Cardiac action potential

Question 1

What are the three phases of SA node AP

Answer 1

Phase 4,0,3

Question 2

What is Phase 4 depolarization also referred to as

Answer 2

Normal automaticity
Spontaneous depolarisation
Diastolic Depolarisation

Question 3

What is the physiological basis of Phase 4 depolarisation

Answer 3

Slow influx of Ca2+ and Na+ through funny Na+ channels

Question 4

What is the ion change in Phase 0

Answer 4

Influx of Ca2+ not K+

Question 5

What is the ion change in Phase 3

Answer 5

Efflux of K+

Question 6

What phases are absent in SA node AP

Answer 6

Phase 1 and Phase 2

Question 7

How does sympathetic Stimulation affect SA node

Answer 7

Increases the activity of funny channels
Which increase the influx of Ca2+ and Na+ during Phase 4 hence shorting the phase 4

Question 8

What is the difference btwn the Phase 4 of SA node and ventricular muscle AP

Answer 8

Ventricular muscles have a stable phase 4 with an influx of K+ ions but SA node is unstable with influx of Ca2+ or Na+

Question 9

Describe AP of Ventricular muscle cells

Question 10

What is responsible for LONG the duration of ventricular action potential

Answer 10

Long Plateaus

Question 11

What is the function of gap junctions at the intercalated disc