Module 4: Lecture 4

Question 1

True or False
Every time the cross-bridge cycles occur it utilizes ATP.

Answer 1

True

Question 2

Where does ATP bind for the successful power stoke to occur?

Answer 2

myosin head

Question 3

If we have M-ADP-P, with tropomyosin removed and the presences of calcium will cross bridges form?

Answer 3

yessir

Question 3

What does the Myosin ATPase site do?

Answer 3

when ATP binds the site it hydrolyzes ATP making ADP and Pi (organic phosphate molecule)

Question 4

What are the names of the 4 steps using ATP for cross-bridges?

Answer 4

1. Energized
2. Binding
3. Bending
4. Detachment

Question 5

what is the controllable portion of your nervous system? (voluntary activating muscles)

Answer 5

motor unit

Question 6

How long does a single action potential last?

Answer 6

1-2 milliseconds

Question 7

What is the latent period?

Answer 7

the time frame from when the action potentials first initiated in the muscle fibre to the onset of mechanical tension

• time from action potential to the calcium releasing and cross bridges forming

Question 8

How long is the mechanical activity?

Answer 8

about 100 milliseconds

Question 9

What is the peak tension?

Answer 9

when calcium is pumped back into the SR allowing tropomyosin to recover the myosin active sites and the myosin heads can enter the relaxed state

Question 10

The whole process of going from contraction to relaxation is called what?

Answer 10

muscle twitch

Question 11

what is the smallest amount of force that a muscle fibre can produce?

Answer 11

muscle twitch

Question 12

What is the name of the phases where calcium is being release

Answer 12

contraction phase/time

Question 13

True or False
The contraction time and relaxation time are roughly equal in length?

Answer 13

true

Question 14

True or False
A single action potential in a muscle fibre causes a twitch which is a very brief and weak contraction

Answer 14

True

Question 15

How does our muscle control how many muscle fibres e need in order to generate a given force?

• how do we control our voluntary force output?
  2 Ways!

Answer 15

1. By changing the number of fibres contracting

ie. increasing the number of fibres for greater force

2. Changing the amount of tension each fibre develops

ie. increasing the amount of calcium!! How?? Increasing the activation rate of our motor neurons (increasing the frequency of the number of action potential)

Question 16

What is the motor unit made of?

Answer 16

ONE motorneuron (somatic system) + ALL the myofibres it connects with

Question 17

True or False
The motor unit will always send action potentials

Answer 17

True

Question 18

What is motor unit recruitment?

Answer 18

all muscle fibres within a motor unit are activated when a motor unit is recruited

Question 19

What is involved in the Energized state?

Answer 19

• ATP is bound to the myosin heads and is split into ADP and an organic phosphate molecule

Question 20

What is involved in the Binding state?

Answer 20

• when the Ca+2 is released and removed inhibitory proteins
• allows myosin head to bind to actin active site on think filament

A-M.ADP.Pi

Question 21

What is involved in the Bending state?

Answer 21

• POWER STROKE
• where cross bridge is triggered on contact between myosin and actin
• Organic phosphate is released DURING power stroke
• ADP is released after a power stroke

Question 22

What is involved in the Detachment state?

Answer 22

• The linkage between the myosin head and actin molecule is broken
• A fresh ATP binds to the myosin head
• ATP will hydrolyze and go back to an energized state

Question 23

What is Rigor Complex?

Answer 23

• This is when there is no more FRESH ATP available (ie. after death), where actin and myosin remain bound and muscles become rigor

Question 24

What is the resting phase? (not part of a continuous cycle)

Answer 24

• ADP and organic phosphate are bonded to the myosin head
• there is NO calcium available, no cross-bridge cycle aka muscle fibre remains relaxed!!1