Action potential phases

Question 1

phase 4

Answer 1

Resting membrane potential

• constant k leakiness
• Na+/k+ pump
• VG channels are closed

Question 2

phase 0

Answer 2

depolarization
- depolarizing events ( ions move through the gap junctions) trigger VG Na+ channels
-Threshold potential is at -70 mV
-overshoot is at 0 mV
-L type Ca2+ channels begin to open
-

Question 3

phase 1

Answer 3

early repolarization

-few VG k+ channels open

Question 4

phase 2

Answer 4

Plateau phase

-electrical balancing due to Ca2+ influx and K+ efflux

Question 5

phase 3

Answer 5

repolarization

• Ltype Ca2+ channels close
• K+ efflux exeeds the Ca+ influx
• pumps restore ion balances