S2W4 L2- Circulatory Physiology- Special Circulations- Prof Derek Steele

Question 1

total blood flow average (CO)

Answer 1

5.8 L/min

Question 2

why do we have coronary arteries and veins

Answer 2

heart is too large to be oxygenated by just blood passing through myocardium

Question 3

where do right and left coronary arteries supply

Answer 3

walls of myocardium

Question 4

where does most venous blood drain via

Answer 4

coronary sinus

Question 5

why do the myocardial capillaries have very small max diffusion distance

Answer 5

high density
small diameter of myocytes

Question 6

why are coronary arteries compressed during systole

Answer 6

3D structure

Question 7

what does obstruction in coronary arteries cause

Answer 7

ischemia of tissue downstream, leads to myocardial infraction

Question 8

what does gradual obstruction of coronary arteries cause

Answer 8

development of collateral vessels

Question 9

why are pulmonary capillaries more susceptible to stress failure than systemic

Answer 9

they are not surrounded by supporting tissues

Question 10

why is blood flow unevenly sitribted in lungs of an upright subject

Answer 10

pulmonary pressure higher at base than apex

Question 11

why is there a lower resitance and higher blood flow at base of lung

Answer 11

pressure higher at base, high pressure distends vessels of microcirculation

Question 12

what happens to the vessels of the apex during systole

Answer 12

collapse

Question 13

what becomes the primary determinant of systemic vascular resistance during exercise

Answer 13

skeletal muscle resistance

Question 14

which type of muscle has greater capillary density

Answer 14

slow twitch (red) greater than fast twitch (white)

Question 15

active hyperaemia

Answer 15

increase in blood flow associated with an increase in metabolism

Question 16

6 local changes during exercise which induce vasodilation

Answer 16

decreased O2
increased adenosine
K+
CO2
H+
NO

Question 17

something which facilitates skeletal muscle blood flow

Answer 17

vasoconstriction in other areas e.g digestive tract

Question 18

where does most of the CO to the brain go to

Answer 18

grey matter

Question 19

what arteries form circle of willis

Answer 19

basillar and carotid

Question 20

at what BP does cerebral autoregulation fail below

Answer 20

50mmHg

Question 21

effect of hypercapnea on cerebral circulation

Answer 21

vasodilation

Question 22

effect of hypocapnea of cerebral circulation

Answer 22

vasoconstriction

Question 23

symptom of tumour/ haemorrage blocking occupying skull space

Answer 23

raises intracranial pressure, restricts cerebral blood flow, increases sympathetic outflow from vasomotor centre, increases MAP to maintain cerebral perfusion

Question 24

what are the 3 main functions of skin blood flow

Answer 24

1. heat exchanger for thermal regulation
2. supply of nutrients to cell
3. blood reservoir

Question 25

what are AV shunts richly supplied with

Answer 25

sympathetic nerve endings

Question 26

what are AV shunts linked to

Answer 26

temp receptors or hypothalamus signals

Question 27

result of heat on skin

Answer 27

hypothalamus reduces vasomotor tone substances in sweat stimulate endothelial cells to release NO, further vasodilation occurs

Question 28

effects of cold on skin

Answer 28

superficial vessels contact strongly blood bypasses capillaries via AV shunts, diverts to vital organs rosy skin due to blood trapped in superficial capillary loops after rapid vasoconstriction