m7 + 8 lab - EKG

Question 1

what does an ECG do?

ECG

Answer 1

electrocardiogram (ECG or EKG) = takes .80 sec per beat = 75bpm
- measures the electrical activity of the nodal system + the myocardium
—> determines activity or inactivity due to damage or ischemia to the myocardium

Question 2

what is the nodal system?

ECG

Answer 2

• initiated by the intrinsic conduction system —> initiates heart contractions independently of all CNS activity (reason why brain dead patient has a heart beat - bc heart has O2 + nutrient supply)
• made from autorhythmic cells

Question 3

what do autorhythmic cells do in the nodal system?

ECG

Answer 3

• spontaneously depolarize to trigger contraction - called pacemaker potential (set @ 100 bpm)
• some regulation by the ANS
  1. SNS = cardioacceletory —> increased HR
  2. PSNS = cardioinhibitory —> decreased HR
  => thru vagus nerve stim.
  => vagal response - stimulate vagus nerve to decrease HR 1)valsalva
  2) carotid

Question 4

aspects of the myocardium:

ECG

Answer 4

• connected by gap-junctions
• two units: atria + ventricles

Question 5

what happens during isovolumetric time?

valves + filling of blood

Answer 5

volume in ventricle is not changing due to valve action
- depo. (right after Q wave)
- repo. (right before T wave)

Question 6

when do the AV and semilunar valves open + close?

valves + filling of blood

Answer 6

AV valves
- closes at beginning of depo. at the Q-wave
- opens at the end of repo. at the T-wave
semilunar valves
- opens at the end of depo. at the Q-wave
- closes at the beginning of repo. at the T-wave

Question 7

what happens at the beginning of the P-wave?

valves + filling of blood

Answer 7

• SA node initiates atrial depo. leading to contraction (helps fill ventricles)

Question 8

what happens at the beginning of the Q-wave?

valves + filling of blood

Answer 8

• signal is conducted to purkinje fibers

Question 9

what happens between the Q-wave (depo.) and the T-wave (repo.)?

valves + filling of blood

Answer 9

blood is ejected from the ventricles creating:
- circulation
- pressure

• BP: systole (120mmHg) = contraction

Question 10

what happens between the end of the T-wave and the Q-wave?

valves + filling of blood

Answer 10

ventricles are refilling (this is occuring durring the SA node initiating atrial contraction)
- 80% is by gravity and circulation
- 20% is by the atrial contraction occuring at the P-wave by the SA node

• BP: diastole (80mmHg) = relaxation

Question 11

what happens at the sinoatrial node (SA node)?

cardiac intrinsic conduction

Answer 11

• called the pacemaker
• largest
• initiates depolar. leading to contraction of atria @ 100bpm
• depo. wave starts + spreads out to both atria through intercolated discs –> atria contract at the same time

Question 12

what happens at the atrioventricular node (AV node)?

cardiac intrinsic conduction

Answer 12

delays signal by 0.1 second to allow blood to drain from atria into ventricles

Question 13

what happens at the atrioventricular (AV) bundle? (bundle of His)

cardiac intrinsic conduction

Answer 13

• carries electrical impulses from the atrioventricular (AV) node to the ventricles
• bundle of His and Purkinje fibers work together to create ventricular contractions in the heart
  —> descends down the interventricular septum, which separates the right and left ventricles.

Question 14

what happens at the purkinje fibers?

cardiac intrinsic conduction

Answer 14

• initiates ventricular depo. = then a contraction occurs = ejecting blood = creating pressure and circulation
• ventricles pump same volume
  —> RV = pumps deoxygenated blood to lungs
  —> LV = pumps oxygenated blood thru the aorta and to the rest of the body

Question 15

what happens at the P-wave?

electrocardiography

Answer 15

initated by SA node - atrial depo. = then atrial contraction

Question 16

what happens during the QRS complex?

electrocardiography

Answer 16

stimulated by purkinje fibers = causes ventricular depo. = then contraction = ventricles eject blood

• atrial repo. occurs during QRS complex

Question 17

what happens during P-Q interval?

electrocardiography

Answer 17

• point of conduction from SA node to Purkinje
• atria are depo. = then contracting = filling the last 20% of the the ventricles
• normal time: .12 - .20 sec
• > = heart block
• < = tachycardia or fibrillation

Question 18

what happens during the Q-T interval?

electrocardiography

Answer 18

• ventricles depo. at Q-R wave = causing a contraction
• during S-T interval, ventricles are ejecting blood = circulation + pressure
• then ventricular repo. at T-wave
• normal time: .31 - .41 sec ( < or > = problems w/ circulation)
• < = dec. filling + ejection = tachycardia
• > = dec. ejection, dec. flow = long Q-T , genetic condition

Question 19

when do systole and diastole occur?

electrocardiography

Answer 19

systole - during Q-T interval (120mmHg)
- blood is ejected from ventricles by contraction
diastole - during T-Q interval (80mmHg)
- ventricles are refilling with blood - relaxation period
- 80% by gravity + circulation, 20% by atrial contraction

Question 20

what is einthoven’s triangle?

standard limb leads

Answer 20

lead I = RA - LA
lead II = RA - LL
lead III = LA - LL

Question 21

what is a normal ECG cycle length?

ECG cycle

Answer 21

.8 seconds long

Question 22

what are the two divisions of an ECG cycle?

ECG cycle

Answer 22

diastole = relaxation
- ventricular filling (passive + active refilling)
- from T-Q wave

systole = ejection
- ventricular contraction + ejection = circulation
- from QRS to end of T-wave

Question 23

what happens during the P-Q interval?

ECG cycle

Answer 23

• AV node delays signal .1 sec to allow ventricular filling
• normal time: .12-.20 sec
• > .20 sec = heart block (usually at AV node)

Question 24

what happens at the Q-T interval?

ECG cycle

Answer 24

• all ventricular activity (systole=contraction)
• normal time: .31-.41 sec
• stays around the same even during exercise
• if it elongates, could cause syncope or fibrillation

Question 25

what are the two ways to cause a vagal response? | lower BP

Answer 25

1) rectum - straining can cause fainting 2) carotid sinus - massaging can cause fainting

Question 26

how long are each square on a ECG? | ECG examples - sinus rhythms

Answer 26

each square = .20 sec 1/5 of the square = .04 sec find average by adding three sections together / by 3 = average ex.) .76 + .70 + .76 / 3 = .74 normal sinus rhythm: 60 / average = HR ex.) 60 / .74 = 81 bpm

Question 27

what indicates sinus bradycardia and sinus tachycardia? | ECG examples - sinus rhythms

Answer 27

bradycardia - HR is below 60 bpm tachycardia - HR is above 100 bpm

Question 28

what indicates atrial fibrillation? | ECG examples - fibrillation

Answer 28

no P wave

Question 29

what indicates ventricular fibrillation? | ECG examples - fibrillation

Answer 29

no pattern visible