Module 4: Lecture 4 Flashcards
what is used to power the cross bridge cycle?
the free energy that is released from splitting ATP
how does cross-bridge cycling initiate?
all comes down to the calcium signal from the action potential
what splits the ATP for cross-bridge cycling?
myosin ATPase head
- which then they energize after the split in order to form cross-bridges
when ATP is split on the myosin head, what happens to its products immediately?
nothing, they remain attached to the myosin
when is the inorganic phosphate going to be released from the myosin ATPase head?
during the power stroke
when is the ADP going to be released from the myosin ATPase head?
after the power stroke
when does the myosin head detach from the actin?
when a new/fresh ATP molecule binds to the myosin head/ATPase active sites
why after someone passes, they get a very stiffening of all their skeletal muscles?
no more ATP production to detach the myosin head from actin
- CALLED RIGOR MORTIS/COMPLEX
- cross-bridge has formed and its undergone a power stroke
- ADP and Pi have left and it will remain in this state
what is responsible for ensuring the cyclical cross bridge process?
the hydrolysis of ATP
what is the end goal of an action potential?
to get calcium in the cytosol to increase
what is the latent period?
the time it takes for an action potential to travel along the muscle fiber, enter the t-tubule, causes the release of calcium
- all of those processes
- the time from when the action potential is first initiated in the muscle fiber to the onset of actual mechanical tension
about how long is mechanical activity?
about 100ms (varies widely)
- much longer than an action potential which lasts 1-2 msec
what is a muscle twitch?
the whole process of contraction as well as the relaxation
what is the smallest activation signal an individual fiber can receive?
the action potential
what is a single action potential in a single muscle fibre?
very brief and weak contraction
- it is a muscle twitch
can a twitch have a real effect at the level of the entire muscle and the body?
a twitch is too weak and too short to have a real effect at the level of the entire muscle and the body
why can we vary the force developed by our muscles?
because muscle fibres cooperate to produce muscle contractions for variable strength
what are the two mechanisms of how our central nervous system controls how much force our skeletal muscles use?
- by changing the number of fibres contracting (recruited) within the muscle
- by affecting the tension developed by each contracting fibre (ie. activation rate)
do we control our individual muscle fibres?
no. we control out motor units
what is a motor unit?
one motor neuron + all the myofibres it innervates (different size depending on muscle types)
what is motor unit recruitment?
all muscle fibres within a motor unit are activated when a motor unit is recruited
what is the neuromuscular junction?
upon reaching a muscle, the axon makes several divisions/branches, and each branch will form one connection with one fibre
what happens anytime you activate your motor unit (motor neurons fires an action potential)?
every single one of the fibres that the motor unit innervates, will generate an action potential and they will generate force
when are the number of fibres contracting changed?
whenever a motor unit is recruited
