USMLE Step 1 Physiology Review 56 11 Frank-Starling Curve (3_3)

USMLE Step 1 Physiology Review 56 11 Frank-Starling Curve (3_3)

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Play USMLE Audio MP3 56 11 Frank-Starling Curve (3_3) Below

Begin 56 11 Frank-Starling Curve (3_3) Transcription

Now back to some more questions on the Frank-Starling mechanism. List four beta blocking drugs that are selective for beta 1 receptors, each one except for the first one will have a clue or a cue.

  • First, Acebutolol.

Second this drug is used primarily in the treatment of angina pectoris and hypertension. It possesses low lipid solubility than other members of this class and hence apparently fewer nervous system side effects, what is the drug?

  • Atenolol

This beta blocker is used primary in the treatment of ocular hypertension and chronic open angle glaucoma?

  • Betaxolol hydrochloride

Fourth, this beta blocker is used in the treatment of hypertension and it starts with the letter M for Mary?

  • Metoprolol tatrate

How is ejection fraction defined?

  • It is the stroke volume divided by the end diastolic volume

How is stroke volume computed?

  • End diastolic volume minus end systolic volume

What is the normal range for ejection fraction?

  • 60-80% of the VEDV

An ejection fraction of less than 60% indicates which one of the following two options that the VEDV has falling or that the stroke volume has fallen?

  • The stroke volume has fallen

What is the definition of resistance particularly as it applies to arteriole flow through the periphery? (Please pause the tape)

  • Resistance is equal to the difference in the pressure at two different points in a blood vessel divided by the flow of blood between those same two points.

What are the three factors that increase peripheral resistance? First initiating the diving reflex can lead to this factor?

  • Vasoconstriction

Second, friction between the lamina of the fluid?

  • Increased viscosity of the blood.

And third this factor has to do with retention?

  • Fluid retention leading to increased blood volume

What two factors could increase the viscosity of the blood?

  • Increased hematocrit and increased blood protein

Myocardial oxygen demand positively and directly relates to what two factors?

  • Heart rate and afterload.

Student doctor please pause the tape and summarize the information discussed since the last summary of the Frank-Starling mechanism

  • The first question was a request for a list of four beta blocking drugs selective for beta 1 receptors. Four beta blocking drugs that are selective for beta 1 receptor are Acetabutolol, Atenolol, Betaxolol bydrochloride, Metoprolol tatrate. The ejection fraction is the stroke volume divided by the end diastolic volume. Stroke volume is end diastolic volume minus end systolic volume. The normal range for ejection fraction is 60-80% of the VEDV. An ejection fraction of less than 60% indicates that the stroke volume has fallen. Resistance is equal to the difference in the pressure at two different points in a blood vessel divided by the flow of blood between those same two points.  Vasoconstriction, increased viscosity of the blood, and fluid retention leading to increased blood volume, increase peripheral resistance. Increased hematocrit and increased blood protein could increase the viscosity of the blood. Myocardial oxygen demand positively and directly relates to Heart rate and afterload.

****END OF TRANSCRIPTION****

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