Final answer:
In heart failure, the sympathetic nervous system constricts as a compensatory mechanism to maintain cardiac output.
Step-by-step explanation:
In heart failure, the sympathetic nervous system constricts as a compensatory mechanism to maintain cardiac output. Heart failure is a chronic condition where the heart muscle is unable to pump blood adequately to meet the body's needs. The sympathetic nervous system increases its activity to increase heart rate and vasoconstriction, which helps improve cardiac output. However, prolonged sympathetic stimulation can lead to further damage and worsen heart failure.