Which of the following describes sympathetic stimulation of the heart?

Sympathetic stimulation of the heart plays a crucial role in preparing the body for "fight or flight" responses. When the sympathetic nervous system is activated, it releases neurotransmitters like norepinephrine that bind to beta-adrenergic receptors in the heart. This interaction results in an increase in the force of contraction of the heart muscle, known as positive inotropic effect. The enhanced contraction strength increases cardiac output, which is essential during periods of stress or physical activity when the body requires more blood flow to meet heightened metabolic demands.

Additionally, sympathetic stimulation also has effects on heart rate, typically increasing it, but the key aspect highlighted here is the increased contraction strength. This is vital for facilitating more efficient blood pumping during times of elevated activity, contributing to the overall stress response of the cardiovascular system. Therefore, this understanding of how sympathetic stimulation enhances the heart's performance directly supports why the choice regarding increased contraction strength accurately describes this physiological response.