Final answer:
Cardiac output is determined by heart rate and stroke volume, and it adjusts in response to stress to maintain adequate blood flow. Positive and negative factors influence heart contractility and cardiac reserve measures the heart's efficiency. Understanding these factors can assess cardiovascular stress and health.
Step-by-step explanation:
The student is asking about how to determine the stress on the heart, specifically referring to cardiac output, which is the measurement of blood flow from the heart through the ventricles and is usually measured in liters per minute. Cardiac output is affected by several factors; an increase is generally promoted by sympathetic stimulation, epinephrine, norepinephrine, thyroid hormones, and increased calcium ion levels. Conversely, decreases in cardiac output can result from parasympathetic stimulation, abnormal potassium ion levels, decreased calcium levels, anoxia, and acidosis.
Positive factors affecting heart contractility, which refers to the strength of heart contractions, include increased sympathetic stimulation and higher calcium ion levels. Negative factors include elevated or decreased potassium ion levels and decreased calcium levels. Stroke volume, the amount of blood the heart pumps with each beat, also plays a crucial role in cardiac output. When stroke volume or heart rate increases, so does cardiac output, leading to higher blood pressure and greater blood flow.
The heart's response to stress, such as during intense exercise, involves a rise in heart rate and stroke volume to ensure adequate blood circulation to meet the body's increased demand for oxygen and nutrients. Psychological factors, environmental influences, and the autoregulation of cardiac cells contribute to the dynamic regulation of cardiac output.