a. High blood pressure:
When blood volume is increased (high blood pressure), afterload and heart rate also increases, thus increasing cardiac output.
b. Massive bleeding:
Massive bleeding lowers blood pressure and volume, which means there is a decrease in preload, contractility, and afterload. Altogether, it causes decreased stroke volume and cardiac output.
c. The drug dopamine:
Dopamine is used to treat low blood pressure. When taken, it increases heart rate and contractility, leading to increased stroke volume and cardiac output.
d. Running a sprint:
Exercises such as running a sprint leads to an increased venous return, thus increasing the preload. This means that stroke volume is increased, thus cardiac output is also increased.
e. Hyperthyroidism with increased secretion of thyroid hormones:
Hyperthyroidism leads to an increased cardiac output because thyroid hormones increase heart rate and contractility (increased stroke volume).
f. Massive myocardial infarction (cardiac tissue death):
Cardiac tissue death leads to a decrease in contractility, thus increasing afterload. Due to this, cardiac output is reduced.
g. Hypothermia:
Hypothermia causes our body to vasoconstrict, thus increasing cardiac output due to an increase in contractility which raises the stroke volume.
h. Emotional distress:
When we are in emotional distress, the body releases epinephrine and norepinephrine, leading to an increased heart rate and contractility, and thus increased cardiac output.