What is the primary function of Beta 1 receptors?

The primary function of Beta 1 receptors is to increase heart rate. These receptors are predominantly located in the heart, especially in the sinoatrial (SA) and atrioventricular (AV) nodes, as well as the myocardium (heart muscle). When activated by catecholamines such as epinephrine and norepinephrine, Beta 1 receptors stimulate increases in heart rate (positive chronotropic effect), conduction velocity (positive dromotropic effect), and contractility (positive inotropic effect). This response is vital during situations requiring enhanced cardiac output, such as physical exertion or stress.

In contrast, the other options refer to different receptor actions; inducing bronchodilation is primarily associated with Beta 2 receptors, enhancing smooth muscle contraction does not typically involve Beta 1, and causing vasodilation is more aligned with Beta 2 receptor activity as well, particularly in the vascular smooth muscle. This distinction helps clarify the specific role of Beta 1 receptors in cardiac function.