1. Adequate cardiac output is necessary to supply oxygen and other nutrients to all body tissues. Cardiac output is influenced by stroke volume and heart rate. Factors affecting the stroke volume include PRELOAD, CONTRACTILITY, and AFTERLOAD.
In the following conditions, indicate what factor/s influence the cardiac output: PRELOAD, CONTRACTILITY, AFTERLOAD, HEART RATE. Explain why the factor/s affects cardiac output in 1 to 2 sentences.
a. High blood pressure: High blood pressure reduces the elasticity of the arteries, which contributes to the heart's workload, increasing the force needed to pump blood. Thus, afterload is the factor observed affecting cardiac output.
b. Massive bleeding: Massive loss of blood causes a decrease in cardiac output and arterial pressure. This is due to the increase of heart rate, whereas oxygenated blood is distributed first to the vital organs to reduce the trauma caused by the massive bleeding and restore the arterial pressure and cardiac output.
c. the drug dopamine: Dopamine, a neurotransmitter in some areas of the CNS, affects the cardiac output as it helps increase heart rate, as well as cardiac contractility.
d. Running a sprint: In this activity, the heartbeat fastens due to the loss of oxygen during exercise and as the body's response in order to supply enough oxygen-rich blood in the different areas of the body, hence, increasing cardiac output.
e. Hyperthyroidism with increased secretion of thyroid hormones: Hyperthyroidism increases cardiac output, as this condition results in the increase of blood volume and preload. The increased secretion of thyroid hormones causes an increase in red cell mass, thus, explaining why the blood volume increased.
f. Massive myocardial infarction (cardiac tissue death): most commonly known as heart attack, this damage results in a decrease in cardiac output, as blood flow is compromised, which also leads to the myocardium being deprived of oxygen.
g. Hypothermia: During hypothermia, the body's core temperature falls below 34 degrees Celcius, leading to bradycardia (slow heart rate) and an increase in arterial blood pressure. With that being said, cardiac output drops.
h. Emotional stress: Intense emotional stress causes the elevation of heart rate and blood pressure and the release of stress hormones. Although different individuals have different responses to stressors, it may still cause in the rising of cardiac output.