CR: PBL 2 (Heart and Exercise)

Question 1

Define pulse pressure

Answer 1

Systolic BP - Diastolic BP (difference)

Question 2

Define mean arterial pressure

Answer 2

Arithmetic mean of arterial blood pressure (CO x TPR)

Question 3

Define pre-load

Answer 3

Pressure of blood in the ventricle before contraction

Question 4

What is central venous pressure?

Answer 4

Pressure of blood in the great veins as they enter the right atrium

Question 5

Define venous return

Answer 5

The volume of blood returning to the right atrium in one minute

Question 6

Define total peripheral resistance

Answer 6

Resistance to the flow of blood in the whole system (MAP/CO)

Question 7

Define systemic vascular resistance

Answer 7

Resistance to blood flow offered by all of the systemic vasculature (not pulmonary) - (MAP - RA pressure)/CO

Question 8

Define ‘ejection fraction’

Answer 8

Proportion of EDV which is ejected by contraction

Question 9

What is meant by ‘central command’

Answer 9

The anticipatory response of the autonomic nervous system to exercise which causes CO and arteriole adjustment

Question 10

How does the cardiovascular system respond to exercise immediately?

Answer 10

Local chemicals cause arteriole dilation (lactic acid, nitric oxide and increased CO2, H+ and K+ levels)

Question 11

How does the autonomic nervous system respond to exercise?

Answer 11

Sympathetic fight or flight response initiated:
a1 receptor –> causes blood shunting from digestion
B1 receptor –> increases HR and contraction force (SV)
B2 –> bronchodilation

Question 12

Why does heart rate change after exercise?

Answer 12

Increased sympathetic stimulation to SAN

Question 13

Why does systolic blood pressure change after exercise?

Answer 13

Greater volume of blood in ventricles due to increased venous return –> exerts greater pressure on arterial walls in systole

Question 14

Why does diastolic blood pressure change after exercise?

Answer 14

Decreases due to vasodilation to the actively respiring muscles/tissues

Question 15

Why does stroke volume change after exercise?

Answer 15

Starling’s law - greater distension of ventricular sarcomere with increased preload –> greater contraction –> greater volume of blood ejected in one beat

Question 16

How do you calculate mean arterial blood pressure?

Answer 16

1/3(pulse pressure) + diastolic BP

OR CO x TPR

Question 17

How may mean arterial pressure values be indicative of ischaemia?

Answer 17

MAP is considered to represent perfusion pressure, so less than 65mmHg may be indicative of ischaemia

Question 18

What are normal BP values?

Answer 18

Systolic: Below 120mmHg
Diastolic: Below 80mmHg

Question 19

What are normal HR values?

Answer 19

60-100bpm

Question 20

What are normal stroke volume values?

Answer 20

70ml

Question 21

What are normal cardiac output values?

Answer 21

4.9-5.6 L/min

Question 22

What are normal pulse pressure values?

Answer 22

40mmHg

Question 23

What are normal mean arterial pressure values?

Answer 23

65-110mmHg

Question 24

Why doesn’t MAP change after exercise?

Answer 24

Despite increased cardiac output, there is vasodilation of muscles which counteracts increased pressure

Question 25

Why does pulse pressure increase after exercise?

Answer 25

Due to increased difference in blood pressures (systolic up, diastolic down)

Question 26

What factors affect heart rate?

Answer 26

autonomic innervation, hormones, fitness and age

Question 27

What factors affect stroke volume?

Answer 27

Heart size, fitness, gender, contractility, duration of contraction, preload and afterload

Question 28

How do you calculate stroke volume?

Answer 28

EDV - ESV

Question 29

How does preload affect SV and CO?

Answer 29

Increased preload increases SV and CO

Question 30

How does afterload affect SV and CO?

Answer 30

Increased afterload (resistance) decreases SV and CO

Question 31

Outline the Frank-Starling mechanism

Answer 31

Increased venous return --> increased EDV (ventricular filling) --> increased preload --> increased myocyte stretch or sarcomere --> greater recoil --> greater ejection --> greater SV and CO

Question 32

What is a baroreceptor?

Answer 32

Stretch receptor

Question 33

Where are baroreceptors found?

Answer 33

Aorta, carotid arteries, vena cava and atria

Question 34

How do baroreceptors respond to an increase in stretch?

Answer 34

Parasympathetic stimulation increased --> decreased HR and SV --> decreased BP

Question 35

How do baroreceptors respond to a decrease in stretch

Answer 35

Parasympathetic stimulation suppressed --> increase HR and SV --> increased flow and BP

Question 36

What are chemoreceptors?

Answer 36

Receptors that respond to changes in chemicals such as pO2, pCO2, H+ and lactic acid

Question 37

Where are chemoreceptors found?

Answer 37

CNS and by baroreceptors

Question 38

How do chemoreceptors respond to an increase level of chemicals?

Answer 38

Sympathetic stimulation suppressed --> decreased HR and SV

Question 39

How do chemoreceptors respond to a decreased level of chemicals?

Answer 39

Sympathetic stimulation increased --> increased HR and SV

Question 40

What would exercise-induced hypotension indicate?

Answer 40

Coronary artery disease if drop of more than 10mmHg systolic BP during exercise

Question 41

What would exercise-induced angina indicate?

Answer 41

Angina is severe chest pain that radiates to shoulder/arm and is due to inadequate cardiac blood supply --> coronary artery disease

Question 42

Name the two main mechanisms blood flow to tissues can be increased during exercise

Answer 42

Greater stroke volume --> greater CO | Vasodilation