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Efferent Division: Autonomic and Somatic Motor Control
Chapter 11 Efferent Division: Autonomic and Somatic Motor Control
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Somatic motor division
About this Chapter Autonomic division Autonomic reflexes Antagonistic controls Control of cardiac and smooth muscle, and glands in homeostasis Agonists and antagonists in research and medicine Somatic motor division CNS control of skeletal muscles through neuromuscular junctions
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Role of the Autonomic Division in Homeostasis
Antagonistic branches Parasympathetic “Rest and digest” Restore body function Sympathetic “Fight or flight” Energetic action
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Role of the Autonomic Division in Homeostasis
Figure 11-1
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Coordination of homeostatic responses
The Hypothalamus, Pons, and Medulla Initiate Autonomic, Endocrine, and Behavioral Responses Coordination of homeostatic responses Autonomic Endocrine Behavioral Figure 11-2
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Autonomic Control Centers in the Brain
Hypothalamus Water balance, temperature, and hunger Pons Respiration Medulla Cardiac Vomiting Swallowing Temperature control Water balance Eating behavior Hypothalamus Pons Urinary bladder control Medulla Secondary respiratory center Blood pressure control Respiratory center Figure 11-3
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Autonomic Pathways Figure 11-4
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Antagonistic Control of the Autonomic Division
Most internal organs are under antagonistic control One autonomic branch is excitatory and the other branch is inhibitory Example: Effector organ: heart Parasympathetic response: slows rate Sympathetic response: increases rate and force of contraction
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Autonomic Sympathetic and Parasympathetic Pathways
Hypothalamus, Reticular formation Ganglion Pons Medulla Vagus nerve Spinal cord Sympathetic chain Pelvic nerves KEY Parasympathetic Sympathetic Figure 11-5
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Autonomic Sympathetic and Parasympathetic Pathways
Sympathetic versus parasympathetic pathways Spinal cord exit Neurotransmitters Receptors The major parasympathetic tract is the vagus nerve Medulla Vagus nerve Right lung Left lung Liver Spleen Stomach Pancreas Proximal two-thirds of colon Entire small intestine Figure 11-6
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Autonomic Sympathetic and Parasympathetic Pathways
use acetylcholine and norepinephrine. Parasympathetic pathways use acetylcholine. CNS ACh Nicotinic receptor Autonomic ganglion Norepinephrine ACh Adrenergic receptor Muscarinic receptor T Target tissue T Figure 11-7
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Sympathetic and Parasympathetic Neurotransmitters
Table 11-1
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Autonomic pathways control: Smooth muscle Cardiac muscle
Autonomic Targets Autonomic pathways control: Smooth muscle Cardiac muscle Exocrine glands (select) Endocrine glands (select) Lymphoid tissue Adipose tissue
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Autonomic Neuron Structure
Neuroeffector junction Postganglionic axon Varicosities Axon Neurotransmitter synthesis
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Varicosities in Autonomic Neurons
Axon of postganglionic autonomic neuron Vesicle containing neurotransmitter Mitochondrion Varicosity Figure 11-8 Varicosities Smooth muscle cells Figure 11-8
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Norepinephrine Release at a Varicosity of a Sympathetic Neuron
1 Action potential arrives at the varicosity. 2 Depolarization opens voltage-gated Ca2+ channels. Axon varicosity MAO Tyrosine 3 Ca2+ entry triggers exocytosis of synaptic vesicles. 8 Axon 7 Voltage-gated Ca2+ channel NE 1 Action potential 4 NE binds to adrenergic receptor on target. Exocytosis 3 Active transport 5 Ca2+ 2 Receptor activation ceases when NE diffuses away from the synapse. 6 NE 5 Diffuses away 4 Blood vessel G 6 NE is removed from the synapse. Response Adrenergic receptor Target cell 7 NE can be taken back into synaptic vesicles for re-release. 8 NE is metabolized by monoamine oxidase (MAO). Figure 11-9, steps 1–8
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Sympathetic Branch: Stimulation
Pupil dilation Salivation Heart beat and volume Blood vessel and bronchiole dilation Fat breakdown Ejaculation
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Sympathetic Branch: Inhibition
Digestion Pancreas secretion Urination
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Multiple and distant targets
Adrenal Medulla Primary neurohormone Epinephrine Multiple and distant targets
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The Adrenal Medulla Figure 11-10 Adrenal cortex is a
true endocrine gland. Adrenal medulla is a modified sympathetic ganglion. Adrenal gland Kidney (b) (a) The chromaffin cell is a modified postganglionic sympathetic neuron. ACh Blood vessel Preganglionic sympathetic neuron Spinal cord Epinephrine is a neurohormone that enters the blood. To target tissues (c) Adrenal medulla Figure 11-10
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The Adrenal Medulla Adrenal gland Kidney (a) Figure 11-10a
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The Adrenal Medulla Adrenal cortex is a true endocrine gland.
Adrenal medulla is a modified sympathetic ganglion. (b) Figure 11-10b
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The Adrenal Medulla The chromaffin cell is a modified postganglionic
sympathetic neuron. ACh Blood vessel Preganglionic sympathetic neuron Spinal cord Epinephrine is a neurohormone that enters the blood. To target tissues (c) Adrenal medulla Figure 11-10c
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Parasympathetic Branch
Acetylcholine Muscarinic receptors G protein-coupled Second messenger pathways At least five subtypes
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Parasympathetic Branch: Actions
Constricts pupils and bronchioles Slows heart Stimulates Digestion Insulin release Urination Erections
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Autonomic Agonists and Antagonists
Agonists and antagonists are important tools in research and medicine Table 11-3
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Efferent Pathways of the Peripheral Nervous System
SOMATIC MOTOR PATHWAY AUTONOMIC PATHWAYS Parasympathetic pathway Sympathetic pathways Adrenal sympathetic pathway CNS CNS CNS CNS ACh Nicotinic receptor Adrenal cortex Adrenal medulla Ganglia E ACh Nicotinic receptor Ganglion receptor NE ACh Muscarinic receptor Autonomic effectors: Blood vessel • Smooth and cardiac muscles • Some endocrine and exocrine glands • Some adipose tissue 1 receptor E ACh Nicotinic receptor 2 receptor KEY Skeletal muscle ACh= acetylcholine E= epinephrine NE= norepinephrine Figure 11-11
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Efferent Pathways of the Peripheral Nervous System
AUTONOMIC PATHWAYS Parasympathetic pathway Sympathetic pathways Adrenal sympathetic pathway CNS CNS CNS ACh Nicotinic receptor Adrenal cortex Adrenal medulla Ganglia E ACh Nicotinic receptor Ganglion receptor NE ACh Muscarinic receptor Autonomic effectors: Blood vessel • Smooth and cardiac muscles • Some endocrine and exocrine glands • Some adipose tissue 1 receptor E 2 receptor KEY ACh= acetylcholine E= epinephrine NE= norepinephrine Figure (2 of 5)
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Efferent Pathways of the Peripheral Nervous System
Figure (3 of 5)
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Efferent Pathways of the Peripheral Nervous System
Figure (4 of 5)
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Efferent Pathways of the Peripheral Nervous System
Figure (5 of 5)
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Somatic versus Autonomic Divisions
Table 11-5
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Somatic Motor Division
Single neuron CNS origin Myelinated Terminus Branches Neuromuscular junction
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Somatic Motor Division
Figure (1 of 5)
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Anatomy of the Neuromuscular Junction
Somatic motor neuron The neuromuscular junction Muscle fiber Terminal bouton Figure (1 of 3)
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Anatomy of the Neuromuscular Junction
Schwann cell sheath Axon terminal Mitochondria Motor end plate Figure (2 of 3)
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Anatomy of the Neuromuscular Junction
Synaptic vesicle (ACh) Presynaptic membrane Synaptic cleft Postsynaptic membrane Nicotinic ACh receptors Figure (3 of 3)
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Events at the Neuromuscular Junction
Somatic motor neuron Axon terminal Ca2+ Ca2+ Action potential ACh Acetyl + choline Voltage-gated Ca2+ channel Skeletal muscle fiber AChE Motor end plate Nicotinic receptor (a) Figure 11-13a
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Events at the Neuromuscular Junction
Open channel Closed channel K+ ACh Na+ K+ Na+ (b) Figure 11-13b
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Cigarette Smoking Among American High School Students
Questions 11-1
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