Parasympathetic nervous system

Definition

The parasympathetic nervous system (PNS) is a division of the autonomic nervous system that conserves energy by slowing the heart rate and increasing intestinal and gland activity. It is often referred to as the 'rest and digest' system.

5 Must Know Facts For Your Next Test

1. The PNS uses acetylcholine as its primary neurotransmitter.
2. It primarily acts through muscarinic receptors located in various organs such as the heart, lungs, and digestive tract.
3. The vagus nerve is a major component of the PNS, controlling many functions including heart rate and digestion.
4. Parasympathetic activation results in decreased heart rate, increased salivation, increased gastrointestinal activity, and constriction of pupils.
5. Pharmacological agents like anticholinergics can inhibit parasympathetic activities leading to effects like dry mouth and constipation.

Review Questions

• What neurotransmitter is primarily associated with the parasympathetic nervous system?
• Which cranial nerve is a major player in mediating parasympathetic functions?
• Name two physiological changes that occur when the parasympathetic nervous system is activated.

Related terms

Autonomic Nervous System: A part of the peripheral nervous system responsible for regulating involuntary body functions.

Sympathetic Nervous System: A division of the autonomic nervous system that prepares the body for 'fight or flight' responses.

Acetylcholine: A neurotransmitter used by both the central and peripheral nervous systems, particularly significant in activating muscles and regulating endocrine functions.