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If the left ventricle moves 50 mL of blood with each heart beatagainst a mean afterload pressure of 110 mmHg with an averagediastolic filling pressure of 10 mmHg, what is the stroke work ofthe LV given a heart rate of 55 beats per minute? (Hint: 1 mmHg =0.0113 N/cm^2)

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Jamar Ferry
Jamar FerryLv2
28 Sep 2019
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Related questions

Potentially useful information: one mL = one cm3 = 10-6 m3, one mmHg = 133.3 Pa (N/m2). SV = EDV – ESV. CO = HR X SV. Ejection Fraction = SV/EDV


Hints: calculate heart rate for each condition. Remember to calculate work for the entire volume of blood that is pressurized i.e., end diastolic volume (EDV). Therefore you will need to use the data provided to calculate the EDV to answer this question.

The work done by the heart is Pressure-Volume work. While both ventricles are doing work, in this problem you will just calculate the work done by the left (high pressure) ventricle. In lecture you saw that if both pressure and volume are expressed in SI units, their product is N·m (work!) In this assignment you will calculate the work done by the left ventricle of the heart each minute to support a cardiac output of 5L/min.

1.)In a healthy person make the following assumptions: Stroke volume is 70mL and the Ejection Fraction is 58% (these are normal values). If systolic pressure is 120 mmHg, what is the work that the heart must perform each minute to produce a cardiac output of 5 L/min?

2.) Individuals with hypertension (high blood pressure) have a much greater resistance in their blood vessels and thus their heart not only has to produce greater pressure, it will have a much greater volume left following contractions (end systolic volume, ESV) Calculate the work the heart (for the identical cardiac output of 5L/min) in an individual with stage one hypertension for which these values apply: systolic blood pressure of 150 mmHg, an ejection fraction of 40% and a stroke volume of 60mL.

3.) 150mmHg is 25% greater than 120 mmHg. In this individual, how much greater is their cardiac work?

Potentially useful information: one mL = one cm3 = 10-6 m3, one mmHg = 133.3 Pa (N/m2). SV = EDV – ESV. CO = HR X SV. Ejection Fraction = SV/EDV

Hints: calculate heart rate for each condition. Remember to calculate work for the entire volume of blood that is pressurized i.e., end diastolic volume (EDV). Therefore you will need to use the data provided to calculate the EDV to answer this question.

The work done by the heart is Pressure-Volume work. While both ventricles are doing work, in this problem you will just calculate the work done by the left (high pressure) ventricle. If both pressure and volume are expressed in SI units, their product is N·m (work!) In this assignment you will calculate the work done by the left ventricle of the heart each minute to support a cardiac output of 5L/min.

B) Individuals with hypertension (high blood pressure) have a much greater resistance in their blood vessels and thus their heart not only has to produce greater pressure, it will have a much greater volume left following contractions (end systolic volume, ESV) Calculate the work the heart (for the identical cardiac output of 5L/min) in an individual with stage one hypertension for which these values apply: systolic blood pressure of 150 mmHg, an ejection fraction of 40% and a stroke volume of 60mL.

C) In this individual, how much greater is their cardiac work (@ blood pressure 150 mmHg) than a normal individual with normal blood pressure (120 mmHg)?

Please answer these questions COMPLETELY and I'll be sure to leave a "thumbs up"! Thank you!

Part C, General Science (questions 34-40)

34.If the electrical charge inside a cell was -70 millivolts,how many volts would this be?

a.-0.7 volts b. -0.07 volts c.-7.0 volts d. -70,000 volts e. -70 volts

35. What is the pH of solution that has a concentration of H+that is 0.001 moles/liter (hint: express this number usingscientific notation, then use the equation. pH = - log [H+].

a. -1 b. 3 c. 13 d. 7 e. -3

36. Using the graph below, with a ventricular stretch of 200 ml,what would be the stroke volume?

a.50 ml b. 70 ml c. 90 ml d. 110 ml e. 200 ml

37. If your heart pumps out 70 ml of blood per beat (strokevolume) and your heart rate is 60 beats per minute, what is theoutput of your heart in ml per minute (this is your cardiacoutput)

a.10 ml

b. 420 ml

c. 4,200 ml

d. 420 liters

e. 2.1 liters

38. 3,500 excess calories will eventually be converted to 1pound of fat tissue. If you consume 70 calories a day more than youburn, how long would it take you to gain one pound of fat

a. 5 days b. 2 weeks c. 50 days d. 2 months e. 5 months

39. Following rigorous exercise, your heart rate was 40 beats in20 seconds. What is your heart rate in beats per minute?

a.80 b. 160 c. 100 d. 90 e. 120

40. The amount that you learn in physiology is positivelycorrelate with

a. the frequency of your attendance

b. your desire to engage in lectures and labs

c. your asking questions when you don’t understandsomething

d. your willingness to address and work on youracademic weaknesses

e. all of these

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