| Describe the cardiac cycle | Systole - Blood flows passively from the atria to ventricles (Early Filling), followed by an atrial contraction (Late Filling). Diastole - The pulmonic and aortic valves open topermit blood flow from the ventricles into the pulmonary and systemic circulation. For there to be a cardiac output, the Left Ventriclemust develop enough pressure to open the aortic valve. |
| What is the formula for cardiac output? | Formula: Cardiac output = stroke volume x heart rate Cardiac output = blood ejected from the left ventricle each minute Stroke volume = blood ejected from the left ventricle with each cardiac cycle. |
| What is the control of cardiac output? | Most healthy individuals can increase their cardiac output 4 to 6-fold such as during exercise. Increases in cardiac output can be achieved through Intrinsic cardiac regulation of the output. Changes in heart rate via autonomic nervous system control. |
| What is the Frank-Sterling Mechanism and how does it relate to intrinsic cardiac regulation of output? | Simply put: the greater the return of venous blood to the heart, the greater the subsequent output that can be achieved. Note: a useful addition to the effect of venous return on cardiac output is a reflex known as the Bainbridge Reflex, which stimulates an increase in HR with increased atrial stretch. |
| What is arterial pressure? | Blood pressure therefore influenced by altered cardiac output and changes in vascular resistance. A major contributor of peripheral vascular resistance is sympathetic vasoconstrictor nerves Arterial pressure controlled acutely through baroreflex. |
| What is the formula for arterial pressure? | Formula - Ohm’s Law: (Δ) Pressure = Flow x Resistance |
| Describe the cardiac responses to physiological stressors such as exercise. | During exercise HR increases in proportion to metabolic demand. Stroke volume increases with the onset of exercise but plateaus after ~50% of peak workload Net effect is an increase in cardiac output in proportion to the degree of O2 demand. |
