Module 4: Lecture 4 Flashcards
True or False
Every time the cross-bridge cycles occur it utilizes ATP.
True
Where does ATP bind for the successful power stoke to occur?
myosin head
If we have M-ADP-P, with tropomyosin removed and the presences of calcium will cross bridges form?
yessir
What does the Myosin ATPase site do?
when ATP binds the site it hydrolyzes ATP making ADP and Pi (organic phosphate molecule)
What are the names of the 4 steps using ATP for cross-bridges?
- Energized
- Binding
- Bending
- Detachment
what is the controllable portion of your nervous system? (voluntary activating muscles)
motor unit
How long does a single action potential last?
1-2 milliseconds
What is the latent period?
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
How long is the mechanical activity?
about 100 milliseconds
What is the peak tension?
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
The whole process of going from contraction to relaxation is called what?
muscle twitch
what is the smallest amount of force that a muscle fibre can produce?
muscle twitch
What is the name of the phases where calcium is being release
contraction phase/time
True or False
The contraction time and relaxation time are roughly equal in length?
true
True or False
A single action potential in a muscle fibre causes a twitch which is a very brief and weak contraction
True
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!
- By changing the number of fibres contracting
ie. increasing the number of fibres for greater force
- 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)
What is the motor unit made of?
ONE motorneuron (somatic system) + ALL the myofibres it connects with
True or False
The motor unit will always send action potentials
True
What is motor unit recruitment?
all muscle fibres within a motor unit are activated when a motor unit is recruited
What is involved in the Energized state?
- ATP is bound to the myosin heads and is split into ADP and an organic phosphate molecule
What is involved in the Binding state?
- 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
What is involved in the Bending state?
- 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
What is involved in the Detachment state?
- 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
What is Rigor Complex?
- This is when there is no more FRESH ATP available (ie. after death), where actin and myosin remain bound and muscles become rigor
What is the resting phase? (not part of a continuous cycle)
- 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
