regulation of arteriolar resistance

Question 1

what is used to vary total peripheral resistance?

Answer 1

radius of vessels

Question 2

what does varying the radius of vessels affect?

Answer 2

mean arterial pressure (the difference in pressure)

Question 3

increasing TPR does what to mean arterial pressure?

Answer 3

increases it

Question 4

what is the function of intrinsic mechanisms of controlling arteriolar constriction?

Answer 4

they are concerned with meeting the selfish needs of each individual tissue

Question 5

what is the function of extrinsic mechanisms of controlling arteriolar constriction?

Answer 5

they are concerned with ensuring that total peripheral resistance of the whole body stays in the right ball park

Question 6

what are the extrinsic mechanisms for controlling arteriolar constriction

Answer 6

• sympathetic nerve innervation

- hormonal control (adrenaline, ADH, angiotensin II, atrial natriuretic peptide and brain natriuretic petide)

Question 7

describe how sympathetic innervation affects the constriction of arterioles

Answer 7

1. they release noradrenaline
2. this binds to alpha-1 receptors
3. this causes smooth muscle contraction and arteriolar constriction.
4. decreases flow through that tissue and increases TPR

Question 8

does the parasympathetic system have an effect of arteriolar constriction?

Answer 8

no

Question 9

how does adrenaline affect arteriolar radius?

Answer 9

1. binds to alpa-1 receptors in most tissues causing a arteriolar constriction, decreased flow and increased TPR
2. in some tissues like skeletal and cardiac muscle it binds to beta 2 receptors causing arteriolar dilation therefore increasing flow and decreasing TPR

Question 10

how does angiotensin II affect arteriolar constriction?

Answer 10

produced in response to low blood volume it causes arteriolar constriction

Question 11

how does antidiuretic hormone affect arteriolar radius?

Answer 11

released response to low blood volume it causes arteriolar constriction

Question 12

how do atrial and brain natriuretic peptide affect arteriolar radius?

Answer 12

released in response to high blood volume

causes arteriolar dilation

Question 13

what are the intrinsic contol mechanisms for arteriolar constriction?

Answer 13

1. active (metabolic) hyperaemia
2. pressure (flow) autoregulation
3. reactive hyperaemia
4. injury response

Question 14

describe the process of metabolic hyperaemia?

Answer 14

1. as metabolic activity increases the conc. of metabolits in the blood increases
2. this triggers the release of EDRF
3. this causes arteriolar dilation to wash out the metabolites

Question 15

describe the process of pressure (flow) autoregulation?

Answer 15

1. a decrease mean arterial pressure causes a decrease in flow through arterioles and capillaries
2. this reduces the movement of metabolites away from tissues
3. this causes metabolites to accumulate
4. EDRF is released and causes vasedilation to wash out metabolites

Question 16

describe the process of reactive hyperaemia?

Answer 16

occlusion of blood supply causes a subsequent increase in blood flow

Question 17

describe the process of injury response?

Answer 17

1 injury to an area sends a action potential up a C-fibre

2. a branch of the C-fibre releases substance P
3. this substance stimulates mast cells to release histamine which causes arteriolar dilation
4. this aids the delivery of blood-borne leucocytes to the injured area

Question 18

when is blood supply to the heart interrupted?

Answer 18

during systole

Question 19

how does the heart deal with increased demand during exercise with its interrupted blood supply?

Answer 19

• it shows excellent active hyperaemia

- also expresses many beta 2 receptors which swamp any arteriolar constriction

Question 20

what sort of arteriolar regulation do the arterioles in the brain show?

Answer 20

excellent pressure autoregulation in order to keep a stable circulation

Question 21

what happens to the arterioles in the lungs when oxygen conc. decreases?

Answer 21

they constrict (opposite to most other tissues to ensure blood gets to the best ventilated parts)

Question 22

what sort sort of arteriole constriction are the arterioles in the kidneys particularly good at?

Answer 22

pressure autoregulation, as changes in MAP would have big effects on blood volume