Question

What happens when both sympathetic and parasympathetic neurons innervate a target organ?

A) Their effects tend to be antagonistic.
B) They always innervate the organ through different plexuses.
C) Their effects tend to be synergistic.
D) One division always exerts greater control over the target organ.

Answer 1

When sympathetic and parasympathetic neurons innervate the same organ, their effects are antagonistic (option A). They contribute to homeostasis by exerting opposite effects on target organs through neurotransmitters norepinephrine and acetylcholine, respectively.

Step-by-step explanation:

When both sympathetic and parasympathetic neurons innervate a target organ, their effects tend to be antagonistic. This is due to each system having a different role in regulating the body's involuntary functions. The sympathetic nervous system activates the "fight or flight" response, leading to actions like increasing heart rate and dilating the bronchi, while the parasympathetic nervous system induces the "rest and digest" state, promoting relaxation and digestion, slowing heart rate, and constricting the bronchi. Their neurotransmitters, norepinephrine and acetylcholine, bind to adrenergic and muscarinic receptors on the target cells, respectively. The autonomic nervous system maintains homeostasis by the balance of these two divisions, manipulating organ function through dual innervation where one system's activation can increase a certain function while the other decreases it.