L 6 Autonomic Nervous System

Physiology 0510/0520/0550, 2025: Autonomic Nervous System

Introduction to the Peripheral Nervous System

  • The peripheral nervous system (PNS) comprises two main components:

    • Somatic Nervous System: Regulates voluntary contraction of skeletal muscle.

    • Autonomic Nervous System (ANS): Continuously regulates the function of glands, smooth muscle, heart, and visceral organs.

  • The ANS is distinct and separate from the somatic nervous system.

  • The ANS is composed of three unique divisions:

    • Sympathetic Division

    • Parasympathetic Division

    • Enteric Division

  • These divisions work together, either antagonistically or synergistically, to maintain a constant internal environment (homeostasis).

  • Dual Innervation:

    • Most organs receive innervation from both sympathetic and parasympathetic divisions, allowing for wide and fine reflex control.

    • In dually-innervated organs, control by both divisions can be equal, or one division may exert more influence, leading to a