Cardiovascular Physiology 11

Question 1

What are the phases in the Ventricular Muscle Cell action potential?

Answer 1

• Resting membrane potential
• Depolarization phase
• The notch phase
• The plateau
• Repolarization

Question 2

What is the resting membrane potential of a Ventricular Muscle Cell close to?

Answer 2

The equilibrium potential of potassium

Question 3

What must the Ventricular Muscle Cell receive in order to bring it to threshold?

Answer 3

Stimulus

Question 4

What is the stimulus to bring the Ventricular Muscle Cell to threshold?

Answer 4

Depolarization in an adjacent cell that is either a contractile cell or a cell of the conducting system

Question 5

In a ventricular muscle cell action potential which channel open when threshold is reached?

Answer 5

Voltage gated sodium channels

Question 6

What occurs in a Ventricular Muscle Cell action potential after the voltage gated sodium channels open and then close?

Answer 6

ito channels open allowing a small amount of potassium to leave the cell, causing the notch

Question 7

What happens after the notch occurs and the ito channels close in a Ventricular muscle cell action potential?

Answer 7

L-type calcium channels open allowing calcium to enter the cell at the same time as potassium leaving the cell by the K1 channels causing a plateas

Question 8

Which channels cause the plateau phase of the Ventricular Muscle Cell action potential?

Answer 8

They K1 channels allowing potassium to leave and the L-type calcium channels allowing calcium to enter

Question 9

Which additional channels open during the Plateau phase in Ventricular Muscle Cell action potential and what do they do?

Answer 9

Kr and Ks channels which allow more potassium to leave the cell causing depolarization

Question 10

Which channels close during the Plateau of the Ventricular Muscle Cell Action Potential?

Answer 10

K1 potassium channels and the L-type calcium channels

Question 11

Which channels maintain resting potential in a Ventricular Muscle Cell action potential?

Answer 11

K1 potassium channels

Question 12

What do all the channels in a Ventricular Muscle Cell action potential open and close in response to?

Answer 12

Voltage, so they are all voltage gated channels

Question 13

Where can the slow-type action potential occur?

Answer 13

• Sinoatrial node cells

* Atrioventricular node cells

Question 14

Where can fast-type action potentials occur?

Answer 14

• Atrial myocardial cells

* Ventricular myocardial cells

Question 15

What is the difference between the slow-type action potential in the SA node and the AV node?

Answer 15

The AV cells take longer to reach threshold and as a result has a longer pacemaker potential

Question 16

Which cells set the heart rate?

Answer 16

The Sinoatrial nodal cells

Question 17

What is the difference between Atrial Myocardial and Ventricular Myocardial action potentials?

Answer 17

Atrial Myocardial action potentials have a much shorter duration and have a shorter plateau

Question 18

What is responsible for the AV Nodal delay?

Answer 18

The AV node has the slow type action potential and its depolarization is due to slow L-type calcium channels and not the fast type sodium channels