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2024 Vet physiology > Exam 2: Lecture 16: Cardiac Electrophysiology 1 > Flashcards

Exam 2: Lecture 16: Cardiac Electrophysiology 1 Flashcards

1
Q

What two types of muscle cells make up the heart

A

Contractile
Conducting

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2
Q

What type of cells constitute the majority of atrial and ventricular tissues and are the working cells of the heart

A

Contractile cells

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3
Q

What cells constitute the tissues of the SA node, the atrial internodal tracts, the AV node, the bundle of His, and the Purkinje system

A

Conducting cells

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4
Q

Which muscle cells do not contribute sig. to generation of force, instead they function to rapidly spread action potent ions over the entire myocardium

A

Conducting cells

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5
Q

What is described as the action potential of the heart is initiated in the specialized tissues of the SA node, which serves as the pacemaker of the heart

A

SA node

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6
Q

What is described as the AP spreads from the SA node to the right and left atria via the atrial internodal tracts. Simultaneously the AP is conducted to the AV node

A

Atrial internodal tracts and atria

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7
Q

What node of conduction velocity is considerably slower than in the other cardiac tissues

A

AV node

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8
Q

Does slow or fast conduction through the AV node ensures that the ventricles have sufficient time to fill with blood before they are activated and contract.

A

Slow

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9
Q

Does an increase or decrease in conduction velocity of the AV node can lead to decreased ventricular filling and decreased stroke volume and cardiac output

A

Increases in conduction velocity

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10
Q

What describes the pattern and timing of the eletrical activation of the heart are normal

A

Normal sinus rhythm

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11
Q

For normal sinus rhythm where must the AP originate

A

SA node

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12
Q

Define membrane potential in cardiac cells

A

Determined by the relative conductance’s to ions and the concentration gradients for the permeate ions

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13
Q

If the cell membrane has a higher conductance or permeability to an ion, that ion will flow down its electrochemical gradient and attempt to drive the membrane potential towards its ?

A

NERST equation

Equilibrium potential

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14
Q

What is resting membrane potential of cardiac cells determined by

A

Determined mainly by K+

Na+ contributes to the resting membrane potential

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15
Q

What is the role of Na+ / K+ ATPase

A

Maintain NA and K concentrations

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16
Q

Define Stable resting membrane potentials

A

The cells of the atria, ventricles, and Purkingie system exhibit a stable or constant RMP

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17
Q

what is the term for when excess calcium enters into the cell and there is a stable depolarized membrane potential

A

Plateau

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18
Q

What are the latent pacemakers of the heart

A

AV node, bundle of His and Purkinje fibers

  • although they have potential for automaticity it normally is not expressed. they work if they SA node does not
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19
Q

When does the latent pacemakers have the oppertunity to drive the heart rate?

A

If the SA node is suppressed or if the intristic firing rate of a latent pacemaker becomes faster than that of the SA node

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20
Q

what is conduction velocity

A

speed at which AP are propagated within the tissue

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21
Q

what determines how long it takes the action potential to spread to various locations in the myocardium

A

Conduction velocity

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22
Q

Where are the slow conduction fibers in the heart and what is the purpose of them?

A

AV node
- ensures that the ventricles do not activate too early (before they have time to fill with blood from the atria)

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23
Q

Where are the fast conduction fibers in the heart and what is the purpose of them?

A

Purkinjie fiber
- ensures that the ventricles can be activated quickly and in a smooth sequence for efficient ejection of blood

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24
Q

What determines the conduction velocity

A

size of the inward current

25
Q

What does it mean when there is a larger inward current during an AP

A

the more rapidly it will spread to ajacent sites and depolarize them to threshold

26
Q

Does conduction velocity depend on AP duration

A

NO!!
- the AP duration is the time it takes a given site to go from depolarization to complete repolarization. AP duration implies nothing about how long it takes for that AP to spread to neighboring sites

27
Q

What is defined as the capacity of myocardial cells to generate AP in response to inwards depolarizing current

A

Excitability

28
Q

Define refactory period

A

When the Na+ channels are closed and unavailable, inward depolarizing current cannot flow through them, there can be no upstroke or AP

29
Q

What is defined as the most duration of an AP the ventricular cell is completly refractory to fire another AP. No matter how large the stimulus the cell is incapable of generating a second AP

A

Absolute Refactory Period

30
Q

What is defined as absolute means absolutely no stimulus is large enough to generate another AP. Means that a conducted AP cannot be generated (There is not enough inward current to conduct to the next site)

A

Effective Refactory Period

31
Q

When during a AP is most Na+ channels are closed an unavailable to carry inward current

A

Absolute Refactory Period

32
Q

When during the AP does Na+ channels start to recover and become available to carry an inwards current

A

Effective Refactory Period

33
Q

What is defined as the portion of an AP where is almost fully repolarized and a greater than normal stimulus is needed to cause an AP

A

Relative Refactory Period

34
Q

When during the AP have Na+ recovered and available state and it is possible to generate a second AP

A

Relative Refactory period

35
Q

Where is majority of blood at any time in the vasculature

A

veins and venules

36
Q

What is defined as amount of blood that returns to the heart

A

preload

37
Q

What is defined as contraction of the heart to move blood from the left ventricle to the aorta

A

afterload

38
Q

What can determine cardiovascular disease and grade

A

Ejection fraction

39
Q

What is normal ejection fraction in a healthy animal

A

50%

40
Q

What is said to be ventricular wall stretch prior to contraction

A

preload

41
Q

What is said to be the forces (pressure) that oppose the venticular ejection of blood

A

afterload

42
Q

What valve opens when afterload begins

A

aortic

43
Q

end-diastolic volume and end-diastolic pressure is proportional to (preload or afterload)

A

preload

44
Q

What is defined when pressure reaches max then relaxes to fall back to where it was (closer to 0)

A

ventricular pressure

45
Q

What is the mean pressure of the aorta

A

100 mmHg

46
Q

What is the mean pressure of the large arteries

A

100 mmHg
- systolic 120 mmHg
- diastolic 80 mmHg

47
Q

What is the mean pressure of the right atrium

A

0-2 mmHg

48
Q

Is flow or pressure more important because new oxygen to tissues

A

flow

49
Q

Can you have flow without pressure under normal circumstances

A

NO

50
Q

If pressure is good does that indicate good flow

A

if pressure is good that doesnt mean there is good flow

51
Q

Will turbulent or laminar flow eventually produce a sound

A

turbulent

52
Q

In the following graph is the top or bottom laminar flow

A

top

53
Q

In the following graph is the top of bottom turbulent flow

A

bottom

54
Q

What happens to resistance as radius increases
- vessels in series they are additive, but if they are in parallel they are divided
- in series every time the vessels get worse the more problems you have

A

resistance decreases

55
Q

What happens to velocity when you narrow the blood vessel
- turbulence
- sound and vibrational changes at points of constriction
- artery breaks down over time and aneurism occurs

A

increase in velocity

56
Q

What happens to flow as you increase resistance

A

decrease in flow

57
Q

The proxinal large arterial vessels store approx. ________% of the left ventricular stroke volume during systole. The elastic forces of the aortic wall propel this volume to the peripheral circulation during diastole

A

50%

58
Q

What type of receptor send messages to the brain stem to modulate PNS and SNS tone

A

Baroreceptors

59
Q

What is defined as the period of time during a heart contraction

A

force

2024 Vet physiology (28 decks)

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