Flashcards in Autonomics I Deck (23):
What are key diffs btw the autonomic and somatic peripheral nerves? (3 key differences)
ANS efferents synapse at the ganglia outside the CNS. somatic efferent nerves synapse w skeletal muscle.
motor nerves to skeletal muscles are myelinated; post-ganglionic ANS efferent nerves to visceral organs nonmyelinated
In ANS, denervated muscles/glands show spontaneous activity (in somatic system muscles are paralyzed and atrophy)
Characteristics of afferent fibers of ANS
typically cary signals in the vagus, pelvic, splanchnic nerves; some in somatic nerves
mediate visceral sensations
What body functions are controlled by the hypothalamus? (8)
body temp, fluid balance, glucose and fat metab, bp, emotions, sleep, sexual reflexes
What body functions are controlled by the medulla oblongata and the nucleus tractus solitarius?
bp and respiration
What are the neurotransmitters of the parasympathetic system? What are the receptors?
neurotransmitter released by both pre- and post- synaptic neurons is ACh
the nicotinic ACh receptor receives ACh in the body of the post-synaptic ganglion; muscarinic receptors are found in the effector organs
What is the neurotransmitter released in the somato-sensory system? What is the receptor?
ACh; receptor is nicotinic AChR
What is the neurotransmitter used by preganglionic neurons in the sympathetic nervous system?
What is the receptor in the post-ganglionic neuron of the sympathetic nervous system?
What neurotransmitter is typically used in the post-ganglionic neurons of the sympathetic nervous system? What are the exceptions?
typically norepinephrine is used
excpetions involve the sweat glands and piloerector muscles. in these cases, the neurotransmitter is ACh; these nerves are called cholinergic sympathetics
the adrenal medulla secretes epinephrine and norepinephring into the blood stream as hormones
What are the two responises mediated by nicotinic receptors?
muscle contraction at the NMJ
stimulatory responses at the cell bodies of post-ganglionic ANS nerves
What should I know about the dose response of nicotinic receptors?
BELL CURVE. small doses of nicotinic receptor agonists stimulate the response; large doses inhibit the response
Where do we see muscarinic receptors?
parasympathetic postganglionic neurons- the receptors of target organs are muscarinic. some are stimulatory; others inhibitory
also in the target organs of the cholinergic sympathetic nerves. these are all stimulatory
What are the main body responses to muscarinic receptors? (not vascular)
Heart: decr. HR and contractility
contract muscles of gut, bronchil, bladder
incr. salivary, bronchiol, gastric glands
Miosis (closing of iris) by contraction of sphincter muscles
decr. intraocular pressure by incr. outflow of aqueous humor
accomodation via contraction of ciliary muscle (focus on near objects)
stimulates piloerector muscles (cholinergic sympathetics)
stimulates sweat glands (cholinergic sympathetics)
What are the muscarinic responses in the vasulature?
vasodialtion via stim of mAChRs on vascular endothelial cells
stim of mAChRs on endothelial cells leads to the release of NO
NO difuses to vascular smooth muscle to activate guanylyl cylcase, leading to incr. in cGMP.
incr. in cGMP causes musle relaxation/vasodilation
What is the MOA of sildenafil?
sildenafil = viagra
inhibits the enzyme (PDE) that breaks down cGMP, thus maintaining state of vasodilation.
(long explanation: arousal --> NO release from endothelial cells --> cGMP in vascular smooth muscle --> vasodilation)
What are the major body effects of adrenergic receptors?
heart: incr. HR and contractility
contract most visceral vasculature; dilate skeletal muscle vasculature
relax gut/bronchiolar smooth muscle
release glucose/fatty acids from liver and fat cells
decr. glandular secretions
mydriasis (dilation of the iris)
Describe how parasympathetics and sympathetics influence vascular tone
sympathetics major determinant of vascular tone
PNS only has minor effects on vasular tone most of the time, except in salivary gland and penis. But, ACh and muscarinic agonists are vasodilators in all vascular beds.
What factors influence the action of autnomic drugs?
effects on peripheral autonomic nerves
reflex responses that participate in the action of the drug
Biosynthesis of ACh: what are the building blocks, what enzyme catalyzes the rxn, what is the rate limiting part?
acetyl CoA + choline
catalyzed by choline acetyltransferase
choline is limiting
What three drugs act presynaptically with ACh?
1. hemicholinium: inhibitor of choline uptake and therefore of ACh synthesis
2. vesamicol: inhibitor of vesicular uptake system for ACh
3. botulinum toxin: inhibitor of ACh exocytotic release
What is hemicholinium?
inhibitor of choline uptake and ACh synthesis
What is vesamicor?
inhibitor of vesicular uptake system of ACh