3- Mechanisms of Dysrhythmias

Question 1

what phases correspond to the absolute refractory period?

Answer 1

phase 0,1, and2

Question 2

time that the cell is unable to respond to another incoming impulse

Answer 2

absolute refractory period

Question 3

relative refractory period phase

Answer 3

phase 3

Question 4

sustained inability to respond to an incoming impulse under normal conditions

Answer 4

relative refractory period

Question 5

why doesn’t the heart tetanize like skeletal muscle?

Answer 5

extended absolute refractory period due to calcium channels

AND

no recruting

*everything is all or none

Question 6

define calcium spark

Answer 6

calcium-induced(voltage) calcium release(SR calcium channels)

Question 7

name of calcium release channels

Answer 7

ryanodine receptors

Question 8

increased activity of SERCA by SNS =

Answer 8

calcium taken away to increase relaxation faster ALSO SNS increases rate of calcium release from ryanodine.
Together = increased contractions

Question 9

classify: abnormal or enhanced automaticity

Answer 9

active arrhytmia

Question 10

classify: triggered activity

Answer 10

active arrhythmia

Question 11

classify: reentrant circuits

Answer 11

active arrhythmias

Question 12

slower than normal

Answer 12

sinus bradycardia

faster (>100) would be sinus tachycardia

Question 13

effect of hypokalemia

Answer 13

decreases phase 4 K availabale –> easier depolarization and less time between AP

Question 14

effect of mild hyperkalemia

Answer 14

increased AP

Question 15

effect of severe hyperkalemia

Answer 15

unexcitable, no AP

Question 16

“triggered activity”

Answer 16

delayed or early afterdepolarization

Question 17

arrhythmia is generated at a time when the cell is fully repolarized

Answer 17

DAD

Question 18

arrhythmia generated during phase 2 or phase 3 depending

Answer 18

EAD

Question 19

characteristically extended action potential duration indicates…

Answer 19

EAD

Question 20

reduced potassium current –>

Answer 20

repolarization takes longer than normal –> prolonged APD

Question 21

increased intracellular calcium –>

Answer 21

extended plateau phase and extra calcium can activate an additonal sodium current –> prolonged APD

Question 22

mutation of NCX to increase current during the end of phase 2 –>

Answer 22

prolonged APD

Question 23

when can EADs be accentuated..

Answer 23

at lower heart rates due to the physiologically natural longer APDs at this point

Question 24

exacerbated by higher HR…

Answer 24

DADs

because ther is not sufficient time to reduce intracellular calcium between successive beats

Question 25

a fixed pathway exists which connects atrial tissue to ventricular tissue and in doing so, bypasses the AV node

Answer 25

wolff-parkinson-white syndrome

Question 26

how does wolff parkinson white syndrome manifest on ECG

Answer 26

shortened PR interval (because the bypass impulse travels faster to ventricles than normally conducted signal)

Question 27

core of inexciteable tissue would be..

Answer 27

functional reentract obstacle

Question 28

associated with spiral wae

Answer 28

anatomical-define reentrant circuit

Question 29

stable spiral wave originating from one position within the ventricular mass

Answer 29

monomorphic ventricular tachycardia

Question 30

meandering or drifting spiral waves throughout the ventricular mass

Answer 30

polymorphic tachycardia

Question 31

rely on the principles of electrical anisotropy and spatial inhomogeneities

Answer 31

reentrant circuits

Question 32

conduction abnormality as a result of tissue structure

Answer 32

passive arrhythmia

Question 33

"source sink"

Answer 33

a smaller sink will increase APD and a larger sink will reduce APD and conduction velocity contributes to anisotropy and inhomogeneity in the propogating wavefront

Question 34

true or false: changing the AP duration will change the refractory period

Answer 34

true

Question 35

vagal stimulation would have what effect on HR

Answer 35

vagal is parasympathetic so it would derease automaticity and decrease HR --> sinus brady cardia sympathetic would be the opposite: sinus tachyccardia

Question 36

if both para and symp are stimulate who will win for HR?

Answer 36

para

Question 37

how does Ach change automaticity

Answer 37

slower by increasing potassium current

Question 38

how does NE change automaticity

Answer 38

faster by increasing calcium and funny current

Question 39

how do hypokalemia and ischemia change automaticity

Answer 39

faster becasue of a decreased potassium current

Question 40

what 4 things could cause a prolonged APD?

Answer 40

1. reduced potassium current 2. increased calcium 3. increased sodium-calcium exchanger activity 4. increased late sodium current

Question 41

true or false: only anatomically defined reentrant circuits rely on electrical anisotropy and tissue inhomogeneiteies

Answer 41

FALSE both anatomical and cuntionally defined reentrant ircuits rely on electrical anisotropy and tissue inhomogeneiteies

Question 42

spiral wave

Answer 42

functioanlly defined reentrant circuit

Question 43

fixed pathway with excitable gap

Answer 43

anatomically defined reentrant circuit