Lecture 24- Cardiovascular Electrophysiology

Question 1

Why are cardiomyocytes excitable?

Answer 1

There is an electrochemical gradient maintained across the cell membrane

Question 2

What ions are most important for myocardial contraction?

Answer 2

Na, K, and Ca

Question 3

What is the equation for conductance?

Answer 3

1/resistance

Question 4

What is conductance?

Answer 4

How easily a current flows

Question 5

What type of cells can depolarize spontaneously and found in nodes and the bundle of His?

Answer 5

Specialized Conduction Cells

Question 6

What cells are found in the cardiac muscle, and are excitable if given a stimulus?

Answer 6

Working cardiocytes

Question 7

What is normal automaticity?

Answer 7

The ability to spontaneously generate an action potential

Question 8

What is the dominant pacemaker of the adult heart?

Answer 8

SA node

Question 9

What is inherent rate?

Answer 9

Rate of firing independent of autonomic influence

Question 10

What does sympathetic tone do to sinus rate

Answer 10

Increases

Question 11

What does vagal tone do to sinus rate?

Answer 11

Decreases

Question 12

What is the only electrical connection between the atria and the ventricles?

Answer 12

The AV node

Question 13

What part of the heart is a “functional syncytium” and why

Answer 13

The myocardium- because it acts as if it is one cell due to the intercalated discs and gap junctions allowing rapid ion diffusion

Question 14

What is moved using the sodium potassium pump?

Answer 14

3 Na+ out
2 K+ in

Question 15

What is the Donnan effect

Answer 15

Large anions (proteins) are enclosed by a membrane

Question 16

What ion is the selective permeability of the cardiomyocytes permeable to when resting?

Answer 16

K leaks out

Question 17

What are voltage-gated K ion channels responsible for?

Answer 17

Repolarization

Question 18

What is the inward rectifier K ion channel responsible for

Answer 18

Maintaining resting membrane potential

Question 19

What are the voltage-gated sodium channels responsible for?

Answer 19

Letting Na+ in for depolarization

Question 20

When do voltage-gated Ca channels open

Answer 20

When the inside of the cell becomes positive

Question 21

What are the types of Ca voltage-gated ion channels?

Answer 21

L- type (slow)
T-type

Question 22

What is different between cardiomyocyte and neuron action potentials?

Answer 22

Cardiac APs last longer (plateau)

Question 23

What does the cardiomyocyte action potential plateau cause?

Answer 23

No physiological tetanus

Question 24

Is the plateau longer in the SA node or the Purkinje fibers?

Answer 24

The Purkinje fibers

Question 25

What is another name for Bundle of His

Answer 25

AV bundle

Question 26

Depolarization of working cells is driven by

Answer 26

Sodium channels

Question 27

Depolarization of nodal cells is driven by

Answer 27

Calcium channels

Question 28

Arrhythmias should be treated in nodal cells or working cells?

Answer 28

Working cells

Question 29

What phase do fast Na channels open

Answer 29

0

Question 30

What phase do slow Ca channels open

Answer 30

2

Question 31

What phase do K channels open?

Answer 31

3- repolarization (delayed rectifier)
4- inward rectifier

Question 32

What is overdrive suppression

Answer 32

The nodal cell depolarizing at the fastest rate sets the pace for the other nodal cells

Question 33

What kind of Na channels is used in spontaneous depolarization in addition to Ca and K?

Answer 33

If (funny)

Question 34

How are sympathetic neurons distributed through the myocardium?

Answer 34

Diffusely

Question 35

How are parasympathetic neurons distributed through the myocardium

Answer 35

Regionally localized

Question 36

What are the sympathetic vs parasympathetic neurotransmitters?

Answer 36

S: Epi and Norepi
P: Ach