ANP1106#4- Autonomic NS

Autonomic Nervous System Overview

• Course Information

  • ANP 1106 Winter 2025

  • Instructor: Katalin Tóth, Ph.D

Functions of Autonomic Nervous System

• Control Pathways

  • Communicates from skin/muscles/joints to brain and vice versa.

  • Involuntary functions include control of heart, smooth muscles, gut, and glands.

• Divisions

  • Somatic Division: Controls voluntary movements and sensory input.

  • Autonomic Division: Manages involuntary functions.

    • Includes sympathetic and parasympathetic systems.

    • Motor control of viscera, vascular system, and exocrine glands.

• Key References: Kandel, Koester, Mack, Siegelbaum: Principles of Neural Sciences, 6th Edition.

Structural Organization of the Nervous System

• Nervous System Components:

  • Central Nervous System (CNS): Brain and spinal cord.

  • Peripheral Nervous System (PNS): Connects CNS to limbs and organs.

    • Sensory (Afferent) Division: Transmits sensory information to CNS.

    • Motor (Efferent) Division: Carries commands from CNS to effectors.

      • Somatic Nervous System: Controls skeletal muscles.

      • Autonomic Nervous System (ANS): Regulates involuntary actions (sympathetic and parasympathetic).

Sympathetic and Parasympathetic Divisions

• Differences and Functions:

  • Sympathetic Division: Activates fight or flight responses.

  • Parasympathetic Division: Promotes rest and digest functions.

Anatomical Differences Between ANS Divisions

• Origin in the CNS:

  • Sympathetic: Thoracolumbar (T1-L2).

  • Parasympathetic: Craniosacral (brainstem nuclei and S2-S4).

• Location of Ganglia:

  • Sympathetic: Close to spinal cord.

  • Parasympathetic: Within or near target organs (intramural).

• Functionality & Neurotransmitters:

  • Pre- and postganglionic fiber lengths differ: long preganglionic in parasympathetic, short in sympathetic.

• Neurotransmitters:

  • All preganglionic: Acetylcholine (ACh).

  • Postganglionic:

    • Sympathetic: Mostly norepinephrine; some ACh (e.g., sweat glands).

    • Parasympathetic: ACh.

Cranial Nerves and Parasympathetic Innervation

• Cranial Nerve Functions:

  • CN III (Oculomotor): Eye muscle control, lacrimal gland.

  • CN VII (Facial): Controls salivary and tear glands.

  • CN IX (Glossopharyngeal): Tongue and pharynx.

  • CN X (Vagus): Controls heart, lungs, and digestive tract.

• Parasympathetic Ganglia Locations:

  • Oculomotor: Ciliary ganglia near the eye.

  • Facial: Pterygopalatine and submandibular ganglia.

  • Glossopharyngeal: Otic ganglia.

  • Vagus: Intramural ganglia in target organ walls.

Sympathetic Pathways

• Three Pathways of Sympathetic Innervation:

  • Innervates various organs including heart, lungs, blood vessels, and glands.

• Sympathetic Innervation:

  • Primarily through thoracic and lumbar splanchnic nerves to collaterals.

Autonomic Tone and Interaction

• Visceral organs often have dual innervation (sympathetic vs. parasympathetic).

• Dynamic Antagonism: Allows precise control of visceral activities—e.g., heart rate adjustment, digestion.

• Basal Tone: Both divisions are partially active to maintain homeostasis.

Effects of Autonomic Divisions on Organs

• General Effects:

  • Parasympathetic: Reduces heart rate, stimulates digestion, promotes urination.

  • Sympathetic: Increases heart rate, dilates bronchioles, inhibits digestion, and promotes blood flow to muscles.

• Target Systems for Each Division:

  • Cardiovascular, respiratory, digestive, and urinary systems exhibit contrasting effects when either system is activated.

Neurotransmitters and Receptors

• Types of Receptors:

  • Cholinergic Receptors: Act on ACh, categorized into nicotinic and muscarinic.

  • Adrenergic Receptors: Act on norepinephrine; alpha and beta types mediate various functions (e.g. vasoconstriction, increased heart rate).

Visceral Reflexes

• Components of Visceral Reflex Arcs:

  • Sensory neurons sending information about internal state (chemical, stretch).

  • Include receptors, sensory neurons, integration centers, motor pathways, and effectors (smooth/cardiac muscle and glands).

CNS Control of ANS

• Hierarchy of Control:

  • Hypothalamus: Integrates autonomic activity, influenced by emotional input from the limbic system.

  • Brain Stem: Regulates basic autonomic functions like heart rate and respiration.

  • Cerebral Cortex: Engages in more complex controls and behaviors regarding the autonomic system.