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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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