Electrical activity of the heart

Question 1

The path of an electrical impulse from the SA node to the left atrium is facilitated by:

Answer 1

Bachmanns bundle

Question 2

What are the 4 characteristics nodal tissue in the heart?

Answer 2

Excitability
Automaticity
Conductivity
Contractility

Question 3

What is excitability?

Answer 3

The ability of cells to respond to electrical chemical or mechanical stimulation

Question 4

What is automaticity?

Answer 4

The unique ability of cardiac muscle to initiate a spontaneous electrical impulse

Question 4

What is conductivity?

Answer 4

The ability of the myocardial tissue to spread or radiate electrical impulses

Question 5

What is contractility?

Answer 5

The ability of a cardiac cell to contract

Question 6

What is the period of time during which the myocardium cannot be stimulated?

Answer 6

Refractory period

Question 7

What is the intrinsic rate of contraction set by the SA node?

Answer 7

60-100 bpm

Question 8

What is the intrinsic rate of contraction set by the AV node?

Answer 8

40-60 bpm

Question 9

Myocytes at rest are referred to as _______

Answer 9

Polarized

Question 10

When myocytes are at rest they have a ______ charge

Answer 10

Negative

Question 11

What is the role of sodium in the electrical activity of the heart?

Answer 11

cause atrial and ventricular depolarization and contraction

Question 12

What is the role of calcium in the electrical activity of the heart?

Answer 12

maintains/slows impulse movement through the AV node to allow for ventricular filling
Follows sodium in to cell

Question 13

What is the role of potassium in the electrical activity of the heart?

Answer 13

Repolarization of myocytes

Question 14

What happens to the net charge of a cell when it is depolarized

Answer 14

Becomes positively charged

Question 15

Depolarization of the myocardial cells cause the cells to _______

Answer 15

Contract

Question 16

What is another term for repolarization?

Answer 16

Recovery phase

Question 17

What ion initially enters the cell, making it positive and causing depolarization?

Answer 17

Sodium

Question 18

Describe ion movement during depolarization and then repolarization

Answer 18

Sodium moves into the cell, starting depolarization. Calcium follows and strengthens and prolongs depolarization. The entry of sodium and potassium push potassium out of the cell initially, however during repolarization potassium reenters the cell pushing sodium and calcium out of the cell

Question 19

What is the intrinsic rate set by ectopic foci?

Answer 19

20-40 bpm

Question 20

What portion of the nervous system can alter the rhythmic intrinsic contraction of the heart?

Answer 20

Autonomic nervous system

Question 21

What is the autonomic nervous system composed of?

Answer 21

The sympathetic nervous system
The parasympathetic nervous system

Question 22

What does the sympathetic nervous system do to the heart?

Answer 22

Speed up heart rate
Increase the strength of the contraction

Question 23

What does the parasympathetic nervous system do to the heart?

Answer 23

Slow down heart rate
Decrease strength of contractility

Question 24

What does the P wave on an EKG represent?

Answer 24

Atrial contraction/atrial depolarization

Question 25

What does the QRS complex represent on an EKG?

Answer 25

Ventricular contraction/ventricular depolarization

Question 26

What does the T wave represent on an EKG?

Answer 26

Ventricular repolarization

Question 27

What does the isoelectric line represent?

Answer 27

Polarization Resting state

Question 28

What does the Q wave represent on an EKG?

Answer 28

The arrival of the electrical impulse at the bundle of His

Question 29

What does the R wave represent on an EKG?

Answer 29

Contraction of the left ventricle

Question 30

What does the S wave represent on an EKG?

Answer 30

Contraction of the right ventricle

Question 31

What are the 2 phases of ventricular repolarization?

Answer 31

Plateau phase Rapid phase

Question 32

Where does the absolute refractory period start?

Answer 32

The beginning of QRS complex

Question 33

Where does the absolute refractory period end?

Answer 33

The middle of the T wave

Question 34

Where does the relative refractory period begin?

Answer 34

The beginning of the down slope of the T wave

Question 35

Where does the supernormal refractory period begin?

Answer 35

The end of the T wave

Question 36

T/F: A strong electrical stimulus cannot cause a depolarization of myocardial tissue during the relative and supernormal refractory period

Answer 36

False. A strong electrical stimulus can cause a depolarization of myocardial tissue during the relative and supernormal refractory period

Question 37

The rapid phase of ventricular repolarization is represented by the:

Answer 37

The T wave

Question 38

Ventricular repolarization is represented on an EKG by

Answer 38

The ST segment and the T wave

Question 39

On an electrocardiogram, the end of the PR segment close to the apex of the T wave represents

Answer 39

The absolute refractory period