Cardiac Electrophysiology

Question 1

What is the pacemaker of the heart

Answer 1

SA node

Question 2

What is the resting membrane potential of the heart

Answer 2

70 bpm

Question 3

What kind of cells make up the SA node

Answer 3

Non contractile cardiomyocytes

Question 4

Where is the SA node located

Answer 4

Right atrium

Question 5

What is the resting membrane potental of the SA node

Answer 5

-60

Question 6

What causes the spontaneous depolarization in the SA node

Answer 6

Na and Ca move into the cell and reduced activity of the outward K current

Question 7

What causes repolarization of the SA node

Answer 7

Closing of ca channels and opening of K plus channels

Question 8

In contrast to the SA node and AV node which require _____ for depolarization, other cells requre______

Answer 8

Ca2+ , Na+

Question 9

Phase 4 is associated with

Answer 9

Resting membrane potential

Question 10

What is the main event that happens during phase 4

Answer 10

Ion concentrations of the previous action potentials are restored by the sodium potassium pump, na/k exchanger and ATP dependent calcium pump

Question 11

What happens during phase 0

Answer 11

Upstroke of the action potential . Rapid depolarization occurs when the cells reach threshold and fast sodium channels open

Question 12

What happens during phase 2

Answer 12

The plateau. The membrane remains depolarized because of voltage sensitive ca channels and inward current of calcium . Also an outward current of K, through a delayed K channel

Question 13

What happens during phase 1

Answer 13

Rapid depolarization to the plateau . This phase is caused by inactivation of Na channels and opening of K channels.

Question 14

What happens during phase 3

Answer 14

Inactivation of calcium channels leading to activation of K channels causing rapid repolarization because of an inward rectified K current

Question 15

Why is the pleteau of an action potential important

Answer 15

It prevents depolarization of cardiac cells and and arrhythmias

Question 16

What does an effective refractory period look like

Answer 16

Begins with phase 1 and extends thru phase 3

Question 17

The relative refractory period follows the ______ period

Answer 17

Effective

Question 18

During the conduction of an action potential ______ propagation occurs and _______depolarization is maintained

Answer 18

Forward , unidirectional

Question 19

A Normal ECG consists of

Answer 19

P wave caused by depolarization
QRS complex representing ventricular depolarization
T wave representing ventricular repolarization

Question 20

Why is the heart considered to be in sinus rhythm

Answer 20

Because the rhythm is being regulated by the SA node .

Question 21

How much blood is ejected

Answer 21

60%

Question 22

Closing of av valves produces the ____ heart sound

Answer 22

First

Question 23

The second clap represents what valve closure

Answer 23

Semi lunar valve

Question 24

S1 respresents the beginning of

Answer 24

Contraction