1. 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 include PRELOAD, CONTRACTILITY and AFTERLOAD.
In the following conditions, indicate what factor/s influence the cardiac output: PRELOAD, CONTRACTILITY, AFTERLOAD, HEART RATE. Explain why the factor/s affects cardiac output in 1 to 2 sentences.
a. High blood pressure
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When blood volume is increased, afterload and heart rate are also increased, which increases cardiac output, high blood pressure or hypertension follows.
b. Massive bleeding
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The central venous pressure and heart filling are both reduced by significant blood loss. As blood volume and blood pressure drop during bleeding, preload, contractility, and afterload also decrease. As a result, cardiac output and arterial pressure also fall.
c. the drug dopamine
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The direct inotropic impact of dopamine on the myocardium is associated with an increase in cardiac output because of enhanced contractility or force of contraction.
d. Running a sprint
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When sprinting or exercising in general, heart rate rises, which raises cardiac output.
e. Hyperthyroidism with increased secretion of thyroid hormones
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Tachycardia, or an increased resting heart rate, is one symptom of hyperthyroidism. The thyroid hormones, which improve cardiac contractility and raise heart rate and, as a result, increase cardiac output, are responsible for this resting heart rate.
f. Massive myocardial infarction (cardiac tissue death)
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Increased preload and afterload in the heart caused by myocardial infarction might lead to a reduction in cardiac output.
g. Hypothermia
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The metabolism is slowed by hypothermia, which lowers the need for oxygen in tissues. This reduces contractility, boosts cardiac output, and improves the heart's and brain's ability to survive short setbacks in blood supply.
h. Emotional distress
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Epinephrine and norepinephrine, which are present during emotional distress, cause the heart rate to rise, increasing cardiac output and contractility.
REFERENCES:
Noori, S. et al. (2019). Pulmonary-Cardiovascular Interaction. https://www.sciencedirect.com/topics/nursing-and-health-professions/heart-afterload
Bruss, Z. et al. (2019). Physiology, Stroke Volume. https://www.ncbi.nlm.nih.gov/books/NBK547686/
Dopamine: LBP, Uses, Side Effects, Dosages, Interactions, Warnings. (2022, July 18). RxList. https://www.rxlist.com/dopamine-drug.htm
Evans D.L. (n.d.). Cardiovascular adaptations to exercise and training. https://pubmed.ncbi.nlm.nih.gov/3877552/
Hyperthyroidism - Symptoms and causes. (2020, November 14). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/hyperthyroidism/symptoms-causes/syc-20373659
Nall, R. M. (2018, September 29). What’s the Difference Between Epinephrine and Norepinephrine? Healthline. https://www.healthline.com/health/epinephrine-vs-norepinephrine