Blood Vessels

Question 1

anatomical: what type of fibers for blood vessels? how do they travel?

Answer 1

post ganglionic C-fibers. travel from ganglia along complex routes, often via somatic nerves

Question 2

anatomy of blood vessel innervation: where? general structure?

Answer 2

autonomic fibers as perivascular axons found in every organ of body. nerve bundles (1-100 axons) branch + merge in adventitia to form meshwork

Question 3

anatomy: how many varicosities? each varicosity contains? spacing of varicosities?

Answer 3

10^4 to 2X10^6 varicosities per mm3 of tissue; regularly spaced along axon. each varicosity: 0 - 1000 vesicles (with NA)

Question 4

anatomy: also have ___ fibers, and their vesicles have?

Answer 4

sensory fibers: substance P and CGRP (involved in axon reflex, inflammation, etc)

Question 5

anatomy: where are vesicles found close to?

Answer 5

many vesicles found in close apposition to muscle cells, others deep within nerve bundle, collagen or near fibroblasts or endothelial cells

Question 6

anatomy: small granular vesicles characteristic of NA nerve endings contain? (2)

Answer 6

NA + ATP

Question 7

anat: larg granular vesicles contain?

Answer 7

one or more peptides + other transmitters

Question 8

structural organization of autonomic junctions vs. NMJ?

Answer 8

somatic NMJ: clearly defined structural organization. but extent of organization at autonomic junctions debated

Question 9

effector connection vs. NMJ?

Answer 9

unlike skeletal NMJJ, are electrically connected via gap junctions

Question 10

variation in effector properties : 6?

Answer 10

myogenic activity, hormonal sensitivity, stretch sensitivity, cell cell coupling, NO/endothelin, prostacyclin released from endothelium, accumulation of metabolites in exercising muscle produces vasodilation

Question 11

electrophysiology: failure? not due to?

Answer 11

high rate of release failure at each varicosity (unlike NMJ, super reliable where one AP = contraction). low prob. of release NOT due to transmission failure

Question 12

each varicosity releases how many vesicles? what % fibers release?

Answer 12

each varicosity releases 0 - 10 vesicles. 1-2% of fibers release NA/ATP when stimulation occurs

Question 13

if you stimulate sympathetic nerves to vascular smooth muscle: 3 phases of electrical response?

Answer 13

ATP/P2X fast EJPs. a-adrenergic slow depolarization. NPY/Y1 depolarization.

Question 14

if you stimulate symp nerve to vascular smooth muscle: what’s associated with contraction?

Answer 14

a-adrenergic and NPY components associated with contraction (so fast ATP EJPs don’t evoke contractions)

Question 15

low freq. APs in sympathetic nerve: effect and mediated by?

Answer 15

each nerve AP = one brief vasocontraction, mediated by alpha adrenergic effect of NA

Question 16

high freq APs in sympathetic nerve: effect? mediated by?

Answer 16

sustained contraction; preferential release of NPY

Question 17

low freq. stimulation preferentially releases? which acts on? effect?

Answer 17

NA: acts on presynpatic alpha 2 adrenoreceptors. limit duration of NA release, reduces release of NPY.

Question 18

NPY Y2 autoreceptors effect on NA?

Answer 18

also reduce NA release. so NPY on post synpatic Y1 = vasoconstriction. Y2 feedback = presynpatic inhibition of NA

Question 19

if high freq of APs persists: what happens to NPY? vasoconstrictor response?

Answer 19

NPY depleted. vaconstrictor response maintained by NA, because its release is no longer restricted by NPY effects on Y2 autoreceptors

Question 20

concl: peptides do what for NA output? does that idea fit?

Answer 20

may alter NA output so that it is appropriate for a particular target. fits w/ idea that functionality of ANS is coded by peptides