Cardiovascular System: Electrocardiography Lab

Question 1

What causes heart contractions?

Answer 1

results form a series of electrical potential changes (depolarization waves) that travel through the heart at the beginning of each beat .

Question 2

Cardiac muscle cells are electrically connected via __________? ;therefore the entire myocardium behaves like a ________?

Answer 2

gap junctions, syncytium (coordinated unit)

Question 3

T/F: cardiac muscle contacts/ beats intrinsically and does not depend on impulses from the nervous system to initiate contraction (cardiac heart will continue to contract rhythmically even if all nerve connections are severed)

Answer 3

TRUE

Question 4

the autonomic nervous system can accelerate heart rate via?

Answer 4

sympathetic nervous system

Question 5

the autonomic nervous system can decelerate heart rate via?

Answer 5

parasympathetic nervous system

Question 6

another name for the intrinsic conduction system

Answer 6

nodal system

Question 7

what kind of tissue does the intrinsic conduction system consist of and what does it ensure?

Answer 7

• specialized non contractile myocardial tissue.
• it ensures that heart muscle depolarizes in a special manner (from arteries to ventricles)

Question 8

What are the components of the intrinsic conduction system?

Answer 8

• Sinoatrial (SA) node
• Atrioventricular (AV) node)
• AV bundle (bundle of His)
• Purkinje fibers

Question 9

where is the Sinoatrial (SA) node located?

Answer 9

right atrium just inferior to the entrance to the superior vena cava

Question 10

where is the Atrioventricular (AV) node located?

Answer 10

the lower atrial septum at the junction of the atria and ventricles

Question 11

where are the AV bundles located?

Answer 11

located in the inter ventricular septum

Question 12

what are purkinje fibers?

Answer 12

long strands of barrel shaped cells called purkinje myocytes

Question 13

where are purkinje fibers located?

Answer 13

ramify within the muscle bundles of the ventricular walls

Question 14

why are purkinje fibers more dense and elaborate in the left ventricle?

Answer 14

because the left ventricle is larger in size

Question 15

what does the SA node do?

Answer 15

sets the rate of depolarization for the heart as a whole

Question 16

what is the SA node referred to as?

Answer 16

pacemaker

Question 17

From the SA node, where does the impulse spread to?

Answer 17

Spreads throughout the atria and to the AV node. The electrical signal is immediately followed by atrial contraction.

Question 18

from the AV node, where does the impulse spread to?

Answer 18

the impulse is monetarily delayed (0.1 sec) allowing the atria to complete the contraction. the wave then passed through the AV bundle and the purkinje fibers and results in ventricular contraction.

Question 19

what are the atria and ventricles are separated from one
another by? what does this do?

Answer 19

• electrically inert connective tissue.
• So the depolarization wave can be transmitted to the ventricles only via the tract between the AV node and AV bundle.

Question 20

Impulses through the heart can be detected on the
body’s surface and recorded with an instrument called?

Answer 20

electrocardiograph

Question 21

The recording of the electrical changes (depolarization followed by repolarization) occurring during the cardiac cycle is called an?

Answer 21

electrocardiogram (ECG or EKG)

Question 22

what does an ECG record?

Answer 22

records the electrical events occurring in the bulk of the heart muscle (not the activity of nodal tissue).

Question 23

what are the intervals in a ECG?

Answer 23

Time measurement that includes a wave and/or a complex

Question 24

what are the segments in a ECG?

Answer 24

Time measurement that does not include a wave and/or a complex

Question 25

The baseline of an ECG tracing is called?

Answer 25

isoelectric line

Question 26

what does an isoelectric line suggest?

Answer 26

no electrical activity detected

Question 27

An ECG is recorded as a pattern of a baseline and is broken by a?

Answer 27

P wave, a QRS complex, and a T wave

Question 28

ECG summary of the SA node

Answer 28

• SA node initiates depolarization in the right and left atria causing contraction (corresponds to the P wave).
• SA node also sends the depolarization wave to the AV node (with a 0.1 sec delay to let the atria finish contracting), which in turn, causing contraction in both ventricles (corresponds to the QRS wave). At the same time, the atria repolarize and relax (hidden by the QRS complex).

Question 29

Ventricles repolarize and relax

Answer 29

corresponding to the T wave