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Cardio (A&P) > Ch. 12 &13 > Flashcards

Ch. 12 &13 Flashcards

1
Q

What is an action potential?

A

Electrical currents that travel across the cell membranes of the heart.

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2
Q

What is another term for polarized state?

A

Resting state

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3
Q

What is a transmitted action potential called?

A

Nerve impulse

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4
Q

What happens during polarize (resting state)?

A

The heart is relaxed (i.e., not generating an action potential)

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5
Q

What makes the heart contract?

A

Action potentials

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6
Q

This electrical difference between the electrolytes inside the cell membranes and the electrolytes outside of the cell membranes is called…

A

Resting membrane potential (RMP)

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7
Q

What are the primary electrolytes responsible for the electrical difference across the RMP?

A

Potassium (K)
Sodium (Na+)
Calcium (Ca2+)

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8
Q

What phase do changes occur?

A

0,1,2,3 and 4

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9
Q

What happens during phase 0?

A

Rapid depolarization (early phase) what triggers contraction. Everything inside is negative (resting state) -90mV polarized stage.

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10
Q

What happens during phase 1?

A

Initial repolarization; cells go into resting state and potassium channels open.

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11
Q

What happens during phase 2?

A

Plateau (balanced) state; slow influx of calcium; as calcium comes in potassium comes out.

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12
Q

What happens during phase 3?

A

Final rapid repolarization; the flow of calcium inward stops and flow of potassium outward speeds up

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13
Q

What happens during phase 4?

A

Resting or polarized state; back to depolarization, and everything is normal.

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14
Q

What is the baseline?

A

Where you start and end. Horizontal or flat line.

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15
Q

What are contractile muscle fibers?

A

They’re what makes the heart pump

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16
Q

What are the properties of cardiac muscle?

A

•Automaticity
•excitability
•conductivity
•contractility

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17
Q

What is automaticity?

A

It is the unique ability of the cells in the SA node (pacemaker cells) to generate an action potential without being stimulated.

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18
Q

What are autorhythmic cells?

A

These cells have the unique ability to initiate an action potential spontaneously, which, in turn, triggers the myocardial fibers to contract.

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19
Q

What is excitability (irritability)?

A

It is the ability of a cell to reach its threshold potential and respond to a stimulus or irritation.

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20
Q

What is conductivity?

A

It is the unique ability of the heart cells to transmit electrical current from cell to cell throughout the entire conductive system.

21
Q

What is contractility?

A

It is the ability of cardiac muscle fibers to shorten and contract in response to an electrical stimulus.

22
Q

What is absolute refractory period?

A

It is the time in which the cells cannot respond to a stimulus. The ionic composition of the cells is not in place to receive a stimulus. Phases 0, 1, 2, and about half of phase 3 represent this period.

23
Q

What is the relative refractory period?

A

It is the time in which repolarization is almost complete and where a strong stimulus may cause depolarization of some of the cells. Some cells may respond normally, some in an abnormal way, and some not at all. The second half of phase 3 represents this period.

24
Q

What is the non-refractory period?

A

occurs when all the cells are in their resting or polarized state. The cells are ready to respond to a stimulus in a normal fashion. Phase 4 represents this period.

25
Q

What are the major components that make up the conductive system of the heart?

A

SA node
AV junction
Bundle of his
Right & left bundle branches
Purkinje fibers
Anterior internodal tract
Middle internodal tract
Posterior internodal tract

26
Q

Where do all internodal tracts become one?

A

The AV junction

27
Q

What is the Bachmann’s bundle and it’s function?

A

conducts electrical impulses from the SA node directly to the left atrium. Causes the right and left atria to contract simultaneously. This action forces the blood in the atria to move into the ventricles.

28
Q

Describe the cardiac effects of the sympathetic nervous system.

A

Sympathetic neural fibers innervate the atria and ventricles of the heart. When stimulated, the sympathetic fibers cause an increase in the heart rate, AV conduction, cardiac contractility, and excitability.

29
Q

Describe the cardiac effects of the parasympathetic nervous system.

A

Parasympathetic neural fibers, via the vagus nerve, innervate the SA node, atrial muscle fibers, and the AV junction. Stimulation of the parasympathetic system causes a decrease in heart rate, AV conduction, contractility, and excitability.

30
Q

What is the total time for an impulse from the SA node to the purkinje fibers?

A

0.22 seconds

31
Q

How long is the p-wave on and ECG?

A

0.08 to 0.11seconds

32
Q

What are the standard limb leads?

A

leads I, II, III, aVR, aVL, and aVF

33
Q

What are the bipolar leads and why are they called that?

A

Leads I, II, and III are bipolar leads, which means they use two electrodes to monitor the heart, one positive and one negative.

34
Q

What do the imaginary lines represent?

A

the axis of each lead

35
Q

What is Einthoven’s triangle?

A

The triangle formed around the heart by the three axes

36
Q

Describe how an electrical impulse of the heart is recorded when it moves toward a positive electrode.

A

They are recorded as positive deflections in that lead.

37
Q

Describe how an electrical impulse of the heart is recorded when it moves away from a positive electrode.

A

They are recorded as negative deflections in that lead.

38
Q

Describe how an electrical impulse of the heart is recorded when it moves perpendicular to a positive and negative electrode.

A

It is recorded as an equiphasic (half up and half down deflection) or a straight line.

39
Q

What are the unipolar leads?

A

aVR, aVL, and aVF

40
Q

Identify how the left lateral leads and inferior leads monitor the frontal plane of the heart.

A

from the base to the apex of the heart, in a right to left direction

41
Q

Describe the components of the precordial (chest) leads.

A

V1,V2, V3,V4, V5, V6
V1-V4 anterior leads
V5 & V6 lateral leads

42
Q

Identify how precordial leads monitor the horizontal plane of the heart.

A

They record the electrical activity that transverses the heart. Leads V1 and V2 monitor the right ventricle, V3 and V4 monitor the ventricular septum, and V5 and V6 view the left ventricle.

43
Q

Describe the modified chest lead.

A

The modified chest lead (MCL1) is a bipolar chest lead similar to the precordial lead V1. The positive electrode is placed on the chest (in the same position as V1) and the negative electrode is placed on the left arm or left shoulder area). The MCL1 may be helpful in visualizing some waveforms.

44
Q

Explain the normal electrocardiogram (ECG) configurations and their expected measurements.

A

Each large square has five small squares, and a duration of 0.20 seconds. ECG paper runs at a speed of 5 large squares per second, or 300 large squares per minute (5 large squares x 60 seconds = 300 squares/min). The vertical portion of each small square represents an amplitude (or voltage) of 0.1 millivolt (mV), and 1 millimeter (1 mm) in distance. Prior to each test, the ECG monitor is standardized so that 1 mV is equal to 10 mm (10 small vertical squares) most ECG paper has small vertical line marks in the margins of every 15 large squares, or every 3 seconds (0.20 x 15 = 3 seconds).

45
Q

Why is it called the 12 lead ECG?

A

Because there are actually 10 leads that view the heart from 12 positions

46
Q

What are the different leads of the heart?

A

4 limb leads
6 chest electrodes

47
Q

What are unipolar leads?

A

Unipolar leads monitor the electrical activity of the heart between the positive electrode (i.e., aVR, aVL, aVF) and the zero-electrical reference point at the center of the heart.

48
Q

What do the limb leads cover?

A

The frontal plane (anterior portion) of the heart

49
Q

How do you calculate the boxes on and ECG?

A

Every 5 boxes = 1 sec; so 15 boxes = 3 seconds, 30 boxes = 6 seconds

Cardio (A&P) (5 decks)

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