Question

Which reaction is the result of parasympathetic nervous system stimulation?

Option 1: Decreased GI motility
Option 2: Decreased heart rate
Option 3: Bronchodilation
Option 4: Pupil dilation

Answer 1

The result of parasympathetic nervous system stimulation is pupil dilation. Parasympathetic stimulation originates from the cardioinhibitory region with impulses traveling via the vagus nerve (cranial nerve X). ACh slows HR by opening ligand-gated potassium ion channels to slow the rate of spontaneous depolarization.

Step-by-step explanation:

The result of parasympathetic nervous system stimulation is pupil dilation. Parasympathetic stimulation originates from the cardioinhibitory region with impulses traveling via the vagus nerve (cranial nerve X). Parasympathetic stimulation releases the neurotransmitter acetylcholine (ACh) at the neuromuscular junction. ACh slows HR by opening ligand-gated potassium ion channels to slow the rate of spontaneous depolarization. Without any nervous stimulation, the SA node would establish a sinus rhythm of approximately 100 bpm. Since resting rates are considerably less than this, it becomes evident that parasympathetic stimulation normally slows HR.