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Block 6 > Phys: Cardiodynamics > Flashcards

Phys: Cardiodynamics Flashcards

1
Q

What is cardiodynamics?

A

The movement and forces generated during cardiac contractions

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2
Q

Why are physicians interested in cardiac output?

A

Because cardiac output is an indication of blood flow through the peripheral tissues

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3
Q

What is altered in the heart when adjusting the amount of blood being pumped? (3 things)

A

-heart rate (HR)
-stroke volume (SV)
-cardiac volume (CV)

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4
Q

What is frank sterling law?

A

The ability of the heart to stretch and increase the force of contraction

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5
Q

What is heart rate controlled by?

A

-Sympathetic and parasympathetic nervous system
-electrolytes (Na+, K+, Ca2+)
-chemicals
-hormones

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6
Q

What is stroke volume?

A

The amount of blood that is pumped out of the heart

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7
Q

What is stroke volume regulated by?

A

-preload
-afterload
-contractility

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8
Q

Preload:

A

Volume of blood in the ventricles at the end of diastole

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9
Q

Afterload:

A

Resistance that the heart has to overcome as it is pumping blood out of the aorta

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10
Q

If preload increases, how does it affect stroke volume?

A

It causes stroke volume to increase

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11
Q

How is stroke volume affected when there is an increase in afterload?

A

SV decreases

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12
Q

How does increased contractility affect stroke volume?

A

Stroke volume will increase

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13
Q

What 4 things increases venous return, and in turn, increases stroke volume?

A

-constriction of veins
-skeletal muscle pump
-thoracic pump
-nervous stimulation increasing heart rate

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14
Q

How much blood is in end-systolic volume?

A

50 mL

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15
Q

Approximate volume that represents stroke volume:

A

70 mL

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16
Q

What can cause stroke volume to decline during prolonged exercise?

A

-increase body temp
-redistribution of blood flow to the skin
-excessive fluids loss due to sweating
-decrease plasma volume
-dehydration

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17
Q

What is the best index for preload? why?

A

Left ventricular end diastolic volume because its the only one that can be measured clinically using echocardiography

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18
Q

Increase in contractility causes an increase in what?

A

Cross-bridge cycling and sensitivity of contractile machinery to calcium —->increase stroke volume

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19
Q

Cardiac output:

A

The amount of blood pumped by each ventricle in one minute

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20
Q

4 factors that determine cardiac output:

A

-heart rate
-myocardial contractility
-preload
-afterload

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21
Q

Coupling factors for cardiac output:

A

Preload and afterload

22
Q

Cardiac factors for cardiac output:

A

-heart rate
-myocardia contractility

23
Q

Cardiac output =

A

Stroke volume x heart rate

24
Q

Stroke volume =

25
Increase in preload causing what to SV and EDV:
Increase SV, increase EDV
26
Increase in afterload causing what in SV and ESV:
Decrease SV and increase in ESV
27
Increase in inotrophy causes what in SV and ESV:
Increase SV and decreased ESV
28
Stretch of the sinus node causes increase in the heart rate as much as ___-___%
10-15%
29
Bainbridge reflex is initiated by:
Stretch of right atrium
30
How does right atrial pressure affect venous return?
Exerts a backward force on the veins to impede flow of blood from veins into right atrium
31
Mean systemic filling pressure affecting venous return:
Measurement of the degree of filling of the systemic circulation which forces the systemic blood toward the heart
32
Resistance to blood flow affects venous return by….
Increasing the resistance of blood flow into the right atrium from the peripheral vessels
33
Venous return is affected by which three things:
-systemic filling pressure -right atrial pressure -resistance to venous return
34
If you increase resistance there is…
Less blood return into the heart
35
If you decrease resistance there is…
More blood flow to the heart
36
What drugs have stimulatory effects on cardiac output?
Caffeine and nicotine
37
How does abnormal variations in ion concentrations or body temperature change heart rate?
The increase the SA nodal cells and increase contractility by affecting the cardiac muscle cells
38
How does hyperkalemia affect cardiac output?
muscle cells depolarize -> repolarization is inhibited -> cardiac contractions weaker and irregular -> will eventually stop in diastole
39
How does hypokalemia affect cardiac output?
The muscle cells become hyperpolarized -> less responsive to stimulation -> bradycardia -> heart will eventually stop in systole
40
How does hypercalcemia affect cardiac output?
Cardiac muscle is extremely excitable and contractions became more powerful and prolonged
41
How does hypocalcemia affect cardiac output?
Contractions become weaker
42
How does a decrease in body temperature affect cardiac output?
decreased metabolic processes -> decrease depolarization of the SA -> lowers the heart rate -> decreases force of contraction
43
Equation for venous return:
VR = Psf - PRA/RVR
44
Psf stands for
Mean systemic filling pressure
45
PRA stands for the…
Right atrial pressure
46
RVR stands for the…
Resistance to venous return
47
Two thirds of resistance to venous return is determined by _________ and one third is determined by the _____________
Venous resistance, arteriolar resistance
48
Forces generated during cardiac contractions depend on the:
-heart rate -stroke volume -cardiac output -contractility
49
_______________is the most important factor when examining the cardiac cycle
Stroke volume
50
________________ is a good index for ventricular contractility and physicians use it to determine cardiac function
Ejection fraction
51
Ejection fraction =
EDV - ESV / EDV

Block 6 (32 decks)

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