POST-LECTURE ACTIVITY
THE CARDIOVASCULAR SYSTEM
Week 10
Please submit your answers in this forum.
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
Two important risk factors for the cardiovascular system are obesity and hypertension. Whereas arterial hypertension increases afterload to the left ventricle, obesity produces an increase in stroke volume and increases preload (Schmieder, R. E., & Messerli, F. H., 1987).
b. Massive bleeding
The initial compensatory responses to reduced circulating blood volume due to hemorrhage is an increased heart rate and systemic vascular resistance in order to maintain perfusion to vital organs (Gutierrez et al. 2004).
c. the drug dopamine
Mod dose (3 – 10 mcg/kg/min): primarily activates β1 adrenergic receptors in heart increasing heart rate (positive chronotropic agent), contractility (positive inotropic agent)
d. Running a sprint
Cardiac output during exercise increases greatly owing to the relatively high heart rates that are achieved during exercise. Heart rate increases proportionately with workload until heart rates close to maximal are attained (Evans D. L. 1985).
e. Hyperthyroidism with increased secretion of thyroid hormones
Overall, hyperthyroidism is characterized by an increase in resting heart rate, blood volume, stroke volume, myocardial contractility, and ejection fraction (Vargas-Uricoecheato et al. 2014).
f. Massive myocardial infarction (cardiac tissue death)
Coronary blood flow decreases in patients with severe myocardial damage when cardiac output decreases and heart rate rises (Mechanic OJ, Gavin M, Grossman SA. 2022).
g. Hypothermia
Hypothermia also caused a significant increase in stroke volume and a significant decrease in heart rate with no change in cardiac output (Brooks et al. 1984).
h. Emotional distress
Under any type of stress, the blood pressure and heart rate will significantly go up emotional distress have varying effects on the cardiac output; sadness produced a distinct pattern with moderate increases in blood pressure and vascular resistance and a decrease in cardiac output compared with changes during neutral imagery. Fear, action, and joy produced similar blood pressure changes in which systolic pressure increased and diastolic pressure was relatively unchanged (Sinha, R., Lovallo, W. R., & Parsons, O. A. 1992).