Emergency Medical Technician (EMT) Basic Certification Practice Exam

What effect do beta 1 receptors have on the heart?

1. Decrease heart rate

2. Increase heart rate and contractility

3. Inhibit conduction

4. Regulate blood pressure

The correct answer is: Increase heart rate and contractility

Beta 1 receptors are a type of adrenergic receptor predominantly found in the heart. When they are stimulated, usually by catecholamines like adrenaline (epinephrine) or norepinephrine, they have a direct effect on the cardiovascular system. The activation of beta 1 receptors leads to an increase in the heart rate (positive chronotropic effect) and an enhancement of the force of heart muscle contractions (positive inotropic effect). This physiological response is part of the body's fight-or-flight mechanism, where the heart needs to pump more blood to meet the demands of the body during stress or physical activity. Increased heart rate and contractility ensure that more oxygen and nutrients are delivered to tissues, which is crucial during times of increased activity or stress. In contrast, other options like decreasing heart rate or inhibiting conduction do not align with the role of beta 1 receptors. Beta 1 receptors facilitate rather than inhibit cardiac functions, playing a critical role in the body's overall response to stress. They also do not directly regulate blood pressure, although their influence on heart rate and contractility can indirectly affect systemic vascular resistance and blood pressure.