What is extrinsic control of the heart?
Extrinsic controls of the cardiovascular system include neuronal, humoral, reflex, and chemical regulatory mechanisms. These extrinsic controls regulate heart rate, myocardial contractility, and vascular smooth muscle to maintain cardiac output, blood flow distribution, and arterial blood pressure.
What is the intrinsic control of stroke volume?
Stroke volume is intrinsically controlled by preload (the degree to which the ventricles are stretched prior to contracting). An increase in the volume or speed of venous return will increase preload and, through the Frank–Starling law of the heart, will increase stroke volume.
What intrinsic factors affect stroke volume?
Stroke volume, like heart rate, is dependent upon factors intrinsic and extrinsic to the heart. As all myocytes within the heart contract during each beat, the primary intrinsic factors which determine stroke volume are the inherent contractile properties of each muscle fiber and the resting lengths of all the fibers.
Does stroke volume increase with EDV?
This leads to an increase in the force of ventricular contraction and enables the heart to eject the additional blood that was returned to it. Therefore, an increase in EDV results in an increase in SV. Conversely, a decrease in venous return and EDV leads to a decrease in SV by this mechanism.
What are the intrinsic and extrinsic controls of the heart?
Blood Flow Regulation The heart has both intrinsic (situated within the heart) and extrinsic (originating outside the heart) regulation. Many myocardial cells have unique potential for spontaneous electrical activity (intrinsic rhythm). In normal heart, spontaneous electrical activity is limited to special region.
What are the three factors that affect stroke volume?
There are three variables affecting stroke volume, which include contractility, preload, and afterload.
What affects the stroke volume?
Stroke volume index is determined by three factors: Preload: The filling pressure of the heart at the end of diastole. Contractility: The inherent vigor of contraction of the heart muscles during systole. Afterload: The pressure against which the heart must work to eject blood during systole.
What happens when end-diastolic volume increases?
Preload. At all ages, ventricular output depends on end-diastolic volume. An increase in stroke volume or cardiac output occurs when end-diastolic volume is increased (the Frank-Starling relation).