CHEDS- theme 9- Parasymp and ANS Flashcards
What are the main nerves of the pasrasympathetic NS?
the tenth cranial nerves (vagus). they originate int eh medulla oblongata. Other perganglionic parasympathetic neurons also extend from the brain and from the lower tip of the spinal cord.
in times of danger, what does the sympathetic nervous system do?
it prepares the body for violent activity. the parasympathetic nervous system reverses these changes when the danger has passed.
the para sympathetic functions with actions that do not require ———-
immediate attention.
the parasymp. functions return what functions to come back to normal?
heartbeat blood pressure construction of pupil increase blood flow to skin and viscera peristalsis of GI tract.
SLUDDSA.
the function of the parasymp system:
salivation lacrimation unrination digestion defecation sexual arousal.
where is Acetyl Choline released in the ANS?
- all preganglionic neurons
- symp and parasymp divisions
- all post-ganglionic parasympathetic neurons.
what are the effects of ACh?
Nicotinic and muscarinic
Nicotinic effect of ACh?
it is mediated by nAChRs, expressed in the postsynaptic side of the neuromuscular junction of th skeletal voluntary muscles in the CNS.
-ionotropic, they re permeable to Na+, K+ and Cl+
what are the two types of nAChR?
muscle type- selectively blocked by curare
neuronal type- selectively blocked by hexamethonium
Musarinic effect of ACH?
mediated by mAChR’s. expressed mainly i the postganglionic parasympathetic terminals of exocrine glands and smooth and cardiac muscles.
mAChR’s are also called…
Metabotropic receptors.
metabotropic receptors ..
NOT ion channels
they belong to a family of G-protein-coupled receptors
-they activeateother ion channels with second messenger signals
where odes the term “Muscarinic” come from?
Muscarin(e) is a natural product in some mushrooms.
both Nicotinic and muscarinic receptors are activated by the neurotransmitter…..
ACh!!!
- when the ionotrpic receptor is activated it ion the channels for the passage of ions.
- in contrast, when the mAChR is activated, a series od intracellular events are triggered that results in the activation of intracellular signals and the opening of sodium, potassium and calcium channels.
how are metabotropic receptors involved in opening channels???
the G-a-subunit deactivated AC.
while the Beta-y-subunit activates k-channels and therefore hyperpolarize the membrane. this causes a decrease in cardiac activity.
why are mAChR’s not involved in mechanisms that require quick responses?
they take longer to open channels than inotropic receptors. they remain activated from seconds to minutes. the plus side is hat they have a longer lasting effect that that of nAChR.
what is the M1 stage of cholinergic stimulation of the mAChR ? fuck to meny werdds. too bad it gets worse.
m1 is stimulatory- expressed in the neural system.
M3 cholinergic stimulation of the mAChR. GO
stimulatory as well. but it’s expressed in organ and tissues.
-brochoconstriction
vasodilation, peristalsis of G.I.T., secretion in GIT, contraction of the dittos muscle of the bladder.
how does vasodilation work?
ACh causes endothelial cells to produce nitric oxide, which diffuses to smooth muscles and results in dilation.
Cholinergic inhibition of mAChR.
M2- in the heart, bring things back to normal after the sympathetic nervous system fuck shit up. :
slows bmp, reduces contractile forces of atrial cardiac muscle, reduces velocity of senatorial node and atrioventricular node. (not a whole lot of effect on vent muscle. there are few nerves from the prams. division in ventricular muscle)
describe the compensatory mechanisms in the ANS.
both para and symp divisions act on the same organs, but with opposing actions.
memorise the nasty tables.
it’s not a table, it’s ikea.
what is the function of IP3, Inositol Triphosphate?
it stimulates movement in the endoplasmic reticulum. google says it’s used in signal transduction.
