BIOS1170 Lecture Notes - Lecture 4: Aortic Valve, Parasympathetic Nervous System, Sympathetic Nervous System

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goldduck450

4 Sep 2018

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Lecture 1 regulation of cardiac output and venous return. Venous return must be returned to the heart for the heart to be able to pump blood around the body. Stroke volume the volume of blood ejected per contraction. Co = hr x sv amount of blood leaving the heart and going to muscles and tissues. Average co = hr (75beats/min) x sv (80ml/beat) = 6000ml/min (resting) Exercise co = 180beats/min x 120ml/beat = 21. 6l/min. Trained athlete co = 190beats/min x 210ml/beat = 39. 9l/min (efficiency of heart increases) Changing heart rate autonomic nervous system (sympathetic activation, parasympathetic activation) Changing stroke volume change pre-load (end diastolic volume) Determined by sa node, regulated by autonomic nervous system. How quickly the cells reach threshold activation of sympathetic nervous system = quicker hr. Activation of parasympathetic nervous system = slower. Adjusted by adjustment to sensitivity of the funny channels and how much sodium or potassium is moving through it (fire action potential)

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Potentially useful information: one mL = one cm³ = 10^-6 m³, one mmHg = 133.3 Pa (N/m²). SV = EDV â 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 NÂ·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?

silverdinosaur935

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

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 NÂ·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!

mauveminnow262

BIOS1170 Lecture Notes - Lecture 4: Aortic Valve, Parasympathetic Nervous System, Sympathetic Nervous System

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