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Autonomic Nervous System

Autonomic Nervous System. Biology 2121 Chapter 14. Introduction. The Autonomic Nervous System Motor neurons that innervates smooth and cardiac muscle and glands ( effector organs) Responds to changing conditions within the body Divisions (1). Parasympathetic

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Autonomic Nervous System

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  1. Autonomic Nervous System Biology 2121 Chapter 14

  2. Introduction • The AutonomicNervousSystem • Motor neurons that innervates smooth and cardiac muscle and glands (effector organs) • Responds to changing conditions within the body • Divisions • (1). Parasympathetic • Conserves energy; BP and heart rates normal; GI tract contains appropriate blood supplies for digestion of food; pupils constricted; normal saliva output; bronchioles constricted. • (2). Sympathetic • Increased heart rate, BV constriction, increases blood glucose levels; shunting of blood from digestive organs to the skeletal muscles and heart; pupils are dilated; increased nasal, gastric, lacrimal gland secretions; increased sweat gland activity; vasodilation of BVs; bronchioles dilated. • ‘DuelInnervation’

  3. Parasympathetic and Sympathetic Interactions • (1). AntagonisticInteractions • Vasomotor Tone • Heart; Respiratory and Gastrointestinal organs • See table 14.5 • (2). CooperativeInteractions • PS stimulation – erection (vasodilation of BVs) • S stimulation – ejaculation or orgasim • See table 14.5

  4. Knowthefollowing: Eye (iris and ciliary muscle); Glands; Salivary and Sweat Glands; Lungs; Heart Muscle; Arrectorpili; Coronary Blood Vessels; Bladder

  5. Unique Roles of the Sympathetic System • (1). Thermoregulatory • Body experiences heat, sympathetic nerves cause vasodialation (activates sweat glands) • (2). Renin • Sympathetic impulses cause renin to be released (kidneys) • Enzyme increases BP • (3). Metabolic • Increases metabolic rate of cells; raises blood glucose; allows for cells to use fats or lipids as fuels

  6. Somatic vs ANS Fibers (1). Preganglionic neuron vs Postganglionic neuron (2). Somatic Neurons – one neuron chain (3). ANSneurons– two neuron chain

  7. Somatic vs ANS

  8. The Adrenal Medulla • Some sympathetic preganglion axons release ACh to stimulate the adrenal glands to release Epinenphrine and Norepinephrine. • Norepinephrine is converted into epinephrine. • These NTs reinforce the ‘sympathetic response’ • Increased heart rate, BV constriction, increases blood glucose levels; shunting of blood from digestive organs to the skeletal muscles and heart.

  9. Neurotransmitters and Receptors • (1). FibersthatreleaseACh– ‘cholinergic fibers’ • Nicotinic receptors: skeletal muscle cells; adrenal medulla cells; all ganglionic neurons (S and PS) • Always stimulatory! • Muscarinic receptors: all parasympathetic organs. (only sympathetic targets are eccrine sweat glands and BVs of skeletal muscles • Mostly stimulatory ; some inhibitory • (2). FibersthatreleaseNE– ‘adrenergic fibers’ • Betareceptors: • increase heart rate; • inhibitory (dilates BVs and bronchioles); • relaxes smooth muscle walls of digestive and Urinary organs • Relaxes the uterus ; stimulates lipolysis • Alphareceptors • Constricts BVs and visceral organ sphincters • Dilates pupils; inhibits insulin secretion; helps blood clotting

  10. Neurotransmitters and Receptors

  11. Parasympathetic Division (Craniosacral)

  12. Sacral Division • Serve the lower organs • Reproductive • Bladder and ureters

  13. Sympathetic Division

  14. Sympathetic Division • (1). Cell bodies of preganglionic neurons – T1toL2 • (2). LateralHorn– Visceral Motor Zones • (3). Post-Spinal Cord

  15. Sympathetic Pathway

  16. Sympathetic Division • (4). Preganlionicfiberstakingpathway#3 • Form the splanchnic nerves (synapse in the collateral ganglia • Not apart of the ‘trunk glanglia’ • (5). Synapseinthetrunkganglia • As preganglionic neurons enter the ganglia via the ‘gray ramicommunicantes’ • They synapse and then the postganglionic neuron continues to the effector • White rami found in T1 – L2 only!

  17. Splanchnic Nerves • (1). Pre-ganglionicaxonsthat do not synapse in the sympathetic chain ganglia • Form Splanchnic Nerves • (2). LumbarSplanchnicNerves • Distal large intestine, rectum, genitals, bladder • (3). GreaterSplanchnicNerve • Kidney, adrenal, spleen, stomach, liver, upper small intestine and gall bladder • (4). LesserSplanchnicNerve • Small intestine

  18. Specific Pathways • T1-T4 (Head) • Synapse in superior cervical ganglia • Enter CN 1-3 • Skin; BVs; dilator muscles of iris; inhibits salivary and nasal glands; smooth muscles of eye; direct service to heart • T1-T6 (Thorax) • Synapse in middle and inferior cervical ganglia; enter CNs 4-8 • Heart via cardiac plexus • Thyroid; skin; esophagus

  19. Specific Pathways – Collateral Ganglia • T5-L2 will bypass chain ganglia and synapse in the collateral ganglia • Form ‘splanchnic’ nerves • Greater, lesser, lumbar and sacral • Splanchnicnervesform plexuses • 1. Greater ------ celiac and superior mesenteric • 2. Lesser --------- Aortic plexus • 3. Lumbar -------- Inferior mesenteric and hypogastric

  20. Specific Pathways – Collateral Ganglia • T5-L2 • serve the abdomen • Stomach; intestine; liver; spleen; kidneys • T10–L2 • Distal large intestine; urinary bladder; reproductive organs • Sympathetic fibers mostly play inhibitory role with these organs

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