18 11-15

Question 1

Energy requirements/metabolism of the heart?

Answer 1

1. Relies exclusively on aerobic respiration for energy metabolism 2. Has a very extensive blood supply 3. Many mitochondria 4. Myoglobin/creatine kinase 5. Uses multiple fuel molecules . Capable of switching nutrient pathways - uses fat under

Question 2

Intrinsic cardiac conduction system

Answer 2

Consists of noncontractile cardiac cells specialized to initiate and distribute impulses throughout the heart so it contracts in an orderly and sequential manner. Myogenic rather than neurogenic.

Question 3

Autorythmic cells?

Answer 3

Have an unstable resting potential, spontaneously depolarize to fire action APs (“pacemaker potentials”) then spontaneously repolarize, connected via conduction fibers with larger diameters than muscle fibers and can conduct APs more rapidly

Question 4

SA node

Answer 4

“pacemaker” (because it depolarizes faster than other component it sets the pace.) sinoatrial node Will spontaneously depolarize 100x/min. However, vagus nerve slows it to 75/min Depolarizes the atria and the AV node.

Question 5

AV node

Answer 5

“gatekeeper” atrioventricular node Will spontaneously depolarize about 40-50x/min Inferior to entrance of SVC

Question 6

AV bundle

Answer 6

“bundle of His” superior part of the interventricular septum

Question 7

R/L bundle branches

Answer 7

No nickname…

Question 8

Purkinje fibers

Answer 8

“subdenoardial conducting network”

Question 9

Pacemaker/autorythmic cells

Answer 9

Unstable resting potential that continuously drifts towards depolarization . These spontaneously changing membrane potentials (pacemaker potentials/prepotentials) initiate Aps.

Question 10

Order of the impulses passing through the heart?

Answer 10

SA node –> AV node –> AV bundle –> R/L bundle branches –> Purkinje fibers

Question 11

5 steps in intrinsic conduction system showing the sequence of electrical excitation.

Answer 11

1. SA node generates impulse
2. The impulses pause 0.1s at the AV node (allowing the atria to respond and contract, delay is cause by smaller diameter fibers/fewer gap junctions)
3. AV bundle connects the atria to the ventricles (no gap junctions, AV bundle is only connection between atria and ventricle)
4. Splits into the R+L bundle branches, impulse conducted through the interatrial septum
5. Purjinke fibers/subendocardial cunducting network depolarizes the contractile cells of both ventricles.

Question 12

Ectopic focus

Answer 12

A pacemaker other than the SA node

Question 13

Arrythmia

Answer 13

Irregular heart rhythm

Question 14

Fibrillation

Answer 14

Rapid and irregular or out of phase contractions in which control of the heart rhythm is taken away from the SA node by rapid activity in other heart regions

Question 15

EKG/ECG

Answer 15

A graphic record of heart activity - reflects patterns of Ap firings in the entire population of cells (nodal and contractile) that make up the heart. Electrocardiogram

Question 16

P wave

Answer 16

(Patrial depolarization) Lasts 0.08s, results from movement of the depolarization wave from the SA node through the atria. Appx. 0.1s after P wave begins, the atria contract.

Question 17

QRS wave

Answer 17

(Ventricular depolarization) Lasts 0.08s, results from ventricular depolarization and precedes ventricular contraction.

Question 18

T wave

Answer 18

(Ventricular repolarization) Lasts 0.16s, caused by ventricular repolarization

Question 19

S-T segment

Answer 19

corresponds to plateau, elevation here is called tombstoning. A disruption of rhythm/calcium

Question 20

Heart sounds are the?

Answer 20

Valves closing.

First the AV valves (when ventricular pressure rises above atrial pressure, ventricle systole) lub or S1 - soft, low pitched.

Then the SL valves (snap shut at the beginning of ventricular diastole) Dup or S2 - sharper, louder, higher-pitched.

Question 21

What kind of abnormalities can be traced on an ECG?

Answer 21

Junctional rhythm, heart block, ventricular fibrillation, flatline

Question 22

heart murmurs

Answer 22

When blood flow becomes turbulent and generates abnormal heart sounds.

Common in young with healthy hearts but thin heart walls which vibrate.

Can indicate valve problems though.–

• Insufficient/Incomplete valves fail to close completely and the sound is swishing as blood backflows.
• Stenotic valves fail to open completely and narrowness restricts blood flow resulting in a high pitched click.

Question 23

Heart sounds are the?

Answer 23

Valves closing. First the AV valves (when ventricular pressure rises above atrial pressure, ventricle systole) lub or S1 - soft, low pitched. Then the SL valves (snap shut at the beginning of ventricular diastole) Dup or S2 - sharper, louder, higher-pit

Question 24

Duration of a heartbeat?

Answer 24

0.8s - 0.5s in diastole, 0.3s in systole

Question 25

heart murmurs

Answer 25

When blood flow becomes turbulent and generates abnormal heart sounds. Common in young with healthy hearts but thin heart walls which vibrate. Can indicate valve problems though. Insufficient/Incomplete valves fail to close completely and the sound is s

Question 26

Sign of a heart attack?

Answer 26

Creatine kinase and troponin in the blood (from cardiac cells rupturing)

Question 27

Junctional rhythm

Answer 27

Sa node is nonfunctional, P waves absent, AV node paces heart at 40-60

Question 28

Heart block

Answer 28

Some P waves are not conducted thru the AV node, hence more P than QRS waves are seen

Question 29

Ventricular fibrillation

Answer 29

Chaotic irregular ect deflections