Post-lecture activity (Week 10)

GONZALES, Aldrix J. - The Cardiovascular System: The Heart and Blood Vessels Activity

GONZALES, Aldrix J. - The Cardiovascular System: The Heart and Blood Vessels Activity

by Aldrix Gonzales -
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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.

  1. High blood pressure

  • Whenever the heart is subjected to high blood pressure, it becomes stressed, constricted, and its arteries become less elastic in pumping the blood to the body. As such the heart becomes less efficient and decreases its heart rate (Perez, 2022). 

  1. Massive bleeding

  • Massive bleeding or hemorrhage is characterized by the loss of blood which then poses a drastic alteration towards the performance done by the heart in order to compensate (Sapirstein et.al, 1960). As the heart’s arterial pressure decreases, its preload decreases due to lesser blood and the contractility increases in response with the compensation needed.

  1. the drug dopamine

  • Dopamine is a medication commonly used in treating low blood pressure. When taken, it increases heart pressure or heart rate that resonates to visible increase in contractile pressure too (Holmes & Fowler, 1962). 

  1. Running a sprint

  • When engaging in exercise or any physical activity like running, the heart’s rate increases as more oxygen is needed to be supplied as it is taken up faster. As a result, the heart’s cardiac output also increases due to changes in its contributing factors such as an increased preload, reduced afterload, and an increased contractile state (Wolfe & Cunnigham, 1982). 

  1. Hyperthyroidism with increased secretion of thyroid hormones

  • Excessive secretion of the thyroid hormone or hyperthyroidism causes changes in the cardiac function and structure as it becomes too worked and worn out. It causes high cardiac output characterized by high contractility, increased preload yet decreased afterload pressure due to being worn out (Osuna et al., 2017). 

  1. Massive myocardial infarction (cardiac tissue death)

  • Myocardial infarction, or heart attack as we commonly know it, happens when oxygen is being deprived from the muscles of the heart due to decreased or total loss of blood supply to the heart. In terms of cardiac output, all factors significantly decrease due to the lack or absence of blood supply in the heart.

  1. Hypothermia

  • Hypothermia is the reduction in the body’s core temperature resulting in shivers and in worst cases, mental confusion and death. Our body reacts with vasoconstriction making the cardiac output increase and manifesting the increase in contractility and stroke volume produced by the heart (Deussen, 2007). 

  1. Emotional distress

  • When episodes of emotional distress occur, the heart’s cardiac output increases mainly because of its increased contractility. The stimulation causes left ventricular contractile dysfunction and disturbances in the cardiac rhythm to the heart, which results with an increased stroke volume and contractility increased cardiac output (Ziegelstein, 20017).

 

REFERENCES

Deussen, A. (2007). Hyperthermie und hypothermie. Der Anaesthesist, 56(9), 907–911. https://doi.org/10.1007/s00101-007-1219-4

Holmes, J. C., & Fowler, N. O. (1962). Direct cardiac effects of dopamine. Circulation Research, 10(1), 68–72. https://doi.org/10.1161/01.res.10.1.68

Osuna, P. M., Udovcic, M., & Sharma, M. D. (2017). Hypothyroidism and the heart. Methodist DeBakey Cardiovascular Journal, 13(2), 60. https://doi.org/10.14797/mdcj-13-2-60

Perez, R. (2022, April 8). What is the effect of high blood pressure on cardiac output? Stamina Comfort. Retrieved November 9, 2022, from https://staminacomfort.com/what-is-the-effect-of-high-blood-pressure-on-cardiac-output

SAPIRSTEIN, L. E. O. A., SAPIRSTEIN, E. L. I. Z. A. B. E. T. H. H., & BREDEMEYER, A. N. T. O. N. I. E. (1960). Effect of hemorrhage on the cardiac output and distribution in the rat. Circulation Research, 8(1), 135–148. https://doi.org/10.1161/01.res.8.1.135

Wolfe, L. A., & Cunningham, D. A. (1982). Effects of chronic exercise on cardiac output and its determinants. Canadian Journal of Physiology and Pharmacology, 60(8), 1089–1097. https://doi.org/10.1139/y82-157

Ziegelstein, R. C. (2007). Acute emotional stress and cardiac arrhythmias. JAMA, 298(3), 324. https://doi.org/10.1001/jama.298.3.324