Autonomics Flashcards by A K

PS Spinal Cord Segments

cranial/sacral

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cranial portion of parasympathetic system

3, 7, 9, 10

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sacral portion of parasympathetic system

form the pelvic nerves, innervate the bladder, rectum, and sex organs

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parasympathetic ganglionic structure

long presynaptic, short postsynaptic, ganglia within innervated organ

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parasympathetic organization

discretely

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sympathetic spinal cord segments

thoracic to 2nd to 3rd lumbar

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axons emerge from

anterior roots and synapse in para/preverterbral ganglia

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paravertebral ganglia

form chains beside the vertebral column

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sympathetic organization

ganglia near spinal cord allows for diffuse branching (generalized response)

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transmitter at sympathetic ganglia

is Ach

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transmitter at sympathetic neuroeffector juctions

almost always norepinephrine (some sympathetic cholinergic fibers to sweat glands and a tiny amount of blood vessels

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sympathetic

adrenergic

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parasympathetic

cholinergic

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somatic nervous system has

long myelinated fibers in cranial and spinal nerves, no ganglia outside the CNS, Ach transmitter at NMJ

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PS and S have afferent neruons

that carry information back to the CNS (reflex circuits)

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reflex circuits coordinate

things such as blood pressure, heart rate, and response to stress

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classic example of autonomic reflex

baroreceptor reflex that impacts response to drugs for CV disorders

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Ach is made from

choline + acetyl coA —CAT–>

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Ach is made where?

cytoplasm –> stored in vesicles (VAT)

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Ach vesicle release is triggered by

depolarization, voltage sensitive Ca2+ channel influx, vesicular exocytosis

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Ach is degraded by

hydrolyzation via membrane bound ACE in less than a millisecond

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Botox A

blocks Ach exocytosis –> causes flaccid paralysis

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black widow spider

alpha-latrotoxin, massive Ach vesicle release

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nicotinic receptors

skeletal NMJ & chromaffin cells of the adrenal medulla, ligand gated ion channels, must bind 2 molecules of Ach

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muscarinic receptors

smooth, G protein coupled, 5 localized subtypes,

curare

blocks nicotinic response

atropine

atropa belladonna, blocks muscarinic response

dale principle

chemical and electrical signals in the nervous system

structure of nicotinic receptor

pentamers of 1-4 distinct by homolgous subunits

nicotinic channel activation results in

increase in Na+ and Ca2+ permeability

receptor found at autonomic ganglia

nicotinic (Ng)

activation of nicotinic receptors causes

depolarization/contraction in skeletal muscle, depolarization/firing in nerves, secretion in the adrenal medulla

M1, M3, M5

G(q) ---> PLC ---> Ca2+ release --> smooth muscle contraction/secretion

M2, M4

G(i/o) ----> activate K+ channels, inhibit adenylyl cyclase, inhibit voltage gated Ca2+ channels

M2 receptors

found in the heart, modulate at the ANS ganglia

adrenergic neurons synthesize

norepinephrine and dopamine

peripheral sympathetic neurons synthesize

norepinephrine

adrenal medulla secretes

80% epinephrine, 20% norepinephrine

rate limiting step for transmitter synthesis

tyrosine ---TH---> DOPA

DOPA ---> dopamine enzyme

DOPA decarboxylase

dopamine is put into vesicles and

THEN it is converted into norepinephrine via DBH

adrenal medulla converts

norepinephrine into epinephrine via PNMT

predominant inactivation of norepinephrine

reuptake (diffusion away from site of action also plays a role)

MAO and COMT

inactivate, but do not remove Ach ---> byproduct is VMA

COMT

widely distributed and thought to degrade epinephrine

VMA

MAO and COMT mediated Ach breakdown byproduct, measured in urine as diagnostic test for pheochromocytoma

norepinephrine and epinephrine interact with

pre AND post synaptic receptors

all adrenergic receptors are

G protein coupled

tyramine

cheese effect

α1

PLC --> Ca2+

α2

Gi/Go ---| adenyl cyclase

Gi/Go

inactivate adenyl cyclase, activate certain K+ channels, inhibit voltage sensitive Ca2+ channels

in the periphery, alpha 2 receptors

are found on presynaptic terminals and therefore mediate feedback inhibition of norepinephrine release

beta1/2

coupled to Gs

--> adenylyl cyclase ----> increase in cAMP

β3

found on adipose tissues (hopefully the future lipolytic drugs)

epinephrine vs. norepinephrine

norepinephrine is a poor β2 agonist

metyrosine

blocks TH

reserpine

blocks VMAT

adrenergic vesicles end up containing

about to be converted dopamine AND norepinephrine from reuptake

vascular system

IS ESSENTIALLY NOT INNERVATED BY THE PS SYSTEM

vasocontriction

sympathetic

there are no good

selective muscarinic agonists

false neurontransmitter

methyl-dopa

blockage of adrenergic neurotransmitter reuptake

cocaine, tricyclic anitdepressants

trimethaphan

blocks GANGLIONIC nicotinic receptors

curare

blocks nicotinic (Nm) receptors

tyramine is usually

metabolized by MAO

adrenergic transmitter release

potentiation: tyramine, amphetamine

block adrenergic transmitter release

guanethidine, bretylium

somatic nervous system nerves

are myelinated, all or none depolarization

tricyclic antidepressant

imipramine, prevents adrenergic neurotransmitter reuptake

α2 purpose

inhibits secretion, decrease aqueous humor production, negative feedback for norepinephrine release, increase glucose (inhibit insulin, activate glucagon breakdown)

parasympathetic reflexes

mechanoreceptor and chemosensory information (bp, CO2, gut distension), return to CNS via vagus/CNs

sympathetic reflexes

temperature and tissue injury information (viscerla pain, etc), return to CNS via dorsal horn and spinal column