Local regulation of blood flow

Question 1

what are the physical determinants of blood flow within the vascular system?

Answer 1

viscosity of blood
pressure difference
vessel radius
length of vessel

Question 2

what is the most important factor in local regulation of blood flow?

Answer 2

vessel radius

in the equation radius is raised to the power of 4

Question 3

what determines vessel radius?

Answer 3

vascular smooth muscle tone

Question 4

a change in vascular tone of which vessel type is most influential in regulating local blood flow?

Answer 4

arterioles

Question 5

how is blood flow regulated?

Answer 5

neurologically
humorally
locally

Question 6

neurological regulation of blood flow

Answer 6

autonomic nervous system

alpha 1 adrenoreceptors - sympathetic NS

Question 7

humoral regulation of blood flow

Answer 7

angiotensin 2
vasopressin
adrenaline
atrial natriuretic peptide

Question 8

local regulation of blood floq

Answer 8

autoregulation and active hyperaemia - metabolic hypothesis

Question 9

what is hyperaemia?

Answer 9

excess of blood in the vessels supplying an organ

Question 10

flow

Answer 10

Q

Question 11

how to calculate flow

Answer 11

Q ∝ pressure change x r^4 / n x L
L = vessel length
n = blood viscosity

Question 12

what is the name of the formula used to calculate flow?

Answer 12

Poiseuille’s formular

Question 13

what are the main sites of resistance to blood flow?

Answer 13

arterioles, they are the control valves into capillary beds

Question 14

structure of arterioles

Answer 14

thick layer of smooth muscle in walls - tunica media

Question 15

normal arteriolar tone

Answer 15

normal blood flow

Question 16

vasoconstriction of arterioles

Answer 16

increases resistance

decreases blood flow

Question 17

vasodilation of arterioles

Answer 17

decreases resistance

increases blood flow

Question 18

what does local regulation of blood flow do?

Answer 18

controls regional/ organ blood flow

Question 19

humoral factors

Answer 19

vasoactive hormones

Question 20

neurogenic factors

Answer 20

sympathetic nerves

Question 21

local factors

Answer 21

active hypereamia

autoregulation

Question 22

how do humoral factors regulate vascular tone?

Answer 22

adrenaline - beta 2 receptors on vascular smooth muscle and natriuretic peptides - ANP and BNP cause vasodilation

Angiotensin II, vasopressin/ ADH and adrenaline at alpha 1 receptors cause vasoconstriction

Question 23

how do neurogenic factors regulate vascular tone?

Answer 23

release of noradrenline via sympathetic NS bind to alpha 1 receptors on vascular smooth muscle and cause vasoconstriction

Question 24

what metabolic changes occur during exercise/ in active tissue?

Answer 24

cell respiration and metabolic demand increase
pO2 decreases
pCO2 increases
lactate increases
pH decreases
Adenosine/ K+ increases
temperature increases 
there are chemical and physical changes in extracellular fluid

Question 25

what happens when pCO2 increases in active tissue?

Answer 25

cause release of nitric oxide from vascular endothelium causes relaxation of underlying vascular smooth muscle vasodilation and increased blood flow supply meets demand

Question 26

what is active hyperaemia?

Answer 26

local/ intrinsic mechanism of increasing blood flow to tissues/ organs to meet metabolic demand

Question 27

what happens during tissue injury?

Answer 27

histamine, bradykinins, prostaglandins released | cause vasodilation

Question 28

what do vascular endothelial cells

Answer 28

provide low resistance protective lining to blood vessels release nitric oxide release endothelin release vascular endothelial growth factor

Question 29

what causes nitric oxide release?

Answer 29

local chemical and physical changes due to increased metabolic demand increased shear stress on endothelium

Question 30

release of endothelin

Answer 30

stimulated by angiotensin II and vasopressin | inhibited by nitric oxide

Question 31

what is endothelin?

Answer 31

potent vasoconstrictor

Question 32

what does the release of vascular endothelial growth factor do?

Answer 32

promotes angiogenesis | long term adaptation in response to decreased blood flow to a tissue

Question 33

increased blood flow to skeletal muscle during exercise

Answer 33

blood flow to active skeletal muscle increases by as much as 1000% compared to resting supplying arterioles vasodilate increase in blood flow brought on by local/intrinsic factors in response to metabolic changes within tissue extracellular fluid

Question 34

what else can influence arteriolar vascular tone?

Answer 34

fluctuations in mean arterial pressure and blood supply to a tissue/ organ

Question 35

what happens when there is an increase in mean arterial pressure or blood supply?

Answer 35

increased stretch of arteriolar smooth muscle increased Ca2+ influx into smooth muscle smooth muscle contract causing increased vascular tone and vasoconstriction blood flow to tissue/ organ returned to normal

Question 36

what happens when there is a decrease in mean arterial pressure or blood supply?

Answer 36

decreased stretch of arteriolar smooth muscle no Ca2+ influx to smooth muscle smooth muscle relaxes causing decreased vascular tone and vasodilation blood flow returned to normal

Question 37

what is autoregulation?

Answer 37

intrinsic myogenic response to changes in mean arterial pressure or blood supply to a tissue or organ

Question 38

active hyperaemia

Answer 38

responds to changes in demand

Question 39

autoregulation

Answer 39

responds to changes in supply

Question 40

where is local metabolic control of blood flow most important?

Answer 40

cerebral, coronary, renal, pulmonary and exercising skeletal muscle vascular beds

Question 41

control of blood flow in skeletal muscle

Answer 41

active hyperaemia most influential during exercise due to large increase in metabolic demands - lactate, adenosine and K+ autoregulation contributes in exercise nerves/ hormones are most influential at rest sympathetic innervation via alpha 1 adrenoreceptors and circulating adrenaline via beta 2 adrenoreceptors

Question 42

control of cerebral blood blow

Answer 42

active hyperaemia contributes - sensitive to increases in pCO2 and H+ autoregulation contributes to maintain constant blood flow to brain nerves and hormones have little influence as cerebral vascular smooth muscle has no alpha 1 receptors

Question 43

control of coronary blood flow

Answer 43

active hyperaemia is most influential as coronaries are sensitive to hypoxia and adenosine autoregulation contributes to maintain constant blood flow to heart nerves and hormones have little influence

Question 44

control of blood flow to skin

Answer 44

active hyperaemia has little influence except when there is damage and release of histamine autoregulation has little influence nerves and hormones had varied sympathetic innervation via alpha 1 adrenoreceptors in response to changes in temperature

Question 45

control of pulmonary circulation

Answer 45

active hyperaemia but there is vasoconstriction in response to low pO2 - hypoxic vasoconstriction autoregulation and nerves and hormones have little influence