Local regulation of blood flow

Question 1

1. When is adrenaline released?

Answer 1

released in response to lowered BP

Question 2

3. What two things does adrenaline do?

Answer 2

1. Speeds heart rate and force of ventricular contraction
2. Dilates skeletal muscle vascular beds and constricts the splanchnic (mesenteric) vascular beds

Question 3

4. What does the things that adrenaline does result in

Answer 3

results in increased cardiac output and systolic BP

Question 4

What is the main role of ADH

Answer 4

Main role is formation of concentrated urine by retaining water to control plasma osmolarity

Question 5

6. What are 2 other names for anti-diuretic hormone

Answer 5

Arginine vasopressin or vasopressin

Question 6

7. What can slow down the release of ADH

Answer 6

alcohol

Question 7

9. What is the function of the ventricles

Answer 7

pumping chamber

Question 8

10. What is the function of arterioles

Answer 8

resistance vessels

Question 9

11. What is the function of capillaries

Answer 9

Exchange vessels

Question 10

12. What is the function of venules/veins

Answer 10

Capacitance vessels

Question 11

13. What is the function of the atrium

Answer 11

Receiving chamber

Question 12

14. What is a metarteriole continuous with

Answer 12

A metarteriole is continuous with the thoroughfare channel passing between terminal arteriole and postcapillary venule

Question 13

14. What do capillaries enable?

Answer 13

enable the exchange of water, O2, CO2 and many other nutrient and waste chemical substances between blood and surrounding tissues

Question 14

16. What does metarterioles being continuous cause?

Answer 14

This causes blood to be shunted between the two vessels when precapillary sphincters are closed, bypassing the capillary bed

Question 15

17. What does basal flow vary by?

Answer 15

flow varies by tissue

Question 16

18. Where is are examples of basal flow being high and it being low

Answer 16

High: Kidneys
Low: skeletal muscle

Question 17

19. What happens when cells become more active

Answer 17

When cells become more active this increases circulation to the region, at the expense of other tissues.

Question 18

20. what 3 things mediate the regulation of blood flow

Answer 18

The regulation of local flow is mediated by:

1. Neural factors (sympathetic nervous system)
2. Endocrine factors (hormones)
3. Local factors (bi-products signaling metabolic demand)

Question 19

21. what are 2 factors that affect blood flow

Answer 19

1. Pressure (driving force) of the flow (Cardiac Output)
2. Total peripheral resistance

Question 20

22. what is Total Peripheral resistance (TPR)?

Answer 20

the sum of the resistance of all peripheral vasculature in the systemic circulation

Question 21

23. what are 4 factors that affect TPR

Answer 21

Affected by:
- Mean arterial pressure
- Viscosity/ volume of the blood
- Turbulence
- Length/volume of the conduction system

Question 22

25. what 2 things is varying the resistance of the arterioles used to control?

Answer 22

1. flow to a particular organ/organs
2. whole-body perfusion pressure

Question 23

29. where does neural input come from

Answer 23

comes via the sympathetic nervous system

Question 24

30. what does sympathetic nervous system release to cause vascoconstriction

Answer 24

releases noradrenaline

Question 25

31. what does noradrenaline bind to on vascular smooth muscle

Answer 25

binds to α1 adrenoreceptors

Question 26

32. where are the effects of neural input the strongest

Answer 26

effects are strongest in the skin, kidney, skeletal muscle and digestive tract vessels

Question 27

33. which 2 instances is blood flow regulation most important

Answer 27

Flow regulation is most important: 1. in organs that require constant perfusion 2. where local metabolic conditions may change rapidly and markedly

Question 28

34. what are the 2 primary functions of local mechanism

Answer 28

1. autoregulation 2. Metabolic vasodilation

Question 29

35. what is autoregulation

Answer 29

adjustment of local resistance over a large range of arterial pressures to provide constant local flow

Question 30

36. what is metabolic vasodilation

Answer 30

upregulation of flow when local metabolic demands increase achieved by dilating muscular vessels to decrease resistance

Question 31

37. outline the mechanism of autoregulation

Answer 31

1. Stretch receptors (mechanically gated ion channels) open, leading to constriction in vessels 2.This allows influx of Na+ ions and Ca2+ ions 3. Vasodilating metabolites (adenosine, K+ ions) act on smooth muscle cells to cause relaxation 4. As flow increases these substances are washed out of the tissue and muscle tone increases again

Question 32

38. what type of vasodilator is nitric oxide?

Answer 32

A potent vasodilator

Question 33

39. What produces nitric oxide

Answer 33

vascular endothelium

Question 34

40. What are the 2 forms of NOS

Answer 34

1. endothelial NOS (eNOS) 2.inducible NOS (iNOS)

Question 35

41. How is NO synthesised

Answer 35

NO is synthesised from L-arginine and oxygen by the nitric oxide synthase (NOS) enzyme in response to increased intracellular Ca2+

Question 36

42. outline the mechanism for NO signalling

Answer 36

1. NO quickly diffuses out of the endothelium and into vascular smooth muscle 2. in vascular smooth muscle, it activates guanylyl cyclase 3. This increases cyclic GMP levels, leading to relaxation

Question 37

44. what does sildenafil citrate AKA Viagra cause when it acts on the NO signalling pathway?

Answer 37

it causes the enhancement of the NO signalling pathway