MCQ Physiology Answer 15

The Correct Answer is D

Norepinephrine is the neurotransmitter used by the sympathetic division of the ANS. Efferent sympathetic stimulation suppresses motility and secretion, decreases blood flow to intestine and contracts sphincter muscles. The neurotransmitter released, norepinephrine, binds to pre-synaptic alpha2 adrenergic receptors to suppress the release of excitatory neurotransmitters.

The overall result of sympathetic activations is a state of paralysis of intestinal motility and reduced blood flow. If the condition persists to a pathological state, it is called paralytic ileus.

Inhibitory input by the parasympathetic NS relaxes the appropriate sphincter muscles.

Sensory neurons in the gut inform the brain of glucose concentration, pH, osmolality, movement of material past mechanoreceptors and the level of contractile strength or stretch. The majority of parasympathetic input is through the vagus nerve, which innervates the GI tract from the esophagus to the transverse colon. The pelvic nerves provide parasympathetic innervation to the remainder of the colon, the rectum, and anus.

These functions are monitored by sensory neurons; however, they are monitored by Afferent, not Efferent fibers.

Category: Physiology MCQs