Ionic Basis of Ventricular Action Potential

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What is the term used to describe the time period during which a cell is unexcitable to stimulation?

Absolute refractory period (correct)

Relative refractory period

Supranormal period

Effective refractory period

Which type of fibers can spontaneously generate action potentials without neural input?

Atrial fibers

SA Node fibers (correct)

Purkinje fibers

Ventricular fibers

What is a key difference between the resting membrane potential of the SA Node and the Atrial, Ventricular, and Purkinje fibers?

Stable resting membrane potential

Unstable resting membrane potential (correct)

Long duration of action potential

Sustained plateau

During which period does stimulation produce a weak action potential that propagates more slowly than usual?

Relative refractory period Signup and view all the answers

Which type of stimulus can trigger an action potential during the supranormal period?

Weaker-than-normal stimulus Signup and view all the answers

What distinguishes the ERP (effective refractory period) from the ARP (absolute refractory period)?

Localized depolarisation that does not propagate Signup and view all the answers

Which phase of the cardiac action potential is characterized by the movement of the membrane potential towards the resting potential?

Phase 3 Signup and view all the answers

Which type of potassium current is responsible for maintaining the resting membrane potential?

I$_K1$ Signup and view all the answers

What is the primary difference between the delayed rectifier potassium currents I$_Ks$ and I$_Kr$?

I$_Ks$ is a slow current, while I$_Kr$ is a rapid current Signup and view all the answers

What is the primary ionic mechanism responsible for the repolarization phase (phase 3) of the ventricular action potential?

Decrease in the inward calcium current (I$_Ca$) and increase in the outward potassium currents (I$_Ks$, I$_Kr$) Signup and view all the answers

Which phase of the cardiac action potential is characterized by a stable membrane potential?

Phase 4 Signup and view all the answers

Which phase of the SA node action potential is characterized by repolarization?

Phase 3 Signup and view all the answers

Which type of potassium current is responsible for the transient outward phase (phase 1) of the cardiac action potential?

I$_to$ Signup and view all the answers

What ion current contributes to the slow depolarization in Phase 4 of the SA node action potential?

Inward Na+ current Signup and view all the answers

Which phase of the SA node action potential accounts for the automaticity of SA node cells?

Phase 4 Signup and view all the answers

What sets the heart rate in relation to the SA node action potential?

Rate of phase 4 depolarization Signup and view all the answers

What is the most negative value of the membrane potential in the SA node action potential?

~ -65 mV Signup and view all the answers

In the SA node action potential, what brings the membrane potential to threshold for Ca2+ channels to open?