Lecture 29- EC Coupling/Sliding Filament Theory

Question 1

In the first step of EC Coupling, An _______ _______ propagates along the plasma membrane and travels down the _______ _______.

Answer 1

Action Potential
Transverse Tubules (T-Tubules)

Question 2

In the second step of EC Coupling, ______ is released in the ____ _____.

Answer 2

Calcium
Sarcoplasmic Reticulum (SR)

Question 3

In the third step of EC Coupling, Calcium binds to ______ __ which moves _____, exposing the _____ binding sites.

Answer 3

Typonin C
Tropomyosin
Myosin

Question 4

In the fourth step of EC Coupling, _____ binds to _____ which causes muscle contraction by pulling the ____ filaments towards the ____ filaments.

Answer 4

Myosin
Actin
Thin
Thick

Question 5

In the fifth step of EC Coupling, the cycle resets by _____ being removed from the binding site, allowing _____ to be blocked again by ______.

Answer 5

Calcium
Actin
Tropomyosin

Question 6

What are the three major thin filament cytoskeleton proteins?

Answer 6

1. Actin filament
2. Typonin C
3. Tropomyosin

Question 7

What cytoskeleton protein covers the myosin binding sites on actin filaments?

Answer 7

Tropomyosin

Question 8

What causes tropomyosin to move, exposing the myosin binding sites?

Answer 8

Calcium binding to Troponin C

Question 9

What is Z-line sliding filament theory?

Answer 9

Myosin filaments use energy from ATP to “walk” along the actin filaments with their cross bridges.This pulls the actin filaments closer together. The movement of the actin filaments also pulls the Z lines closer together, thus shortening the sarcomere.

Question 10

In the first step of muscle contraction, ____ on the myosin head is cleaved into ____ and __ which moves the myosin head back, so it’s ready to bind.

Answer 10

ATP
ADP
Pi

Question 11

In the second step of muscle contraction, _____ binds to ____ to form a “cross bridge”.

Answer 11

Myosin
Actin

Question 12

In the third step of muscle contraction, the cleaved ATP ____ and __ leave myosin.

Answer 12

ADP
Pi

Question 13

In the fourth step of muscle contraction, the ____ head moves, causing the phenomena known as a ________.

Answer 13

Myosin
Powerstroke

Question 14

In the fifth step of muscle contraction, a new ____ binds, allowing the detachment of _____ from _____.

Answer 14

ATP
Myosin
Actin

Question 15

In the final step of muscle contraction, _____ depletes and ______ covers the myosin binding site again.

Answer 15

Calcium
Tropomyosin

Question 16

What is the “cross bridge”?

Answer 16

The attachment of myosin with actin within the muscle cell

Question 17

What is a “powerstroke”?

Answer 17

A series of structural changes in the actomyosin cross-bridge driven by hydrolysis of ATP.

Question 18

What is “rigor mortis”?

Answer 18

Myosin heads are locked onto actin because there is no ATP to relax the body (stiffens the body).

Death

Question 19

What is the function of Dihydropyridine (DHP) receptors in T-Tubule?

Answer 19

Functions as voltage sensors which undergo fast transition to control the release of Ca2+ from the SR

Must open first to uncork the ryano receptors to release Ca2+

Question 20

What is the function of Ryanodine Receptors in the SR?

Answer 20

Functions to release Ca2+ from intracellular stores during EC coupling in cardiac/smooth muscle