Final answer:
Positive inotropes enhance the heart's contractility by increasing the strength of the heart's contractions, often through increasing the concentration of intracellular calcium. They do not directly affect heart rate, blood pressure, or vessel dilation. The correct answer to the student's question is C. Enhancing contractility.
Step-by-step explanation:
Positive Inotropes and Heart Function
Positive inotropes are substances that enhance the contractility of the heart. They do not increase the heart rate, decrease blood pressure, or dilate blood vessels directly. Rather, they work by causing a stronger contraction of the heart muscles. One way they do this is by increasing the concentration of intracellular calcium ions, which leads to stronger heart contractions.
Cardiac contractility can be affected by various factors, including positive inotropes like dopamine and isoproterenol, which mimic the effects of epinephrine and norepinephrine by stimulating the influx of calcium ions. Other examples of positive inotropes include digitalis, which increases the strength of heart contractions by blocking the sequestering of calcium ions into the sarcoplasmic reticulum, as well as thyroid hormones and glucagon, which also have positive inotropic effects.
The correct answer to the student's question is that positive inotropes allow the heart to pump by C. Enhancing contractility. They increase the strength of contraction, and this is how they effectively support the cardiac output and blood flow through the body.