heart

Question 1

how is local blood flow controlled

Answer 1

by tissues, not the heart

most vascular beds can auto-regulate flow to match metabolic demand

reflexes hold arterial blood pressure constant, allowing local resistors to regulate blood flow locally

Question 2

major method of changing perfusion

Answer 2

through resistance

as changes in pressure could have dangerous effects

Question 3

capillary recruitment

Answer 3

important in skeletal muscle
not all capillaries have flow at rest
during vasodilation, rest of capillaries have flow at a higher perfusion pressure

Question 4

myogenic autoregulation

Answer 4

tissues control perfusion independent of ABP

• through arterioles, changes in resistance with small changes in radius (as multiplied to power of 4 in equation)
• mechanisms through stretch activated channels, stretch increases tension causes calcium entry and contraction

Question 5

where is myogenic a major mechanism

Answer 5

renal, cerebral, coronary

Question 6

metabolic autoregualtion

Answer 6

matching local perfusion with local metabolism

- skin and kidney relatively over perfused, brain and kidney under

Question 7

methods for metabolic autoregulation

Answer 7

• vasodilate for tissues with higher oxygen demand, arterioles sensitive and vasoconstrictor in certain beds
• adenosine as a marker of metabolic insufficiency, AMP release, binds to Gs and causes vasodilation
• acidity marker of high metabolic demand, more CO2 produced, less MLCK and more vasodilation
• extracellular accumulation of K, causes hyperpolarisaiton and vasodilation
• reactive hyperaemia, vasodilation after ischamia

Question 8

effect of vasodilation on downstream flow

Answer 8

increases pressure downstream

Question 9

autocoids effect

Answer 9

histamine cause arteriole dilation and increased venular permeability

Question 10

endothelial cells effect

Answer 10

release paracrine regulators

secretes NO, causes vasodilation

Question 11

neuronal control of blood flow

Answer 11

parasym = release ACh, causes vasodilation 
sym = increased acitivty casques vasoconstriction, have basal level of activity, NA, raises peripheral resistance, increases central blood volume

Question 12

hormonal control of blood flow

Answer 12

adrenaline, vasopressin, angiotensin, ANP
adrenaline/ NA = constrict
vasopressin = vasoconstrictor, rescind to change in BP
angiotensin = constrict
ANP = dilate

Question 13

coronary circulation specialisations

Answer 13

high ability for oxygen extraction
metabolic vasodialtion for reguation
good auto regulation
vascular beta 2 receptors

Question 14

skeletal muscle specialisations

Answer 14

metabolic vasodilation during exercise
vasodilation from adrenaline during stress
capillary recruitment

Question 15

cutaneous specialisoans

Answer 15

sympaehtic servers not metabolic hyperaemia for control
controlled with temperature and baroreflex with hypotension
stress causes vasoconstriction, embarrassment vasodilation

Question 16

cerebral specialisations

Answer 16

high basal flow from low arteriolar reisistance
brain controls through baroreflex to safeguard its own perfusion pressure
good autoregulation if BP falls
strong vasodilation to CO2 and asphyxia
good metabolic hyperaemia

Question 17

pulmonary specialisations

Answer 17

hypoxic pulmonary vasoconstriction matches local alveolar blood perfusion and local ventilation
flow increases in proportion to pressure
get blood/alveolar gas equilibrium
low capillary pressure

Question 18

renal specialistions

Answer 18

primarily controlled by tubuloglomerular feedback