Wk 2 - LE 3: neuromuscular (motor unit) Flashcards
What is the equation for force?
f = mxa
Concentric muscle action is…
shortening of the muscle (real contraction)
Eccentric muscle action is…
lengthening of the muscle
Isometric muscle action is…
No length change in muscle
Is the number of myocytes within a muscle proportional the the muscle size?
Yes
The diameter of myocytes varies in in different muscle sizes (T/F)?
False
What type of neuron is responsible for initiating and controlling muscle action?
alpha-motor neuron
What is a motor unit?
A single alpha neuron AND the muscle fibres it innervates
The number of motor units within a muscle ranges from…
100-1000 MUs proportional to muscle size
The number of myocites within a muscle ranges from…
1-1,000000 (million)
What is force DEVELOPED by in the muscle?
The myocytes (not neuron!)
what is force CONTROLLED by in muscle (firing, impulses)?
The alpha- motorneuron
What are the 2 ways to vary the force output of a muscle?
1) by varying the number of motor units recruited
2) varying the firing rate of a-motorneurons
‘Firing’ refers to _____ of the neuron
Depolarisation
Firing at a low rate (1-2 Hz) leads to a muscle _____
Twitch
What is a complete tetanus?
when firing rate is so frequent, twitches become a line instead of fluctuating
What is an incomplete tetanus?
Twitching rates too frequent to fall back to zero so gradually increases until at complete tetanus
What is Hennemans size principle?
That MU are generally recruited from smallest to largest as the force is increased
Movement velocities are influenced by what 3 factors?
1) instrinsic shortening velocity of myocytes
2) MU recruitment speed
3) MU firing rate
Maximum force is produced by recruiting ___% of the MU pool
100% (extremely difficult to do)
The type of MUs and myocytes involved in movement depends on the ____ and/or ____ of the task
Force and/or speed
An alpha motorneuron innervates what type of myocyte?
slow to slow, fast to fast
