Lecture 4: Excitation Contraction Coupling

Question 1

motorneuron axon depolarization leads to ….

Answer 1

the opening of Ca++ channels

• dissolves actin tethering ACH vesicles
• vesicles migrate to axolemma
• ach released into synaptic cleft

Question 2

what is the primary difference in the transverse tubule system??

Answer 2

mammalian t-tubules system is more efficient deliver of calcium when the z disk is alighted over the myosin itself

Question 3

in the ringer experiment in 1883 an isolated frog heart stops beating without ____ in the bathing medium

Answer 3

Ca++

Question 4

Ashley and rdgeway 1968-70

Answer 4

barnacle muscle fiber experiment

Question 5

aqueroin

Answer 5

protein which luminesces in presence of Ca++

Question 6

Triad

Answer 6

t-tubule + 2 SR on either side

-feet

Question 7

feet

Answer 7

connection between t-tubule and SR

Question 8

dihydropyridine

Answer 8

DHP receptor (embedded in the t-tubule)

• 50-100x more concentrated in the t-tubule membrane than any other tissue
• acts as a voltage sensor

Question 9

DHP receptors are opened by

Answer 9

plasmalemma depolarization

-come in groups of 4 near every other RYR receptor

Question 10

DHP receptors at blocked by

Answer 10

DiHydroPyridine (anti-arrhythmic drugs)

Question 11

RYR Ca++ channels

Answer 11

4 subunit protein embedded in the SR

Question 12

RYR channels are opened by

Answer 12

the interaction with DHP channel (locked open by ryanodine)

Question 13

potential mechanisms for the Ca++ rise with action potentical

Answer 13

chemical

• inositol Triphosphate IP3
• Ca++ from intracellular side of TT

Question 14

How does intracellular Ca++ rise with action potential in the heart

Answer 14

Ca++ induced Ca++ release

• extracellular Ca++ enters cell through DHP receptor
• rising but low Ca++ causes Ca++ release through RYR
• every other RYR receptor, the ones without DHP

Question 15

DHP receptors in the heart require _____ but DHP receptors in the muscles only need ______.

Answer 15

DHP receptors in the heart required CA++ but DHP receptors in the muscles only need DEPOLARIZATION