cardiac electrophysiology

Question 1

observe the action potentials in relation to the ECG tracing

Answer 1

Question 2

what type of an event does teh ECG show?

Answer 2

Electrical event (depolarization) not mechanical contraction

Question 3

What type of action potential is this? and explain all reason you know it is and what happens in each phase!!

Answer 3

• Ventricular Action potential b/c RMP is at -90mV
• 4- RMP (diastole)
• 0- rapid depolarization Na+ influx
• 1- transient repolarization Cl- influx and K+ efflux
• 2- Plataeu Ca++ influx K+ efflux
• 3- Repolarization (delayed or late) K+ efflux
• 4- Na+ / K+ pump regains intracellular balance

Question 4

See the picture to compare everything of last slide

Question 5

What type of muscle has a RMP at -90mV

Answer 5

Classic striated cardiac and Skeletal muscle

Question 6

What type of action potential is this? and explain all reason you know it is and what happens in each phase!!

Answer 6

• SA node action potential b/c the RMP is -70mV
• 4- (diastole) spontaneous depolarization to threshold K+ efflux and Na+ and Ca++ influx (Ca++ influx only during last 1/3 of phase)
• 0- SLOW depolarization (notice the slanted line versus the abprupt straight line of the ventriculars fast depolarization) Ca++ and Na+ influx
• 3- Repolarization K+ efflux
• 4- Diastole again