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Anatomy / Physio II > Electrical Activity of the Heart > Flashcards

Electrical Activity of the Heart Flashcards

1
Q

What are the 5 phases of cardiac muscle action potential?

A

Phase 0 - Depolarization due to Na+ influx
Phase 1 - Initial repolarization due to K+ outflux
Phase 2 - Plateau due to increase of Ca2+
Phase 3 - Repolarization due to outflux of K+ and decreased influx of Ca2+
Phase 4 - Resting potential

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2
Q

What period of a cardiac action potential ensures that cardiac muscle cells cannot be tetanized?

A

Absolute refractory period. No activation potential can be generated at this point

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3
Q

What period of a cardiac action potential is abnormal?

A

Period of Supernormality. Reduced level of stimulation produces same action potential

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4
Q

What do Catecholamines do?

A

Enhance calcium movement and increase size of action potential

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5
Q

What are calcium channel blockers used for?

A

To treat cardiac arrhythmia and high blood pressure. They depress calcium movement resulting in smaller action potentials

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6
Q

What is the pacemaker of the heart?

A

SA node

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7
Q

What are two important things to keep in mind about SA node action potentials?

A
  1. Phase 4 imparts arrhythmia; baseline is not flat but slopes toward theshold
  2. Calcium depolarizes
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8
Q

What does an ECG NOT do?

A

ECG can NOT give direct info about contractile performance

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9
Q

Know the different wave points of an ECG.

A

Got it?!?! P, Q, R, S, T.

Figure out what is happening at P and you should be able to figure it out from there

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10
Q

What is Eintoven’s Triangle?

A

3 leads that are the electrical discharge values across the chest are measured across the distance between the 3 leads, respectively. If the values are summed, they add up to 0.

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11
Q

What is a respiratory sinus arrythmia?

A

Found in healthy hearts. Due to cyclic changes in autonomic activity to SA nodes

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12
Q

What is sinus tachycardia?

A

interval between cycles is shorter; opposite for sinus bradycardia

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13
Q

What is premature ventricular/atrial contraction?

A

Spontaneous generation of action potentials. Increased by smoking, stress, caffeine, fatigue

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14
Q

What is atrial fibrillation?

A

Small, random waves of depolarization in ECG. Bad sign.

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15
Q

What happens if ventricular fibrillation is left uncorrected?

A

patient dies

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16
Q

What is the first sign of a myocardial infarction on an ECG?

A

Inversion of T wave

17
Q

In a myocardial infarction, progressive ischemia results in elevation of - segment.

A

ST segment

18
Q

Infarction leads to development of __ waves in front of an elevated ___

A

development of Q waves in front of ST segment

19
Q

Modification of contractile force at the cellular level, independent of loading, is called ____ _____

A

ionotropic modification

20
Q

What is the Bowditch phenomenon?

A

Gradual increase in muscular contraction following rapidly repeated stimulation

21
Q

What does digitalis do?

A

Inhibits Na-K ATPase, resulting in an increased intracellular concentration of Na which in turn increases intracellular Ca. This strengthens muscle contraction.

22
Q

What is the first heart sound in a cardiac cycle?

A

The closure of mitral and tricuspid valves

23
Q

What is the second heart sound in a cardiac cycle?

A

Closure of aortic and pulmonary semilunar valves. Transition to diastole.

24
Q

What is the difference between ventricular end-diastolic volume and end-systolic volume?

A

Stroke Volume

25
Q

What is the stroke volume/end diastolic volume?

A

Ejection fraction

26
Q

What are the factors affecting contractile strength of the heart?

A
  1. Preload - initial muscle length
  2. Afterload - Forces against which muscle must contract to shorten
  3. Contractility - inotropic state
  4. Inotropic effect of increased heart rate
27
Q

What is cardiac output?

A

Volume of blood ejected from the heart per unit of time?

28
Q

What is Starling’s Law of the heart?

A

Within physiological limits, the more the heart fills, the more it pumps

29
Q

What factors increase contractility and cardiac output?

A
  1. Increased intracellular Ca
  2. Decreased extracellular Na
  3. Digitalis
  4. Sympathetic stimulation
30
Q

What factors decrease contractility and cardiac output?

A
  1. heart failure

2. loss of myocardial cells due to infarction, acidosis, or hypoxia

31
Q

What are the four pressures within Arterial Pressure Waveform?

A
  1. Arterial - ratio of systolic over diastolic
  2. Systolic
  3. Diastolic
  4. Pulse - systolic minus diastolic pressure
32
Q

Why might older adults with atherosclerosis give a false high blood pressure reading?

A

a greater external pressure is required to compress the blood vessels and stop the flow

Anatomy / Physio II (9 decks)

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