A patient receives a rapid infusion of saline; which explains the expected heart rate change?

Prepare for the Anatomy and Physiology II Milestone 1 Test with engaging questions, in-depth explanations, and focused study resources. Start your journey to excel in your exam!

Multiple Choice

A patient receives a rapid infusion of saline; which explains the expected heart rate change?

When saline is infused rapidly, venous return to the heart increases, filling the right atrium more. The stretch receptors in the right atrium respond to this increased filling. Their stimulation signals the autonomic nervous system to boost heart rate via sympathetic activation to the SA node (and reduce parasympathetic influence), a response known as the Bainbridge reflex. This helps the heart handle the greater venous return by increasing cardiac output, so the expected change is an increased heart rate. The other ideas don’t fit because an infusion that raises venous return wouldn’t lead to decreased filling or no change, nor would the brain spontaneously dampen sympathetic activity to slow the rate in this immediate reflex.

When saline is infused rapidly, venous return to the heart increases, filling the right atrium more. The stretch receptors in the right atrium respond to this increased filling. Their stimulation signals the autonomic nervous system to boost heart rate via sympathetic activation to the SA node (and reduce parasympathetic influence), a response known as the Bainbridge reflex. This helps the heart handle the greater venous return by increasing cardiac output, so the expected change is an increased heart rate.

The other ideas don’t fit because an infusion that raises venous return wouldn’t lead to decreased filling or no change, nor would the brain spontaneously dampen sympathetic activity to slow the rate in this immediate reflex.

More practice questions