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Medical Physiology > Exam #2: Cardiac Output > Flashcards

Exam #2: Cardiac Output Flashcards

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USMLE® Step 1 flashcards
1
Q

What is cardiac output?

A

Heart Rate x Stroke Volume

CO=HR x SV (LVEDV- LVESV)

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2
Q

What are the determinants of cardiac output?

A

1) Preload
2) Contractility
3) Afterload
4) Heart rate

*1-3= SV 
4= HR
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3
Q

Draw the cardiac length-tension curve.

A 
Y= Tension
X= Length

Increased length= increased tension

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4
Q

Draw the Frank-Starling Curve.

A 
X= End diastolic volume 
Y= Intraventricular systolic pressure

Increased EDV= increased developed tension & intraventricular systolic pressure

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5
Q

Pathophysiology of heart failure.

A

asdf

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6
Q

What is the effect of decreased HR on Frank-Starling curve?

A

Decreased rate= increased EDV
Increased SV

CO maintained

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7
Q

What is the effect of increased HR on Frank-Starling curve?

A

Increased HR= decreased EDV= decreased SV

CO maintained

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8
Q

Draw the left ventricular volume & pressure curve.

A

N/A

A= mitral valve filling (ESV) 
B= mitral valve closed (EDV) 
C= Isovolumic contraction & aortic semilunar valve opens
D= Blood ejected into periphery & aortic valve closes
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9
Q

What is preload?

A

End diastolic pressure when ventricle has become filled

- Venous return

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10
Q

What is afterload?

A

Aortic pressure

  • TPR
  • Pressure the heart has to pump into/against
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11
Q

Draw the Frank-Starling Curve on Pressure-Volume.

A

N/A

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12
Q

What is the effect of increased preload on SV?

A

Increased SV

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13
Q

Draw the Effect of Preload.

A

N/A

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14
Q

What is the effect of afterload on SV?

A

Decreased SV

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15
Q

Draw the effect of afterload on SV.

A

N/A

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16
Q

Draw the Sarnoff curve of the heart.

A

N/A

Contraction curve

17
Q

Draw the effect of contractility with pressure-volume curve.

A

N/A

18
Q

What does a positive ionotropic agent do to the afterload curve?

A

Shifts the afterload curve upward

19
Q

What will a decrease in contractility to do to afterload curve?

A

Shift downward

20
Q

What is the difference between a systolic dysfunction & a diastolic dysfunction?

A

Systolic= unable to contract efficiently

Diastolic= unable to relax

21
Q

What is the Frank-Starling’s law of the heart?

A

Increased stretch of the sinus node, increases heart rate

22
Q

Draw the venous return curve. What happens when there is a sudden drop in venous return/ volume?

A

Decreased right atrial pressure & decreased systemic filling pressure

23
Q

Draw the venous return curve. What happens when there is a change in TPR i.e. vasodilation or vasoconstriction?

A

Changes in ateriolar resistance change what is coming back to the heart, but NOT overall pressure of systemic filling

24
Q

Draw cardiac function curves.

A

N/A

25
Q

Draw the cardiac function curves with autonomic control: maximal SNS, normal, sympathetic withdrawal, & PNS.

A

N/A

26
Q

How the sympathetic input effect CO?

A

Increases the force & rate of contraction

27
Q

How does SNS increase the force of cardiac contraction?

A
  • Increased slope of phase 4 depolarization in nodal cells= increased HR
  • Alteration of Ca++ permeability (more inward)= increased contraction
  • Glyogenolysis= breakdown of glycogen (energy)

BOTH= large increase in CO

*Note that the SNS innervates the SA/AV nodes & cardiac myocytes

28
Q

How does parasympathetic input effect CO?

A

Massive decrease in heart rate

29
Q

Physiologically, what happens during systole with acute exercise because of sympathetic activity?

A
  • Increased glycogenolysus leads to energy mobilization & enhanced substrate for contraction
  • Increase contractility via increasing Ca++ permeability during Phase 2
  • Increased heart rate

All leads to an increase in CO

30
Q

Physiologically, what happens during diastole with acute exercise because of sympathetic activity?

A
  • Increased HR leads to decreased filling time
  • Changes in Ca++ permeability go BOTH ways i.e. enhanced efflux (Na+ -Ca++ exchanger) & sequestration

Shorter relaxation & filling time but increased contractility & efficiency

31
Q

Draw the cardiac output & venous return curves.

A

N/A

32
Q

What is the equilibrium point of the cardiac output and venous return curves?

A

Right atrial pressure

33
Q

Draw the change that occurs with cardiac output and venous return with increases SNS innervation.

A

N/A

34
Q

How is cardiac output measured?

A

Fick Principle

35
Q

What is the Fick Principle?

A

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36
Q

What is the Indicator Dilution Method used to measure cardiac output?

A

asdf

37
Q

List some factors that increase CO.

A

Reduced TPR

  • AV shunt
  • Hyperthyroidism
  • Anemia
38
Q

List some factors that decrease CO.

A

Heart damage

  • Ischemia
  • Valvular disease

Decreased blood volume
Acute venous dilation or obstruction
Decreased tissue mass or tissue metabolism

Medical Physiology (74 decks)

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