1. Adequate cardiac output is necessary in order 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 includes PRELOAD, CONTRACTILITY and AFTERLOAD.
In the following conditions, indicate what factor/s influence the cardiac output: PRELOAD, CONTRACTILITY, AFTERLOAD, HEART RATE. Explain the why the factor/s affects cardiac output in 1 to 2 sentences.
a. High blood pressure - High blood pressure produces a resistant force to systolic contractions. It increases afterload and decreases stroke volume
b. Massive bleeding - Blood loss makes the blood volume to decrease, decreasing cardiac output. The body responds by increasing the heart rate and contractility.
c. the drug dopamine - It is used to increase cardiac output by increasing the heart rate and contractility.
d. Running a sprint - Heart rate and contractility is increased since the body needs more O2 for energy. Cardiac output increases.
e. Hyperthyroidism with increased secretion of thyroid hormones - It increases preload and contractility, decreases afterload, and increases cardiac output because of the high levels of thyroid hormone.
f. Massive myocardial infarction (cardiac tissue death) - Cardiac output is reduced due to the insufficient blood flow. The preload increases while the contractility decreases.
g. Hypothermia - The decrease of body temperature causes the heart rate to decrease and the stroke volume to increase.
h. Emotional distress - Heart rate increases and afterload increases in response to the narrowing of blood vessels.