Final answer:
Increased atrial and ventricular contractility due to beta-2 receptor actions lead to an increased cardiac output in response to sympathetic stimulation, which is part of the body's stress reaction.
Step-by-step explanation:
Actions of the beta-2 receptor include increased atrial and ventricular contractility. This enhancement in contractility leads to an increase in cardiac output as part of the sympathetic response. When sympathetic fibers cause the release of neurotransmitters like epinephrine and norepinephrine, they bind to both alpha and beta receptors on the cardiac muscle cell membrane.
This interaction increases the metabolic rate and the force of contraction, resulting in a higher stroke volume (SV) and a smaller residual end-systolic volume (ESV) in the ventricles. Consequently, this increase in SV contributes to a higher cardiac output. Sympathetic stimulation, as opposed to parasympathetic stimulation which acts as a negative inotrope, is a positive inotrope that contributes to this effect.