a. High blood pressure:
Factors: Afterload
Explanation: Pressure increase in the left ventricles or increased afterload is needed in order to overcome elevated blood pressure within the blood vessels and push the valves open. Afterload increase lowers the stroke volume which leads to a decrease in cardiac output, lowering the blood pressure.
b. Massive bleeding
Factors: Preload, afterload, contractility, and heart rate.
Explanation: In the occurrence of massive bleeding, blood volume is decreased leading to decrease in preload and afterload. To compensate for the loss of blood, sympathetic activation increases the contractility of the heart and the heart rate.
c. the drug dopamine
Factors: Contractility and Heart rate
Explanation: Dopamine increases cardiac output by producing chronotropic and inotropic effects on the myocardium or heart muscle; leading to increased heart rate and cardiac contractility.
d. Running a sprint
Factors: preload, contractility, and heart rate
Explanation: Since the muscles need more oxygen during exercise, greater cardiac output is required. Heart rate increases to increase the blood flow throughout the body while the stroke volume is elevated by increasing the heart’s preload and contractility.
e. Hyperthryoidism with increased secretion of thyroid hormones
Factors: Preload, afterload, contractility, and heart rate
Explanation: Elevated levels of thyroid hormones in the system constitutes produce positive inotropic and chronotropic effects on the heart that lead to increased contractility and heart rate. As hyperthyroidism promotes sodium reabsorption and greater blood volume, this leads to an increase in cardiac preload and a decrease in cardiac afterload.
f. Massive myocardial infarction (cardiac tissue death)
Factors: Contractility
Explanation: The heart is unable to pump due to inadequate oxygen flowing through the cardiac muscles; decreasing its contractility. Therefore, cardiac output is reduced.
g. Hypothermia
Factors: Heart rate
Explanation: As the body is cooled during hypothermia, metabolism is slowed which reduces oxygen intake of the tissues in the body. Because there is lesser blood flow required, heart rate is slowed.
h. Emotional distress
Factors: Afterload and heart rate
Explanation: Due to the elevated levels of stress hormones and increased metabolic requirement during emotional distress, heart rate is increased which promotes blood flow. Also, afterload is also increased to counteract the higher blood pressure induced by vasoconstriction that occurs during stressful situations.
REFERENCES:
https://www.bionity.com/en/encyclopedia/Afterload.html#:~:text=Hypertension%20(Increased%20blood%20pressure)%20increases,than%20the%20elevated%20blood%20pressure.
Sapirstein, L. A., Sapirstein, E. H., & Bredemeyer, A. (1960). Effect of hemorrhage on the cardiac output and distribution in the rat. Circulation Research, 8(1), 135-148. https://doi.org/10.1161/01.res.8.1.135
https://www.rxlist.com/dopamine-drug.htm#description
https://myhealth.alberta.ca/Health/Pages/conditions.aspx?hwid=tx4080abc
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2774583/#:~:text=Ischemia%20due%20to%20decreased%20coronary,in%20the%20arterial%20blood%20pressure.
https://jamanetwork.com/journals/jama/fullarticle/208031
Tortora, G. J., & Derrickson, B. H. (2015). Principles of anatomy and physiology. Wiley Global Education.