What potential effect does BETA 1 receptor stimulation from adrenaline have on the heart?

Stimulation of BETA 1 receptors by adrenaline has a significant impact on the heart, primarily by increasing myocardial excitability. When BETA 1 receptors, which are primarily located in the heart, are activated, they lead to an increase in heart rate (positive chronotropy) and enhanced contractility (positive inotropy). This means that the heart not only beats faster but also with more force. As a result, the heart is able to pump more blood with each contraction, leading to an overall increase in cardiac output.

The increase in myocardial excitability specifically refers to the heart muscle's responsiveness to stimuli, making it more likely to fire action potentials and contract. This physiological response is crucial during situations where the body requires increased oxygen delivery to tissues, such as during physical exertion or stress.

The other potential effects listed do not accurately reflect the influence of BETA 1 receptor stimulation. For instance, an increase in peripheral resistance would typically occur with alpha receptor stimulation, not BETA 1. Likewise, decreased cardiac output and induced bradycardia would contradict the effects of BETA 1 stimulation. Therefore, an understanding of BETA 1 receptor actions in relation to adrenaline reveals why increasing myocardial excitability is the appropriate and correct