Cardiac Muscle

Question 1

relationship of AP with contraction of heart

Answer 1

1 action potential is shared along the heart and it contracts as one unit

Question 2

these cells have high density of mitochondria b/c requires lots of energy

Answer 2

cardiac myocytes

Question 3

cardiac myocytes are attached together by what

Answer 3

desmosomes

Question 4

cardiac myocytes communicate to each other by

Answer 4

gap junctions

Question 5

position of T tubules on cardiac muscle

Answer 5

Z lines

Question 6

skeletal muscle compared to cardiac muscle in terms of Ca2+ and troponin C

Answer 6

skeletal- all of troponin C is saturated

cardiac- not all of troponin C is saturated

Question 7

Calcium that contributes to heart muscle contraction comes from what channel or what 2 channels

Answer 7

L-type voltage gated Ca2+ channel (DHPR) and RyR

Question 8

puts the breaks on SERCA; if it is removed, increase in Ca2+ sequestration

Answer 8

Phospholamban (PLB)

Question 9

main metabolism of the heart

Answer 9

oxidative metabolism of fatty acids

Question 10

what happens when the heart switches from oxidative metabolism to glycolytic metabolism

Answer 10

heart failure

Question 11

what is this

Answer 11

ventricular myocyte action potential

Question 12

describe the steps:

Answer 12

phase 0: Na+ influx through fast voltage gated Na+ channel opening
phase 1: sets peak (quick K+ appearance)
phase 2: L-type voltage gated Ca2+ channel opening and Ca2+ influx
phase 3: delayed outward rectifier K+ channel (efflux) REPOLARIZATION
phase 4: inward rectifier K+ channel (hyperpolarization)

Question 13

difference b/t phase 3 and phase 4 of ventricular myocyte action potential

Answer 13

phase 3: repolarization (delayed outward rectifier K+ channel)

phase 4: hyperpolarization (inward rectifier K+ channel)

Question 14

main function of inward rectifier K+ channel

Answer 14

keeps membrane potential stable

Question 15

specific type of delayed outward rectifier K+ channel

Answer 15

hERG channel

Question 16

long plateau of ventricular myocyte action potential is due to what

Answer 16

L-type Ca2+ channel (long-lasting, slow)

Question 17

no stimulus will elicit an AP regardless of strength (phase 0-end of 2)

Answer 17

absolute refractory period

Question 18

a larger than normal stimulus can initiate AP (phase 3)

Answer 18

relative refractory period

Question 19

a weaker than normal stimulus can initiate AP (phase 3)

Answer 19

supranormal refractory period

Question 20

what is this

Answer 20

early afterdepolarizations (EADs)

Question 21

can happen during phase 2 and 3 and lead to tachycardia

Answer 21

EADs (early afterdepolarizations)

Question 22

what is this

Answer 22

delayed afterdepolarizations (DADs)

Question 23

can happen in phase 4 and lead to tachycardia

Answer 23

DADs (delayed afterdepolarizations)

Question 24

Answer 24

nodal myocyte action potential (SA or AV node)

Question 25

where do spontaneous action potential’s originate from

Answer 25

pacemaker cells in SA node

Question 26

list the phases

Answer 26

phase 4: Na leaking into cell
phase 0: Ca2+ influx
phase 3: K+ efflux

Question 27

special channels phase 4 deals with

Answer 27

HCN channels (basically during hyperpolarization, Na+ leaking into cell)

Question 28

specific channel seen in phase 3

Answer 28

delayed outward rectifier K+ channel

Question 29

what dictates the pace b/c it has faster phase 4 than the other node

Answer 29

SA node