Autonomics Flashcards
PS Spinal Cord Segments
cranial/sacral
cranial portion of parasympathetic system
3, 7, 9, 10
sacral portion of parasympathetic system
form the pelvic nerves, innervate the bladder, rectum, and sex organs
parasympathetic ganglionic structure
long presynaptic, short postsynaptic, ganglia within innervated organ
parasympathetic organization
discretely
sympathetic spinal cord segments
thoracic to 2nd to 3rd lumbar
axons emerge from
anterior roots and synapse in para/preverterbral ganglia
paravertebral ganglia
form chains beside the vertebral column
sympathetic organization
ganglia near spinal cord allows for diffuse branching (generalized response)
transmitter at sympathetic ganglia
is Ach
transmitter at sympathetic neuroeffector juctions
almost always norepinephrine (some sympathetic cholinergic fibers to sweat glands and a tiny amount of blood vessels
sympathetic
adrenergic
parasympathetic
cholinergic
somatic nervous system has
long myelinated fibers in cranial and spinal nerves, no ganglia outside the CNS, Ach transmitter at NMJ
PS and S have afferent neruons
that carry information back to the CNS (reflex circuits)
reflex circuits coordinate
things such as blood pressure, heart rate, and response to stress
classic example of autonomic reflex
baroreceptor reflex that impacts response to drugs for CV disorders
Ach is made from
choline + acetyl coA —CAT–>
Ach is made where?
cytoplasm –> stored in vesicles (VAT)
Ach vesicle release is triggered by
depolarization, voltage sensitive Ca2+ channel influx, vesicular exocytosis
Ach is degraded by
hydrolyzation via membrane bound ACE in less than a millisecond
Botox A
blocks Ach exocytosis –> causes flaccid paralysis
black widow spider
alpha-latrotoxin, massive Ach vesicle release
nicotinic receptors
skeletal NMJ & chromaffin cells of the adrenal medulla, ligand gated ion channels, must bind 2 molecules of Ach
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
Gq
Gq
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
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