Cardiovascular ExamQ Flashcards
Describe how the heart works as a dual-action pump when circulating blood during
exercise. [6]
The heart acts as a dual-action pump by working as two pumps simultaneously—one side sending oxygenated blood to the body (systemic circulation) and the other side sending deoxygenated blood to the lungs (pulmonary circulation).
Pulmonary Circulation:
-The right atrium receives deoxygenated blood from the body through the vena cava.
-It contracts, pushing blood through the tricuspid valve into the right ventricle.
-The right ventricle then contracts, forcing blood through the pulmonary valve into the pulmonary artery, which carries blood to the lungs to become oxygenated.
Systemic Circulation:
-The left atrium receives oxygenated blood from the lungs via the pulmonary vein.
-It contracts, pushing blood through the bicuspid (mitral) valve into the left ventricle.
-The left ventricle then contracts, forcing blood through the aortic valve into the aorta, which distributes oxygenated blood to the body.
Describe the action of the sympathetic nervous system on the heart prior to and during
exercise (3).
Before exercise, the sympathetic nervous system is activated and stimulates the release of adrenaline, which increases heart rate by acting on the SA node. This anticipatory rise prepares the body for activity.
During exercise, receptors in the cardiac control centre (e.g., chemoreceptors) detect changes such as increased CO₂ levels, leading to further stimulation of the SA node. This increases stroke volume and cardiac output, ensuring more oxygen is delivered to the working muscles.
Additionally, the sympathetic nervous system causes vasodilation of arteries supplying blood to the working muscles and the heart, while reducing blood flow to non-essential areas.
explain the difference in minute ventilation between submaximal and maximal
exercise
Submaximal Exercise:
Moderate increase in VE as the body requires more oxygen and removes more CO₂.
Tidal volume and respiratory rate both increase, but not to their maximum capacity.
The rise in ventilation follows a steady pattern and plateaus once oxygen demand is met.
Maximal Exercise:
VE reaches its highest level as both tidal volume and respiratory rate peak.
Respiratory rate increases significantly (up to 50-60 breaths per minute in trained athletes).
Tidal volume plateaus at high intensities, meaning further increases in VE are driven mostly by respiratory rate.
No plateau occurs—ventilation continues to rise to meet extreme oxygen demands and remove excess CO₂.
Explain how the cardiac control centre (CCC) regulates heart rate during exercise. (6)
The cardiac control centre (CCC) is located in the medulla oblongata of the brain and is stimulated by chemoreceptors, baroreceptors, and proprioceptors. These receptors send signals to the CCC, which then initiates the sympathetic and parasympathetic nervous systems to regulate the heart rate by stimulating the SA node.
During exercise, the sympathetic nervous system, via the accelerator nerve, stimulates the heart to beat faster, increasing the intensity of the heart rate to meet the demands of the working muscles.
The parasympathetic nervous system, via the vagus nerve, is responsible for returning the heart rate to resting levels once exercise intensity decreases.
Chemoreceptors detect an increase in CO₂ levels during exercise, which signals the CCC to increase heart rate to ensure more oxygen is delivered to the muscles and waste products are removed efficiently.
Baroreceptors help establish a set point for blood pressure. During exercise, if arterial pressure decreases, the heart rate increases to compensate and maintain sufficient blood flow.
Proprioceptors, which detect increased muscle movement, also send signals to the CCC to increase heart rate as the intensity of muscle activity rises.
