Lecutre 3 (Pacemaker Cells And The Normal Sequence Of Cardiac Excitation)

Question 1

When are “funny” Na+ channel activated?

Answer 1

Hyper polarization

Question 2

Phase 3 - slow Repolarization

Answer 2

Repolarization is slow
Decrease in Ca++ conductance
An increase in K+ conductance (delayed rectifier)

Question 3

Slow type -phase 0

Answer 3

Ca++ channels begin opening slowly around - 55mV
Slow rising action potential generated due to an increase in Ca++ conductance
Funny Na+ channels close during depolarization

Question 4

Maximum negative potential dependent on

Answer 4

Na+ and K+ conductance interaction

Question 5

Conduction to the left atria is via

Answer 5

Anterior inter atrial band (Bachmann’s bundle)

Question 6

Ventricular myocytes are only electrically coupled to atria via

Answer 6

AV node

Question 7

Myocardial depolarization is followed by

Answer 7

Muscle contraction and then relaxation

Question 8

SA node has an intrinsic rate of

Answer 8

80 - 100 depolarizations/min

Question 9

AV node intrinsic rate

Answer 9

50 - 60 depolarizations/min

Question 10

His/Purkinje system intrinsic rate

Answer 10

30 - 40 depolarizations/min

Question 11

Normal sequence of depolarization

Answer 11

SA node
Atrial tissue
AV node
Septum
Papillary/Purkinje
Apex
Base