Vasculature

Question 1

functions of endothelial cells

Answer 1

physical lining that blood doesn’t adhere to
permeability barrier
regulate transport of macromolecules
mediate angiogenesis
vascular remodelling - detect signals and release paracrine agents that act on adjacent cells
secrete paracrine agents - vasodilators: prostacyclin, nitric oxide (EDRF) and vasoconstrictors: endothelin-1
formation/maintenance of extracellular matrix
growth factors
substances regulating platelet clumping, clotting and anticlotting
synthesise active hormones from inactive precursors
extract/degrade hormones
secrete cytokines in immune response
influence vascular smooth muscle proliferation in atherosclerosis

Question 2

angiogenesis

Answer 2

new capillary growth

Question 3

vasodilators secreted by endothelial cells

Answer 3

prostacyclin
nitric oxide (endothelial derived relaxing factor)

Question 4

vasoconstrictors secreted by endothelial cells

Answer 4

endothelin-1

Question 5

2 roles of arterioles

Answer 5

in individual organs are responsible for determining relative blood flows to organs at any given MAP
major factor in determining MAP

Question 6

flow

Answer 6

function of pressure gradient and resistance to flow

F = deltaP/R

Question 7

tank analogy

Answer 7

pressure reservoir = arteries. Have such large radii that they provide little resistance to flow.
variable resistance outflow tubes = arterioles. smallest arteries offer significant resistance to flow, but narrower arterioles have major resistance. Less flow and pulse pressure.

Question 8

blood flow through any organ

Answer 8

F = MAP/resistance(organ)

Question 9

how can resistance of arterioles be changed?

Answer 9

arteriolar smooth muscle has spontaneous activity - intrinsic tone

Question 10

spontaneous activity

Answer 10

contraction independent of neural, hormonal or paracrine input

Question 11

intrinsic/basal tone

Answer 11

spontaneous contractile activity of arteriolar smooth muscle
sets baseline level of contraction which can be increased or decreased by external signals
increase in contraction force above intrinsic tone causes vasoconstriction, vice versa for vasodilation

Question 12

mechanisms controlling vasoconstriction and vasodilation

Answer 12

local controls

extrinsic/reflex controls

Question 13

local controls

Answer 13

independent of nerves or hormones
organs and tissues alter their own arteriolar resistances, thus blood flow
includes changes by autocrine and paracrine agents

Question 14

where is self-regulation apparent?

Answer 14

active hyperemia
flow autoregulation
reactive hyperemia
local response to injury

Question 15

active hyperemia

Answer 15

most organs manifest an increased blood flow when metabolic activity is increased

Question 16

hyperemia

Answer 16

increased blood flow

Question 17

factors causing arteriolar smooth muscle to relax in active hyperemia

Answer 17

local chemical changes in ECF surrounding arterioles from metabolic activity

Question 18

local chemical changes in ECF surrounding arterioles

Answer 18

decrease in conc of oxygen, used in oxidative phosphorylation
increase in CO2
increase in H+, e.g. from lactic acid
increase in adenosine
increase in K+ - action potential repolarisation
increase in eicosanoids - breakdown product of membrane phospholipids
increase from osmotically active products from breakdown of high molecular weight substances
increase in bradykinin, peptide generated from kininogen by enzyme kallikrein secreted by active gland cells
increase in nitric oxide, secreted by endothelial cells

Question 19

bradykinin

Answer 19

peptide generated from kininogen by enzyme kallikrein secreted by active gland cells

Question 20

where is active hyperemia highly developed?

Answer 20

skeletal muscle, cardiac muscle and glands

Question 21

flow autoregulation

Answer 21

changes in arteriolar resistance when a tissue or organ experiences a change in blood supply due to a change in pressure
tries to keep flow constant

Question 22

flow autoregulation mechanism

Answer 22

same metabolic factors for active hyperemia

myogenic responses - decreased