Regulation of blood pressure

Question 1

What is blood vessel capacitance?

Answer 1

blood volume held at a given pressure (related to distensibility)

Question 2

What type of muscle is present in arterioles?

Answer 2

active vascular smooth muscle (VSM)

Question 3

What 3 reasons change the resistance to blood flow?

Answer 3

1. sympathetic nerves - decreased diameter of arteriole/increased resistance to blood flow
2. circulating catecholamines (e.g. adrenaline)
3. other vascular substances

Question 4

What are capillaries?

Answer 4

site of exchange - but not all perfumed with blood

Question 5

What controls capillaries?

Answer 5

dilation/ constriction of arterioles (pre-capillary sphincters in mesentery & brain)

Question 6

What regulates capillaries?

Answer 6

sympathetic innervation of vascular smooth muscle & vasoactive metabolites produced in the tissue

Question 7

Describe how much elastin is found in veins vs arteries?

Answer 7

more elastic tissue in arteries

Question 8

What blood vessel contains the largest % of blood in the cardiovascular system?

Answer 8

veins

Question 9

What can increase the activity of veins?

Answer 9

alpha-adrenergic receptors

Question 10

What is the equation for the velocity of blood?

Answer 10

v = Q/A
velocity = flow/cross-sectional area

Question 11

What is blood flow determined by?

Answer 11

• pressure difference between vessel inlet & outlet
• resistance of vessel to blood flow

Question 12

What is the blood flow equation?

Answer 12

Q = change P/R
flow = difference in pressure/resistance

Question 13

What is the TPR (total peripheral resistance)?

Answer 13

resistance of entire systemic vasculature

Question 14

Who’s law can be used to figure out the resistance to blood flow?

Answer 14

Poiseullie’s law

Question 15

What is Poiseuille’s law?

Answer 15

R = 8nl/pieR^4
resistance = 8 x viscosity of blood x length of blood vessel/ pie x radius of blood vessel (^4)

Question 16

describe the relationship between resistance to flow & vessel length & blood viscosity

Answer 16

RESISTANCE TO FLOW DIRECTLY proportional to vessel length and blood viscosity

Question 17

describe the relationship between resistance to blood flow & the radius

Answer 17

resistance to flow is INVERSELY PROPORTIONAL to 4th power of the radius

Question 18

Where is series resistance seen in blood vessels?

Answer 18

series resistance can be seen within an organ

Question 19

What is the total resistance?

Answer 19

sum of individual resistances

Question 20

What is the benefit of parallel resistance?

Answer 20

no loss of pressure

Question 21

Why does pressure decrease with blood flow?

Answer 21

energy lost overcoming frictional resistance

Question 22

What level of compliance (elasticity) does the aorta have?

Answer 22

low

Question 23

What level of cardiac output is in the arteries?

Answer 23

remain high

Question 24

Why is there a decrease in pressure in the arterioles?

Answer 24

high resistance of flow

Question 25

What is the compliance + pressure in veins?

Answer 25

high compliance + low pressure

Question 26

What is systolic pressure?

Answer 26

pressure when heart is contracting

Question 27

What is diastolic pressure?

Answer 27

pressure when the heart is relaxing

Question 28

What is the arterial pressure like during systolic pressure?

Answer 28

highest following ventricular blood ejection during contraction

Question 29

What is the arterial pressure like during diastolic pressure?

Answer 29

lowest during ventricular relaxation

Question 30

What is the pressure in veins?

Answer 30

<10mmHg

Question 31

Why is pressure so low in veins?

Answer 31

result of decreased resistance of each level of vasculature

Question 32

What is pulse pressure?

Answer 32

- reflects blood volume ejected from the left ventricle (stroke volume) pulse pressure = systolic - diastolic pressure

Question 33

What is mean arterial pressure?

Answer 33

- average pressure in one complete cardiac cycle mean arterial pressure = diastolic pressure + 1/3 pulse pressure

Question 34

Why is only 1/3 pulse pressure included to work out mean arterial pressure?

Answer 34

as the heart spends a longer time in diastole than in systole

Question 35

Throughout the day, what happens to the systolic & diastolic pressure?

Answer 35

reduces during sleep & increases in the morning

Question 36

What regulates blood pressure?

Answer 36

baroreceptors (mechanoreceptors) - carotid & aortic sinuses

Question 37

Describe how baroreceptors respond to an increase in pressure

Answer 37

increase in pressure = increased stretch = increased afferent nerve firing

Question 38

Describe how baroreceptors respond to an decrease in pressure

Answer 38

decrease in pressure = decreased stretch = decreased afferent nerve firing

Question 39

What nucleus receives input regarding blood pressure from the baroreceptors and directs the SNS + PNS changes via medullary CV centres?

Answer 39

Solitary Nucleus

Question 40

How does the peripheral nervous system cause a decrease in heart rate + blood pressure?

Answer 40

via vagus nerve

Question 41

How does SAN lead to increased heart rate?

Answer 41

increased cardiac muscle contractility = increased stroke volume

Question 42

What hormonal system can control arterial pressure?

Answer 42

medium/long term control of arterial pressure (Pa) can be controlled Renin angiotensin-aldosterone system (RAAS)

Question 43

Renin angiotensin-aldosterone system (RAAS)

Answer 43

regulates blood volume, electrolyte balance + systemic vascular resistance

Question 43

How does kidneys decrease arterial pressure (Pa)?

Answer 43

decrease perfusion pressure detected by kidney afferent arteriole mechanoreceptors, prorenin - renin released into blood

Question 44

Angiotensinogen - angiotensin I - angiotensin II What are the effects of angiotensin II?

Answer 44

- increase in sodium reabsorption - stimulates Na+-H+ exchange with kidney = hypothalamus - increases thirst & ADH secretion - increase water reabsorption in collecting ducts

Question 45

How do chemoreceptors in carotid & aortic bodies that detects O2 regulate blood pressure?

Answer 45

arteriole vasoconstriction

Question 46

How can Atrial natriuretic peptide regulate blood pressure?

Answer 46

V1Rec = vasoconstriction V2Rec = water retention

Question 47

What is chronic hypertension ?

Answer 47

elevated blood pressure

Question 48

What are the effects of chronic hypertension?

Answer 48

leads to desensitisation of baroreceptors

Question 49

What are the effects of hypertension?

Answer 49

- small increase in blood pressure - increased risk of morbidity + mortality. - if BP is too high - extra strain on blood vessels + other organs

Question 50

What does persistent high BP lead to increased risk of?

Answer 50

- heart disease - heart attacks - strokes - heart failure - aortic aneurysms - peripheral arterial disease - kidney disease - vascular dementia

Question 51

What are 3 hypertension treatments?

Answer 51

- angiotensin-converting enzyme (ACE) inhibitors - angiotensin II receptor blockers (ARBs) - Renin inhibitors

Question 52

What is the effect of diuretics (Thiazide) as a hypertension treatment?

Answer 52

decreases extracellular fluid

Question 53

What is the effect of beta-blockers as a treatment for hypertension?

Answer 53

decreased heart rate + contractility

Question 54

What is the effect of calcium channel blockers as a treatment for hypertension?

Answer 54

decreased contractility + increased vessel relation

Question 55

What is the effect of alpha-blockers as a treatment for hypertension?

Answer 55

inhibit alpha adrenoreceptors - decreased vasoconstriction