Question

Assume that the triangular and circular molecules shown in the illustration represent specific neurotransmitters. Which of the following best describes the effect on the heart of neurotransmitters released from the postganglionic neurons of B and C?

Options:
A) B would increase heart rate, while C would decrease it.
B) B and C would act in synergy to decrease heart rate and contraction force.
C) C would increase heart rate, while B would decrease it.
D) B and C would act in synergy to increase heart rate and contraction force.

Answer 1

The answer is A) B would increase heart rate, while C would decrease it, based on whether norepinephrine or acetylcholine is released onto cardiac cells and their respective receptor interactions.

Step-by-step explanation:

The effect on the heart of neurotransmitters released from the postganglionic neurons of B and C depends on the type of neurotransmitter they release. If neurotransmitter B releases norepinephrine (NE) onto cardiac cells, it binds to adrenergic receptors, leading to increased heart rate and contractile force (positive inotrope). In contrast, if neurotransmitter C releases acetylcholine (ACh) onto those cells, it binds to muscarinic receptors, causing cells to hyperpolarize and decrease heart rate and contractile force (negative inotrope).

Thus, the correct answer is:

A) B would increase heart rate, while C would decrease it.