Electric Activity Of The Heart

Question 1

SA node intrinsic rate?

Answer 1

60-100 x min

Question 2

AV node intrinsic rate?

Answer 2

40-60 x min

Question 3

Purkinge cell intrinsic rate?

Answer 3

~35 x min

Question 4

Types of cardiac K+ Channels ? (3)

Answer 4

1. Ungated K+ Channels
2. Inward K+ Rectifying Channels (IK1)
3. K+ delayed Rectifier (IKR)

Question 5

Inward K+ Rectifying Channels close and open in what stages ?

Answer 5

1. Close: Depolarization

2. Open: Repolarization (rest)

Question 6

Phase 0 of the CARDIAC MUSCLE is due to the action of these type of channels?

Answer 6

Opening of Na+ Channels

Question 7

Phase 0 represents what phase of the EKG?

Answer 7

QRS complex

Question 8

Phase 1 of the CARDIAC MUSCLE is due to the action of which channel?

Answer 8

Na+ Channels inactivate and K+ slightly open

Question 9

Phase 2 (Plateu) of the CARDIAC MUSCLE is due to the interaction of which channels?

Answer 9

1. Opening of Ca++ Channels (L-Type)

2. Opening of Delayed Rectifying Channels

Question 10

What channels are involved in torsade de pointes prolongation of QT interval?

Answer 10

Fast Na+ channels that are still opened in phase 2.

Question 11

Class 1 antiarrhythmics act in what phase of the action potential?

Answer 11

Phase 0

Question 12

Name some Type 1 Antiarrhythmic drugs:

Answer 12

1A: -procainamide 
      -quinidine 
1B: -lidocaine 
      -Phenytoin 
1C: -flecainide 
       -propafenone

Question 13

Phase 2 represents what part of the EKG?

Answer 13

ST segment

Question 14

What channels are involved in the 3rd phase of the cardiac membrane potential?

Answer 14

1. Ca++ Channels close.

2. Inward K+ Rectifying (IK1) reopen .

Question 15

Phase 3 reflects what wave in the EKG?

Answer 15

T wave

Question 16

What antiarrhythmic agents act on phase 3?

Answer 16

Class III

Question 17

Class III agents work blocking this type of channel:

Answer 17

K+ Channels

Question 18

Name clase III antiarrhythmic agents :

Answer 18

1. Amiodarone

2. Sotalol

Question 19

Phase 4 is caused by the interaction of the following channels:

Answer 19

1. Closed Na+, Ca++, and delayed Rectifying K+ (IKR) Channels
2. Inward Rectifying Channels (IK1) are still opened

Question 20

Action potential of nodal cells has 3 phases:

Answer 20

Phase 4
Phase 0
Phase 3

Question 21

How is Phase 4 of nodal potential produced?

Answer 21

1. T-type Ca++ channels open.
2. Funny Inward Na+ Current.
3. Reduced K+ current

Question 22

Phase 0 of nodal membrane potential involves what Channels?

Answer 22

Opening of L-Type Ca++ Channels

Question 23

Phase 3 of nodal action potential is caused by which channel ?

Answer 23

K+ channel

Question 24

These 2 broad types of antiarrhythmics cause a reduction in automaticity and conduction of the heart:

Answer 24

Type II (betaclockers) 
Type IV (Ca++ Channel Blockers)

Question 25

Name Type IV antiarrhythmic agents :

Answer 25

1. Verapamil

2. Diltiazem

Question 26

Mechanism of action for Ivabradine?

Answer 26

Blocks Na+ funny current (heart rate)

Question 27

What’s Ivabradine used for?

Answer 27

1. CHF second line treatment

2. Idiopathic Sinus Tachycardia

Question 28

Sympathetic nervous system acts through these receptors :

Answer 28

1. B1 Receptors

Question 29

Parasympathetic nervous system acts through these receptors :

Answer 29

M2 (Muscarinic) Receptors

Question 30

What type of receptors are B1 receptors?

Answer 30

Gs-cAMP ⬆️⬆️

Question 31

What type of receptors are M2 muscarinic receptors?

Answer 31

Gi/G0 (inhibit cAMP)

Question 32

B1 receptors open the following ion Channels:

Answer 32

1. Ca++ Channels

2. Funny Na+ Channels

Question 33

Muscarinic M2 receptors open the following Channel:

Answer 33

K+ Channels