Chapter 11: EKG

Question 1

Atrioventricular Valves

Answer 1

(No. 2) right AV also called tricuspid and (No. 8) left AV also called bicuspid

Question 2

Semilunar Valves

Answer 2

(No. 4) pulmonary semilunar

(No. 11) aortic semilunar

Question 3

Arteries

Answer 3

Send blood away from heart, most carry oxygenated blood except pulmonary arteries

Question 4

Veins

Answer 4

Bring blood back to the heart, most carry deoxygenated blood except pulmonary veins

Question 5

Electrical Conduction System

Answer 5

Sinoatrial (SA) node – is the heart’s pacemaker, (60-80 BPM)

Atrioventricular (AV) Node (40-60 BPM)

AV bundle (Bundle of His) (20-40 BPM)

Purkinje system (Less than 20 BPM if heart fails)

Question 6

SA Node

Answer 6

Found at the junction of right ventricle with superior vena cava

Pacemaker, 60-80 BPM

Question 7

SA Node Potential

Answer 7

Membrane potential starts at –60 mV
Slow influx of Na+ (without a corresponding K+ outflow),

Results in gradual depolarization - this is called the pacemaker potential,

When –40 mV threshold is reached, voltage-gated Ca+2 channels open,

Ca+2 influx depolarizes cells to 0 mV, at this time voltage-gated K+ channels open,

K+ flows out and cells repolarize, K+ channels close and cycle begins again.

Question 8

Hyperpolarization _____ threshold

Answer 8

INHIBITS

Question 9

Resting Membrane Potential of Cardiac muscles

Answer 9

-90 mV, just like skeletal muscle

Question 10

Myocardial Electrical Behavior

Answer 10

Stable resting potential of –90 mV,

Stimulus opens voltage-gated Na+ channels,
Na+ enters cell depolarizing it,

Peaks at +30 mV, Na+ channels close, voltage-gated K+ channels open starting the repolarization

Voltage-gated slow Ca+2 channels open (due to depolarization), Ca+2 flows in from ECF,

Ca+2 binds to Ca+2-gated fast Ca+2-channels on the sarcoplasmic reticulum, and more Ca+2 is released into the cytoplasm from sarcoplasmic reticulum, extending the depolarization time (plateau). Process called calcium-induced calcium-release.

Question 11

Myocardial Contraction and Action Potential

Answer 11

Stimulus from conduction system (SA or AV node) depolarizes myocyte,

Voltage-gated Na+ channels open,

Voltage gated K+ channels open and voltage gated Ca+2 channels open,

Ca+2-gated Ca+2 channels on SR open,

All Ca+2 channels close

Question 12

Plateau of ventricular myocyte action potential coincides in time with the ____ segment of EKG this is the time in which ventricular contraction (systole) takes place

Answer 12

S-T segment

Question 13

EKG

Answer 13

P-wave: atrial depolarization

P-Q segment: Atrial systole

QRS Complex: Ventricular depolarization/atrial repolarization

S-T segment: Ventricular Systole

T-wave: Ventricular depolarization

Question 14

Sinus Rhythm

Answer 14

Normal EKG

Question 15

Nodal Rhythm

Answer 15

No SA node/ no P-wave

Question 16

Heart block

Answer 16

No QRS, not a medical emergency

Question 17

Ventricular fibrillation

Answer 17

is an emergency; not sufficient blood leaves

Ventricles to perfuse (take blood to) organs for survival.

Question 18

Calcium blockers _____ the repolarization

Answer 18

Shorten

Question 19

P-R interval

Answer 19

SA node firing, interval between atrial depolarization and ventricular depolarization/atrial repolarization

Question 20

Q-T interval

Answer 20

Interval between Electrical depolarization and repolarization of the ventricles

Question 21

S-T interval

Answer 21

Interval between Ventricular depolarization and repolarization