Lecture 8

Question 1

Resting membrane potential for cardiac myocytes

Answer 1

-85 mv

Question 2

Speed of AP conduction

Answer 2

Fastest 
axon 
Skeletal muscle
SAN
Cardiac ventricles

Question 3

Ventricular myocytes AP

Answer 3

1. Wave of electrical excitation
2. Na+ channels open - upstroke
3. Transient outflow of K+ - transient repolarisation
4. Voltage gated calcium channels open causing influx - plateau
5. Calcium channels inactivate and K+ open - repolarisation

Question 4

Resting membrane potential for SAN

Answer 4

-60mv

Never stays at resting potential

Question 5

SAN node depolarisation

Answer 5

1. Long, slow depolarisation (pace maker potential) to threshold due to funny current influx of sodium (HCN) activated by hyperpolarisation (-50mv)
2. Upstroke - voltage gated calcium channels open - influx
3. Downstroke - voltage gated potassium channels - efflux and inactivation of of calcium channels

Question 6

Hyperkalaemia

Answer 6

Above 5.5 mmol

Question 7

Hypokalaemia

Answer 7

Below 3.5 mmol

Question 8

Hyperkalaemia risks

Answer 8

Asystole

Question 9

Hypokalaemia risks

Answer 9

Ventricular fibrillation

Question 10

Treatment of hyperkalaemia

Answer 10

Calcium gluconate

Insulin and glucose