Cardiovascular system reading 3

Question 1

List in order the events of the cardiac conduction system, starting with the first at the top.

Answer 1

1. The SA node fires.
2. Excitation spreads through the atrial myocardium.
3. AV node fires
4. Excitation spreads down the AV bundle.
5. Purkinje fibers distribute excitation through the ventricular myocardium

Question 2

The structure that relays excitation from the atria to the ventricles is known as the _____.

Answer 2

atrioventricular node

Question 3

The electrical pathway by which signals leave the AV node to move to the interventricular septum is the atrioventricular _______.

Answer 3

bundle

Question 4

The sinoatrial node is located in the wall of the ______.

Answer 4

right atrium

Question 5

True or False: Action potentials from the SA node travel to all cells in the atria and the AV node at the same rate.

Answer 5

False

Question 6

Purkinje fibers _____.

Answer 6

are terminal branches of the cardiac conduction system

Question 7

What is the importance of the action potential delay at the AV node?

Answer 7

Allows the completion of atrial contraction before ventricular contraction

Question 8

The terminal branches of the conduction system that distribute the electrical signals throughout the ventricles are called ______.

Answer 8

Purkinje fibers

Question 9

Where does ventricular contraction begin?

Answer 9

Apex

Question 10

The resting membrane potential primarily depends on the plasma membrane permeability of all of the following ions EXCEPT ______.

Answer 10

chloride

Question 11

The membrane potential when a cardiac muscle cell is relaxed is the resting ______.

Answer 11

membrane potential

Question 12

Which occurs during the repolarization phase of a cardiac muscle cell but not in a skeletal muscle cell?

Answer 12

Calcium channels begin to open

Question 13

At rest, what ion is abundant inside of the cardiac cell membrane, helping to establish the resting membrane potential?

Answer 13

Potassium

Question 14

How is action potential propagation different in cardiac muscle cells than in skeletal muscle cells?

Answer 14

Action potentials are conducted from one cardiac cell to another.

Question 15

The action potential of a cardiac muscle has a plateau due to the opening of ______ channels.

Answer 15

calcium

Question 16

What is the first step in an action potential in a cardiac muscle cell?

Answer 16

Sodium channels open

Question 17

Initial depolarization of a cardiac muscle cell is due to the opening of ______ channels.

Answer 17

sodium

Question 18

The action potential of a cardiac muscle has a plateau primarily due to the diffusion of _____ the cell.

Answer 18

calcium into

Question 19

Electrical changes across the membrane cause the opening and closing of what-gated ion channels.

Answer 19

voltage

Question 20

Repolarization of a cardiac muscle cell is due primarily due to the diffusion of ______ the cell.

Answer 20

potassium out of

Question 21

Depolarization of the cardiac muscle cell is primarily due to the diffusion of ______ the cell.

Answer 21

sodium into

Question 22

What controls the opening of the ion channels in cardiac muscle cells during phases of the action potential?

Answer 22

Electrical changes

Question 23

The movement of calcium into a cardiac muscle cell through the membrane results in calcium release from the ______.

Answer 23

sarcoplasmic reticulum

Question 24

Calcium-induced calcium release occurs when ______.

Answer 24

calcium entering through the plasma membrane stimulates release of calcium from sarcoplasmic reticulum

Question 25

The cardiac muscle cells are described as ______ because individual cells can depolarize on their own without outside stimulation.

Answer 25

autorhythmic

Question 26

A spontaneously developing local potential that generates action potentials in the SA node is called the _____ potential.

Answer 26

pacemaker

Question 27

The pacemaker potential of SA node cells is due to the influx of what ions through special non-gated channels?

Answer 27

sodium or Na

Question 28

The depolarization of the SA node (from threshold to peak) is mainly due to the inflow of ______ ions.

Answer 28

calcium

Question 29

A pacemaker potential and an action potential are the same thing.

Answer 29

False

Question 30

Calcium-induced calcium release occurs when ______.

Answer 30

calcium entering through the plasma membrane stimulates release of calcium from sarcoplasmic reticulum

Question 31

What ions cause the depolarization of the SA node (from threshold to peak) through their movements into the cell?

Answer 31

Sodium

Calcium

Question 32

If another region of the heart other than the SA generates a heartbeat, this region is called a(n) what focus?

Answer 32

ectopic

Question 33

The strongest stimulus will not cause muscle contraction during the ______ refractory period.

Answer 33

absolute

Question 34

What is a normal firing rate of the SA node for a healthy person at rest?

Answer 34

75

Question 35

What causes the long refractory period in cardiac muscle cells?

Answer 35

Plateau phase

Question 36

The frequency of action potential generation in the SA node is ______ than in other foci of the heart.

Answer 36

higher

Question 37

What is an ECG?

Answer 37

A recording of cardiac action potentials measured at the body’s surface

Question 38

An ectopic focus is a region of the heart that generates a heartbeat other than the ______.

Answer 38

SA node

Question 39

The what is a composite recording of all cardiac action potentials?

Answer 39

electrocardiogram, ECG, or EKG

Question 40

The QRS complex is the ECG recording of depolarization of the ______.

Answer 40

ventricles

Question 41

Why does atrial repolarization not appear as a separate wave on an ECG?

Answer 41

It is obscured by ventricular contraction.