Cardiovascular Response to Exercise

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Questions and Answers

What happens to vascular resistance during exercise?

It remains constant, uniformly distributing blood throughout the body.

It decreases, allowing more blood flow to non-active muscles.

It increases, diverting blood away from non-active muscles to active ones. (correct)

It fluctuates randomly, depending on the exercise intensity.

What percentage of cardiac output do the splanchnic and renal vascular beds receive at rest?

20%

15%

25% (correct)

30%

During exercise, blood flow to the splanchnic and renal regions declines in relation to what factor?

The intensity of the work performed. (correct)

The hydration level of the individual.

The age of the individual.

The duration of the exercise session.

What occurs to skin blood flow during exercise as body temperature rises?

It initially decreases, then rises as heat exposure increases. Signup and view all the answers

What is the primary regulation role of the splanchnic and renal regions during exercise?

Regulate blood pressure and redistribute oxygen. Signup and view all the answers

What happens to cerebral blood flow during exercise?

It remains unchanged regardless of exercise intensity. Signup and view all the answers

How does blood pooling affect venous return during heat exposure?

It impairs venous return and reduces central blood volume. Signup and view all the answers

At maximal oxygen consumption levels, what happens to skin blood flow?

It drastically decreases as skin vessels constrict. Signup and view all the answers

What is the equation that represents minute ventilation (VE)?

VE = VT x fb Signup and view all the answers

At what range of VO2 max does the ventilatory response begin to show a curvilinear increase?

65 to 75% Signup and view all the answers

What happens to tidal volume (VT) during heavy exercise intensities?

VT plateaus Signup and view all the answers

If a person has a tidal volume of 0.5 L and a frequency of breathing of 60 breaths per minute, what is their minute ventilation (VE)?

90 L/min Signup and view all the answers

What is a notable change in minute ventilation (VE) during maximal exercise compared to at rest?

VE dramatically increases Signup and view all the answers

What component primarily contributes to the increase in VE during heavy exercise intensities?

Increase in respiratory rate (fb) Signup and view all the answers

How much can performance gains in ‘time to exhaustion’ improve at submaximal exercise intensities?

More than 50% Signup and view all the answers

What is the tidal volume (VT) at rest if the minute ventilation (VE) is 6 L/min and the frequency of breathing (fb) is 12 br/min?

0.5 L Signup and view all the answers

What occurs at the anaerobic threshold during exercise?

Anaerobic glycolysis starts supplying more muscle energy. Signup and view all the answers

At what percentage of VO2 max does the anaerobic threshold typically occur?

65 to 75% Signup and view all the answers

Which parameter is mainly affected during exercise as intensity increases?

Volume of expired CO2. Signup and view all the answers

What physiological change is associated with the transition past the anaerobic threshold?

Development of lactic acidosis. Signup and view all the answers

Which of the following gases is NOT a focus in assessing ventilatory changes during exercise?

Nitrogen oxide Signup and view all the answers

What happens to heart rate (HR) and stroke volume (SV) during prolonged aerobic exercise at a constant workload?

HR increases while SV decreases Signup and view all the answers

What drives the cardiovascular drift observed during prolonged steady-state exercise?

Decrease in central venous pressure Signup and view all the answers

What physiological change occurs as a result of dehydration during exercise?

Decreased skin blood flow Signup and view all the answers

How does sympathetic-mediated vasoconstriction affect cardiac output redistribution during exercise?

It decreases blood flow to the kidneys and splanchnic regions Signup and view all the answers

What is a compensatory response to maintain cardiac output during cardiovascular drift?

Increase in heart rate Signup and view all the answers

What was the percentage of body weight loss experienced by endurance-trained cyclists during a 120-min exercise bout in 35°C?

4.9% Signup and view all the answers

What happens to cardiac output as the intensity of exercise increases?

It increases with sympathetic-mediated responses Signup and view all the answers

During prolonged exercise, which factor primarily affects stroke volume negatively?

Dehydration and blood volume decrease Signup and view all the answers

What primarily contributes to the increase in overall blood volume during aerobic training?

Increase in plasma volume Signup and view all the answers

Which hormone is NOT typically associated with increasing plasma volume during exercise?

Epinephrine Signup and view all the answers

What effect does an increase in plasma protein levels have on the blood?

Increases osmotic pressure Signup and view all the answers

How does endurance training affect hematocrit levels in trained individuals?

Hematocrit levels may decrease Signup and view all the answers

What is the main role of red blood cells in the context of aerobic training?

Transport oxygen bound to hemoglobin Signup and view all the answers

What does the a-vO2 difference represent?

Oxygen concentration difference in arterial and venous blood Signup and view all the answers

What impact does increased oxygen carrying capacity have on athletic performance?

Enhances delivery of oxygen to muscles Signup and view all the answers

Which of the following factors is NOT likely to contribute to an increase in maximal oxygen consumption?

Decreased blood pH levels Signup and view all the answers

Study Notes

Cardiovascular Drift

During prolonged, constant submaximal exercise, heart rate (HR) increases and stroke volume (SV) decreases while cardiac output stays constant.
This happens due to a decrease in blood volume caused by sweating and fluid shifts, leading to increased skin blood flow for thermoregulation.
The redistribution of blood flow reduces central venous filling pressure (preload), which decreases SV.
HR increases to compensate and maintain cardiac output.

Partitioning of Cardiac Output during Exercise

With increasing exercise intensity, there is sympathetic-mediated vasoconstriction in the kidneys, splanchnic regions, and inactive muscles.
This redirects blood flow from these areas to active muscles, increasing their blood supply.
The splanchnic and renal vascular beds each receive about 25% of cardiac output (CO) at rest, but utilize only 15-20% of available oxygen.
Blood flow to these regions decreases during exercise, proportionate to the intensity of the work.
Cutaneous blood flow initially decreases during exercise, but increases with rising body temperature as exercise duration and intensity increase.
Skin blood flow eventually decreases when skin vessels constrict as overall oxygen consumption nears maximal values.
Cerebral blood flow remains unchanged during exercise.

Blood Volume Changes

Increased blood volume during exercise results mainly from elevated plasma volume (PV), but also involves a rise in red blood cell (RBC) volume.
Increased PV with aerobic training is thought to be caused by increased plasma protein levels, particularly albumin, which raises osmotic pressure, retaining fluid in the blood.
Exercise also triggers the release of antidiuretic hormone (ADH) and aldosterone, promoting water and sodium reabsorption in the kidneys, further increasing PV.
Increased RBC volume with endurance training contributes to overall blood volume increases. While RBC count and hemoglobin concentration may rise, hematocrit (RBC volume to blood volume ratio) may decrease.

Oxygen Carrying Capacity and Performance Impact

Highly trained athletes typically demonstrate higher absolute amounts of hemoglobin and RBCs.
These changes enhance oxygen carrying capacity, improve oxygen delivery to muscles, and contribute to increased maximal oxygen consumption (VO2 max) and aerobic capacity.
Oxygen extraction is the amount of oxygen removed from blood by tissues during blood flow.
The arteriovenous oxygen difference (a-vO2 difference) represents the difference in oxygen concentration between arterial and venous blood.
Submaximal exercise gains include more than 50% improvement in time to exhaustion with standardized exercise tests.

Ventilatory Responses to Exercise

Minute ventilation (VE) is determined by tidal volume (VT) and breathing frequency (fb).
Both VT and fb increase linearly with exercise until heavy exercise.
At heavy exercise intensities, VT plateaus, and further VE increases are driven by increases in fb.

Metabolic Changes with Exercise Intensity

Progressive exercise intensity leads to a range of metabolic changes.
The "anaerobic threshold" or "lactate inflection point" occurs at approximately 65%-75% of VO2 max, where lactic acidosis develops as anaerobic glycolysis becomes more prominent in muscle energy supply.

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Description

This quiz covers key concepts related to cardiovascular drift and the partitioning of cardiac output during exercise. Understand how exercise affects heart rate, stroke volume, and blood flow distribution to active muscles. Test your knowledge of the physiological responses during prolonged physical activity.