Ion Channels of Cardiac Muscle

Question 1

What does dV/dt represent?

Answer 1

The maximum rate of voltage change, of cardiac membrane potential

Question 2

Which ions are involved in each phase of the pacemaker potential?

Answer 2

Question 3

Why is the slope of the phase 0 (upstroke) slow than other cardiac myocytes?

Answer 3

• Due to lack of large Na+ currents in SA and AV nodal cells
• Due to non-rapid Ca2+ movement via channels

Question 4

Fast fibers vs slow fibers

Answer 4

Fast fibers (and long)- Purkinje fibers

Slow fibers (and brief)- SA node and AV node

Question 5

Na- K pump

Answer 5

3 Na out

2 K in

Question 6

Gold-man Hodgkin-Katz

Answer 6

Determine the reversal potential across a cell’s membrane, taking into account all of the ions that permeant through that membrane.

Question 7

Gating can be affected by either ________ or ________.

Answer 7

Voltage

Ligand attachment

*Some channels can be both

Question 8

In the heart, cAMP dependent PKA __________ (increases/decreases) the avalaibility of calcium channels for activation while cGMP dependent protein kinase _________ (increases/decreases) it.

Answer 8

Increases; decreases

Question 9

Which potassium current is restricted to the action potential overshoot?

Answer 9

I_to because it is activated at a membrane potential more positive to around -20mV and inactivated around -35 mV.

*It increases the rate of repolarization