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Cardiovascular - Physiology > Definitions and Cardiac Output Basics > Flashcards

Definitions and Cardiac Output Basics Flashcards

1
Q

What is “pressure”?

A

Force per unit area exerted by gas or fluid on its container - generally expressed as a pressure difference (difference between pressure inside vs. outside), etc.

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2
Q

What is flow rate?

A

“L/min”, ie Volume transferred from one location to another per unit time.

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3
Q

What is flow velocity?

A

Cm/sec. Speed with which volume is moving.

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4
Q

What is flow resistance?

A

Resistance to flow provided by a structure. For blood flow it is related to radius of vessels and viscosity of blood.

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5
Q

What are the units of flow resistance?

A

Wood units. (dynes/sec/cm^5). BP/flow rate. Whatever.

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6
Q

What is compliance?

A

The relationship between a substance distending a structure and its volume; Change in Volume/Change in Pressure. It is a physical property of the walls of the structure.

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7
Q

What is the rule of thumb for compliance? What changes this rule of thumb a bit?

A

Low compliance with stiff walls, higher compliance with stretchy walls. This changes with the LaPlace relationship, that basically states that with increase in size, greater pressure is required to maintain a certain tension.

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8
Q

What is cardiac output?

A

SV * HR

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9
Q

During early stages of exercise, what maintains CO?

A

Increased HR and Increased SV

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10
Q

During the late stages of exercise, what maintains CO?

A

Incr HR only. SV plateaus.

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11
Q

What happens to CO when HR is increased too much?

A

CO can drop because diastole is preferentially shortened with Incr HR, so there is less filling time, and thus less output.

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12
Q

What is the Fick principle? What’s an easier way of arranging it so it makes sense?

A

CO = (rate of oxygen consumption)/(arteriovenous oxygen difference).

Makes more sense like:
Rate of oxygen consumption = CO * AV Diff.

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13
Q

How does mean arterial pressure relate to CO?

A

MAP = CO * Total Peripheral Resistance

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14
Q

How can you calculate MAP?

A

MAP = 2/3 Diastolic + 1/3 Systolic

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15
Q

What is pulse pressure?

A

Pulse pressure = systolic pressure - diastolic pressure.

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16
Q

What causes a widened pulse pressure?

A

Increase in SV, or decrease in arterial compliance.

17
Q

How does cardiogenic shock, heart failure, cardiac tamponade, and aortic stenosis change pulse pressure?

A

Decreases. All lower SV.

18
Q

How do aortic regurgitation, aortic stiffening, exercise, and hyperthyroidism change pulse pressure?

A

Increase pulse pressure.

19
Q

How does obstructive sleep apnea change pulse pressure and why?

A

Incr pulse pressure due to increased sympathetic tone.

20
Q

What factors increase stroke volume?

A

Incr contractility, increased preload, decreased afterload

21
Q

Why do catecholamines increase contractility?

A

Increased activity of Ca2+ pump in sarcoplasmic reticulum

22
Q

What is the effect of increased intracellular calcium on contractility?

A

Increases contractility

23
Q

Why does decreased extracellular Na+ increase contractility?

A

Decreases the activity of the Ca2+/Na+ exchanger, which normally removes Ca2+ from cell by taking in extracellular Na+

24
Q

How does Digitalis increase contractility?

A

Blocks Na+/K+ pump. Increased intracellular Na+ . Less gradient for Na+ to come in, decreased removal of Ca2+ from cell by Na+/Ca2+ antiporter.

25
Q

Why do beta blockers decrease contractility?

A

Decreases intracellular cAMP

26
Q

What is the effect of acidosis on cardiac contractility?

A

Decrease

27
Q

What is the effect of hypoxia/hypercapnia on Contractility?

A

Decrease

28
Q

What is the effect of Non Dihydropyridine Ca2+ blockers on cardiac contractility?

A

Decrease

29
Q

What factors increase myocardial demand?

A

Contractility, Afterload, Heart Rate, Diameter of Ventricle

30
Q

What is the definition of “preload”?

A

Ventricular end-diastolic volume

31
Q

What are the determinants of preload? What decreases preload?

A

Venous tone and circulating blood volume. Venodilaters decrease preload.

32
Q

What is the definition of afterload?

A

Approximated by mean arterial pressure. Increased afterload –> increased pressure –> increased wall pressure.
LV compensates for afterload by thickening in order to decrease wall tension.

33
Q

What is the effect of vasodilators on afterload?

A

Decrease afterload.

34
Q

What is the effect of ACEis and ARBs on cardiac output variables?

A

Decrease both preload and afterload.

Cardiovascular - Physiology (4 decks)

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