Cardiovascular Responses — Exercise

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2020B Q11

Exam question

Describe the changes in the circulatory system that occur during exercise.

CICMWrecks answer

Master answer

Exercise = Strenuous physical activity where there is increased metabolic activity leading to increased requirement for energy and oxygen

CVS changes to accommodate and compensate for such increase in metabolism

Cardiac output	C.O.	5L/min
Heart rate	HR	60-100 bpm
Systemic vascular resistance	SVR	1600 dynes.s.cm-5
Stroke volume	SV	70mls
Blood pressure	BP	120/80
Central venous pressure	CVP	0-5mmHg

Cardiac output	↑	Can increase up to 4-5 folds CO plateaus at near-maximal workload
HR	↑	Max HR = 220-age Increases and plateaus at max
SV	↑→↓	Initially increases, then decreases due to diminishing diastolic time
Contractility	↑	Increased HR → increased contractility (treppe effect)Activation of sympathetic nervous system → increased contractility

CVP	↑	Increases

Systolic BP	↑	Increases
Diastolic BP	↓	Decreases
MAP	↑	Increases slightly
Pulse pressure	↑	Widens

PVR	↑	Decreases overall

Increased muscle activity -> increased o2 demand
Regional vasodilation
- Increased local concentration of metabolites ie Co2, lactate, K+
- Vasoactive mediator released by endothelium ie NO, ATP
- Sympathetic stimulation -> B2 adrenoceptor activation
Overall: decrease in vascular resistance to muscles -> increased blood flow
Corresponding vasoconstriction of viscera and skin

Cardiac output can increase up to 0L/min
Due to both increase in HR and SV and decreased afterload
With increasing workload HR increases but SV decreases due to dec diastolic time

Guo 2021

Answer by Guo

Past papers

1 appearance

Exam	Exact exam wording	Candidate success
2020B Q11	Describe the changes in the circulatory system that occur during exercise.	22%