Excitatory Contractile Coupling

Question 1

What is excitation contraction coupling?

Answer 1

The process by which an electrical stimulus triggers the release of calcium by the sarcoplasmic reticulum, initiating the mechanism of muscle contraction by sarcomere shortening

Question 2

What is anterograde transport?

Answer 2

Towards the axon terminal

Question 3

What is retrograde transport?

Answer 3

Towards the cell body

Question 4

How many vesicles per release of AP?

Answer 4

125 vesicles

Question 5

What is the purpose of the subneural clefts?

Answer 5

Increase the surface area at the synaptic cleft in order to receive more signals from the axon terminus

Question 6

What happens once acetylecholine binds to ligand gated sodium channels?

Answer 6

Sodium rushes in and creates a potential difference, which will open voltage gated sodium channels, allowing more sodium to enter and create an action potential down sarcolemma

Question 7

How does the DHP receptor get triggered? What does the DHP receptor do?

Answer 7

An action potential goes down the t-tubule and causes a conformational change in the DHP receptor

It then causes change in ryanidine receptor and opens sacroplasmic reticulum; all calcium rushes out into sarcoplasm

Question 8

What does calcium ATPase do?

Answer 8

Pumps calcium back into the SR

Question 9

What does calsequestrin do?

Answer 9

Binds calcium to hold more of it in the SR

Question 10

What does troponin T do?

Answer 10

Binds tropomyosin; part of the troponin complex

Question 11

What does troponin I do?

Answer 11

Binds actin; a part of the troponin complex

Question 12

What does troponin C do?

Answer 12

Binds calcium; part of the troponin complex

Question 13

Steps of ratchet theory

Answer 13

ATP binds myosin head

ATP dissociates to ADP and Pi

That potential energy creates cocking mechanism on myosin head

Myosin binds to the active site because its near and has a high affinity for it to bind

Inorganic phosphate will leave and that energy is used to create the powerstroke

The powerstroke is the pulling of actin towards the M line

To release, an ATP will come in and exchange for ADP. Releases actin to get it back into its resting position

Question 14

What does length tension curve show?

Answer 14

The relationship between sarcomere length and relative tension

Question 15

When is relative tension the highest?

Answer 15

When sarcomere length is between 2 and 2.5 micrometers

This is the perfect tension; all of the myosin heads are attached to actin and there is the right amount of overlap

Question 16

What is a motor unit?

Answer 16

All the muscles innervated by a single nerve fiber

Question 17

How do small muscles compare to larger muscles?

Answer 17

Small muscles have more nerve fibers for more precise movements

Question 18

What is summation and what does it lead to?

Answer 18

Adding together all individual twitch contractions to increase intensity of overall muscles contraction; increase number of motor units contracting simultaneously; increases the frequency of contraction

It leads to tetanization (can’t recover from contraction and so they stay contracted)

Question 19

What is rigor mortis?

Answer 19

A state of contracture; lasts 15-25 hours

Because the myosin heads stay in a cocked state because there is no new ATP to displace the ADP

Question 20

What is phosphocreatine?

Answer 20

A molecule that is abundant in the muscles which gives a phosphate to ADP to make ATP. Creation of ATP will allow for muscle contraction

It only lasts for about 8-10 more seconds

Question 21

When does glycolysis begin for muscle contraction?

Answer 21

After the phosphocreatine reserves are depleted

It will add another 1.3 -1.6 minutes

Question 22

What does strength training increase?

Answer 22

Increases myofibrils; the diameter of muscles, not the number of fibers.

More sarcomeres per muscle fiber.