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Autonomic and Somatic Motor Control: Efferent Division in Chapter 11

This chapter explores the efferent division of the nervous system, including the autonomic and somatic motor control. It covers the pathways, receptors, neurotransmitters, and the antagonistic controls of the sympathetic and parasympathetic systems. The chapter also discusses the CNS control of skeletal muscles through neuromuscular junctions.

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Autonomic and Somatic Motor Control: Efferent Division in Chapter 11

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  1. Chapter 11 Efferent Division: Autonomic and Somatic Motor Control

  2. 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

  3. Autonomic Division: Homeostatic balancing • Controls • Smooth & cardiac muscle • Glands & adipose • Antagonistic branches • Parasympathetic • "Rest & digest" • Restore body • Sympathetic • "Fight or flight" • Energetic action

  4. Autonomic Division: Homeostatic balancing Figure 11-1: Homeostasis and the autonomic division

  5. Autonomic Control Centers • Hypothalamus • Water balance • Temperature • Hunger • Pons • Respiration • Cardiac • Vasoconstriction • Medulla • Respiration Figure 11-3: Autonomic control centers in the brain

  6. Autonomic Pathways: Communicate to Body • Coordinates homeostatic responses • Autonomic • Endocrine • Behavioral • Blood pressure • Osmolarity • Tonic regulation • Antagonistic control • Receptor directed response

  7. Autonomic Pathways: Communicate to Body Figure 11-2: The hypothalamus and brain stem initiate autonomic, endocrine, and behavioral responses

  8. Autonomic Pathways: Two Efferent Neurons • CNS • Preganglionic neuron • Ganglion • Postganglionic neuron • Target tissue Figure 11-4: Autonomic pathways

  9. Comparison of sympathetic and Parasympathetic Pathways • Neurotransmitters • Receptors Figure 11-7: Sympathetic and parasympathetic pathways

  10. Parasympathetic Branch: “Rest and Digest” • Preganglionic neurons • Originate in • Brain stem • Lower cord • NT: cholinergic • Ganglion • Near target • Nicotinic receptors • Postganglionic neuron

  11. Figure 11-5: Autonomic sympathetic and parasympathetic pathways

  12. Actions of Parasympathetic Branch • Constricts • Pupil • Bronchioles • Slows heart • Stimulates • Digestion • Insulin release • Urination • Erections

  13. Sympathetic Branch: “Fight or Flight” • Preganglionic neuron • Short • Origin: spinal cord • NT: cholinergic • Ganglia • Sympathetic chain • Near spinal cord • Postganglionic neuron • Long • NT: adrenergic

  14. Autonomic Reflexes: “visceral reflexes” Figure 13-2: Autonomic reflexes

  15. 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

  16. Autonomic Effects on Cardiovascular System Heart

  17. Autonomic Effects on Blood Vessels Blood vessels

  18. Stimulatory Actions of Sympathetic Branch • Pupil dilation • Salivation • Heart beat & volume • Dilation • Blood vessels • Bronchioles • Catecholamine release • Fat breakdown • Ejaculation

  19. Inhibitory Actions of Sympathetic Branch • Digestion • Pancreas secretion • Urination

  20. Adrenal Medulla: A Modified Sympathetic Ganglion • Sympathetic stimulation • Catecholamine release to blood • Epinephrine • Norepinephrine • Travel to: • Multiple targets • Distant targets

  21. Adrenal Medulla: A Modified Sympathetic Ganglion Figure 11-10: The adrenal medulla

  22. 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

  23. Mechanism: Norepinephrine Release and Recycling Figure 11-9: Norepinephrine release at a varicosity of a sympathetic neuron

  24. Review of Efferent Pathways: Motor & Autonomic Figure 11-11: Summary of efferent pathways

  25. Somatic Motor Division: Controls Skeletal Muscles • Body movement • Appendages • Locomotion • Single neuron • CNS origin • Myelinated • Terminus • Branches • Neuromuscular junction Figure 11-11: Summary of efferent pathways

  26. 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

  27. Neuronmuscular Junction: Overview Figure 11-12: Anatomy of the neuromuscular junction

  28. 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

  29. Neuronmuscular Junction: Mechanism of Signal Conduction Figure 11-13: Events at the neuromuscular junction

  30. 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

  31. Summary • Efferent motor neurons control skeletal muscles • Single long myelinated neuron from CNS • Neuromuscular junction structure & mechanism

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