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Autonomic and Somatic Motor Control: Efferent Division

This chapter discusses the efferent division of the nervous system, including its control over cardiac, smooth muscle, adipose tissue, and glands. It also explores the autonomic division's role in homeostasis and the coordination of autonomic responses.

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Autonomic and Somatic Motor Control: Efferent Division

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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. WHAT IS ROHHAD? • ROHHAD is an acronym for rapid-onset obesity with hypothalamic dysregulation, hypoventilation and autonomic dysregulation. • It affects the part of the nervous system that controls involuntary actions and the endocrine system. • Scientists suspect the condition is genetic but are still unsure. • The disease is incredibly rare, and less than 100 people in the world have been diagnosed with it.  • Signs and symptoms: • Dramatic weight gain over a six to 12-month period • Inability to maintain normal water balance in the body • Inability to regulate body temperature • Slow heartbeat and excessive sweating • Very shallow breathing during sleep • There is currently no cure for ROHHAD, with the average life expectancy being between five and nine, reports suggest. • Because it can affect many different parts of the body, children are often cared for by a team of healthcare providers from various fields. • The weight gain is often hard to control through exercise and diet - but keeping active helps to avoid excess from being piled on.

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

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

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

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

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

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

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

  15. Homeostasis Hypothalamus: Homeostatic Functions • Hunger, stress • Thirst: body osmolarity • Flight/fight pathways • Anger & fear • Circadian rhythms • Coordinates with endocrine system

  16. Additonal Functions of Hypothalamus • heart rate • urinary bladder contraction • blood pressure • oxytocin release • vasopressin release • corticotropin-releasing hormone release[8] • thermoregulation • panting • sweating • thyrotropin inhibition • GI stimulation • satiety • neuroendocrine control • Gonadotropin-releasing hormone (GNRH), also known as Luteinizing-hormone-releasing hormone(LHRH) • pupillary dilation • shivering

  17. 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

  18. Autonomic Effects on Cardiovascular System Heart

  19. Autonomic Effects on Blood Vessels Blood vessels

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

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

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

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

  24. 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

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

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

  27. 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

  28. 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

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

  30. 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

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

  32. 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

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

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