Sympathetic & Parasympathetic — Part of Which Nervous System

Sympathetic & parasympathetic divisions are the part of:

Correct Answer: Autonomic Nervous System (ANS)

The sympathetic and parasympathetic divisions are the two major subdivisions of the Autonomic Nervous System (ANS).

Classification of the Nervous System

(A) By Location:

• CNS: Brain + Spinal cord
• PNS: Cranial nerves + Spinal nerves

(B) By Function:

• ANS: Sympathetic + Parasympathetic (controls involuntary functions)
• SNS (Somatic): Somatic sensory + Somatic motor (controls voluntary functions)

ANS — Sympathetic vs Parasympathetic

• Sympathetic ('fight or flight'): Increases heart rate, dilates bronchi, inhibits digestion, dilates pupils. Neurotransmitter: Norepinephrine.
• Parasympathetic ('rest and digest'): Decreases heart rate, constricts bronchi, stimulates digestion, constricts pupils. Neurotransmitter: Acetylcholine.

Examples in Animals

• A cow being chased by a predator → sympathetic activation → heart rate increases, blood flow to muscles increases, digestion slows down.
• After eating, a resting cow → parasympathetic activation → increased gastric secretion, active rumination and digestion.