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Efferent Division: Autonomic and Somatic Motor Control
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About this Chapter Autonomic division Somatic motor division
Antagonistic controls Somatic motor division CNS control of skeletal muscles through neuromuscular junctions ****** Review the overall organization of the NS
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Autonomic Division: Homeostasis
Antagonistic branches Parasympathetic “Rest and digest” Restore body function Sympathetic “Fight or flight” Energetic action
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Autonomic Division: Homeostasis
Figure 11-1
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Autonomic Pathways Coordination of homeostatic responses Autonomic
Endocrine Behavioral Figure 11-2
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Autonomic Control Centers
Hypothalamus Water balance, temperature, and hunger Pons Respiration, cardiac, and urinary Medulla Respiration Figure 11-3
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Two Efferent Neurons in Series
Autonomic pathways Figure 11-4
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Two Efferent Neurons in Series
CNS- tracts coming from brain to spinal cord Preganglionic neuron- exits spinal cord and goes to ganglion Ganglion- sympathetic chain ganglion runs along vertebral colum Postganglionic neuron- runs down spinal nerve Target tissue- can be muscle or gland
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Sympathetic versus Parasympathetic
Figure 11-7
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Antagonistic Control Autonomic sympathetic and parasympathetic pathways Notice the mention of antagonistic responses & receptors involved Figure 11-5
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Sympathetic vs Parasympathetic
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Nerves are found in the PNS
III. Nerves- these are bundles of axons (nerve fibers) that are myelinated or unmyelinated. Each axon is surrounded by an endoneurium, groups of nerves are bundles into nerve fascicles surrounded by perineurium and the whole nerve is surrounded by epineurium. *Know the difference between neuron, nerve fiber, and nerve.
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Sympathetic versus Parasympathetic
Spinal cord exit Neurotransmitters Receptors
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Sympathetic versus Parasympathetic
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Autonomic Targets Smooth muscle Cardiac muscle Exocrine glands
Endocrine glands Lymphoid tissue Adipose tissue
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Autonomic Neuron Structure
Neuroeffector junction - synapse between a postganglionic autonomic neuron and target cell Postganglionic axon - exits spinal cord to target cell Varicosities - instead of axon terminals, there are multiple branches and varicosities along the axon over the surface of the target cell
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Synapses in Autonomic Neurons
Neurotransmitter released to ECF No synaptic cleft Impact Large area Slow acting Long duration
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Review of Efferent Pathways
Summary of the efferent pathways of the peripheral nervous system ACh Somatic motor pathway Parasympathetic Ganglion Nicotinic receptor CNS AUTONOMIC PATHWAYS Adrenal medulla cortex E Sympathetic pathways Ganglia Ach = acetylcholine E = epinephrine NE = norepinephrine b1 receptor b2 Blood vessel Autonomic effectors: • Smooth and cardiac muscles • Some endocrine and exocrine glands • Some adipose tissue KEY a receptor Skeletal muscle Muscarinic Nicotinic receptor NE sympathetic pathway Figure 11-11
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Review of Efferent Pathways
Somatic motor pathway CNS Ach = acetylcholine E = epinephrine NE = norepinephrine KEY Skeletal muscle Nicotinic receptor ACh Figure (1 of 5)
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Review of Efferent Pathways
ACh Somatic motor pathway Parasympathetic Ganglion Nicotinic receptor CNS AUTONOMIC PATHWAYS Ach = acetylcholine E = epinephrine NE = norepinephrine Autonomic effectors: • Smooth and cardiac muscles • Some endocrine and exocrine glands • Some adipose tissue KEY Skeletal muscle Muscarinic Nicotinic receptor Figure (2 of 5)
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Review of Efferent Pathways
AUTONOMIC PATHWAYS Somatic motor pathway Parasympathetic pathway Sympathetic pathways CNS CNS CNS ACh KEY Nicotinic receptor Ach = acetylcholine E = epinephrine NE = norepinephrine Ganglia ACh Nicotinic receptor Ganglion NE ACh a receptor Muscarinic receptor Autonomic effectors: • Smooth and cardiac muscles • Some endocrine and exocrine glands • Some adipose tissue ACh Nicotinic receptor Skeletal muscle Figure (3 of 5)
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Review of Efferent Pathways
ACh Somatic motor pathway Parasympathetic Ganglion Nicotinic receptor CNS AUTONOMIC PATHWAYS Sympathetic pathways Ganglia Ach = acetylcholine E = epinephrine NE = norepinephrine b1 receptor Autonomic effectors: • Smooth and cardiac muscles • Some endocrine and exocrine glands • Some adipose tissue KEY a receptor Skeletal muscle Muscarinic Nicotinic receptor NE Figure (4 of 5)
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Review of Efferent Pathways
ACh Somatic motor pathway Parasympathetic Ganglion Nicotinic receptor CNS AUTONOMIC PATHWAYS Adrenal medulla cortex E Sympathetic pathways Ganglia Ach = acetylcholine E = epinephrine NE = norepinephrine b1 receptor b2 Blood vessel Autonomic effectors: • Smooth and cardiac muscles • Some endocrine and exocrine glands • Some adipose tissue KEY a receptor Skeletal muscle Muscarinic Nicotinic receptor NE sympathetic pathway Figure (5 of 5)
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Sympathetic versus Parasympathetic
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Referred Pain- Visceral Sensory Division
Visceral sensory neurons- Receptors in the viscera are free dendritic ends that send afferent signals caused by stretching, temperature and chemical changes, and irritation. Integration translates these signals into hunger, fullness, pain, or nausea. Visceral sensation may be hard to localize. Sometimes pain is called referred pain. A problem with an organ like the heart may send pain down the arm (not an area where the heart is located.) A map of referred pain: these are skin or body regions that present pain when there is visceral pain. The organ and site of referred pain are innervated by the same nerve.
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Somatic Motor Division
Skeletal muscle- target effector Body movement- main function, voluntary or a reflex Appendages- fine and gross motor skills Locomotion- movement of body at different speeds
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Somatic Motor Division
Single neuron CNS origin Myelinated Terminus Branches Neuromuscular junction Figure (1 of 4)
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Neuromuscular Junction: Overview
Terminal boutons- insulate the site of the neuromuscular juction and secrete supportive growth factors Synaptic cleft- space between the axon terminal and the sarcolemma Acetylcholine- neurotransmitter released involves calcium and binds to nicotinic receptors Motor end plate- folds on the sarcolemma of the muscle On muscle cell surface Nicotinic receptors
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Anatomy of the Neuromuscular Junction
Figure (1 of 3)
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Anatomy of the Neuromuscular Junction
Figure (2 of 3)
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Anatomy of the Neuromuscular Junction
Figure (3 of 3)
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Mechanism of Signal Conduction
Axon terminal (of presynaptic cell) Action potential signals acetylcholine release Motor end plate – series of folds in the plasma membrane of the postsynaptic cell Two acetylcholine bind Opens cation channel Na+ influx – K+ efflux Membrane depolarized Stimulates fiber contraction as a result in increased intracellular calcium concentration
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Events at the Neuromuscular Junction
Figure 11-13a
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Events at the Neuromuscular Junction
Notice that both Na and K use the same channel unlike those of neurons Figure 11-13b
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Somatic and Autonomic Divisions
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Summary Autonomic division Role in homeostasis
Sympathetic and parasympathetic branches Regulate glands, smooth and cardiac muscles CNS control centers Antagonistic regulation
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Summary Somatic division
Efferent motor neurons control skeletal muscles Single long myelinated neuron from CNS Neuromuscular junction structure and mechanism
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