POST-LECTURE ACTIVITY
THE CARDIOVASCULAR SYSTEM
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: In this condition, contractility influences the cardiac output because an increase in contractility causes an increase in stroke volume and consequently, a person’s blood pressure may move to higher levels.
b. Massive bleeding: In this condition, afterload influences the cardiac output because as the afterload increases, the stroke volume decreases as the body loses more blood which results in a reduced cardiac output.
c. the drug dopamine: When we take the drug dopamine, it produces positive chronotropic and inotropic effects on the myocardium which results in increased heart rate and cardiac contractility thus influencing the cardiac output.
d. Running a sprint: Whenever we run a sprint, our heart usually beats faster so that more blood gets out to our body. This suggests that an increase in our heart rate causes an increase in our cardiac output.
e. Hyperthryoidism with increased secretion of thyroid hormones: In this condition, preload and heart rate influences cardiac output because in a state of hyperthyroidism, preload is increased and the reduced peripheral vascular resistance and elevated heart rate increases the cardiac output.
f. Massive myocardial infarction (cardiac tissue death): In this condition, preload and afterload influences cardiac output because preload will decrease because the heart is not able to relax as it should while the afterload will decrease in an attempt to increase blood pressure by tightening blood vessels.
g. Hypothermia: In this condition, our heart rate influences cardiac output because it falls below a core temperature of 34 degrees C due to increasing bradycardia.
h. Emotional distress: In this condition, our heart rate influences cardiac output because emotional distress causes an increase in heart rate, elevation of blood pressure and release of stress hormones which prepares our body to deal with stress.
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