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Chapter 11 Efferent Division: Autonomic and Somatic Motor Control.

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1 Chapter 11 Efferent Division: Autonomic and Somatic Motor Control

2 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

3 Role of the Autonomic Division in Homeostasis Antagonistic branches Parasympathetic “Rest and digest” Restore body function Sympathetic “Fight or flight” Energetic action

4 Role of the Autonomic Division in Homeostasis Figure 11-1

5 The Hypothalamus, Pons, and Medulla Initiate Autonomic, Endocrine, and Behavioral Responses Coordination of homeostatic responses Autonomic Endocrine Behavioral Figure 11-2

6 Figure 11-3 Autonomic Control Centers in the Brain Hypothalamus Water balance, temperature, and hunger Pons Respiration Medulla Respiration Cardiac Vomiting Swallowing Eating behavior Secondary respiratory center Respiratory center Hypothalamus Medulla Pons Urinary bladder control Water balance Temperature control Blood pressure control

7 Figure 11-4 Autonomic Pathways

8 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

9 Autonomic Sympathetic and Parasympathetic Pathways Figure 11-5 Ganglion Pons Medulla Spinal cord V agus nerve Sympathetic chain Pelvic nerves Hypothalamus, Reticular formation KEY Parasympathetic Sympathetic

10 Autonomic Sympathetic and Parasympathetic Pathways Sympathetic versus parasympathetic pathways Spinal cord exit Neurotransmitters Receptors The major parasympathetic tract is the vagus nerve Figure 11-6 Right lung Liver Proximal two-thirds of colon Entire small intestine Pancreas Spleen Stomach Left lung Medulla Vagus nerve

11 Figure 11-7 Autonomic Sympathetic and Parasympathetic Pathways CNS Autonomic ganglion Norepinephrine ACh Adrenergic receptor Sympathetic pathways use acetylcholine and norepinephrine. Parasympathetic pathways use acetylcholine. Nicotinic receptor Muscarinic receptor ACh Target tissue TT

12 Table 11-1 Sympathetic and Parasympathetic Neurotransmitters

13 Autonomic Targets Autonomic pathways control: Smooth muscle Cardiac muscle Exocrine glands (select) Endocrine glands (select) Lymphoid tissue Adipose tissue

14 Autonomic Neuron Structure Neuroeffector junction Postganglionic axon Varicosities Axon Neurotransmitter synthesis

15 Figure 11-8 Varicosities in Autonomic Neurons Mitochondrion VaricositiesSmooth muscle cells Vesicle containing neurotransmitter Axon of postganglionic autonomic neuron Varicosity

16 Figure 11-9, steps 1–8 Norepinephrine Release at a Varicosity of a Sympathetic Neuron NE Axon varicosity Adrenergic receptor Tyrosine Exocytosis Ca 2+ Voltage-gated Ca 2+ channel Action potential Axon Active transport Response MAO Blood vessel Diffuses away Action potential arrives at the varicosity. Depolarization opens voltage-gated Ca 2+ channels. Ca 2+ entry triggers exocytosis of synaptic vesicles. NE binds to adrenergic receptor on target. NE is metabolized by monoamine oxidase (MAO). Receptor activation ceases when NE diffuses away from the synapse. NE can be taken back into synaptic vesicles for re-release. NE is removed from the synapse. NE Target cell G

17 Sympathetic Branch: Stimulation Pupil dilation Salivation Heart beat and volume Blood vessel and bronchiole dilation Fat breakdown Ejaculation

18 Sympathetic Branch: Inhibition Digestion Pancreas secretion Urination

19 Adrenal Medulla Primary neurohormone Epinephrine Multiple and distant targets

20 Figure The Adrenal Medulla ACh Adrenal medulla is a modified sympathetic ganglion. Adrenal medulla Adrenal cortex is a true endocrine gland. Adrenal gland (b) Kidney (a) The chromaffin cell is a modified postganglionic sympathetic neuron. Preganglionic sympathetic neuron Spinal cord (c) Blood vessel Epinephrine is a neurohormone that enters the blood. To target tissues

21 Figure 11-10a The Adrenal Medulla Adrenal gland Kidney (a)

22 Figure 11-10b The Adrenal Medulla Adrenal medulla is a modified sympathetic ganglion. Adrenal cortex is a true endocrine gland. (b)

23 Figure 11-10c The Adrenal Medulla ACh Adrenal medulla The chromaffin cell is a modified postganglionic sympathetic neuron. Preganglionic sympathetic neuron Spinal cord (c) Blood vessel Epinephrine is a neurohormone that enters the blood. To target tissues

24 Parasympathetic Branch Acetylcholine Muscarinic receptors G protein-coupled Second messenger pathways At least five subtypes

25 Parasympathetic Branch: Actions Constricts pupils and bronchioles Slows heart Stimulates Digestion Insulin release Urination Erections

26 Table 11-3 Autonomic Agonists and Antagonists Agonists and antagonists are important tools in research and medicine

27 Figure Efferent Pathways of the Peripheral Nervous System Ganglion Ganglia ACh Nicotinic receptor Nicotinic receptor Autonomic effectors: Smooth and cardiac muscles Some endocrine and exocrine glands Some adipose tissue CNS AUTONOMIC PATHWAYS Skeletal muscle KEY ACh= acetylcholine E= epinephrine NE= norepinephrine ACh  1 receptor  2 receptor  receptor Muscarinic receptor CNS Adrenal medulla Adrenal cortex Blood vessel E E NE Nicotinic receptor SOMATIC MOTOR PATHWAY Parasympathetic pathway Sympathetic pathways Adrenal sympathetic pathway ACh

28 Figure (2 of 5) Efferent Pathways of the Peripheral Nervous System Ganglion Ganglia Nicotinic receptor Nicotinic receptor Autonomic effectors: Smooth and cardiac muscles Some endocrine and exocrine glands Some adipose tissue CNS AUTONOMIC PATHWAYS KEY ACh= acetylcholine E= epinephrine NE= norepinephrine ACh  1 receptor  2 receptor  receptor Muscarinic receptor CNS Adrenal medulla Adrenal cortex Blood vessel E E NE Parasympathetic pathway Sympathetic pathways Adrenal sympathetic pathway ACh

29 Figure (3 of 5) Efferent Pathways of the Peripheral Nervous System

30 Figure (4 of 5) Efferent Pathways of the Peripheral Nervous System

31 Figure (5 of 5) Efferent Pathways of the Peripheral Nervous System

32 Table 11-5 Somatic versus Autonomic Divisions

33 Somatic Motor Division Single neuron CNS origin Myelinated Terminus Branches Neuromuscular junction

34 Figure (1 of 5) Somatic Motor Division

35 Figure (1 of 3) Anatomy of the Neuromuscular Junction Somatic motor neuron Muscle fiber The neuromuscular junction Terminal bouton

36 Figure (2 of 3) Anatomy of the Neuromuscular Junction Motor end plate Mitochondria Schwann cell sheath Axon terminal

37 Figure (3 of 3) Anatomy of the Neuromuscular Junction Synaptic vesicle (ACh) Presynaptic membrane Synaptic cleft Postsynaptic membrane Nicotinic ACh receptors

38 Figure 11-13a Events at the Neuromuscular Junction Skeletal muscle fiber AChE Voltage-gated Ca 2+ channel Action potential ACh Ca 2+ Acetyl + choline Nicotinic receptor (a) Motor end plate Somatic motor neuron Axon terminal

39 Figure 11-13b Events at the Neuromuscular Junction K+K+ Na + K+K+ ACh Closed channel (b) Open channel

40 Questions 11-1 Cigarette Smoking Among American High School Students


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