Autonomic Nervous System Lecture Notes

Introduction

• Presenter: Dr. Mike
• Topic: Autonomic Nervous System (ANS)
• Focus: Sympathetic and parasympathetic divisions

Nervous System Overview

• Central Nervous System (CNS)

  • Includes brain, brain stem, spinal cord, cerebellum
  • Central to anatomical and functional integration

• Peripheral Nervous System (PNS)

  • Neurons that extend away from and return to CNS
  • Divided into sensory (incoming) and motor (outgoing) aspects

Sensory System

• Somatic Sensory: Conscious awareness (touch, temperature, pain)
• Visceral Sensory: Unconscious information about internal organs (e.g., blood vessel dilation)

Motor System

• Somatic Motor: Conscious movement (skeletal muscles)
• Visceral Motor (Autonomic): Unconscious control (cardiac muscle, smooth muscle, glands)

Autonomic Nervous System

• Purpose: Maintain homeostasis unconsciously
• Divisions:
  • Sympathetic: Fight or flight
  • Parasympathetic: Rest and digest

Sympathetic Nervous System

• Functions: Prepare body for stress (Four F's: Fight, Flight, Fright, Fornication)
• Effects:
  • Increases heart rate and contractile force
  • Increases respiratory rate; bronchodilation
  • Peripheral blood vessel constriction; muscle blood vessel dilation
  • Pupil dilation

Parasympathetic Nervous System

• Functions: Promote relaxation and digestion
• Effects:
  • Decreases heart rate and contractile force
  • Decreases respiratory rate; bronchoconstriction
  • Peripheral blood vessel dilation; muscle blood vessel constriction
  • Pupil constriction

Anatomy and Neurotransmitters

• Sympathetic (Thoracolumbar System)

  • Short preganglionic, long postganglionic neurons
  • Neurotransmitter: Noradrenaline (postganglionic)

• Parasympathetic (Craniosacral System)

  • Long preganglionic, short postganglionic neurons
  • Neurotransmitter: Acetylcholine (both pre- and postganglionic)

• Receptors:

  • Sympathetic: Adrenergic (Alpha and Beta)
  • Parasympathetic: Muscarinic (on target organs)

Adrenergic Receptors

• Alpha 1: Stimulate (smooth muscle contraction, gland secretion)
• Beta 1: Stimulate (heart rate and force)
• Beta 2: Inhibit (smooth muscle relaxation, e.g., bronchodilation)
• Alpha 2: Inhibit presynaptic terminals of sympathetic neurons

Parasympathetic Cranial Nerves

• Cranial nerves involved: III (Oculomotor), VII (Facial), IX (Glossopharyngeal), X (Vagus)

Clinical Relevance

• Adrenal Gland: Releases adrenaline as a hormone, influencing sympathetic response systemically
• Beta Blockers:
  • Non-specific: Affect heart and possibly bronchoconstriction
  • Specific: Primarily aim to reduce heart rate and blood pressure

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