Bio211 Lecture 21

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Autonomic Nervous System
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Lecture Overview

• Review/Questions from last lecture (Brain
  II/Cranial Nerves)
• Autonomic Nervous System, ANS (pp. 87-89)
• Overview
• Divisions
• Structure
• Neurotransmitters
• Actions

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Review from Last Lecture (Brain II/CN)

• Brain II (pp. 84-87)
• Cerebrum
• Myelinated tracts
• Basal ganglia
• Sensory areas
• Motor areas
• Brain coverings (meninges)
• Cerebrospinal fluid (CSF)
• Ventricular System
• Cranial nerves

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Autonomic (Visceral) Nervous System
CNS
PNS
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Autonomic Nervous System

• functions without conscious effort
• controls visceral (squishy!) activities
• regulates smooth muscle, cardiac muscle, and
  glands

• Two Main Divisions
• sympathetic prepares body for fight or flight
  situations
• parasympathetic prepares body for rest and
  digest activities
• Third Division Enteric Nervous System (ENS) for
  alimentary canal

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Somatic vs. Autonomic Nervous Systems
Dual
Figure from Marieb, Human Anatomy Physiology,
Pearson, 2013
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Autonomic Nerve Fibers
ANS a motor division of the PNS
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Sympathetic Division of ANS

Paravertebral ganglion
Effectors in head and thoracic cavity
Effectors in muscles and body wall


(T5 T12)
Figure from Saladin, Anatomy Physiology,
McGraw Hill, 2007
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Autonomic Plexuses
Sympathetic collateral (prevertebral) ganglia
Figure from Martini, Fundamentals of Anatomy
Physiology, Pearson Education, 2004
Autonomic plexuses receive sympathetic and
parasympathetic, postganglionic fibers
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Spinal Nerves Autonomic Fibers
Sympathetic ganglion - cell bodies of
postganglionic sympathetic neurons

Three fates of a preganglionic sympathetic
axon 1) synapse in same chain ganglion 2)
Ascend/descend to synapse in another chain
ganglion 3) Pass through without synapsing
(form prevertebral, or collateral ganglia)



Figure from Martini, Fundamentals of Anatomy
Physiology, Pearson Education, 2004
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Were you paying attention?
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Autonomic Neurotransmitters
always excitatory in ganglia
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Actions of Autonomic Neurotransmitters

• depend on receptor

• Cholinergic receptors
• bind acetylcholine
• nicotinic
• excitatory
• muscarinic
• excitatory or inhibitory

• Adrenergic receptors
• bind norepinephrine
• alpha (Types 1 and 2)
• different responses on various effectors
• beta (Types 1 and 2)
• different responses on various effectors

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Sympathetic Myoneural Junctions
Figure from Martini, Fundamentals of Anatomy
Physiology, Pearson Education, 2004

• NE is either
• reabsorbed and reused or broken down by
  monoamine oxidase (MAO) in varicosities
• or broken down by catechol-O-methyltransferase
  (COMT) in surrounding tissues

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Actions of Cholinergic Receptors
Cholinergic receptors Nicotinic receptors ?
always excitatory Muscarinic ? Excitatory or
inhibitory Remember the RECEPTOR determines the
effect of a neurotransmitter
Always excitatory
(Sweat glands, blood vessels to skeletal muscles,
brain)
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Sympathetic Division - Divergence
NOTE Arrangement of nerves creates DIVERGENCE
Sympathy spreads
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Sympathetic Division of the ANS
SYMPATHETIC (Thoracolumbar outflow)
Fight or Flight
E situations Emergency Embarrassment
Excitement Exercise
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
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Parasympathetic
(Craniosacral outflow)
REST AND DIGEST
SalivationLacrimationUrinationDigestionDefecat
ion 3 decreases - Heart rate - Airway
diameter - Pupil size (constrict)
Figure from Martini, Fundamentals of Anatomy
Physiology, Pearson Education, 2004
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Control of Autonomic Activity
Sympathetic and Parasympathetic
Sympathetic
Parasympathetic
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
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Review of Autonomic Nervous System
Branch of ANS PARASYMPATHETIC SYMPATHETIC
General Function rest and digest (SLUDD) Salivation, lacrimation, urination, digestion, defecation 3 decreases ? heart rate, ? pupil size, ? airway diameter fight or flight E situations Emergency, exercise, embarrassment, excitement
Origin of Preganglionic fiber cranial region of brain or sacral region of spinal cord (craniosacral outflow) thoracic or lumbar region of spinal cord (thoracolumbar outflow) Divergence for widespread activation of body
Location of Ganglia within or near effector organ alongside or in front of spinal cord (paravertebral ganglia collateral ganglia)
NTx secreted by postganglionic fiber acetylcholine Norepinephrine (some acetylcholine sweat glands, smooth muscle on blood vessels, brain)