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THIRD EDITION
HUMAN PHYSIOLOGY
AN INTEGRATED APPROACH
Dee Unglaub Silverthorn, Ph.D.
Chapter 11
Efferent Division: Autonomic and
Somatic Motor Control
PowerPoint® Lecture Slide Presentation by
Dr. Howard D. Booth, Professor of Biology, Eastern Michigan University
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
About this Chapter
• Efferent division and what it controls
• Pathways receptors and neurotransmitters
• Antagonistic controls: sympathetic and
parasympathetic
• Control of cardiac, smooth muscle, some adipose
tissue and glands in homeostasis
• CNS control of skeletal muscles through
neuromuscular junctions
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Autonomic Division: Homeostatic balancing
• Controls
• Smooth & cardiac muscle
• Glands & adipose
• Antagonistic branches
• Parasympathetic
• "Rest & digest"
• Restore body
• Sympathetic
• "Fight or flight"
• Energetic action
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Autonomic Division: Homeostatic balancing
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Figure 11-1: Homeostasis and the autonomic division
Autonomic Control Centers
• Hypothalamus
• Water balance
• Temperature
• Hunger
• Pons
• Respiration
• Cardiac
• Vasoconstriction
• Medulla
• Respiration
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Figure 11-3: Autonomic control centers in the brain
Autonomic Pathways: Communicate to Body
• Coordinates homeostatic responses
• Autonomic
• Endocrine
• Behavioral
• Blood pressure
• Osmolarity
• Tonic regulation
• Antagonistic control
• Receptor directed response
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Autonomic Pathways: Communicate to Body
Figure 11-2: The hypothalamus and brain stem initiate autonomic, endocrine, and behavioral responses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Autonomic Pathways: Two Efferent Neurons
• CNS
• Preganglionic
neuron
• Ganglion
• Postganglionic
neuron
• Target tissue
Figure 11-4: Autonomic pathways
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Comparison of sympathetic and
Parasympathetic Pathways
• Neurotransmitters
• Receptors
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Figure 11-7: Sympathetic and parasympathetic pathways
Parasympathetic Branch: “Rest and Digest”
• Preganglionic neurons
• Originate in
• Brain stem
• Lower cord
• NT: cholinergic
• Ganglion
• Near target
• Nicotinic receptors
• Postganglionic neuron
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 11-5: Autonomic sympathetic and parasympathetic pathways
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Actions of Parasympathetic Branch
• Constricts
• Pupil
• Bronchioles
• Slows heart
• Stimulates
• Digestion
• Insulin release
• Urination
• Erections
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Sympathetic Branch: “Fight or Flight”
• Preganglionic neuron
• Short
• Origin: spinal cord
• NT: cholinergic
• Ganglia
• Sympathetic chain
• Near spinal cord
• Postganglionic neuron
• Long
• NT: adrenergic
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Autonomic Reflexes: “visceral reflexes”
Figure 13-2: Autonomic reflexes
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Examples of Autonomic Reflexes
• Cold Water (Whole Body) Immersion causes tachycardia
• Exposure of face to cold water causes bradycardia: Mammalian Diving
Reflex via Vagal Nerve
• Pupillary Reflex-Pupil Constricting in response to light
• Baroreceptor Reflex- Low BP in carotid sinus results in tachycardia and
blood vessel constriction
• Carotid Sinus Reflex- Increased pressure within or external
manipulation of carotid sinus results in bradycardia
• Dilation of Blood vessels as body temperature increases
• Secretion of epinephrine and norepinephrine from the adrenal medulla
in response to fear or stress
• Sweating in response to increased body temperature
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Autonomic Effects on Cardiovascular System
Target
Sympathetic (adrenergic)
Parasympathetic (muscarinic)
cardiac output
β1, (β2): increases
M2: decreases
SA node: heart rate (chronotropic)
Heart
β1, (β2) [4]: increases
M2: decreases
Atrial cardiac muscle: contractility
(inotropic)
β1, (β2)[4]: increases
M2: decreases
at AV node
β1:
increases conduction
increases cardiac muscle automaticity [4]
M2:
decreases conduction
Atrioventricular block [4]
Ventricular cardiac muscle
β1, (β2):
increases contractility (inotropic)
increases cardiac muscle automaticity [4]
---
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Autonomic Effects on Blood Vessels
Target
Sympathetic (adrenergic)
Parasympathetic (muscarinic)
vascular smooth muscle in general
α1:[5] contracts; β2:[5] relaxes
M3: relaxes [4]
renal artery
α1[6]: constricts
---
larger coronary arteries
α1 and α2[7]: constricts [4]
---
smaller coronary arteries
β2:dilates [8]
---
arteries to viscera
α: constricts
---
arteries to skin
α: constricts
---
arteries to brain
α1[9]: constricts [4]
---
arteries to erectile tissue
α1[10]: constricts
M3: dilates
arteries to salivary glands
α: constricts
M3: dilates
hepatic artery
β2: dilates
---
arteries to skeletal muscle
β2: dilates
---
Veins
α1 and α2 [11] : constricts
β2: dilates
---
Blood vessels
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Stimulatory Actions of Sympathetic Branch
• Pupil dilation
• Salivation
• Heart beat & volume
• Dilation
• Blood vessels
• Bronchioles
• Catecholamine release
• Fat breakdown
• Ejaculation
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Inhibitory Actions of Sympathetic Branch
• Digestion
• Pancreas secretion
• Urination
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Adrenal Medulla:
A Modified Sympathetic Ganglion
• Sympathetic stimulation
• Catecholamine release to blood
• Epinephrine
• Norepinephrine
• Travel to:
• Multiple targets
• Distant targets
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Adrenal Medulla:
A Modified Sympathetic Ganglion
Figure 11-10: The adrenal medulla
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Synapses in Autonomic Nerves
• Varicosities
• NT released to ECF
• No cleft
• Impact
• Large area
• Slow acting
• Long duration
Figure 11-8: Varicosities of autonomic neurons
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Mechanism: Norepinephrine Release and Recycling
Figure 11-9: Norepinephrine release at a varicosity of a sympathetic neuron
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Review of Efferent Pathways: Motor & Autonomic
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Figure 11-11: Summary of efferent pathways
Somatic Motor Division: Controls Skeletal Muscles
• Body movement
• Appendages
• Locomotion
• Single neuron
• CNS origin
• Myelinated
• Terminus
• Branches
• Neuromuscular
junction
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Figure 11-11: Summary of efferent pathways
Neuronmuscular Junction: Overview
• Terminal boutons
• Synaptic cleft
• Filled with a fibrous Matrix (collagen)
• AChE
• Hold axon terminal and motor end plate
together
• Motor end plate
• On muscle
• Nicotinic receptors
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Neuronmuscular Junction: Overview
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Figure 11-12: Anatomy of the neuromuscular junction
Neuronmuscular Junction:
Mechanism of Signal Conduction
• Axon terminal
• AP signals
• ACh release
• Motor end plate
• 2 ACh bind
• opens cation channel
• Na+ influx
• Membrane depolarized
• Stimulates fiber contraction
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Neuronmuscular Junction:
Mechanism of Signal Conduction
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Figure 11-13: Events at the neuromuscular junction
Summary
• Autonomic branches:
sympathetic and parasympathetic
• Regulate glands, smooth & cardiac muscles
• Team with endocrine to regulate homeostasis
• Are regulated by hypothalamus, pons &
medulla
• Have pathways with 2 neurons and a ganglion
• Use varicosities to release NTs
• Have diverse receptors: tonic & antagonistic
regulation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Summary
• Efferent motor neurons control skeletal muscles
• Single long myelinated neuron from CNS
• Neuromuscular junction structure &
mechanism
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings