Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

<3 > Contractility And Cardiac Output > Flashcards

Contractility And Cardiac Output Flashcards

1
Q

What are the differences b/w skeletal and cardiac muscle?

A

In cardiac:

More influence of adrenergic receptor input
&
Relies more heavily on SR Ca levels and release

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are cardiac glycosides used to treat?

Mechanism of Action?

A

Tx heart failure

  • inhibits Na/K ATPase binding K binding site
  • increases Na concentration
  • decreases Ca efflux thru Ca/Na exchanger
  • increases Ca intracellular
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the formula to calculate

Cardiac Output?

A

CO = HR x SV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is stroke volume?

A

Relates partially to myocardial contractility but also to coupling factors (preload & afterload)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do you exact changes in CO?

A

Related to length tension relationship

-generally proportional to amount of Ca that is available to Troponin on actin filaments of contractile apparatus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is Preload?

A

Amount of blood ready to be pumped, diastole

Left Ventricle- End Diastolic VOlume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is LV EDV?

A

Wall tension in LV just before contraction is initiated

Aka fiber length at end of diastole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does more blood returning to the RV mean?

A

Greater preload

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What will volume at EDV be related to>?

A

Related to venous return

CO(Q) = Venous REturn (Steady State)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the Frank Starling Relationship?

A

More blood that comes back to LV, the more that is going to get pumped

—> greater EDV = i am going to get pumped harder

(Volume of ejected blood depends on volume present in ventricle at end of diastole)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is afterload?

A

Pressure required to eject blood (open aortic valve)

Essentially equal to aortic/pulmonary artery pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is velocity of shortening affected by afterload?

A

Decreases as afterload increases

Greatest if afterload = 0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

When is preload measured?

A

At end of isovolumetric contraction period

Remember = end diastolic fiber length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does preload affect contractility?

A

Increase Preload

—> increases CO and contractility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does afterload affect contractilikty?

A

Increase afterload

—> decreases CO
—> increased HR

-heart must increase contractility to overcome decreased CO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How do you calculate Stroke volume?

Normal value?

A

SV = EDV - ESV

~70 mL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the normal value for ESV?

A

~50 mL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is stroke volume?

A

Volume of blood ejected by ventricle w/ each beat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do you calculate Ejection fraction?

Normal value?

A

EF% = SV / EDV

55%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is ejection fraction (EF%)?

A

Fraction of the EDV ejected in each stroke volume

-measure of efficiency and contractility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is cardiac output?

A

Total volume of blood ejected by ventricle per minute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the normal value of CO?

A

5 L per minute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How does HR affect contractility?

A

Increased HR —> increases contractility (SV)

24
Q

What is the Positive Staircase Effect (bowditch staircase)?

A

Auto regulation method by which myocardial tension increases w/ an increase in heart rate

-more stimuli sent to muscle
—> contractions show successive increase in amplitude

25
Q

What is the positive staircase effect caused by?

A

More Ca enters cells and is taken up into SR

26
Q

What is the sympathetic influence on CO?

A

Positive inotropic (SV) effect

-Beta AR activation

  1. Phosphorylates sarcolemma Ca channels
  2. Phosphorylates phospholamban (stimul.)
  3. Phosphorylates Troponin I (inhib.)
27
Q

What is the parasympathetic influence on CO?

A

Negative inotropic effect IN ATRIA ONLY - affecting PHASE 4 (RMP)

(No influence on ventricular myocytes)

Muscarinic receptor activation

  1. Decreases inward ca current during plateau
  2. ACh increases outward k current
28
Q

in a ventricular pressure-volume loop,

What does the right handed vertical line from point 1 —> point 2 represent?

A

Isovolumetric contraction

29
Q

What is point 1 on a Ventricular Pressure-Volume Loop?

A

End of diastole = EDV = preload

  • so pressure is low
  • but volume would be high
30
Q

What is Point 2 on a Ventricular Pressure-Volume loop?

A

Point where ejection of blood begins = when aortic valve opens = Afterload

So pressure is high (around ~70-80)
And volume is same as preload

31
Q

What is Point 3 in a Ventricular Pressure VOlume Loop?

A

End of systole - closing of Aortic valve

ESV too

32
Q

What does the line between points 2-3 represent?

A

Ventricular ejection

-pressure will reach a max. B/w these two points

33
Q

How do you calculate SV using the Ventricular Pressure Volume loop?

A

SV = EDV - ESV (volume)

SV = Point 1/2 - point 3/4

34
Q

What is point 4 in a Ventricular PRessure-VOlume Loop?

A

Represents the opening of the Mitral/tricuspid valve

35
Q

What does the line b/w Points 3 and 4 represent?

A

Isovolumetric relaxation

-ventricular pressure falls quickly but volume (ESV) remains constant

36
Q

What does the line b/w Points 4 and 1 represent?

A

Ventricular filling

37
Q

How will the Ventricular Pressure-volume loop change w/ increased preload?

A

-more venous return, more blood volume

Points 1 and 2 move laterally
=greater EDV = GREATER Stroke volume

-afterload and contractility remain constant

38
Q

How will the Ventricular Pressure-volume loop change w/ increased Afterload?

A

Point 2 moves up, points 3 and 4 move closer (graph becomes taller)

  • greater pressure needed to open aortic valve
  • reduced Stroke volume
  • reduced ejection fraction
39
Q

How will the Ventricular Pressure-volume loop change w/ increased contractility?

A

-points 3 and 4 will move laterally, point 2 up just a bit

  • increased SV
  • increased EF%
  • less blood left in heart
40
Q

What can cause increased afterload?

A

Due to aortic stenosis or hypertension

41
Q

What can cause Increased Contractility

A

Adrenergic stimulation

42
Q

What is volume work?

A

Cardiac ouput

43
Q

What is pressure work?

A

Aortic pressure

44
Q

What is Minute work re: Cardiac work?

A

CO x Aortic pressure

Or

Volume work X Pressure work

45
Q

What is Stroke work?

A

SV x Aortic pressure

= area w/in the pressure volume loop

46
Q

What performs stroke work?

A

Left ventricle

47
Q

Is pressure work or volume work more costly?

A

Pressure work uses the largest percent of O2 consumption

48
Q

Why does the LV work proportionally harder than the RV despite similar COs?

A

Bc systemic pressure is greater than pulmonary pressure and can be further accentuated by conditions that increase LV pressure work

I.e. aortic stenosis or systemic hypertension

49
Q

What is the fick principle?

A

Measure of CO

O2 consumption / [(o2-pulm. V.) - (o2-pulm. A.)]

50
Q

What is the relationship b/w CO adn Venous return?

A

At steady state, the volume of blood as cardiac output ejected by the LV equals the volume it receives in venous return

CO = Venous return

51
Q

What are the parameters needed for CO to equal VR?

A

At equilibrium CO = VR

RA pressure = ~+2 mmHg
CO/VR = 5 L/min.

52
Q

What does the vascular function curve tell us?

A

Can figure out the Mean Systemic Pressure (MSP) by where it crosses x-axis

(Bc there is no CO there and it completely depends on vascular compliance and blood volume)

53
Q

How does Cardiac failure affect cardiac and vascular function?

A

Decreased CO and SV
-veins are normal- just heart is failing

-increased blood volume

But systemic vascular function changes to help restore CO

—> Decreased vascular compliance
—> Increased SVR/TRP

54
Q

How does exercise affect cardiac function?

A

Decreased TPR

—> increased CO
—> increased VR

55
Q

How does hemorrhage affect cardiac function?

A

Increased TPR

—> decreased CO
—> decreased VR

56
Q

How does increased Blood volume affect cardiac function?

A

Increased BV = more for veins to return but heart still pumps out same amt.

= no change in CO
=increased VR

<3 (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions