Cardiac Action Potential

Question 1

SA nodal action potential is exclusively for what function and what is the name of that property?

Answer 1

Heart rate generation
Chronotrophy

Question 2

Ventricular action potential is exclusively for? What type of property?

Answer 2

Contractility of ventricles of heart
inotrophy

Question 3

What are the phases of a SA nodal action potential?

Answer 3

Phase 4 - pre-potential phase
Restless membrane potential (-60 mv to -40)
Ca 2+ influx through T ca2+ channel
Na funny current causing Na influx
Decrease in K efflux

Phase 0 - depolarisation when -40 (threshold or firing level ) reached ,
Ca influx through L type Ca channel

Phase 4 - repolarisation K efflux

At the end K efflux decreases and pre-potential phase begins again

Question 4

Na funny current channel blocker is called?
What its purpose and side effect?

Answer 4

Ivabradine - decreases HR ( bradycardia)
Side effects- decreases visual acquity

Question 5

Ventricular action potentials phase?

Answer 5

Phase 0 - early depolarisation- Na influx
Phase 1 - early repolarisation - K efflux
Phase 2 - plateau phase - ca influx through L type channel to balance K efflux and at the end of plateau phase this Ca channel close
Phase 3- late repolarisation due to continued K efflux
Phase 4 - maintenance of RMP by NA K pump
Na pumped out and K pumbed inside the cell

Question 6

The property of conduction of impulse from SA node to the base of the ventricles is called

Answer 6

Dromotrophy

Question 7

What is the SA node firing rate? Why it is not equal to the resting normal heart rate.?

Answer 7

100 impulse/ minute
Norml hr is 72bpm
It is not equal b/c sa nodal firing is inhibited by parasympathetic nervous system by resting vagal tone

Question 8

What drug increases heart rate to 150 beat per minute due to sole effect of sympathetic nervous system?

Answer 8

Atropine ( anticholinergic , block pns)

Question 9

What are the components of conduction system of heart?

Answer 9

SA node
Av node
His bundle
Purkinje fibres
to
Ventricular myocardial cells

Question 10

What is the goal keeper of heart?

Answer 10

Av node
b/c it perform a physiological impulse conduction delay (0.01 sec) for ventricular relaxation when atria is contracting
Its impulse conduction velocitybis 0.04 m/s

Question 11

Which component of conduction system of heart has highest impulse conduction velocity?

Answer 11

Purkinje fibres due to large numbrr of gap junctions it is 4m/sec

Question 12

Cardiac gap junction is made up of ? And where it is present in cardiac muscles histology?

Answer 12

Connexin a special type of protein
Found in intercalated disc region