Cardio Electrophysiology/ Action Potentials/ ECG

work in progress

________________ is when the ventricles are filling, muscles are relaxed, and AV valves are open.

a. diastole

b. systole

a. Diastole

_______________ is when the ventricles are emptying, muscles are contracting, and AV valves are closed.

a. diastole

b. systole

b. Systole

What part of the heart has a pacemaker ability?

sinoatrial node

Are the action potentials in the nodes and myocytes the same?

no

Electrical signals flow from the SA node to the atria to the ______________.

AV node

What is the resting membrane potential (mV) in the SA node and the cardiac myocytes?

SA node: -60 mV

Myocytes: -90mV

How does sodium enter the cell of the SA node and depolarize? (aka which transporter)

F-type Na channels

What type of transporter causes the rapid depolarization in the SA node?

L-type voltage gated Ca channels

After rapid depolarization, what channels are opened to repolarize the membrane in the SA node?

K channels

How does sympathetic stimulation affect the SA node?

• causes depolarization to occur more rapidly

• steeper

• faster heartbeats

How does parasympathetic stimulation affect the SA node?

• activates K channels

• makes it harder to depolarize

• slower heartbeats

In phase 0 of the cardiac myocyte action potential what happens?

• voltage gated Na+ channels open

• causes depolarization

What happens during phase 1 of the cardiac myocyte action potential?

• transient K+ channels open

• K+ leaves the cell

What happens during phase 2 of the cardiac myocyte action potential?

• Calcium coming in the cell through voltage gated L-type channels

• K+ still leaving the cells

• causes a plateau

What happens during phase 3 of the cardiac myocyte action potential?

• calcium channels close

• K+ channels remain open

• repolarizing

What happens during phase 4 of the cardiac myocyte action potential?

• rest

• leak K+ open

What measures change in polarity that occurs at the heart?

ECG

In an ECG, the P wave represents the…

atria depolarization

In an ECG, the QRS wave represents the…

ventricular depolarization

In an ECG, the T wave represents the…

ventricular repolarization

What event occurs right before the start of the P wave?

SA node depolarizes

What is happening during the PR interval?

We are measuring the conduction of signals from the SA node, AV node, and all the way down the heart before the ventricles

What does the QRS interval tell us about depolarization?

how RAPID/FAST we depolarize our ventricles

The QT interval measures how long our ________ __________ take.

measures how long our ACTION POTENTIALS take.