Blood Pressure and Exercise Quiz

The cardiovascular system delivers nutrients, moves oxygen throughout the body, removes carbon dioxide, thermoregulates, removes waste, assists in clotting, communicates, regulates hormones, and facilitates immune responses.

Cardiac output is the total amount of volume of blood pumped by the heart per minute.

Cardiac output (Q) is equal to stroke volume (SV) multiplied by heart rate (HR), Q = SV x HR.

Stroke volume is the volume of blood pumped per beat by the ventricles of the heart.

End-diastolic volume (EDV) is the volume of blood in the ventricles before they contract.

End-systolic volume (ESV) is the volume of blood in the ventricles after they have contracted.

During exercise, stroke volume can be increased by a rise in end-diastolic volume (EDV) and a drop in end-systolic volume (ESV), resulting in a larger stroke volume (SV).

$Q = 25 L/min$

88% (22,000mL)

4% (1000mL)

3% (900mL)

2% (600mL)

Vessels stop being dilated and metabolites are removed

Low effect due to being on the same level or above the heart

High effect due to more muscle requiring more blood

More resistance in the upper body, leading to higher blood pressure in the upper body compared to the lower body

Pressure = Flow x Resistance

Systolic blood pressure increases with exercise due to increased cardiac output

MAP = \frac{1}{3} \cdot \text{Systolic pressure} + \frac{2}{3} \cdot \text{Diastolic pressure}

Pulse pressure is the difference between systolic and diastolic blood pressure

Resistance (R) = \frac{\text{Pressure}}{\text{Flow}}

Poiseuille's Law describes the influence of vessel diameter on blood flow rate: Q = \frac{\text{Pressure} \cdot \pi \cdot \text{Radius}^4}{8 \cdot \text{Viscosity} \cdot \text{Length}}

Vasodilation is the widening of blood vessels and it is controlled by the sympathetic nervous system (SNS)

Preload refers to the degree of stretching experienced by the muscle cells in the heart during diastole. It is influenced by factors such as venous return and gravity. Preload affects stroke volume by determining the amount of blood that fills the ventricles before contraction. The equation to calculate stroke volume using preload is: SV = EDV - ESV, where SV is stroke volume, EDV is end-diastolic volume, and ESV is end-systolic volume.

The muscle pump plays a crucial role in increasing stroke volume during standing and running. When standing, the muscle pump helps to push blood back up towards the heart against the force of gravity. During running, the muscles contract and pinch the venous valves, pumping more blood and increasing venous return. This leads to an increase in stroke volume. The muscle pump counteracts the effects of gravity by actively assisting in the return of blood to the heart.

The respiratory pump assists in increasing venous return by utilizing changes in pressure during breathing. When inhaling, the pressure in the thoracic cavity decreases, causing the vasculature to open up. This, along with the downward movement of the diaphragm and increased pressure in the abdominal area, forces blood to move towards the chest and increases venous return.

The Frank-Starling mechanism states that an increased stretch in the ventricles (due to increased filling) leads to a more forceful contraction and increased stroke volume. This means that as the heart receives more blood during diastole, it pumps out more blood during systole, resulting in an increased stroke volume.

Afterload refers to the pressure that the heart has to pump against in order to eject blood. It is influenced by factors such as arterial resistance and valve function. An increase in afterload can decrease stroke volume as the heart has to work harder to overcome the pressure. The equation to calculate afterload is: Afterload = SBP - DBP, where SBP is systolic blood pressure and DBP is diastolic blood pressure.

Ejection fraction is defined as the percentage of blood that is ejected from the heart during systole compared to the total volume of blood in the ventricles. It is calculated using the equation: EF = (SV / EDV) x 100%. Ejection fraction is an important measure of heart function, as a decrease in ejection fraction can indicate reduced cardiac output and impaired ventricular function.

During exercise, heart rate and stroke volume are initially positively correlated, meaning that an increase in heart rate is accompanied by an increase in stroke volume. However, as exercise duration increases, there is a phenomenon known as cardiovascular drift, where stroke volume gradually decreases while heart rate continues to rise. This is believed to be caused by factors such as dehydration and increased core body temperature, which can reduce blood volume and impair ventricular filling, leading to a decrease in stroke volume.