Electrical Physiology

Question 1

What is the resting concentration of K+ in and out of cell?

Answer 1

150 mmol in

4 mmol out

Question 2

What is the resting potential of a muscle cell?

Answer 2

-90mV

Question 3

What pumps keeps Ca and Na ions out of the cell (ie. higher concentration)?

Answer 3

Na+/K+ ATPase
Na+/Ca++ exchanger
Ca++ ATPase

Question 4

True False: systole is the state of depolarization

Answer 4

true

Question 5

Describes the phases of myocardial electrical activity:

Answer 5

Phase 0: depolarization –> influx of Na
Phase 1: closure of Na pumps (peak)
Phase 2: plateau phase –> Ca into the cell and K out (membrane voltage stays constant)
Phase 3: K out and hyperpolarises
Phase 4: repolarization to resting membrane

Question 6

What are pacemaker cells?

Answer 6

Cells that can spontaneous trigger another activation by slow deploarization via slow diastolic inward leak of Na+

Question 7

Left anterior descending artery problems can be detected by which leads?

Answer 7

V2 to V5

Question 8

Lateral leads (ie I, and aVL) can detect which coronary problem?

Answer 8

Circumplex artery

Question 9

Inferior Leads (ie. II, III, aVF) can detect which coronary problems?

Answer 9

Posterior descending artery

Question 10

What are the unipolar limb leads?

Answer 10

aVR, aVL, aVF

Question 11

What are the bipolar limb leads?

Answer 11

I, II, III

Question 12

What are the chest leads?

Answer 12

V1 to V6

Question 13

Where does normal beat begins?

Answer 13

sino-atrial node, located at the junction of the right atrium and the superior vena cava

Question 14

T or F: the wave of depolarization from SA node travels rapidly within the AV node?

Answer 14

False: there is an expected delay

Question 15

What does a P wave represent?

Answer 15

deploarization of atria

Question 16

What does th QRS complex represent?

Answer 16

depolarization of ventricle muscle cells (endocardium)

Question 17

What does T wave represent?

Answer 17

repolarization of ventricle cells (epicardium)

Question 18

When would you expect to see a second upward deflection in a QRS complex?

Answer 18

A second upward deflection (seen in bundle branch blocks) is referred to as R ′

Question 19

Whats the PR(PQ) segment

Answer 19

delay between atrial and ventricular deploarization

Question 20

What is the QT segment?

Answer 20

time from ventricular deploratization until full repolarization (ie. end of T wave)

Question 21

What are the lateral leads?

Answer 21

I, aVL, V5, V6

Question 22

What are the inferior leads?

Answer 22

II, III, aVF, V5, V6

Question 23

What does a large Q wave signify?

Answer 23

myocardial damage/scar

Question 24

When would you expect to see Q waves in inferior leads?

Answer 24

if initial septal depolarization a bit superior as well as left

Question 25

What is the most common cause of of ST/T abnormalities?

Answer 25

ischemia

Question 26

What happens to the electrical activity during ischemia?

Answer 26

less positive systole, and less negative diastole and resting membrane

Question 27

What happens to the ECG for sub-endocardium ischemia?

Answer 27

Marked ST depression, and T wave abnormal (T waves maybe inverted / bi-phasic)

Question 28

What happens to the ECG for trans-mural ischemia?

Answer 28

ST- elevation

Question 29

What happens to ECG in K+ imbalances?

Answer 29

severe increase in K+ in blood
(eventually –> sine wave pattern) –> depressed P wave, long QRS complex, increased T wave

derease in K+ (Mg++) in blood
(long QT, T wave changes, U waves)