21-31 - Review of Relevant Physiological Concepts

Question 1

ability for a cell to respond to an external electrical stimulus

Answer 1

excitability

Question 2

ability for a cell or region of cells to initiate an action potential

Answer 2

automaticity

Question 3

ability of a cell or region of cells to receive and transmit an action potential

Answer 3

conductivity

Question 4

ability to alter the rate of electrical conduction

Answer 4

dromotropism

Question 5

the inability of a cell to receive and transmit an action potential

Answer 5

refractoriness

Question 6

what are the consequences of an enhanced late sodium current?

Answer 6

increases intracellular sodium which is used by NCX to increase intracellular calcium –> cellular calcium overload and prolonged action potential = electrical instability, after depolarizations, arrhythmias, mechanical dysfunctions

Question 7

phase 0 depolarization is due to Ca2+ influx

Answer 7

nodal tissue

Question 8

phase 0 depolarization is due to Na influx

Answer 8

non-nodal tissue

Question 9

review slide 10

Answer 9

AP graphs with ion flow for the different phases

Question 10

which is longer: APD action potential duration or ERP effective refractory period

Answer 10

APD is longer, consists of time from phase 0 to next phase 0

ERP = phase 0- halfway through phase 3

Question 11

effective v. relative refractory period

Answer 11

effective: no AP whatsoever can be generated
relative: after effective, a larger stimulus can generate an AP

Question 12

do you want a lower or higher ERP/APD ratio?

Answer 12

lower ERP/APD ratio is bad because the tissue is easily depolarized by abnormal impulses

Question 13

every P wave has a QRS, it is just at a faster rate

Answer 13

sinus node tachycardia - disorder of impulse formation

Question 14

not every p wave has a QRS complex, 2:1 ratio

Answer 14

atrial tachycardia from the top of the atria - disorder of impulse formation

(there is foci generating impulses between SA node and AV node)

Question 15

risk with marked prolongation of cardiac action potential

Answer 15

early afterdepolarizations –> abnormal rhythms

Question 16

consequence of cytoplasmic or SR Ca2+ overload

Answer 16

delayed after depolarization –> abnormal rhythms

Question 17

what might cause cytoplasmic or SR calcium overload?

Answer 17

• MI
• adrenergic stress
• digitalis intoxication
• heart failure

Question 18

all P waves have a QRS but the PR interval is increased

Answer 18

primary AV nodal block

Question 19

not all p waves have a QRS, PR interval varies

Answer 19

secondary AV nodal block

Question 20

no P/QRS relationshiip, each at their own pace

Answer 20

tertiary AV nodal block

Question 21

2 conduction paths with different conduction velocities –>

Answer 21

AV nodal reentrant tachycardia AVNRT

Question 22

longer QRS time because going through muscular pathway

Answer 22

ventricular re-entry

Question 23

result of a single reentrant circuit in the RA with AV blockade

Answer 23

atrial flutter (4:1)

Question 24

consequences of arrhythmia

Answer 24

• compromise of mechanical performance
• proarrhythmic/arrhythmogenic
• thrombogenesis (especially with afib and aflutter)