w5 electrocardiogram theory

Question 1

what is an ecg, what does it measure?

Answer 1

sequential processes of depolarization and depolarization in cardiac cells an electrical field is created, currents flow from region of higher potential to lower potential. these changing potentials recorded on surface of body using a voltmeter called an electrocardiograph

Question 2

what is an electrocardiogram

Answer 2

mechanical tracing that records records waves of depolarization and depolarization of the heart muscles, records the rising and falling voltages of heart in respect to time

Question 3

how is ecg performed.

Answer 3

using electrodes or sensors on the surface of the body and connecting them to electrocardiograph. if positive and negative electrodes attached to body, the electrical activity will be recorded.

Question 4

what is an ecg used for

Answer 4

detect disturbances in electrical conduction within heart. - visualize rhythm of depolarization and depolarization.

Question 5

what are conditions that cause irregularities or arrhythmias in heart

Answer 5

cardiac muscle
external nervous control
blockage of impulses caused by myocardial infarction
medications
metabolic imbalances
congenital defects

Question 6

what are waves caused by on ecg

Answer 6

activity of myocardial cells of the heart. (contractile muscles)
depolarization and depolarization of these cells.

Question 7

characteristics of ecg waves

Answer 7

duration-how long it lasts
amplitude-millivolts-how high is wave
configuration- shape of wave

Question 8

x and y axis of graph-what is measured?

Answer 8

time or duration on horizontal x axis- one small square=0.04s and one large square is 0.2s
voltage or amplitude is measured on the y axis or vertical axis.0.1 mV small square, 0.5 mV for large square.

Question 9

what are waves on ecg? What do they measure?

Answer 9

P-QRS-T

these waves are created as depolarization and depolarization spread through heart muscles

Question 10

what are depolarization and depolarization linked to?

Answer 10

intrinsic conduction of the heart system

Question 11

P wave

Answer 11

occurs once sinoatrial node fires, a wave of depolarization spreads into the atrial myocardium causing the atria to contract. (right atria depolarizes first- this is p wave, left one right after) wave ends when they both are depolarized

Question 12

AV pause

Answer 12

conduction slowed in atrioventricular node, this is when the atria have contracted and pushed all blood into ventricles, the pause is so the blood has time to get to the ventricles before the contract and push the blood to the body or lungs
-this phase can be detected on the graph- it is right after p wave and no electricity detected- flat line.

Question 13

what structures are important in ventricle depolarization (from AV node)

Answer 13

1. bundle of his from AV bundle-emerges from av node and goes into left and right branches.
2. bundle branches left and right
3. purkinje fibres-branch from bundles and they deliver electrical current to myocardial radium of ventricles

Question 14

QRS complex

Answer 14

• this is the depolarization of the ventricles.
• larger than p wave, due to large amount of muscle in ventricles.
• first deflection downward is called Q wave.
• first deflection upward is R wave and this is the early depolarization of the ventricles
• first downward deflection following the upward deflection is the s wave and this is late depolarization
• depolarization of inter ventricular septum may be seen as q wave -can be overshadowed by ventricular depolarization and not seen

Question 15

when do ventricles depolarize

Answer 15

at the same time but on the ecg only the left one is recorded because it has 3 times the cardiac muscle in the walls

Question 16

when do the atria repolarize?

Answer 16

takes place at the same time of the depolarization of the ventricles but it is not detected on ecg

Question 17

t wave

Answer 17

repolarization of the ventricles