Alpha 1 receptors6/17/2023 ![]() Cardiac output is influenced by heart rate and stroke volume, both of which are also variable. Factors influencing CO are summarized in the image below.įigure 1. Remember, however, that these numbers refer to CO from each ventricle separately, not the total for the heart. Using these numbers, the mean CO is 5.25 L/min, with a range of 4.0–8.0 L/min. An average resting HR would be approximately 75 bpm but could range from 60–100 in some individuals. There are several important variables, including size of the heart, physical and mental condition of the individual, sex, contractility, duration of contraction, preload or EDV, and afterload or resistance. A mean SV for a resting 70-kg (150-lb) individual would be approximately 70 mL. SV can also be measured using a specialized catheter, but this is an invasive procedure and far more dangerous to the patient. ![]() SV is normally measured using an echocardiogram to record EDV and ESV, and calculating the difference: SV = EDV – ESV. It can be represented mathematically by the following equation: To calculate this value, multiply stroke volume (SV), the amount of blood pumped by each ventricle, by heart rate (HR), in contractions per minute (or beats per minute, bpm). Resting Cardiac OutputĬardiac output (CO) is a measurement of the amount of blood pumped by each ventricle in one minute. In addition, the heart is sensitive to several environmental factors, including electrolytes. Neural and endocrine controls are vital to the regulation of cardiac function. The autorhythmicity inherent in cardiac cells keeps the heart beating at a regular pace however, the heart is regulated by and responds to outside influences as well. Describe the cardiac response to variations in blood flow and pressure.Summarize factors affecting stroke volume and cardiac output.Distinguish between positive and negative factors that affect heart contractility.Identify cardiovascular centers and cardiac reflexes that regulate heart function.Describe the effect of exercise on heart rate.By the end of this section, you will be able to:
0 Comments
Leave a Reply. |