EKG

Question 1

depolarization

Answer 1

cell interiors become positive

Question 2

repolarization

Answer 2

cell interiors become negative

Question 3

SA node

Answer 3

known as the hearts pacemaker, its pacing activity is known as sinus rhythm

Question 4

Where is the SA node located

Answer 4

in the upper posterior wall of the R atrium, it initiates a depolarization wave at regular intervals to accomplish its pacemaking responsibility

Question 5

Each depolarization wave emitted by the SA node spreads through both atria producing a _____ wave

Answer 5

P wave

Question 6

P wave represents depolarization and simulatenous atrial

Answer 6

contraction

Question 7

when the wave of atrial depolarization enters the AV node, depolarization slows producing a brief pause … WHY?

Answer 7

allowing time for the blood in the atria to enter the ventricles

Question 8

slow conduction through the AV node is carried by

Answer 8

calcium ions

Question 9

the flat line on the ekg after the p wave means what?

Answer 9

it represents the time it takes for blood to flow through the valves into the ventricles

Question 10

depolarization conducts slowly through the AV node but once it reaches the _______________ depolarization rapidly shoots through the bundle of his and the left and right bundle branches

Answer 10

ventricular

Question 11

last part of ventricular depolarization

Answer 11

terminal filaments of the purkinje fibers distribute depolarization to the ventricular myocytes. Depolarization of the entire ventricular myocardium produces a QRS complex on the ekg

Question 12

qrs complex indicated

Answer 12

ventricular depolarization, and the beginning of ventricular contraction

Question 13

T wave

Answer 13

represents the final rapid phase of ventricular repolarization

Question 14

QT interval

Answer 14

represents the duration of ventricular systole, and is measured from the beginning of the QRS until the end of the Twave

Question 15

the release of free calcium ions into the interiors of myocytes produce myocardial

Answer 15

contraction

Question 16

following depolarization, repolarization is due to the controlled outflow of _________________ ions from the myocyes

Answer 16

K+

Question 17

cell to cell conduction of ( depolarization) through the myocardium is carried by the Na+ ions however, av node conduction is due to the slow movement of _________________

Answer 17

Ca ions

Question 18

sinoatrial node

Answer 18

represented as the p wave on the ekg, rate 60-100, located in upper portion of the right atrium

Question 19

AV node

Answer 19

• *Slows conduction of the impulse from atria to ventricles allowing time for ventricular filling; can initiate impulses and act as backup PM of heart; “escape pacemaker”; screen rapid atrial impulses to protect the ventricles from dangerously fast heart rates, such as a-fib (where atrial rate much faster than ventricular rate); the only conduction pathway between the atria and ventricles
   Rate: 40-60 bpm
   Location: Near the tricuspid valve

Question 20

bundle of HIS

Answer 20

the common bundle”; begins the ventricular conduction system, thus everything above it is “supraventricular”; only route of communication between atrium and ventricles
 Location: partially in right atrium and upper portion of interventricular septum that connects the AV node and 2 bundle branches

Question 21

purkinje fibers

Answer 21

• hair-like fibers that spread out from bundle branches into the ventricles; innervate myocardial cells directly; initiate ventricular depolarization; endocardium to epicardium; rapid conduction using Na+ ions

Question 22

resting membrane potential

Answer 22

electrical charge of cardiac muscles at rest

Question 23

depolarization

Answer 23

change in the electrical charge of a stimulated cell from negative to positive by the flow of ions; Na+ allows for depolarization, except in AV node which depends on the slow moving Ca2+

Question 24

repolarization

Answer 24

recharging of a cell to its normal polarity; K+ allows for repolarization

Question 25

repolarization

Answer 25

recharging of a cell to its normal polarity; K+ allows for repolarization

Question 26

action potential

Answer 26

as cardiac cells reverse polarity, the electrical impulse generated during that event creates an energy stimulus that travels across the cell membrane

Question 27

phase 4 action potential

Answer 27

Resting state: Na+ and Ca2+ channels are closed; increase in K+ permeability to allow for a new cycle

Question 28

rapid depolarization

Answer 28

Rapid depolarization: Opening of voltage-gated fast Na+ channels; cell fires to initiate transmission of electrical impulse

Question 29

phase 1 action potential

Answer 29

Depolarization: Peak positive charge; K+ closes, Cl- enters to slow channels, slow Ca2+ channels open

Question 30

phase 2 action potential

Answer 30

Plateau: Opening of voltage gated slow Ca2+ channels and closing of some K+, some Na+ enters to maintain; membrane potential is maintained or plateaued

Question 31

phase 3 repolarization

Answer 31

Repolarization: Opening of voltage-gated K+ channels and closing of Ca2+ channels; K+ moves from ICF to ECF

Question 32

refractory periods

Answer 32

time from phase 0 until the repolarization of a myocyte or when enough Na+ have recovered

Question 33

absolute refractory

Answer 33

occurs with the early part of the T-wave when most of the ventricle is depolarized and is “refractory” to new stimuli

Question 34

refractory period

Answer 34

occurs towards the end of the T-wave when most ventricular cells are repolarized and vulnerable to new stimuli; can lead to VT if PVC lands during this time Refractory = resistant