12.ANS..pdf - BIOL 2401 Autonomic Nervous System: Page |1...

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B I O L 2 4 0 1A u t o n o m i c N e r v o u s S y s t e m : P a g e | 11General CharacteristicsA.Regulates the activity of smooth muscle, cardiac muscle and glandsa.Underinvoluntarycontrolb.two main componentsi.general visceralsensory(afferent) neuronsii.general visceralmotor(efferent) neurons1.sympatheticdivisiona.excitation(increased activity) of gland or organ2.parasympatheticdivisiona.inhibition(decreased activity) of gland or organB.Organizationa.sensory input (afferent neurons)i.special sensesii.general somatic sensesiii.general visceral senses (from interoreceptor)b.integration center: Hypothalamus, brainstem, spinal cordc.Motor output (efferent neuron)i.two-neuron pathway (ligand gated synapse)1.1stneuron = preganglionic(presynaptic)a.Releases neurotransmitteri.Directly from cranial nervesii.From spinal cord as1.preganglionic neuron2.autonomic ganglia2.2ndneuron = postganglionic(postsynaptic)a.Receives neurotransmitteri.To Effector gland or muscleAnatomy of autonomic motor pathwaysA.originsa.sympathetici.known asthoracolumbar division1.cell bodies locationa.Thoraco= lateral gray horns of the12 thoracic vertebraeb.Lumbar=first 2 or 3 lumbarsegments of spinal cordb.Parasympathetici.known ascraniosacral division1.cell bodies locationa.Cranio= nuclei of four pairs of cranial nervesb.Sacral=2nd through 4th sacral segmentsof spinal cordB.preganglionic neuronsa.sympathetici.myelinatedneurons pass out oflateral grey horn of thoracic and lumbar spinal cord1.separates from spinal cord and to synapse with postganglionic neurons in sympathetictrunk gangliaa.Fibers shortdue to nearness of sympathetic trunk gangliab.parasympathetici.myelinatedneurons pass out ofcranial nerves III, VII, IX, Xand2 to 4 sacral spinal cord1.extend from CN and spinal segment directly to target organa.fibers longbecause they travel to postganglionic neuron in target organ
B I O L 2 4 0 1A u t o n o m i c N e r v o u s S y s t e m : P a g e | 22C.Postganglionic neuronsa.sympathetic pathwaysi.Synapsein chain ganglia1.Spinal nerve pathwaya.Synapsedirectlyat same leveli.to integument structures in neck torso and limbs2.

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Term
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sympathetic trunk

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