Final answer:
Due to the dilation of blood vessels in the erectile tissue initiated by ACh acting on muscarinic receptors.The correct response mediated by parasympathetic muscarinic receptors is (B) Erection,
Step-by-step explanation:
This response is mediated by the parasympathetic nervous system, specifically by the release of acetylcholine (ACh) by postganglionic parasympathetic fibers. ACh then binds to the muscarinic receptors in the erectile tissue of the reproductive organs, causing the blood vessels to dilate and leading to the engorgement of the erectile tissue. Other options, such as ejaculation, increased cardiac contractility, and dilation of the bronchi, are typically mediated by the sympathetic nervous system.
It's also important to note that parasympathetic effects often involve slowing down the heart rate, activating digestion, and promoting bodily functions that are necessary for rest and conservation of energy.
The correct option is (B) Erection.