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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Dee Unglaub Silverthorn, Ph.D.
HUMAN PHYSIOLOGY
PowerPoint® Lecture Slide Presentation byDr. Howard D. Booth, Professor of Biology, Eastern Michigan University
AN INTEGRATED APPROACH
T H I R D E D I T I O N
Chapter 11Efferent Division: Autonomic and
Somatic Motor Control
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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
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• Controls• Smooth & cardiac muscle • Glands & adipose
• Antagonistic branches• Parasympathetic
• "Rest & digest"• Restore body
• Sympathetic• "Fight or flight"• Energetic action
Autonomic Division: Homeostatic balancing
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Autonomic Division: Homeostatic balancing
Figure 11-1: Homeostasis and the autonomic division
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• Hypothalamus• Water balance• Temperature• Hunger
• Pons• Respiration• Cardiac• Vasoconstrictio
n• Medulla
• Respiration
Autonomic Control Centers
Figure 11-3: Autonomic control centers in the brain
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• Coordinates homeostatic responses• Autonomic • Endocrine • Behavioral
• Blood pressure• Osmolarity• Tonic regulation• Antagonistic control• Receptor directed response
Autonomic Pathways: Communicate to Body
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Autonomic Pathways: Communicate to Body
Figure 11-2: The hypothalamus and brain stem initiate autonomic, endocrine, and behavioral responses
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• CNS• Preganglionic
neuron• Ganglion• Postganglioni
c neuron• Target tissue
Autonomic Pathways: Two Efferent Neurons
Figure 11-4: Autonomic pathways
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• Neurotransmitters
• Receptors
Comparison of sympathetic and Parasympathetic Pathways
Figure 11-7: Sympathetic and parasympathetic pathways
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• Preganglionic neurons• Originate in
• Brain stem• Lower cord
• NT: cholinergic• Ganglion
• Near target• Nicotinic receptors
• Postganglionic neuron
Parasympathetic Branch: “Rest and Digest”
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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 11-5: Autonomic sympathetic and parasympathetic pathways
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• Constricts • Pupil• Bronchioles
• Slows heart• Stimulates
• Digestion• Insulin release• Urination• Erections
Actions of Parasympathetic Branch
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• Preganglionic neuron• Short• Origin: spinal cord• NT: cholinergic
• Ganglia• Sympathetic chain• Near spinal cord
• Postganglionic neuron• Long• NT: adrenergic
Sympathetic Branch: “Fight or Flight”
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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
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Autonomic Effects on Cardiovascular System
Target Sympathetic (adrenergic) Parasympathetic (muscarinic)
cardiac output β1, (β2): increases M2: decreases
SA node: heart rate (chronotropic) β1, (β2) [4]: increases M2: decreases
Atrial cardiac muscle: contractility (inotropic) β1, (β2)[4]: increases M2: decreases
at AV node
β1:increases conductionincreases cardiac muscle automaticity [4]
M2:decreases conductionAtrioventricular block [4]
Ventricular cardiac muscle
β1, (β2):increases contractility (inotropic)increases cardiac muscle automaticity [4]
---
Heart
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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] : constrictsβ2: dilates ---
Blood vessels
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• Pupil dilation• Salivation• Heart beat &
volume• Dilation
• Blood vessels• Bronchioles
• Catecholamine release
• Fat breakdown• Ejaculation
Stimulatory Actions of Sympathetic Branch
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• Digestion• Pancreas secretion• Urination
Inhibitory Actions of Sympathetic Branch
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• Sympathetic stimulation• Catecholamine release to blood
• Epinephrine• Norepinephrine
• Travel to:• Multiple targets• Distant targets
Adrenal Medulla: A Modified Sympathetic Ganglion
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Adrenal Medulla: A Modified Sympathetic Ganglion
Figure 11-10: The adrenal medulla
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• Varicosities• NT released to
ECF• No cleft• Impact
• Large area• Slow acting• Long duration
Synapses in Autonomic Nerves
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
Figure 11-11: Summary of efferent pathways
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• Body movement• Appendages• Locomotion• Single neuron
• CNS origin• Myelinated
• Terminus • Branches• Neuromuscular
junction
Somatic Motor Division: Controls Skeletal Muscles
Figure 11-11: Summary of efferent pathways
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• 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
Neuronmuscular Junction: Overview
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Neuronmuscular Junction: Overview
Figure 11-12: Anatomy of the neuromuscular junction
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• Axon terminal• AP signals• ACh release
• Motor end plate• 2 ACh bind• opens cation channel• Na+ influx• Membrane depolarized
• Stimulates fiber contraction
Neuronmuscular Junction: Mechanism of Signal Conduction
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Neuronmuscular Junction: Mechanism of Signal Conduction
Figure 11-13: Events at the neuromuscular junction
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• 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
Summary
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• Efferent motor neurons control skeletal muscles• Single long myelinated neuron from CNS • Neuromuscular junction structure &
mechanism
Summary