What effect do catecholamines have on heart rate and oxygen demand?

Catecholamines, such as epinephrine and norepinephrine, play a critical role in the body's fight-or-flight response. When these hormones are released into the bloodstream, they bind to adrenergic receptors in various tissues, including the heart. This binding results in an increase in heart rate (often referred to as positive chronotropic effect) and an increase in the force of heart contractions (positive inotropic effect).

As heart rate increases, the heart pumps more blood per minute, which elevates overall cardiac output. This heightened cardiac output leads to an increased oxygen demand because the heart muscle itself requires more oxygen to function under these conditions. Moreover, the increased blood flow to muscles and organ systems that occurs with catecholamine release further necessitates higher levels of oxygen to meet the metabolic needs during stressful situations.

Therefore, catecholamines do indeed increase both heart rate and oxygen demand, making the selected answer accurate in the context of their physiological effects.