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autonomic nervous system.docx

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Biological Sciences
Kenneth Welch

The Autonomic Nervous System and Higher Order Functions An Overview of the ANS ANS • Coordinates cardiovascular, respiratory, digestive, urinary and reproductive functions • Preganglionic neurons in the CNS send axons to synapse on ganglionic neurons in autonomic ganglia outside the CNS Divisions of the ANS • Sympathetic division (thoracolumbar, “fight or flight”) • Thoracic and lumbar segments • Parasympathetic division (craniosacral, “rest and repose”) • Preganglionic fibers leaving the brain and sacral segments The Sympathetic Division Sympathetic division anatomy • Preganglionic neurons between segments T1 and L2 • Ganglionic neurons in ganglia near vertebral column • Specialized neurons in adrenal glands Sympathetic ganglia • Sympathetic chain ganglia (paravertebral ganglia) • Collateral ganglia (prevertebral ganglia) Organization and anatomy of the sympathetic division • Segments T1-L2, ventral roots give rise to myelinated white ramus • Leads to sympathetic chain ganglia Postganglionic fibers • Rejoin spinal nerves and reach their destination by way of the dorsal and ventral rami • Those targeting structures in the thoracic cavity form sympathetic nerves • Go directly to their destination Abdominopelvic viscera • Sympathetic innervation via preganglionic fibers that synapse within collateral ganglia • Splanchic nerves Abdominopelvic viscera • Celiac ganglion • Innervates stomach, liver, gall bladder, pancreas, spleen • Superior mesenteric ganglion • Innervates small intestine and initial portion of large intestine • Inferior mesenteric ganglion • Innervates kidney, urinary bladder, sex organs, and final portion of large intestine Sympathetic activation • In crises, the entire sympathetic division responds • Sympathetic activation • Affects include increased alertness, energy and euphoria, increased cardiovascular and respiratory activities, elevation in muscle tone, mobilization of energy resources Neurotransmitters and sympathetic function • Stimulation of sympathetic division has two distinct results • Release of ACh or NE at specific locations • Secretion of E and NE into general circulation • Most postganglionic fibers are adrenergic, a few are cholinergic or nitroxidergic • Two types of receptors are alpha receptors and beta receptors • Sympathetic ganglionic neurons end in telodendria studded with varicosities filled with neurotransmitter The Parasympathetic Division Parasympathetic division • Preganglionic neurons in the brainstem and sacral segments of spinal cord • Ganglionic neurons in peripheral ganglia located within or near target organs Organization and anatomy of the parasympathetic division • Preganglionic fibers leave the brain as cranial nerves III, VI, IX, X • Sacral neurons form the pelvic nerves Parasympathetic activation • Effects produced by the p
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