Cardiac Electrophysiology.

Question 1

The AV Valve:

Answer 1

Regulates the movement of blood between the two chambers.

Question 2

The atrium wall contains less ______ than the ventricular wall:

Answer 2

Cardiac muscle.

Question 3

More cardiac tissue in the left ventricle than the :

Why?

Answer 3

Right ventricle.

This is because the left ventricle needs more pressure to drive blood from through the systemic circuits.

Question 4

Cardiac muscle tissues are linked by:

Answer 4

Electrical synapses.

Question 5

Cardiac electrical synapses are located:

Answer 5

Located in specialized structures called intercalated disks.

They allow for fast synchronized responses to stimuli.

Question 6

Autorhythmic:

Answer 6

An action potential is generated within muscle tissue.

Cardiac muscle is autorhythmic.

Question 7

Types of cardiac muscle cells:

Answer 7

Contractile cell.

Conducting cell.

Question 8

Contractile cells:

Answer 8

Generate the force that pumps blood.

Not autorhythmic.

Question 9

Conducting cells:

Answer 9

Do not generate force.

These cells generate action potentials and rapidly propagate them through muscle tissue.

Question 10

Some conducting cells are located in two groups:

Answer 10

SA node & the AV node.

Both are located in the right atrium.

Question 11

SA node lies:

Answer 11

Near the junction with the superior vena cava.

Question 12

The AV node lies:

Answer 12

Near the right AV valve.

Question 13

Most conducting cells are organized into:

Answer 13

Bundles or tracts.

Question 14

What links the SA node to the AV node:

Answer 14

The Atrial internodal tract.

Question 15

The AV node propagates action potential into the ventricles.

Answer 15

Into the ventricles.

Question 16

The course of action of a cardiac action potential.

Answer 16

AV node.
Bundle of His (common bundle).
R & L bundle branches.
Purkinje fibers.
* Rapid propagation of action potential.

Question 17

Propagation of an action potential from the SA node to all other parts of cardiac muscle takes:

Answer 17

220 msec at a resting heart rate.

Question 18

Propagation between contractile cells occurs at:

Answer 18

1 m/sec.

Question 19

Propagation between most conducting cells is ____ times faster than contracting cells.

Answer 19

2-4 times faster.

Question 20

The slow conduction time of the AV node allows:

Answer 20

Atria to contact before the ventricle.

Question 21

Ventricular bundles:

Answer 21

Large bundles in the intraventricular septum.

Question 22

Cells in SA node:

Answer 22

Generate an action potential at regular intervals.

Question 23

Pacemaker potential:

Answer 23

When a cell completes an action potential, it immediately begins a slow depolarization.

The potential between two action potentials in the SA node.

Question 24

Resting potential:

Answer 24

Membrane potential in the absence of stimulation.

Question 25

SA node action potential:

Answer 25

No resting potential, unstable membrane potential. At the end of an action potential, the membrane potential slowly depolarizes.

Question 26

Two types of ion channels that produce the pacemaker potentials:

Answer 26

F-type channels. T-type channels. Both open during the pacemaker potential but close when the membrane potential reaches the threshold again.

Question 27

F-type channels:

Answer 27

Non-specific cation channels that primarily allow sodium ions to cross the membrane. Open at the end of an action potential, inward sodium depolarizes the membrane. They open fast.

Question 28

T-types channels:

Answer 28

Opens as the membrane potential nears threshold, allowing calcium ions to move in. This further depolarizes the membrane.

Question 29

L-type channels:

Answer 29

At threshold, these voltage-gated channels open gradually. This allows further prolonged inward movement of calcium ions. They begin to close at the same time the potassium ion opens. Resets during repolarization.

Question 30

Potassium ion channels:

Answer 30

Voltage-gated ion channels allow the outward movement of potassium ions which repolarizes the membrane. They open & close slowly.

Question 31

Action potential in contracting cells:

Answer 31

The cell has a stable resting potential. Action potential is divided into 4 phases.

Question 32

In contractile cells Na & K have: ****

Answer 32

2 gates.

Question 33

In a contractile cell threshold:

Answer 33

All signals get the signal to open.

Question 34

Plateau phase:

Answer 34

The movement potential does not change. Outward K+ is the same as inward Ca++.

Question 35

Phase 0:

Answer 35

It occurs when the membrane is depolarized to threshold. It is induced when voltage-gated Na ion channels open. Rapid inward movement of Na ion. Closes after 1 msec.

Question 36

Phases 1-3 are :

Answer 36

Repolarization phases.

Question 37

Phase 1:

Answer 37

Voltage-gated K+ channel 1 opens. K+ Moves outwards. Brief rapid repolarization.

Question 38

The contractile cell action potential has how many phases:

Answer 38

4 phases. Phases 0-3.

Question 39

Phase 2:

Answer 39

Voltage-gated L-type calcium ion channels open. Inward movement of calcium. Voltage-gated K+ channel 1 is still open. Plateau phase.

Question 40

Phase 3:

Answer 40

Both the L-type calcium ion and K+ channel 1 are closed. A second type of K+ ion opens. K+ ions move outwards. Another brief repolarization occurs. Membrane returns to resting potential.

Question 41

When does phase 3 end:

Answer 41

When the membrane potential return to resting potential.