of the parasympathetic nervous system is to slow the heart rate.

Advanced Usage

• "Parasympathetic tone": Refers to the continuous, baseline level of activity of the parasympathetic nervous system, which helps maintain homeostasis.
  • High parasympathetic tone is often associated with good cardiovascular health.
• "Parasympathetic outflow": Describes the signals or nerve impulses originating from the parasympathetic centers and traveling to target organs.
  • The vagus nerve is a major pathway for parasympathetic outflow to the heart and digestive organs.

Variants and Related Words

• Parasympathetic (adj): Pertaining to the parasympathetic nervous system.
  • Parasympathetic activity increases during periods of rest.
• Parasympathomimetic (adj/n): A substance or drug that mimics or enhances the effects of the parasympathetic nervous system.
• Parasympatholytic (adj/n): A substance or drug that blocks or reduces the effects of the parasympathetic nervous system.

Synonyms

• Cholinergic system (in a specific pharmacological/functional context, as parasympathetic nerves primarily use acetylcholine).
• Craniosacral division (an anatomical synonym referring to its origins in the brain stem and sacral spinal cord).

Antonyms

• Sympathetic nervous system: The division of the autonomic nervous system that prepares the body for strenuous activity and stress (the "fight or flight" system).

Noun

1. originates in the brain stem and lower part of the spinal cord; opposes physiological effects of the sympathetic nervous system: stimulates digestive secretions; slows the heart; constricts the pupils; dilates blood vessels