Final answer:
Sympathetic stimulation affects ventricular function by increasing contractility and heart rate, and improving ventricular filling, collectively enhancing cardiac output.
Step-by-step explanation:
The three effects of sympathetic stimulation on ventricular contraction and relaxation are:
Increased Contractility: Sympathetic stimulation releases norepinephrine (NE) and epinephrine, which bind to alpha and beta receptors on the cardiac muscle cells. This increases the metabolic rate and force of contraction, resulting in a higher stroke volume (SV) and a lower end-systolic volume (ESV). Enhanced Heart Rate: NE also shortens the repolarization period, quickening the rate of depolarization and contraction, which elevates the heart rate (HR). Improved Ventricular Filling: Sympathetic stimulation to the venous system increases venous return, contributing to better ventricular filling and end-diastolic volume (EDV), thereby enhancing preload and allowing for a more forceful contraction.
These actions collectively increase the efficacy of cardiac output during periods of heightened demand, such as during exercise or stress.