Introduction to Autonomic Pharmacology Flashcards
Recall that the sympathetic system originates in ________ distribution of the spinal cord, whereas the parasympathetic system originates in the ________ distribution.
Thoracolumbar
Craniosacral
Para v Snymp Fiber Lengths and Ganglion Position
The sympathetic system consists of short preganglionic fibers (paraspinal) and a long post-ganglion fibers. In contrast, the parasympathetic system has a very long pre-ganglionic fibers and short postganglionic fibers.
Thus, the sympathetic ganglia are located far from the target organ and the parasympathetic ganglia are located near the target organ.
Both para and symp use what neurotransmitter for preganglionic
Acetylcholine
Neurotransmitter for postganglionic of para and symp
Para: Acetycholine
Symp: norepinephrine, exceptions being in the adrenal medulla and at sweat glands
Parasympathetic is a ______ system
Sympathetic is a ________ system
Trophotropic (leads to growth)
Ergotrophic (energy expendature)
Blood vessels are mainly controlled by:
Mainly sympathetic
There are parasympathetic responsive receptors in blood vessels but rather than response to acetylcholine, these receptors respond to release of nitric oxide (a potent vasodilator).
Sympathetic and Para actions on gut and bladder
Symp: In the bladder, detrusor muscle relaxation and sphincter contraction. The same occurs within the gut, the sympathetic system causes decreased smooth muscle contraction in the GI system and contraction of the anal sphincter muscles.
Para: relaxation of the sphincter, contraction of the detrusor and increased motility and gut contraction
How does dilation and contraction of the pupil work?
How does accomodation of the lens occur?
Pupil: The pupil is controlled by two muscles of the iris, the radial muscle and the circular muscles. When the radial muscle is contracted, the pupil dilates or exhibits mydriasis (like blinds opening). When the circular muscle is contracted, the pupil becomes constricted or exhibits miosis (like purse string)
Lens: The zonular fibers act to pull the lens taught for distance vision. When the ciliary body fibers contract, zonular fibers relax their pull on the lens and allow it to plump out for near vision.
Autonomics of the eye
Pupil: Sympathetic leads to mydriasis (contraction of radial muscles), parasympathetic leads to miosis (contraction of circular muscles)
Lens: Sympathetic opposes the ciliary bodies, leading to zonular muscles pulling lens taught (distance). Parasympathetic encourages contraction of ciliary bodies, leading to accomodation
What is an agonist? Indirect Agonist?
Agonist: increase the effects at a certain synapse. Direct stimulation of receptor
Indirect Agonist: increase the downstream effects at a synapse through the release and removal sites. This is by either increasing the amount of neurotransmitter released from the presynapse or preventing its metabolism once it has been released into the synapse
Antagonist? Indirect antagonism?
Antagonist: direct blockade at the receptor itself
Indirect anatagonist: decreases the downstream effects of a synapse by some other means along the neurotransmission pathway
What is down regulation of receptors?
If there is axcess agonist, the number of receptors will be fall, untill excess is removed and then number of receptrs can increase to normal
What happens in chronic blockade?
The rate limiting step of adrenergic synthesis is
the conversion of tyrosine to DOPA by the enzyme tyrosine hydroxylase.
What is DOPA?
dihydroxypheylalanine, is the basis of ALL catecholamine neurotransmitters, i.e. norepinephrine, epinephrine, and dopamine. It is important to mention here that DOPA can pass through the blood brain barrier, but its later products are unable to.