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8/14/2019 Autonomic Nervous System, Lect 5
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DefinitionDefinitionThe portion of The portion of
nervous system nervous system
controls most visccontrols most viscfunctions of the bodfunctions of the bod
called thecalled the autonoautono
nervous s stem ANS .nervous s stem ANS .15:23 [email protected]
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DefinitionDefinition
Or it is the motor nervoOr it is the motor nervo
system that controlssystem that controls
glands, cardiac muscleglands, cardiac muscleand smooth muscle.and smooth muscle.
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DefinitionDefinition
It is also called the viscIt is also called the visce
motor system tomotor system to
distinguish it from thedistinguish it from thesomatic motor system somatic motor system
controls the skeletalcontrols the skeletal
muscles.muscles.15:23 [email protected]
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The primary target orgThe primary target org
of the ANSof the ANS
The viscera of the thoraThe viscera of the thoracand abdominal cavities aand abdominal cavities asome structures of the bsome structures of the b
wall, including cutaneouwall, including cutaneoublood vessels, sweat glablood vessels, sweat glaand piloerector muscles.and piloerector muscles.
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ControlControl
Autonomic literallAutonomic literallmeans self-means self-
governed..governed..TheThe ANS usually carries out itANS usually carries out itactions involuntarily, withoutactions involuntarily, withoutconscious intent or awarenesconscious intent or awarenes
contrast to the voluntary natcontrast to the voluntary nat15:23 [email protected]
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ControlControlThis voluntary involuntary distincThis voluntary involuntary distinc
not, however, as clear-cut as it onot, however, as clear-cut as it o
seemed. Some skeletal muscleseemed. Some skeletal muscle
responses are quite involuntary,responses are quite involuntary,as the somatic reflexes, and somas the somatic reflexes, and som
skeletal muscles are difficult orskeletal muscles are difficult or
impossible to control, such as thimpossible to control, such as th
middle-ear muscles.middle-ear muscles.15:23 [email protected]
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ControlControlOn the other hand,On the other hand,
therapeutic uses oftherapeutic uses of
biofeedback show that sobiofeedback show that so
people can learn topeople can learn to
voluntarily control suchvoluntarily control such
visceral functions as bloovisceral functions as bloo15:23 [email protected]
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Visceral effectorVisceral effector
Visceral effectors do noVisceral effectors do no
depend on the ANS todepend on the ANS to
function, but only tofunction, but only toadjust their activity to adjust their activity to
bodys changing needsbodys changing needs15:23 [email protected]
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Visceral effectorVisceral effector
The heart, for example, gThe heart, for example, gon beating even if allon beating even if allautonomic nerves to it aautonomic nerves to it a
severed, but the ANSsevered, but the ANSmodulates (adjusts) themodulates (adjusts) theheart rate in conditions oheart rate in conditions o
rest or exercise.rest or exercise.15:23 [email protected]
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Visceral effectorVisceral effector
If the somatic nerves toIf the somatic nerves to
skeletal muscle areskeletal muscle are
severed, the musclesevered, the muscleexhibits flaccid paralysexhibits flaccid paralys
it no longer functions.it no longer functions.15:23 [email protected]
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Visceral effectorVisceral effector
But if the autonomic neBut if the autonomic ne
to cardiac or smoothto cardiac or smooth
muscle are severed, thmuscle are severed, thmuscle exhibitsmuscle exhibits
exaggerated responseexaggerated responses
denervationdenervation15:23 [email protected]
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striking characteristics
the ANSThe rapidity and intensity.For instance,Within 3 to 5 seconds it can increase the heart
twice normal.Within 10 to 15 seconds the arterial pressure c
doubled.The arterial pressure can be decreased low en
within 10 to 15 seconds to cause fainting. Sweating can begin within seconds, and the ur
bladder may empty involuntarily, also within s15:23 [email protected]
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General OrganizationGeneral Organization
the ANSthe ANSThe autonomic nervous system is ACTIVACTIVmainly by centers located in the spinaspinabrain stem, and hypothalamus.brain stem, and hypothalamus.
Also, portions of the cerebral cortex, esp
of the limbic cortexlimbic cortex, can transmit signthe lower centers and in this way influeautonomic control.
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General OrganizationGeneral Organization
the ANSthe ANSThe autonomic nervous system also oftoperates by means ofVISCERAL REFLVISCERAL REFLThat is, subconscious sensory signa
from a visceral organ can enter the
autonomic ganglia, the brain stem,the hypothalamus and then returnsubconscious reflex responses direback to the visceral organ to contr
activities.15:23 [email protected]
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General OrganizationGeneral Organization
the ANSthe ANSThe EFFERENTEFFERENT autonomic signals aretransmitted to the various organs of thethrough two major subdivisions called
The sympathetic nervoussympathetic nervoussystem.system.
Theparasympathetic nerparasympathetic ner
systemsystem15:23 [email protected]
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Physiologic Anatomy of thePhysiologic Anatomy of the
Sympathetic NSSympathetic NS
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Each sympathetic pathwaysympathetic pathway frocord to the stimulated tissue iscomposed oftwo neuronstwo neurons, a
preganglionic neuron and apreganglionic neuron and apostganglionic neuronpostganglionic neuron, in conto only a single neuron in the sk
motor pathway15:23 [email protected]
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Physiologic Anatomy of thPhysiologic Anatomy of th
Parasympathetic Nervous SyParasympathetic Nervous Sy
Parasympathetic fibers leave the Cthrough cranial nerves III, VII, IX, andIII, VII, IX, and
Additional parasympathetic fibers lethe lowermost part of the spinal cord th
the second and third sacral spinalsecond and third sacral spinal nand occasionally the first and fourth sanerves.
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Physiologic Anatomy of thPhysiologic Anatomy of th
Parasympathetic Nervous SyParasympathetic Nervous Sy
About 75 per cent of allparasympathetic nerve fibers arthe vagus nervesvagus nerves (cranial nervpassing to the entire thoracic anabdominal regions of the body.
Therefore, a physiologist speakinthe parasympathetic nervous sy
often thinks mainly of the two v15:23 [email protected]
i i
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Neurotransmitters in tNeurotransmitters in t
ANSANSSympathetic NS
Preganglionic neuron neurotransmitter: Ach
Postganglionic neuron neurotransmitter:
Norepinephrine, Epinephrine
Parasympathetic NS
Preganglionic neuron neurotransmitter: Ach
Postganglionic neuron neurotransmitter: Ach
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SympathSympath
Nervous SNervous S
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ParasympaParasympa
Nervous SNervous S
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Comparison of Somatic andComparison of Somatic and
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Comparison ofComparison of
Sympathetic and ParasympathetSympathetic and Parasympathet
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Effects of Sympathetic anEffects of Sympathetic an
Parasympathetic NSParasympathetic NS
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ff f h i
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Effects of Sympathetic anEffects of Sympathetic an
Parasympathetic NSParasympathetic NS
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Eff f S h i
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Effects of Sympathetic anEffects of Sympathetic an
Parasympathetic NSParasympathetic NS
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ff f S h iEff t f S th ti
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Effects of Sympathetic anEffects of Sympathetic an
Parasympathetic NSParasympathetic NS
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