MP and AP Flashcards

What is the primary role of cardiac myocytes?

How is contraction initiated?

What is action potential (AP)?

Cardiac myocytes have an ___________________ b/w the intracellular and extracellular regions.

The intracellular region of cardiac myocytes is _____________ charged relative to the extracellular region

A resting ventricular myocyte has a resting membrane potential of ________ relative to the extracellular env.

What is the charge of the extracellular environment of a resting ventricular myocyte?

T/F: The cardiac myocyte in a resting state is said to be depolarized, meaning there is charge separation b/w interior and exterior environments of the cell.

The E_m is determined by _________________

Which four ions are primarily involved in determining the membrane potential during the cardiac cycle?

The current of cell membranes is carried by ______

Which ion is most important for establishing the resting membrane potential?

T/F: Ohm's Law states that the voltage difference b/w two points in a material are indirectly proportional to the current (I) and the resistance (R)

T/F: The inverse of current (I) is known as conductance (g).

V =

I = ΔV(1/R) =

What factors are involved in the membrane potential?

[K⁺] is _______ (high/low) on the inside of the cell.

Where will K⁺ want to move?

Where will Na⁺ want to move?

Where will Ca⁺⁺ want to move?

What equation can be used to calculate ion equilibrium?

T/F: E_K is not the same as E_m because E_K is less negative than E_m

Why is there a small net electromotive driving force resulting in steady and slow leakage of K⁺ in resting nonpacemaker cardiomyocytes?

What is responsible for the flow of K⁺ ions in the resting state?

The higher the permeability, the higher the ______________, meaning the greater the solute transport across the cell membrane

Where is the Na/K pump located?

If the ATPase Na/K pump is inhibited, what happens to intracellular Na?

Na/Ca exchanger rate (Na:Ca)

Na/K exchanger rate (Na:K)

A flux of positive charge into the resting cell results in a(n) __________ (inward/outward) current and ___(de-/hyper-)polarization of the cell.

A flux of positive charge out of the resting cell results in a(n) __________ (inward/outward) current and ___(de-/hyper-)polarization of the cell.

T/F: Ion channels are glycosylated ptns w/ repeating domains

Each domain of ion channels consists of _____ transmembrane segments

Which ion channel has 4 domains that are not bonded together by peptide bonds?

Which loop on the Na channel is believed to be the inactivation gate?

On the Na channel, where is the M gate located?

On the Na channel, where is the H gate located?

When a membrane is depolarized, which Na gate (H or M) rapidly opens allowing Na into the cell?

When does the H gate begin to close?

Sudden depolarization of membrane potential in cardiomyocytes via ion current results in __________

List the 2 general types of cardiac APs

These cells are triggered by APs in adjacent cells w/ depolarizing currents

These cells can spontaneously generate their own APs

The nonpacemaker and pacemaker APs of the heart are different in their ______ and ______ than the APs found in nerve cells and skeletal muscle cells.

Which cells have a true resting potential?

Nonpacemaker AP is divided into how many phases?

Which phase of nonpacemaker cell:

Equilibrium maintained by high gK⁺ through inward rectifying K channel compared to low gNa⁺ and gCa⁺⁺. This is true resting potential.

Which phase of nonpacemaker cell:

Rapid depolarization due to increase in Na conductance of voltage-gated fast ion Na channels. Rush of Na into cell.

Which phase of nonpacemaker cell:

Repolarization due to opening of transient outward K channel incombo w/ inactivation of Na channel. gCa⁺⁺ increased and slow movement of Ca into cell via L-type Ca channel.

What channel is known as the slow inward, long-lasting current?

Which phase of nonpacemaker cell:

Inward movement of Ca through lon-lasting (L-type) voltage gated Ca ion channel = major pathway of entry for Ca

Which phase of nonpacemaker cell:

Repolarization phase. gK conductance increases and initiates an outward K current through K delayed rectifier and gCa conductance decreases

Ventricular cells are unexcitable (refractory) during which phases (absolute refractory period)?

What does the effective refractory period include?

Which refractory period:

Weaker than normal APs may be generated and conducted.

Which refractory period:

Weaker than normal APs may be generated

Which refractory period:

Only localized APs can be generated, but not propagated.

Which refractory period:

No new propagating APs are generated

If the fast response Na channels are blocked/inactivated, the AP upstroke is reduced and can lead to ___________

During phase 3 or phase 4, nonpacemaker cells may start generating spontaneous depolarizations called _________________.

T/F: The depolarizing current in an afterpolarization is from the fast response Na channel, given that the slow Ca channels are closed.

If a drug interacts w/ __________________ it can lead to dangerous arrhythmias

T/F: Pacemaker cells have no true resting potential

What phases are the pacemaker AP divided up into?

Pacemaker cells are ______ and referred to as _________ AP compared to the "fast response" nonpacemaker cells.

What ion is responsible for being the major depolarizing current in pacemaker cells?

Which phase of a pacemaker cell:

1. gK decreases
2. gCa is increasing (in second half of this phase) due to transient (T-type) Ca channels
3. Pacemaker current (funny Na ion current)
4. L-type Ca channels start to open

Which phase of a pacemaker cell:

1. Inward movement of Ca via L-type Ca channels = depolarizes
2. Simultaneous decrease in K channels currents
3. Slope is "softer" than same phase of nonpacemaker cells

Which phase of a pacemaker cell:

Repolarization begins due to decrease in gCa and increase in gK

What is the primary pacemaker site?

What order of nodes would take over if the SA node failed?

The higher intrinsic "firing" rate of the SA node controls the other nodes. This is termed _____________

If the SA node is no longer controlling, secondary pacemaker sites will develop. When this happens, the new site outside of the SA node is referred to as an ______________

What mechanisms can modify the SA node AP?

What are the effects of sympathetic stimulation on the SA node?

What are the effects of vagal (parasympathetic) stimulation on the SA node?

List factors that would increase the SA node firing rate

List factors that would decrease the SA node firing rate