Download autonomic nervous system

Physiology
Unit2
AUTONOMICNERVOUSSYSTEM
InPhysiologyToday
PeripheralNervousSystem
Organization
SomaticDivision
AutonomicDivision
• SingleneuronbetweenCNS
andskeletalmusclecells
• Innervatesskeletalmuscle
• Canonlyleadtomuscle
excitation
• Twoneuronsystem
betweenCNSandeffector
organs
• Innervatessmoothmuscle,
cardiacmuscle,glands
• Canbeeitherexcitatoryor
inhibitory
AutonomicNervousSystem
• 2neuronsinseries
synapsingata
ganglia
• Preganglionic
neuron
– CNStoganglion
• Postganglionic
neuron
– Gangliontoeffector
SympatheticDivision
• FightorFlightresponse
• Increasesactivityunderconditionsofphysicalor
physiologicalstress
• Allresourcesforphysicalexertionareactivated
– HRincreases
– BPincreases
– Bloodflowtoskeletalmuscles,heartandbrain
increases
– Liverreleasesglucose
– Pupilsdilate
– GItractactivityisdampened
– Bloodflowtotheskinisreduced
SympatheticDivision
ThoracolumbarDivision
• Sympatheticneuronsexit
theCNSfromthethoracic
andlumbarregionsofthe
spinalcord
• Gangliaarrangedasthe
sympathetictrunks
– Closetothespinalcord
– 2chainsoneithersideof
thespinalcord
ParasympatheticDivision
• Restanddigestresponse
• Homeostaticfunctionsarepredominant
ParasympatheticDivision
CraniosacralDivision
• Preganglionicneurons
exittheCNSfromthe
brainstemandsacral
regionsofthespinal
cord
• Parasympatheticganglia
liewithinorveryclose
totheeffectororgans
thatthepostganglionic
neuronsinnervate
ActivationPatternsoftheDivisions
• SympatheticDivision
– Moredivergenceofpreganglionicneurons
– Tendstorespondasasingleunit
– Increasedsympatheticactivitytendstooccur
bodywide
• ParasympatheticDivision
– Lessdivergenceofpreganglionicneurons
– Specificorgansareactivatedinapatternthatis
dependentoneachphysiologicalresponse
NeurotransmittersoftheANS
• PreganglionicneuronsreleaseACh
• Postganglionicneurons
– SympatheticdivisionreleaseNE
– ParasympatheticdivisionreleaseACh
• Cotransmittersreleasedbypreganglionicneurons
withtheprimaryneurotransmitteratmany
autonomicganglia
– ATP,dopamine,neuropeptides
• Postganglionicneurons
– Nitrousoxideforsmoothmuscledilation
AdrenalMedulla
• Postganglionicneuronsthatinnervatethe
adrenalmedulladonotdevelopaxons
• Theformtheendocrinegland,theadrenal
medulla
• Onceactivatedbythesympathetic
preganglionicneuron,thecellsoftheadrenal
medullarelease80%Epi,20%NEintothe
blood
TransmittersofthePeripheralNervous
System
DualInnervation
• Theheart,manyglandsandsmoothmuscle
areinnervatedbybothdivisionsoftheANS
• Opposingeffects
• Divisionsareusuallyactivatedreciprocally
– Sympatheticactivityincreases
– Parasympatheticactivitydecreases
– Visversa
• Providesprecisecontroloftheeffector
CooperativeControl
• BothdivisionsoftheANS
operatetogether
• Autonomicresponses
resultfromtheregulated
interactionsofboththe
parasymapathetic and
sympatheticdivisions
• Autonomicresponses
usuallyoccurwithout
awarenessorconscious
control(autonomous)