Post-lecture activity (Week 10)

MANAPOL, Mel Phillip D. — Post-lecture Activity

MANAPOL, Mel Phillip D. — Post-lecture Activity

by Mel Phillip Manapol -
Number of replies: 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 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.

 

a. High blood pressure

 

An elevated blood pressure is often a sign of increased afterload. Feher (2017) stated that increasing afterload can cause a decrease in stroke volume, which would have an impact in the cardiac output because the heart would need more pressure to open the aortic valve.

 

b. Massive bleeding

 

Massive bleeding would cause a drop in blood volume, which would contribute to a decrease in stroke volume and cardiac output. This is because the heart's response to hemorrhage is regulated by both an increase in the sympathetic nervous system activation of the heart, as well as decreased preload and afterload for the heart (McDonough et al., 1999, as cited in Takase et al., 2019).

 

c. the drug dopamine

 

Dopamine is often used as a catecholamine for the treatment of shock and refractory heart failure as it increases myocardial contractility (Reid & Thompson, 1975, as cited in Zhou et al., 2018). An increase in contractility would reduce in a greater stroke volume and cardiac output (Tortora & Derrickson, 2018).

 

d. Running a sprint

 

 

 

e. Hyperthryoidism with increased secretion of thyroid hormones

 

 

 

f. Massive myocardial infarction (cardiac tissue death)

 

Myocardial infarctions, such as those seen in cases of congestive heart failure, can gradually increase preload as more blood remains in the ventricles. As the preload increases further, the heart overstretches and contracts less forcefully (Tortora & Derrickson, 2018).

 

g. Hypothermia

 

Heart rate is decreased when experiencing hypothermia as the sinoatrial node would discharge impulses more slowly. This would slow down body metabolism as well, which would reduce the oxygen needs of tissues, enabling the heart and brain to endure the resulting periods of reduced blood flow due to the decreased heart rate (Tortora & Derrickson, 2018).

 

h. Emotional distress

 

Emotional distress often comes with an increase in blood pressure (Crestani, 2016). With blood pressure, there is an increased afterload, which would reduce the stroke volume and, consequently, the cardiac output, as the heart would take longer to develop enough pressure to open the aortic valve (Feher, 2017).

 

References:

 

Crestani, C. C. (2016). Emotional stress and cardiovascular complications in animal models: A review of the influence of stress type. Frontiers in Physiology, 7, 251.

 

Feher, J. J. (2017). Quantitative human physiology: an introduction. Academic Press.

 

McDonough, K. H., Giaimo, M., Quinn, M., & Miller, H. (1999). Intrinsic myocardial function in hemorrhagic shock. Shock (Augusta, Ga.), 11(3), 205-210.

 

Reid, P. R., & Thompson, W. L. (1975). The clinical use of dopamine in the treatment of shock. The Johns Hopkins Medical Journal, 137(6), 276-279.

 

Takase, B., Higashimura, Y., Hashimoto, K., Asahina, H., Ishihara, M., & Sakai, H. (2019). Myocardial electrical remodeling and the arrhythmogenic substrate in hemorrhagic shock-induced heart: Anti-arrhythmogenic effect of liposome-encapsulated hemoglobin (HBV) on the myocardium. Shock, 52(3), 378-386.

 

Tortora, G. J., & Derrickson, B. H. (2018). Principles of anatomy and physiology. John Wiley & Sons.

 

Zhou, H., Tang, L., Yang, Y., Lin, L., Dai, J., Ge, P., ... & Zhang, L. (2018). Dopamine alleviated acute liver injury induced by lipopolysaccharide/d-galactosamine in mice. International Immunopharmacology, 61, 249-255.

In reply to Mel Phillip Manapol

Re: MANAPOL, Mel Phillip D. — Post-lecture Activity

by Mel Phillip Manapol -

I apologize for the inconvenience. It appeared that my device glitched and managed to paste a previous version of my answers. Please view the answers below instead. Thank you for your consideration.

 

a. High blood pressure

 

An elevated blood pressure is often a sign of increased afterload. Feher (2017) stated that increasing afterload can cause a decrease in stroke volume, which would have an impact on cardiac output because the heart would need more pressure to open the aortic valve.

 

b. Massive bleeding

 

Massive bleeding would cause a drop in blood volume, which would contribute to a decrease in stroke volume and cardiac output. This is because the heart's response to hemorrhage is regulated by both an increase in the sympathetic nervous system activation of the heart, as well as decreased preload and afterload for the heart (McDonough et al., 1999, as cited in Takase et al., 2019).

 

c. The drug dopamine

 

Dopamine is often used as a catecholamine for the treatment of shock and refractory heart failure as it increases myocardial contractility (Reid & Thompson, 1975, as cited in Zhou et al., 2018). An increase in contractility would result in a greater stroke volume and cardiac output (Tortora & Derrickson, 2018).

 

d. Running a sprint

 

As sprinting is a strenuous exercise, it is often met with an increase in body temperature. The increase in body temperature actually impacts the sinoatrial node by making it discharge impulses more quickly; thus, there is an increased heart rate (Tortora & Derrickson, 2018).

 

e. Hyperthyroidism with increased secretion of thyroid hormones

 

One common sign of hyperthyroidism is the manifestation of tachycardia, which is an elevated resting heart rate. The presence of thyroid hormones itself also gives way to increased cardiac contractility, resulting in an overall increase in cardiac output (Tortora & Derrickson, 2018).

 

f. Massive myocardial infarction (cardiac tissue death)

 

Myocardial infarctions can have an overall less efficient cardiac output. For example, although the preload increases in cases of congestive heart failure, it increases to the point where the heart overstretches and contracts less forcefully (Tortora & Derrickson, 2018).

 

g. Hypothermia

 

Heart rate is decreased when experiencing hypothermia as the sinoatrial node would discharge impulses more slowly. This would slow down body metabolism as well, which would reduce the oxygen needs of tissues, enabling the heart and brain to endure the resulting periods of reduced blood flow due to the decreased heart rate and cardiac output (Tortora & Derrickson, 2018).

 

h. Emotional distress

 

Emotional distress often comes with an increase in blood pressure (Crestani, 2016). With blood pressure, there is an increased afterload, which would reduce the stroke volume and, consequently, the cardiac output, as the heart would take longer to develop enough pressure to open the aortic valve (Feher, 2017).

 

References:

 

Crestani, C. C. (2016). Emotional stress and cardiovascular complications in animal models: A review of the influence of stress type. Frontiers in Physiology, 7, 251.

 

Feher, J. J. (2017). Quantitative human physiology: an introduction. Academic Press.

 

McDonough, K. H., Giaimo, M., Quinn, M., & Miller, H. (1999). Intrinsic myocardial function in hemorrhagic shock. Shock (Augusta, Ga.), 11(3), 205-210.

 

Reid, P. R., & Thompson, W. L. (1975). The clinical use of dopamine in the treatment of shock. The Johns Hopkins Medical Journal, 137(6), 276-279.

 

Takase, B., Higashimura, Y., Hashimoto, K., Asahina, H., Ishihara, M., & Sakai, H. (2019). Myocardial electrical remodeling and the arrhythmogenic substrate in hemorrhagic shock-induced heart: Anti-arrhythmogenic effect of liposome-encapsulated hemoglobin (HBV) on the myocardium. Shock, 52(3), 378-386.

 

Tortora, G. J., & Derrickson, B. H. (2018). Principles of anatomy and physiology. John Wiley & Sons.

 

Zhou, H., Tang, L., Yang, Y., Lin, L., Dai, J., Ge, P., ... & Zhang, L. (2018). Dopamine alleviated acute liver injury induced by lipopolysaccharide/d-galactosamine in mice. International Immunopharmacology, 61, 249-255.