C utilized neurotransmitters and their effects

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c.Utilized neurotransmitters and their effects =acetylcholineisreleased in the synaptic cleft (neuromuscular junction) where it alwaysexcites orstimulatesthe fibers to contract.d.Amount of myelination = neurons arehighly myelinated2.Characteristics of the Autonomic Nervous Systema.Effectors or target organs =cardiac muscle, smooth muscle, andglands
b.Effector pathways and ganglia = the motor unit of the ANS is atwoneuron chaini.The cell body of the first neuron (preganglionic neuron) residesin the brain or spinal cord.ii.Its axon, thepreganglionic axon, synapses with the secondmotor neuron called thepostganglionic neuronin and autonomicganglion outside the CNS.iii.The axon of the postganglionic neuron (postganglionic axon)extends to the effector organ.c.Utilized neurotransmitters and their effectsi.The preganglionic neurons always use acetylcholine but thepostganglionic neurons use either acetylcholine or adrenaline.ii.Norepinephrine (NE) and epinephrine= effect varies accordingto target tissues; can bestimulatory or inhibitoryiii.Acetylcholine= again effect varies according to target tissues;can bestimulatory or inhibitoryd.Amount of myelination = preganglionic neurons arelightlymyelinatedwhile postganglionic neurons areunmyelinated.C.Now let’s consider the two divisions of the autonomic nervous system1.Sympathetic (fight or flight) or Parasympathetic (rest and digest OR feedand breed)2.Action via the ANS is by dual innervations, in other words the two divisionscounterbalance each other’s activities in an attempt to maintain homeostasis.3.These two divisions are separated on the basis or three characteristics:a.Origin of the fibersi.Parasympathetic=fibers originate in thecranial and sacralregionsof the spinal cord.ii.Sympathetic=fibers originate in thethoracic and lumbarregionsof the spinal cord.b.The relative lengths of their fibersi.Parasympathetic=long preganglionic and short postganglionicfibersii.Sympathetic=short preganglionic fibers and longpostganglionic fibersc.The location of their gangliai.Parasympathetic=located in the visceral effector organ or nearitii.Sympathetic=located near the spinal cord in a chain of gangliacalled the sympathetic trunkd.Nicknames:i.Parasympathetic = “feed and breed” or “rest and digest” or bythe three Ds:Digestion, Defecation, and Diuresis
ii.Sympathetic = “fight or flight” and by the 4 Es:excitement,emergency, embarrassment, and exercisee.Neurotransmitteri.Parasympathetic = utilizesacetylcholineat both synapses.ii.Sympathetic = utilizesacetylcholinein the first synapse butEpinephrine or NEat the second synapseI.Parasympathetic Nervous SystemA.Also called theCraniosacral Divisionbecause of the origin of the nerves.B.CRANIAL OUTFLOWA.OculomotorNerve(III)1.Innervate smooth muscles in the eyes that cause the pupils to constrict andthe lenses to bulge (focusing on close objects).

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Term
Spring
Professor
ALSTON
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