ANS Review Flashcards
Anatomical divisions nervous system
CNS PNS
CNS
brain spinal cord
PNS
ANS and somatic motor system
ANS
- visceral - involutnary - innervates smooth muscle, cardiac muscle, glands - neuroeffector junctions - central regulator not total control of things it innervates - widely distributed throughout body - Gi gets central regulation through ANS
Somatic Motor System
- voluntary (except breathing which can be voluntary and unconscious) - innervates skeletal muscle at neuromuscular junctions
anatomical connections ANS
- afferent fibers - central connections - efferent fibers
afferent fibers
- first link in reflex arc in ANS - arise from visceral structures, cell bodies in DRG and sensory ganglia - collect info from sensory receptors
afferent fibers convey
- info into system acted on by efferents via reflexes mediated mostly in CNS
central connections what are they and what structures are involved
- synapses happen rapidly in spinal cord and go blackout via efferents or go up to brain w/ in CNS afferent info processed and integrated and efferent response = initiated 1. spinal cord 2. Medulla oblongata 3. Hypothalamus 4. Cerebral cortex
spinal cord
direct connections between afferents and efferents mediate reflex changes in blood pressure, sweat production, micturition
Medulla oblongata
blood pressure and respiration controlled here
hypothalamus
principle locus of integration; control: - body temp - water balance - carbohydrate metabolism - sexual reflexes - autonomic and emotional response
cerebral cortex
- volitional changes and coordinated autonomic response controlled here
Efferent fibers
- can effect output centrally 2 nerve cells plus effector generally involved - preganglionic fibers - post ganglionic fibers
preganglionic fibers
- exit SC terminate in ganglia - acetylcholine neurotransmitter released by preganglionc nerves at autonomic ganglia
chemical connection between pre and post ganglionic fibers
nicotinic cholinergic synapse (acetylcholine)
postganglionic fibers
- exit ganglia innervate effect cells/ organs - acetylcholine from pregang fiber -> action potential -> depolarization nerve ending -> neurotransmitter release at neuroeffector junciton
neuroeffector junction neurotransmitters
- acetylcholine- mediates muscarinic cholinergic transmission - norepinephrine- mediates adrenergic transmission
adrenal medulla ganglionic transmission
causes release of epinephrine and norepinephrine into blood to act as hormone
parasympathetic nervous system
- craniosacral outflow - preganglionic fibers - post ganglionic neurons - innervation discrete - NO HORMONE
craniosacral outflow PNS
- preganglionic fibers originate in midbrain (CN III), medulla oblongata (CN VII, IX, X), Sacral SC segments 2-4
pregandlionc fibers length and synapse where PNS
long synapse on or within target organ
pregangiolic fibers synapse in what galia PNS
- cilliary ganglia (CN III) - Submandbular ganglia (CN VII) - Otic ganglion (CNIX) - Terminal ganglia heart, lungs, liver, spleen, GI tract kidney (CN X) - terminal ganglia bladder, rectum, sex organs (pelvic nerves)
post ganglionic neurons length and innervate what PNS
short, innervate target organs
cranial divisions post ganglionic neurons PNS
innervate eye, salivary glands, heart, bronchi, stomach, intestine
sacral division post ganglionic neurons PNS
innervate bladder, colon, urinary and rectal sphincters, and genital organs
discrete innervation PNS
usually pre:post ganglionic fiber ration 1:1
sympathetic nervous system
- thoracolumbar outflow - pregangionic fibers - postganglionc neurons - adrenal medulla - innervation diffuse
thoracolumbar outflow
- preganglionic fibers originate in intermediolateral columns of SC from 1st thoracic to 3rd lunar section
pregangioèic fibers length synapse symp nervous system
short, synapse before target organ in vertebral ganglia or prevertebral ganglia
vertebral ganglia
symp NS - includes cervical ganglia
prevertebral ganglia
in abdomen - celiac - superior mesenteric - inferior mesenteric
post ganglio neurons length innervation symp ns
- long innervate target organs
post gang neuron fibers from vertebral ganglia
innervate blood vessels, eyes, salivary glands, heart, bronchi, sweat glands, hair follicles
post gang neuron fibers from prevertebral ganglia
innervate stomach, intestine, bladder, urianry and renal sphincters, and genital organs
Adrenal medulla
embryologically and fnx symp ganglion innervated by typically symp pregang neuons
diffuse innervation
symp ns pre: post ganglionic fiber ration 1:10 to 1:20
control ANS vs somatic motor system
ANS unconscious (primary) SMS voluntary
innervation ANS vs somatic motor system
ANS all structures except skeletal muscles SMS only skeletal muscles
synaptic junctions ANS vs somatic motor system
ANS in ganglia outside CNS SMS entirely within CNS
effects of denervation ANS vs SMS
ANS automatic activity independent of innervation (ANS is regulation so can function w/o it just not as well) SMS paralysis and atrophy
chemical transmission
info transferred between neurons or from neuron to effector cell across synaptic/ junctional cleft by neurotransmitters; neurotransmitter acts on specific receptor proteins on postganglionic neuron or target organ cell
neurotransmission and ANS
synaptic jucntions= between neurons; in ANS these exist in ganglia
neuroeffector junction
NEJ- post junctional cell muscle cell, gland. ect.; in ANS on NEJ on effector organs
Neurochemical organization of ANS
- prejuncitonal release - post junctional receptors
prejunctional release neurotransmitters
-acetylcholine (released at all ganglia and parasympathetic neuroeffector junctions and at neuromuscular junctions) - norepinephrine (released at almost all sympathetic neuroeffector junctions)
postjuncitonal receptors
- acetylcholine interacts with cholinergic receptors to produce post junctional receptors: - norepinephrine and epinephrine interact with adrenergic receptors to produce effects at sympathetic NEJ and hormone receptors
cholinergic receptors
- nicotinic receptors- in all ganglia and at NMJ; major distinction between muscle and neuronal receptors; selective activation ny nicotine - muscarinic receptors- in all parasympathetic NEJ; 5 receptor subtypes M1-M5; selective activation by muscarine
adrenergic receptors types
alpha- a1 and a2 subtypes beta- b1 b2 b3 subtypes
events of neurotransmission in prejunctional neuron
- synthesis and storage neurotransmitter - initiation and propagation action potential - release transmitter from nerve terminal - presynaptic modulation release - inactivation of transmitter by reuptake or metabolic alteration
events of neurotransmission in neuroeffector/ synaptic junction (extracellular space)
- diffusion transmitter to effector cell - local inactivation enzymes - nerve terminal for reuptake and/ or into greater extracellular space and transport to other organs for metabolism and excretion
events at effector cell
- interaction transmitter with receptor - signal transduction and cellular response
signal transduction and cellular response steps
- receptor activation specific G-proteins 2. Activated G-proteins interact with various effectors (ex. adenylyl cyclase, phospholipase C, and/ or ion channels) 3. Changes in effector activity affect various protein activities and cell fnxs
activation various protein kinases
- due to Changes in effector activity affect various protein activities and cell fnxs catalyze phosphorylation of proteins and alter protein function
changes in ion channel activity
- due to Changes in effector activity affect various protein activities and cell fnxs either by interaction G-protein or by phosphorylation or dephosphorylation -> changes electrical excitability
increase in intracellular Ca2+
- due to Changes in effector activity affect various protein activities and cell fnxs - result from IP3-induced release from intracellular stores or from increased conductance Ca2+ channels affecting release hormones or transmitters, secretion in gland cells, increased force and frequency of contraction in muscle ect.
Junctional events in neurotransmission
- in prejunecitonal neurons - in neuroeffector/ synaptic junction - events at effector cell - organ effects - elimination of transmitter
Organ effects
- smooth muscle - pacemakers - glands - metabolic changes
smooth muscle
contracts or relaxes (changes in amplitude and/ or frequency)
pacemakers
(ex heart) acceleration or deceleration of rhythmic firing
glands
stimulation or inhibition of secretion
metabolic changes
can be direct (glycogenolysis or lipolysis) or indirect (changes in oxygen consumption consequent to altered contractile state of the heart)
elimination of transmitter
- termination of action by metabolic inactivation or removal by uptake (and diffusion)
outflow parasympathetic vs sympathetic
parasympathetic- craniosacral sympathetic- thoracolumbar
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)
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
receptors parasympathetic vs sympathetic
parasympathetic ganglia- nicotinic cholinergic neuroeffector junecionts- muscarinic cholinergic sympathetic ganglia- nicotina cholinergic neuroeffector junctions- adrenergic
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 NMJs
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
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
