ANS part 2 Flashcards
length efferent fibers parasympathetic vs sympathetic
paraysympathetic preganglionic long post ganglionic short sympathetic preganglionc short post ganglionic long
types of innervation parasympathetic vs sympathetic
parasympathetic- discrete symapthetic- diffuse
neurotransmitters parasympathetic vs sympathetic
parasympathetic ganglia- acetycholine neuroeffector junctions- acetylcholine sympathetic ganglia- acetycholine neuroeffector junctions- norepinephrine (except sweat glands, vasodilators in skeletal muscle and adrenal medulla)
receptors parasympathetic vs sympathetic
parasympathetic ganglia- nicotinic cholinergic neuroeffector junecionts- muscarinic cholinergic sympathetic ganglia- nicotina cholinergic neuroeffector junctions- adrenergic
effector organ responess
- response post ganglionic release transmitter can be excitatory or inhibitory; response is tissue specific - in most organ systems both divisions (symp and parasympathetic) exert tonic action holding effectors in state of intermediate activity
post junctional excitation
- leads to increased force and/or frequency of muscle contraction, increase secretion in glands
examples post junctional excitation
- sympathetic adrenergic innervation -> contraction vascular smooth muscle - parasympathetic cholinergic receptors stimulation contraction GI smooth muscle
post junctional inhibition
- post junctional inhibition, decreasing contraction, secretion ect.
examples post junctional inhibition
- parasympathetic cholinergic innervation -> decreased freqnecy of contraction of cardiac muscles - sympathetic adrenergic innervation -> relaxation GI smooth muscle
parasympathetic nervous system effects
- discrete and selective - important for vegetative functions and maintenance of status quo, acts to conserve and restore energy; rest and digest - its innervation to some organs is essential for life
parasympathetic nervous system dual innervation predominant tone
parasympathetic
parasympathetic nervous system examples of responses
- decrease heart rate - decrease blood pressure - increase GI motility and secretions - increase absorption or nutrients - increase excretory functions - increase salivary section - constriction of bronchioles - miosis
sympathetic nervous system effects
- generally diffuse and nonselective system usually discharges as unit (some selectivity in organs like heart and blood vessels) - important for survival during stress (flight or flight)
body survival without SNS?
- body can survive w/o SNS but some protective functions will be lost
examples of responses from SNS
- increase heart rate - increase blood pressure - increase blood flow to skeletal muscle - decrease blood flow to skin and splanchnic bed - increase blood glucose - dilation of bronchioles - mydriasis
interactions between parasympathetic and sympathetic systems
- most organs have dual innervation - opposing effects - complementary effects - no interaction
what organ does NOT have dual innervation for parasympathetic and sympathetic NS
blood vessels which only receive sympathetic innervation
opposing effects interaction between paraysympathetic and sympathetic systems
- most common balanced antagonism (ex heart and bladder) - most system may heavily predominate (ex. in GI tract parasympathetic)
complementary effects interaction between parasympathetic and sympathetic systems
- ex. in salivary gland PNS stimualtes watery secretion and SNS stimulates viscous secretion - ex. in male genitalia PNS mediates errection SNS mediates ejaculation (point and shoot)
no interaction interaction between parasympathetic and sympathetic systems
- organ innervated selectively by one system (ex blood vessels)
Sites for drug action in ANS
- cerebral cortex (high CNS centers) - lower brain centers and medullary centers - autonomic afferents - autonomic eferents - effector organ
autonomic efferents drug action site ANS
-autonomic ganglia- not selectivity for symp or parasympathetic ganglia but more symp post gang gibers than parasympathetic fibers so predominant response to stimulation at ganglia = sympathetic - neuroeffector junction
effector organ drug action site ANS
- ANS not directly involved - interference with effector function (ex. cardiac glycosides, calcium channel antagonists)
Major considerations in predicting drug action
- pharmacokinetics of drug - mechanism of action of drug - type of receptor/ response altered - effect of stimulation or inhibition of particular receptor on organ - regulation of “normal tone” of organ - Reflex compensation
drug actions at synapse and neuroeffector junction
- agonists or mimetic drugs - antagonists or lytic drugs
agonists or mimetic drugs
- directly acting - indirectly acting
directly aging
effect mediated by direct activation of receptor
indirectly acting
- effect mediated through increased concentration transmitter at receptors by inducing release transmitter from terminal or inhibiting inactivation of transmitter
inhibiting inactivation of transmitter
can be by inhibiting reuptake or of inactivating enzymes
indirectly acting effect can reflect
binding to an allosteric site on receptor which potentiates transmitter action
antagonists or lytic drugs
- competitive antagonists - non-completive/ allosteric antagonists - antagonist at nerve terminal
competitive antagonists
- drugs block receptor activation by occupying agonist binding site preventing transmitter or mimetic drug from interacting with receptor
noncompetitive/ allosteric antagonists
- drugs block receptor activation by binding to site separate from agonist binding site therefore preventing transmitter or mimetic drug from interacting with or activating the receptor
antagonist at nerve terminal
effect mediated through reduced concentration of transmitter at receptor which can be via - inhibition of synthesis of transmitter (by inhibition of uptake of substrate, by interference with synthetic steps, by causing synthesis of “false transmitter” - depletion of transmitter - inhibition of release of transmitter
Heart will beat w/o
autonomic innervation
blood vessels and heart are exception to
they are regulated by sympathetic system and this is exception to fight/ flight bc while this is fight/ flight its tight/ discrete regulation
ANS basically
who = peripheral affects everyone
skeletal muscle primarily effected by
hormone epinephrine these= entities to diff organ systems with diff drugs
tone
parasympathetic and sympathetic = both firing at same level all the time
acetylcholine with ligand gated ion channel opposing it what happens if block these
loose all parasympathetic and sympathetic tone and die
neuroeffector junction follows pattern of
somatic innervation to muscle; innervation by efferents lands on organ system (must. contacts between nerve and innervated organ)
some cholinergic neuroeffector junctions but generally
norepinephrine NT for symp division
nicotinic
nerve to nerve open and depolarize post ganglionic cell and skeletal muscle = not related to muscarinic Its at neuromuscular junctions but both use acetylcholine
muscarinic
GPCRs at NEJs
Adrenergic receptors
norepinephrine NT
AP ->
Ca2+ flow in -> fusion -> NT release b/c vesicle fusion
inactivation of transimitter by reuptake or metabolic alteration
- adrenergic= reuptake
neg feedback controls
how much transmitter release
horse
- adrenergic not cholinergic sweater
adrenal medulla is
ganglia
norepinephrine can be
excitatory or inhibitory depends on organ
vagal tone driven by what system
parasympathetic on heart; increase heart rate if decrease w/ drug HR lead to increase (atropine)
heart / blood vessels =
regulated minute to minute
balanced antagonism
parasympathetic and sympathetic 1 turns it up 1 turns it down
sympathetic and parasympathetic generally
oppose each other
