Phys 01 Cell Physiology Of Cardiac Muscle

Front 1

term meaning the heart stimulates its own contraction

Back 1

myogenic

Front 2

intercalated discs, components and fxns (2)

Back 2

desmosomes (mechanical link), gap junctions (electrical link)

Front 3

What events occur during phase 0 of a cardiac action potential?

Back 3

Phase 0: upstroke, rapid depolarization due to Na channels opening, then closing)

Front 4

What events occur during phase 1 of a cardiac action potential?

Back 4

Phase 1: initial repolarization, inactivation gates closed on Na channels, outward K current

Front 5

What events occur during phase 2 of a cardiac action potential?

Back 5

Phase 2: 2 plateau, inward Ca current by L-type channels, outward K current

Front 6

What events occur during phase 3 of a cardiac action potential?

Back 6

Phase 3: repolarization, decreased Ca current, initially increased K current then reduced as K approaches equilibrium potential

Front 7

What events occur during phase 4 of a cardiac action potential?

Back 7

Phase 4: resting membrane potential, phase 4 channels reestablish rmp (K channel), different from K channels in phase 3 (K1 channels)

Front 8

resting membrane potential, aka

Back 8

electrical diastole

Front 9

"plateau" of action potential in cardiac muscle, def

Back 9

sustained depolarization due to Ca influx and K efflux

Front 10

List the phases of a cardiac action potential (0-5)

Back 10

0 upstroke (rapid depolarization), 1 initial repolarization, 2 plateau, 3 repolarization, 4 resting membrane potential (aka electric diastole)

Front 11

mechanism of Ca channel blockers; examples (3)

Back 11

inhibit L-type Ca channel in heart during phase 2 (plateau). Ex: nifedipine, diltiazem, verapamil.

Front 12

vagal stimulation increases/decreases heart rate

Back 12

decreases (sympathetic increases)

Front 13

Describe ionic flow during the different phases of cardiac action potential

Back 13

0 fast Na influx, 1 transient K efflux, Na-channel inactivation, 2 Ca and Na influx, K efflux, 3 K efflux > Ca and Na influx, 4 Na-K pump

Front 14

"trigger Ca" is what percent of total Ca in cardiac muscle

Back 14

10%

Front 15

Ca released from sarcolemma by what type of Ca channel?

Back 15

L-type

Front 16

Ca released from SR by what type of Ca channel?

Back 16

Ca-release channel (RyR)

Front 17

What pump is responsible for Ca reuptake into the SR in skeletal and cardiac muscle?

Back 17

SERCA (Sarcoplasmic and Endoplasmic Reticulum Ca-ATPase)

Front 18

What pump extrudes Ca across the sarcolemma in skeletal and cardiac muscle?

Back 18

PMCA (Plasma Membrane Ca-ATPase)

Front 19

What exchanger extrudes Ca across the sarcolemma in skeletal and cardiac muscle?

Back 19

Na-Ca exchanger (NCX)

Front 20

Compare the functions of the SERCA pump, PMCA pump, and Na-Ca exchanger

Back 20

PMCA exchanges 1-to-1 H and Ca, SERCA exchange 2-to-2 H and Ca per ATP hydrolyzed, NCX exchanges 3Na-1Ca and Na is later pumped out by Na-K pump

Front 21

PMCA vs. SERCA

Back 21

plasma membrane calcium ATPase (PMCA) and sarcoplasmic and endoplasmic reticulum calcium ATPase (SERCA)

Front 22

Describe the mechanism of cardiac muscle relaxation

Back 22

1 Ca taken up into SR by SERCA, 2 Ca extruded across sarcolemma by Na-Ca exchanger, then Na extruded by Na-K ATPase, 3 Ca is extruded across sarcolemma by PMCA

Front 23

phospholambin; what is it and what does it do?

Back 23

effect is myocite contraction; regulatory protein that inhibits SR Ca pump, but if it is phosphorylated by PKA it can no longer inhibit

Front 24

Effect of PKA activators on myocytes

Back 24

cause relaxation due to inhibition of phospholamban

Front 25

Why is summation not possible in cardiac muscle?

Back 25

extensive coupling between cardiac myocytes

Front 26

Why does your heart beat harder if you exercise more?

Back 26

Cardiac muscle becomes more responsive to norepinephrine (sympathetic nt)

Front 27

effect of norepinephrine on the heart

Back 27

increases generation of cAMP through β adrenergic receptors > activates PKA > PKA phosphorylates L-type channels > increased influx of Ca > increased contractile force

Front 28

2 ways that cAMP increases strength of cardiac contraction

Back 28

1 activate L-type channels to increase intracellular Ca, 2 increase Ca-sensitivity of contractile apparatus

Front 29

What happens when ACh binds to a muscarinic receptor in the heart?

Back 29

activates K+ channel, increases K+ currents, results in slower, less forceful beats (IMAGE)

Front 30

fxn of cardiac length reserve

Back 30

allows heart to stretch to accommodate overfill of blood; contraction following overfill is more forceful

Front 31

How and why is Ca reserved during heart contraction?

Back 31

diads provide insufficient Ca to fully activate contractiole apparatus; allows 'reserve capacity' for enhanced contraction if necessary

Front 32

location of cardiac diads

Back 32

on the Z line

Front 33

Why does passive tension engage at shorter lengths in cardiac muscle?

Back 33

cardiac muscle is always partially contracted (length reserve)

Front 34

term meaning the heart stimulates its own contraction

Back 34

myogenic

Front 35

intercalated discs, components and fxns (2)

Back 35

desmosomes (mechanical link), gap junctions (electrical link)

Front 36

What events occur during phase 0 of a cardiac action potential?

Back 36

Phase 0: upstroke, rapid depolarization due to Na channels opening, then closing)

Front 37

What events occur during phase 1 of a cardiac action potential?

Back 37

Phase 1: initial repolarization, inactivation gates closed on Na channels, outward K current

Front 38

What events occur during phase 2 of a cardiac action potential?

Back 38

Phase 2: 2 plateau, inward Ca current by L-type channels, outward K current

Front 39

What events occur during phase 3 of a cardiac action potential?

Back 39

Phase 3: repolarization, decreased Ca current, initially increased K current then reduced as K approaches equilibrium potential

Front 40

What events occur during phase 4 of a cardiac action potential?

Back 40

Phase 4: resting membrane potential, phase 4 channels reestablish rmp (K channel), different from K channels in phase 3 (K1 channels)

Front 41

resting membrane potential, aka

Back 41

electrical diastole

Front 42

"plateau" of action potential in cardiac muscle, def

Back 42

sustained depolarization due to Ca influx and K efflux

Front 43

List the phases of a cardiac action potential (0-5)

Back 43

0 upstroke (rapid depolarization), 1 initial repolarization, 2 plateau, 3 repolarization, 4 resting membrane potential (aka electric diastole)

Front 44

mechanism of Ca channel blockers; examples (3)

Back 44

inhibit L-type Ca channel in heart during phase 2 (plateau). Ex: nifedipine, diltiazem, verapamil.

Front 45

vagal stimulation increases/decreases heart rate

Back 45

decreases (sympathetic increases)

Front 46

Describe ionic flow during the different phases of cardiac action potential

Back 46

0 fast Na influx, 1 transient K efflux, Na-channel inactivation, 2 Ca and Na influx, K efflux, 3 K efflux > Ca and Na influx, 4 Na-K pump

Front 47

"trigger Ca" is what percent of total Ca in cardiac muscle

Back 47

10%

Front 48

Ca released from sarcolemma by what type of Ca channel?

Back 48

L-type

Front 49

Ca released from SR by what type of Ca channel?

Back 49

Ca-release channel (RyR)

Front 50

What pump is responsible for Ca reuptake into the SR in skeletal and cardiac muscle?

Back 50

SERCA (Sarcoplasmic and Endoplasmic Reticulum Ca-ATPase)

Front 51

What pump extrudes Ca across the sarcolemma in skeletal and cardiac muscle?

Back 51

PMCA (Plasma Membrane Ca-ATPase)

Front 52

What exchanger extrudes Ca across the sarcolemma in skeletal and cardiac muscle?

Back 52

Na-Ca exchanger (NCX)

Front 53

Compare the functions of the SERCA pump, PMCA pump, and Na-Ca exchanger

Back 53

PMCA exchanges 1-to-1 H and Ca, SERCA exchange 2-to-2 H and Ca per ATP hydrolyzed, NCX exchanges 3Na-1Ca and Na is later pumped out by Na-K pump

Front 54

PMCA vs. SERCA

Back 54

plasma membrane calcium ATPase (PMCA) and sarcoplasmic and endoplasmic reticulum calcium ATPase (SERCA)

Front 55

Describe the mechanism of cardiac muscle relaxation

Back 55

1 Ca taken up into SR by SERCA, 2 Ca extruded across sarcolemma by Na-Ca exchanger, then Na extruded by Na-K ATPase, 3 Ca is extruded across sarcolemma by PMCA

Front 56

phospholambin; what is it and what does it do?

Back 56

effect is myocite contraction; regulatory protein that inhibits SR Ca pump, but if it is phosphorylated by PKA it can no longer inhibit

Front 57

Effect of PKA activators on myocytes

Back 57

cause relaxation due to inhibition of phospholamban

Front 58

Why is summation not possible in cardiac muscle?

Back 58

extensive coupling between cardiac myocytes

Front 59

Why does your heart beat harder if you exercise more?

Back 59

Cardiac muscle becomes more responsive to norepinephrine (sympathetic nt)

Front 60

effect of norepinephrine on the heart

Back 60

increases generation of cAMP through β adrenergic receptors > activates PKA > PKA phosphorylates L-type channels > increased influx of Ca > increased contractile force

Front 61

2 ways that cAMP increases strength of cardiac contraction

Back 61

1 activate L-type channels to increase intracellular Ca, 2 increase Ca-sensitivity of contractile apparatus

Front 62

What happens when ACh binds to a muscarinic receptor in the heart?

Back 62

activates K+ channel, increases K+ currents, results in slower, less forceful beats (IMAGE)

Front 63

fxn of cardiac length reserve

Back 63

allows heart to stretch to accommodate overfill of blood; contraction following overfill is more forceful

Front 64

How and why is Ca reserved during heart contraction?

Back 64

diads provide insufficient Ca to fully activate contractiole apparatus; allows 'reserve capacity' for enhanced contraction if necessary

Front 65

location of cardiac diads

Back 65

on the Z line

Front 66

Why does passive tension engage at shorter lengths in cardiac muscle?

Back 66

cardiac muscle is always partially contracted (length reserve)