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2024 Vet physiology > Exam 2: Lecture 18 > Flashcards

Exam 2: Lecture 18 Flashcards

1
Q

What is defined in cardiac muscle translates the AP into the production of tension

A

excitation-coupling

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2
Q

Where is the cardiac AP initiated in the heart and causes depolarization to spread to the interior of the cell via T tubules

A

myocardial cells

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3
Q

What is defined as the inwards current of Ca2+ which allows Ca2+ to move through L-type channels from ECF to ICF

A

Plateau

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4
Q

How does Ca2+ become released from the SR

A

ryanodine receptors

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5
Q

What troponin subtype allows Ca2+ to bind and the interaction of actin and myosin can occur

A

troponin C

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6
Q

what is defined as the intrinsic ability of myocardial cells to develop force at a given muscle cell length

A

contractility or inotropism

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7
Q

Agents that produce a increase in contractality are said to have a + or - inotropic effects

A

+

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8
Q

+ or - inotropic effects increase both the rate of tension development and the peak tension

A

+

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9
Q

Agents that produce a decrease in contractality are said to have a + or - inotropic effect

A

-

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10
Q

+ or - inotropic effects decrease both the rate of tension development and the peak tension

A

-

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11
Q

stimulation of the (SNS or PNS) and circulating catecholamines have a + inotropic effect

A

SNS

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12
Q

Stimulation of the (SNS or PNS) and ACh have a - inotropic effect

A

PNS

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13
Q

What organ does the SNS and circulating catecholamines act on

A

myocardium

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14
Q

What organ does the PNS and Ach act on

A

atria

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15
Q

When you have an increase in HR does it make contractality stronger or weaker

A

stronger

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16
Q

What is positive staircase effect

A

Bowditch staircase. When HR doubles for example, the tension developed on each beat increases in a stepwise fashion to a maximal value

  • increase happens because there is more AP per unit time bc more Ca2+ entering the cell during plateau phases and more Ca2+ gets into the SR
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17
Q

What is defined as when an extrasystole occurs (anomalous extra beat generated by a latent pacemaker)

  • the tension developed on the next beat is greater than normal
A

Postextrasystole Potentiation

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18
Q

What plant acts as a positive inotropic agent. the prototype drug is digoxin

A

Foxglove plant - digitalis purpurea

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19
Q

What inhibits Na+/K+ ATPase at the extracellular K+ binding site

A

Cardiac Glycolysis

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20
Q

When Na+/K+ ATPase is inhibited, less Na+ is pumped out of the cell, increasing the intracellular _______ concentration

A

Na+

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21
Q

The increase in intracellular Na+ concentration alters the Na+ gradient across the myocardial cell membrane, altering the function of what exchanger

A

Ca2+ / Na+

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22
Q

As less _______ is pumped out of the cell by the Ca2+ / Na+ exchanger, the intracellular Ca2+ concentration increases

A

Ca2+

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23
Q

Since tension is directly proportional to the intracellular concentration, cardiac glycolysis produce an increase in tension by increasing intracellular Ca2+ conentration - is this a + or - inotropic effect

A

+

24
Q

The major theraputic use of cardiac glycolysis is in the treatment of congestive heart failure a condition characterized by decreased contractality of ventricular muscle - is this a + or - inotropic effect

A

-

25
Q

Just as skeletal muscle, the maximal tension that can be developed by a myocardial cell depends on what?

A

resting length

26
Q

What is length-tension relationship

A

degree of overlap of thick and thin filaments and the number of possible sites for actin-myosin interaction and cross-bridge formation

27
Q

In myocardial cells, maxinal tension development occurs at cell length of?

A

2.2 um

28
Q

In addition to the degree of overlap of thick and thin filaments what are the two mechanisms in cardiac muscle that alter the tension developed

A
  1. Increasing muscle length increases the Ca2+ sensitivity of troponin C
  2. Increasing muscle length increases Ca2+ release from the SR
29
Q

What coresponds to the to left ventricular end-diastolic volume - length of (single or multiple) left ventricular muscle fibers just prior to contraction

A

Single LV muscle fiber

30
Q

What coresponds to the to tension or pressure developed by the entire Left ventricle - (single or multiple) Left ventricular muscle fibers

A

Single LV muscle fiber

31
Q

On the ascending limb of the graph pressure increases steeply as fiber length increases, which reflects what mechanism to cause greater tension

figure 4.21

A

greater degree of overlap for thick and thin filaments

32
Q

On the descending limb of the graph if end-diatolic volume were to increase further and the fibers were stretched to even longer lengths what would happen to overlap and tension

figure 4.21

A

overlap would decrease and the pressure would decrease

33
Q

Does cardiac muscle have low or high resting tension

A

high

34
Q

Is cardiac muscle held on the ascending or descening limb of the graph

figure 4.21

A

ascending limb

35
Q

What is the name that describes the systolic pressure-volume (length-tension) relationship for the ventricle

A

Frank-starling relationship

36
Q

What does the lower cureve represent when the heart is not contraction

figure 4.21

A

ventricular pressure and ventricular volume during diastole

37
Q

Does pre-load or after-laod describe left ventricular end-diastolic volume or end-diastolic fiber length

A

Pre-load

38
Q

Does pre-load or after-load describe aortic pressure for the LV

A

after-load

39
Q

What is defined as the resting length from which the muscle contracts

A

preload

40
Q

When is the velocity of shortening the cardiac muscle maximal

A

when afterload is 0 and velocity shortening decreases

41
Q

What is described as the volume of blood ejected by the ventricles on each beat

A

stroke volume

42
Q

What is described as the fraction of the end-diastolic volume ejected in each stroke volume, which is a measure of ventricular efficiency

A

Ejection fraction

43
Q

What is described as the total volume ejected by the ventricle pre unit time

A

Cardiac output

44
Q

What can be described as the difference between the volume of blood in the ventricle before ejection and the volume remaining in the ventricle after ejection

A

stroke volume

45
Q

define end-diastolic volume

A

volume of blood in the ventricles before ejection

46
Q

define end-systolic volume

A

volume of blood remaining in the ventricle after ejection

47
Q

What is the typical stroke volume

A

70 mL

48
Q

What is the stroke volume equation

A

stroke volume = End diastolic volume - end systolic volume

49
Q

define ejection fraction

A
  • effectivness of the ventricles in ejecting blood
  • fraction of the end-diastolic volume that is ejected in one stroke volume
50
Q

What is the normal ejection fraction

A

0.55 or 55%

51
Q

What is ejection fraction an indicator of?

A

contractility

52
Q

What does cardic output depend on

A

volume ejected on a single beat and the number of beats per min

53
Q

What is described as the volume of blood ejected by the ventricles depends on the volume present in the ventricles at the end of diastole

A

Frank starling relationship

54
Q

The volume present at the end of diastole in turn depends on the volume returned to the eart, which is known as

A

venous return

55
Q

T/F: cardiac output is larger than venous return?

A

False!!

  • cardiac output equals venous return
56
Q

As venous return (increases or decreases) end diastolic volume increases and because of length-tension relationship in the ventricles stroke volume increases

A

increases

2024 Vet physiology (76 decks)

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