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Physiology Flashcards

1
Q

According to the Fick principle, CO =

A

Rate of O2 consumption / (arterial O2 content - venous O2 content)

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2
Q

Mean arterial pressure (MAP) =

A

CO x total peripheral resistance (TPR)

OR

(2/3 diastolic pressure) + (1/3 systolic pressure)

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3
Q

Pulse pressure =

A

Systolic pressure - diastolic pressure

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4
Q

Relationship between pulse pressure and stroke volume

A

Pulse pressure is proportional to stroke volume

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5
Q

Relationship between pulse pressure and arterial compliance

A

Pulse pressure is inversely proportional arterial compliance.

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6
Q

Stroke volume (SV) =

A

[End-diastolic volume (EDV)] - [end-systolic volume (ESV)]

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7
Q

During the early stages of exercise, CO is maintained by…

A

Increased heart rate and increased stroke volume.

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8
Q

During the late stages of exercise, CO is maintained by…

A

Increased heart rate only (stroke volume plateaus)

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9
Q

…is preferentially shortened with increased heart rate.

A

Diastole – less filling time leads to decreased cardiac output (e.g., ventricular tachycardia)

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10
Q

Conditions associated with increased pulse pressure

A
  1. Hyperthyroidism
  2. Aortic regurgitation
  3. Aortic stiffening (isolated systolic hypertension in elderly)
  4. Obstructive sleep apnea (increased sympathetic tone)
  5. Exercise (transient)
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11
Q

Conditions associated with decreased pulse pressure

A
  1. Aortic stenosis
  2. Cardiogenic shock
  3. Cardiac tamponade
  4. Advanced heart failure
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12
Q

Increased stroke volume is seen with:

A
  1. Increased contractility (e.g., anxiety, exercise, pregnancy)
  2. Increased preload
  3. Decreased afterload
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13
Q

A failing heart is associated with…

A

Decreased stroke volume.

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14
Q

Contractility and stroke volume increase with:

A
  1. Catecholamines – increase activity of Ca2+ pump in sarcoplasmic reticulum
  2. Increased intracellular Ca2+
  3. Decreased extracellular Na+ – due to decreased activity of Na+/Ca2+ exchanger
  4. Digitalis – blocks Na+/K+ pump –> increases intracellular Na+ –> decreases Na+/Ca2+ exchanger activity –> increases intracellular Ca2+
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15
Q

Contractility and stroke volume decrease with:

A
  1. Beta1-blockade – decreases intracellular cAMP
  2. HF with systolic dysfunction
  3. Acidosis
  4. Hypoxia/hypercapnia (decreased PO2/increased PCO2)
  5. Non-dihydropyridine Ca2+ channel blockers
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16
Q

Myocardial O2 demand is increased by:

A
  1. Increased contractility
  2. Increased afterload (proportional to arterial pressure)
  3. Increased heart rate
  4. Increased diameter of ventricle (due to increased wall tension)
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17
Q

Wall tension follows Laplace’s law:

A

Wall tension = (pressure x radius) / (2 x wall thickness)

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18
Q

Preload may be approximated by…

A

Ventricular end-diastolic volume.

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19
Q

Preload depends on…

A

Venous tone and circulating blood volume.

20
Q

Venodilators such as nitroglycerin…

A

Decrease preload.

21
Q

Afterload may be approximated by…

A

The mean arterial pressure.

22
Q

The left ventricle compensates for increased afterload by…in order to decrease…

A

Thickening (hypertrophy); wall tension

23
Q

Vasodilators such as hydralazine…

A

Decrease afterload.

24
Q

ACE inhibitors and ARBs decrease…

A

Both preload and afterload.

25
Q

Chronic hypertension leads to increased…and…

A

MAP; LV hypertrophy

26
Q

CO =

A

Stroke volume (SV) x hear rate (HR)

27
Q

Ejection fraction (EF) =

A

SV / EDV = (EDV - ESV) / EDV

28
Q

Left ventricular EF is an index of…

A

Ventricular contractility.

29
Q

Normal EF is…

30
Q

In diastolic heart failure, EF is…

31
Q

In systolic heart failure, EF is…

A

Decreased.

32
Q

Starling curve plots…vs…

A

Stroke volume (or CO); ventricular EDV (preload)

33
Q

Force of contraction is proportional to…

A

End-diastolic length of cardiac muscle fiber (preload).

34
Q

Increased contractility is observed with…

A

Catecholamines and other positive inotropes like digoxin.

35
Q

Decreased contractility is observed with…

A

Loss of myocardium (e.g., MI), beta-blockers (acutely), non-dihydropyridine Ca2+ channel blockers, dilated cardiomyopathy

36
Q

Volumetric flow rate (Q) =

A

Flow velocity (v) x cross-sectional area (A)

37
Q

Resistance =

A

Driving pressure (DeltaP) / flow (Q) = [8eta x (viscosity) x length] / (pi x r4)

38
Q

Total resistance of vessels in series:

A

TR = R1 + R2 + R3 + …

39
Q

Total resistance of vessels in parallel:

A

1/TR = 1/R1 + 1/R2 + 1/R3 + …

40
Q

Viscosity of blood depends mostly on…

A

Hematocrit

41
Q

Blood viscosity increases in…

A
  1. Hyperproteinemic states (e.g., multiple myeloma)

2. Polycythemia

42
Q

Blood viscosity decreases in…

43
Q

Capillaries have highest…and lowest…

A

Total cross-sectional area; flow velocity

44
Q

What is the consequence of organ removal (e.g., nephrectomy) on total peripheral resistance (TPR) and cardiac output (CO)?

A

Increased TPR and decreased CO

45
Q

Arterioles account for most of…, while veins provide most of…

A

TPR; blood storage capacity

Cardiology (4 decks)

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