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Autonomic Nervous System

Autonomic Nervous System. Sympathetic and Parasympathetic. What is the Autonomic NS?. Visceral motor control Regulation of the “housekeeping” functions of the body Dual innervation Exceptions are sweat glands and smooth muscles of blood vessels - SYMPATHETIC ONLY Antagonistic control

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Autonomic Nervous System

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  1. Autonomic Nervous System Sympathetic and Parasympathetic

  2. What is the Autonomic NS? • Visceral motor control • Regulation of the “housekeeping” functions of the body • Dual innervation • Exceptions are sweat glands and smooth muscles of blood vessels - SYMPATHETIC ONLY • Antagonistic control • One branch is excitatory (sympathetic), the other is inhibitory (parasympathetic) • Regulation of: • Body temperature • Coordination of cardiovascular, respiratory, digestive, excretory, and reproductive systems • Adjusts internal water, electrolyte, nutrient, and gas concentrations in body fluid

  3. Divisions of the ANS

  4. Divisions of the ANS

  5. Neuron pathways in the ANS • In both the Sympathetic and Parasympathetic divisions the impulse travels in a TWO neuron “relay” • Synapse between the two neurons occurs in autonomic ganglia • The location of this ganglia varies depending on which branch of the ANS you are dealing with

  6. ANS Comparison

  7. Parasympathetic pathway

  8. Parasympathetic • Preganglionic neurons in the brain stem and sacral spine • Axons of brain stem neurons travel via cranial nerves III, VII, IX, and X to ganglia and target organs • Axons of sacral neurons travel in the pelvic nerves to ganglia (intramural) in target organs • Kidney, bladder,terminal regions of the large intestine, and the sex organs

  9. Parasympathetic functions • Constriction of pupils • Secretion of digestive glands • Increased smooth muscle activity along digestive tract • Stimulation of defecation • Bladder contraction during urination • Constriction of respiratory pathways • Reduction in heart rate and contraction force • Sexual arousal and stimulation in both sexes

  10. Parasympathetic ganglia • Ganglionic neurons are located very close or even within the target organs • These ganglia are called either • Terminal ganglia – near the target organ • Intramural ganglia – within the target organ

  11. Sympathetic pathway

  12. Sympathetic Division • Preganglionic neurons are located in the lateral grey horns of the spinal cord between T1 – L2 • Axons from these neurons exit via the ventral root from the spinal cord heading toward a synapse with second neuron in the relay - the ganglionic neurons • Ganglionic neurons are found in either the • 1. sympathetic chain ganglia near the spinal cord (paravertebral ganglia) or • 2. collateral ganglia (prevertebral ganglia) that are anterior to the spinal cord

  13. Sympathetic Functions • 1. Increased alertness • 2. Feeling of energy and euphoria, often associated with disregard for danger and insensitivity to pain • 3. Increased activity in cardiovascular and respiratory centers – leads to increased blood pressure, heart rate, breathing rate • 4. Elevation of muscle tone – person looks tense • 5. Mobilization of energy reserves

  14. Sympathetic postganglionic fibers

  15. Sympathetic pathways

  16. Sympathetic - collateral ganglia

  17. White and Gray Ramus • Ramus means branch • White ramus is a branch off the spinal nerve that carries myelinated (white) axons into the sympathetic chain ganglia • Gray ramus carries unmyelinated (gray) axons out of the ganglia to target organs

  18. Collateral ganglia • Synapse of preganglionic fibers that regulate activities of abdominopelvic viscera • Neurons originate in the inferior thoracic and superior lumbar spine • Axons from the neurons pass through the sympathetic chain DO NOT SYNAPSE, exit and form the greater, lesser, lumbar, and sacral SPLANCHNIC (visceral) nerves • These nerves travel to the collateral ganglia

  19. Collateral or Prevertebral Ganglia • These ganglia are different than the sympathetic chain ganglia • 1. Single structures, not paired • 2. Located anterior to the vertebral column (that’s why there are called prevertebral) • 3. Only located in the abdominopelvic cavity

  20. Collateral ganglia • CELIAC ganglia – innervate stomach, duodenum, liver, gallbladder, pancreas, and spleen • SUPERIOR MESENTERIC GANGLIA – small intestine and first part of the large intestine • INFERIOR MESENTERIC GANGLIA – large intestine, kidney, bladder, and sex organs

  21. Collateral ganglia

  22. Adrenal medulla • Center of adrenal gland, the medulla, contains neurons that are stimulated by the sympathetic NS • Stimulation of the adrenal medulla causes the release of epinephrine (adrenaline) and norepinephrine

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