What effect does adrenaline have on the heart?

Adrenaline, also known as epinephrine, is a hormone and neurotransmitter that plays a crucial role in the body's "fight or flight" response. When released, adrenaline binds to adrenergic receptors in the heart, leading to several physiological effects that support increased physical activity and heightened alertness.

One of the primary effects of adrenaline on the heart is an increase in heart rate, known as positive chronotropic effect. This occurs due to enhanced electrical conduction through the sinoatrial node, which is the natural pacemaker of the heart. As the heart rate increases, the amount of blood pumped by the heart also rises, which means more oxygen and glucose can be delivered to vital organs and muscles. This process is essential during times of stress or physical exertion, as it prepares the body to respond to demanding situations. Additionally, adrenaline increases myocardial contractility, which strengthens heart contractions and can lead to increased stroke volume.

With increased heart rate and enhanced blood flow to the muscles, adrenaline supports activities requiring quick bursts of energy, making it a fundamental component of the body’s acute stress response.