3.4 -- Electrical Activity of the Heart

Question 1

Cardiac muscle cells are interconnected by what at intercalated discs?

Answer 1

Gap junctions

Question 2

Once an action potential is initiated, the action potential flows from cell to cell through what?

Answer 2

Gap junctions

Question 3

The area of the heart that contracts together from one stimulation event is called a myocardium or what?

Answer 3

Functional syncytium

Question 4

Are gap junctions between the atria and ventricles? If not, what separates them?

Answer 4

No there are no gap junctions but there is a fibrous skeleton

Question 5

What are the two main cell types in the heart?

Answer 5

Cardiac muscle cells/myocytes and pacemaker cells

Question 6

Which cells are contractile cells and are striated myofibers organized into sarcomeres?

Answer 6

Myocytes/cardiac muscle cells

Question 7

Which cells have force production, which does pressure?

Answer 7

Myocytes/cardiac muscle cells

Question 8

Which cells initiate an action potential with no organized sarcomeres?

Answer 8

Pacemaker cells

Question 9

Which cells are smaller and fewer contractile fibers?

Answer 9

Pacemaker cells

Question 10

Electrical signals in the heart are generated and propagated, not by nerves, but specialized (authorhythmic) what?

Answer 10

Pacemaker cells

Question 11

What node is a pacemaker cell? Where is it located?

Answer 11

Sinoatrial (SA) Node in the right atrium

Question 12

What are the two secondary pacemakers?

Answer 12

AV Node and Purkinje fibers

Question 13

What is the automatic nature of the heartbeat?

Answer 13

Automaticity

Question 14

What is the order of the electrical conduction in the heart?

Answer 14

SA node, atria myocytes, AV node, Bundle of His, Purkinje fibers, and then Ventricular myocytes at the bottom then top

Question 15

Do pacemaker cells have a resting membrane potential? Do they reach the threshold of an action potential on its own?

Answer 15

No and yes

Question 16

Diastolic depolarization, or slow/spontaneous depolarization, occurs between what?

Answer 16

Heartbeats

Question 17

At -40 mV, an action potential is triggered by voltage-gated what channels?

Answer 17

Ca2+ channels

Question 18

Repolarization occurs with the opening of voltage-gated what channels?

Answer 18

K+ channels

Question 19

Pacemaker cells in the sinoatrial (SA) node depolarize spontaneously but the what can be modulated?

Answer 19

Rate

Question 20

What release of epinephrine/norepinephrine and binding Beta1 receptors opens more HCN “pacemaker” channels, or funny Na+ channels? This speeds up what due to increased Na+ influx?

Answer 20

Sympathetic, heart rate

Question 21

What neurons secrete acetylcholine, which binds muscarinic AchR that opens K+ channels? This slows down what due to increased K+ efflux?

Answer 21

Parasympathetic, heart rate

Question 22

Vagal nerve stimulation slows the SA node pacemaker to what?

Answer 22

Resting heart rate

Question 23

Heart rate increases to help supply working tissues (especially skeletal muscles) with more what?

Answer 23

More blood

Question 24

What is the maximum heart rate?

Answer 24

Approximately 220 minus age

Question 25

What is the target heart rate zone?

Answer 25

50-80% max hour

Question 26

Do cardiac muscle cells have a positive or negative resting potential?

Answer 26

Negative

Question 27

What depolarizes cardiac muscle cells to threshold?

Answer 27

Action potentials from SA node

Question 28

In cardiac muscle, there is just a twitch, no summation of force to tetany due to what?

Answer 28

Action potentials being longer

Question 29

What being added to the membrane of cardiac cells ensures the heart cyclically contracts and relaxes?

Answer 29

Voltage-gated calcium channels

Question 30

What are the steps of excitation-contraction coupling in cardiac muscle?

Answer 30

Flashcards

Question 31

How long do ventricles contract after the atria?

Answer 31

0.1-0.2 seconds

Question 32

The ECG records what by picking up the movement of ions in body tissues in response to electrical spread?

Answer 32

Electrical activity of the heart

Question 33

Does the ECG record action potentials or the wave of depolarization spreading from cell to cell?

Answer 33

Wave of depolarization from cell to cell

Question 34

Does the ECG record contraction and relaxation or electrical events leading to contraction and relaxation?

Answer 34

Electrical events leading to contraction and relaxation?

Question 35

The P wave shows what?

Answer 35

Atrial depolarization

Question 36

The P-Q interval shows what?

Answer 36

Atrial contraction

Question 37

The QRS wave shows what?

Answer 37

Ventricular depolarization (Brings about contraction)

Question 38

The S-T segment or the plateau phase shows what?

Answer 38

Ventricular contraction (systole)