Chapter 14 Autonomic Nervous System
Autonomic Nervous System
• = visceral motor
–effectorssmooth muscle of organs cardiac muscle glands
•controls vital bodily functions
•autonomic = w/o consciousness
•sensory neurons ???
visceral motor
•Brain to visceral effectors
–peripheral neurons=ANS
•motor portion of visceral reflex arc
–receptorvisceral sensations
–sensory neuron
–integrationCNS
–motor neuron =ANS
–effectororgans
visceral reflexes
•visceral sensory CNS autonomic (motor)
•pupil reflexretina to iris
•blood pressurebaroceptors to vascular smooth musc medulla vasomotor centers
•heart ratemedulla cardiac centers
•respiratory rateO2, CO2 receptors to diaphragm medulla respiratory centers
•swallowmucosa topharynx musc
•cough ; sneezeresp mucosa to resp musc
•urination bladder mucosa to sphincters
•defecationrectum mucosa to sphincters
ANS = 2 neuron chain
•1st neuronpre-ganglionic axon
•cell body in spinal cord or brain
•2nd neuronpost-ganglionic axon
•cell body in autonomic ganglion
•synapse with target cells
ANS Divisions
•Sympathetic (S-ANS) Thoraco-Lumbar division
•“fight or flight”
–E’semergency excitement exercise
•Parasympathetic (P-ANS)Craniosacral division
•normal maintenance“rest and digest”
–R’srefueling removal
compare
•ParasympatheticSympathetic
•rest and digestfight or flight
•local responsewidespread (mass activation)
•cholinergic receptorsadrenergic receptors
•acetylcholinenorepinephrine
• sympathoadrenal system
ANS neurotransmitters
•parasympatheticacetylcholine
•sympathetic
–preganglionic neuronacetylcholine
–postganglionic neuronnorepinephrine
•cholinergic fibersecretes Ach
•adrenergic fibersecretes NE
•control based on secretions
•diff NT allows opposite effects on target
ANS receptors
•cholinergic receptorsfor Ach
–nicotinic receptorsexcitatory
–muscarinic receptorsexcitatory / inhibitory
•adrenergic receptorsfor NE
–alpha (α) receptorsgenerally excitatory
–beta (ß) receptorsgenerally inhibitory
•organ response based on its receptor
cholinergic receptors
•nicotinic receptorsexcitatory ligand-gated channel Na
–on somatic muscle cells
–on all ANS postganglionic neurons
•muscarinic receptorsexcitatory / inhibitory G-protein mediated K
•on most P-ANS target cells :
–heartinhibitory
–GI smooth muscleexcitatory
–digestive glandsexcitatory
•some S-ANS:
–sweat glands excitatory
–skeletal muscle blood vessel inhibitory (vasodilate)
adrenergic receptors
•alpha (α) receptorsgenerally excitatory
•systemic vasoconstriction
•sphincter constriction
•pupil dilation
•beta (ß) receptorsgenerally inhibitory
•coronary vasodilation
•systemic vasodilation
•cardiac excitatory – heart rate
•all G protein mediatedopen / close ion channel
–αCa 2nd messenger
–ßcAMP
multiple receptors allow different effects
•S-ANS response is widespreadmass activation
•requires some excitatory and inhibitory effects
•mass release of NE and epi gets varied responses :
•increase cardiac HRß1
•skin and visceral vasoconstrictα
•skeletal musc vasodilateß2
•bronchiole smooth musc relaxß2(epi > NE)
•pupil dilateα
•digestive sphincters closeα
•liverα ß
drugs
•anticholinergic :
–atropinepupil dilationmuscarinic salivary, respiratory secretions
–curareparalysisnicotinic
•anticholinesterase :
–neostigmineTX - myasthenia gravis, Alzheimer’s
•epinephrine :bronchodilation TX - asthma , anaphylaxis
•sympathomimetic :
–MAO inhibitorantidepressant
–ephedrinemucosa dilation
–nicotineS-ANS effects
•beta blockers : HR
antagonistic effects
•most organs have dual innervation
•opposite effects
•in general, Sympathetic overules Parasympathetic
parasympathetic tone
•rest and digestoverall maintenance
–refueling and removing wastes
•restores to normal, resting levels
•dominates heart rate and strength digestive smooth muscle urinary smooth muscle
sympathetic tone
•vascular smooth musclemaintain BP= vasomotor tone
•not related to fight or flight response
tissues w/ S-ANS only
•adrenal medulla
•sweat glands
•arrector pili
•kidney
temperature control
•S-ANS affectsblood vessels of skin sweat glands
•reflex:sensory receptors sensory neurons integration (hypothalamus) motor (S-ANS) effectors vasomotor tone sweat
metabolic effects of S-ANS
•increase metabolic rate
•increase blood glucosevia adrenal medulla
•stim RAS
•stim muscle spindles“nervous muscles”
brain stem control of ANS
•most direct influence
•visceral reflexes
•medulla
–cardiac and vasomotor centers
–respiratory centers
–GI activity
•pons
–respiratory center
•midbrain
–pupil reflex (oculomotor n)
higher brain control
•cortical
–thoughts
–sensory
•limbic system
–emotions
•hypothalamus
•
Sympathetic functions
•heart rate
•respiratory rate
•iris
•blood vessels - muscles
•blood vessels - skin
•sweat
•arrector pili
•digestive functions :
–blood vessels
–smooth muscle
–glands
•kidney
•adrenal medulla
–bronchioles
–coronary vessels
–liver
–cell metabolism
•sphincters
•urinary bladder
Parasympathetic functions
•heart rate
•respiratory rate
•iris
•blood vessels - muscles
•blood vessels - skin
•sweat
•arrector pili
•digestive functions :
–blood vessels
–smooth muscle
–glands
•kidney
•adrenal medulla
–bronchioles
–coronary vessels
–liver
–cell metabolism
•sphincters
•urinary bladder
what about sex ?
•erection
•ejaculation