Adequate cardiac output is necessary in order to supply oxygen and other nutrients to all body tissues. Cardiac output is influenced by stroke volume and heart rate. Factors affecting the stroke volume includes PRELOAD, CONTRACTILITY and AFTERLOAD.
In the following conditions, indicate what factor/s influence the cardiac output: PRELOAD, CONTRACTILITY, AFTERLOAD, HEART RATE. Explain the why the factor/s affects cardiac output in 1 to 2 sentences
1. High blood pressure
High blood pressure causes the arteries to be narrower and more elastic, leading to decreased blood flow to the heart and chest pains called angina. The restriction of blood flow due to high blood pressure eventually leads to the stiffening of the heart due to being overworked.
2. Massive bleeding
Losing too much blood leads to decreased blood pressure and perfusion pressure for tissue blood flow. To ensure that adequate amounts of blood are delivered to the organs in need, one's heart rate and systemic vascular resistance are increased as the heart works harder to make up for the loss.
3. The drug dopamine
Dopamine increases sympathetic effects and one's heart rate through vasoconstriction. Along with increasing levels of epinephrine and norepinephrine levels in the body, dopamine is also used to support cardiac output and blood pressure to improve diuresis.
4. Running a sprint
The heart typically beats faster during exercises as there is a greater demand for oxygen for prolonged muscle function. Stroke volume is increased as the heart forcefully pumps out more blood as needed.
5. Hyperthyroidism with increased secretion of thyroid hormones
Hyperthyroidism accelerates metabolism and can cause a rapid or irregular heartbeat as the thyroid hormone affects the heart and peripheral vascular system. The increased amount of thyroid hormones in the body increases both myocardial inotropy and heart rate.
6. Massive myocardial infarction (cardiac tissue death)
Blood clots resulting from a ruptured buildup of plaque in the arteries lead to cardiac tissue death as certain parts of the heart muscle receive inadequate amounts of blood. Damage to cardiac tissue impedes the normal activity of the heart, leading to fatal heart rhythm problems or fatal hemorrhaging due to the tearing of heart muscles.
7. Hypothermia
Cold temperature prompts the heart to work harder for the body to keep its warmth and for enough blood to flow towards major organs. As the blood vessels narrow in cold conditions, blood pressure and heart pumping are increased to maintain proper blood circulation through constricted blood vessels.
8. Emotional distress
Increased cortisol and adrenaline cause the heart to beat more rapidly as the body deals with stress. Along with the increase in heart rate, blood pressure, stroke volume, and cardiac output are elevated as the body undergoes emotional distress.