Excitation Contraction Coupling

Question 1

Which parts of the sarcomere will move?

Answer 1

H and I band move

Question 2

What are the proteins of the thin filaments of the muscle?

Answer 2

actin

tropomyosin

Tropinin (Troponin T, I, and C

Question 3

Troponin T?

Answer 3

binds to tropomysin

Question 4

Troponin I?

Answer 4

binds to actin and inhibits contraction

Question 5

Troponin C

Answer 5

binds to Ca2+

Question 6

What action puts myosin in “high energy” state?

Answer 6

splitting of ATP

Question 7

Is DHP a Ca2+ channel?

Answer 7

no it is more of a voltage sensor

Question 8

RyR?

Answer 8

a calcium channel on SR membrane. When muscle is in resting state RyR is blocked by DHP

Question 9

How is Ca2+ pumped back into SR in sk. muscle?

Answer 9

Ca2+ is pumped back into SR by a calcium ATPase on the SR membrane called Sarcoplasmic endoplasmic reticulum calcium ATPase (SERCA)

Question 10

What is summation?

Answer 10

the principal that because membrane has depolarized well before force development, multiple actin potentials can be generated prior to force development

each pulse of Ca2+ initiates cross-bridge cycling, and because each muscle has not relaxed the mechanical force adds onto (summates) the force from the previous AP

Question 11

What are 2 ways cardiac myocytes remove cytosolic Ca2+?

Answer 11

By 2 mechanisms: SERCA and Na+ ca2+ exchanger

(3Na+ in, 1 Ca2+ out)

Question 12

What are 2 ways smooth muscle produces increase in intracellular Ca2+ levels?

Answer 12

voltage-gated calcium channels reside in sarcolemma of smooth muscle

Increasing IP3 also evokes Ca2+ by binding of agonist to Gq coupled receptor.

Question 13

When cytosolic calcium is high in smooth muscle (MLCK or MLC phosphatase) dominates?

Answer 13

MLCK