2.6 Motor Control Flashcards
What are lower motor neurones of the brainstem and spinal cord?
alpha motor neurone
What do alpha motor neurones innervate?
extrafusal muscle fibres of the skeletal muscles
What does alpha motor neurone activation cause?
muscle contraction
What is a motor neurone pool?
contains all alpha motor neurones innervating a single muscle
What is a motor unit?
a single motor neurone and all of the muscle fibres it innervates.
smallest functional unit with which to produce force
What does stimulation of one motor unit cause?
contraction of all muscle fibres in the unit
How many muscle fibres does a motor neurone supply
more than 1!
about 600
What are the 3 types of motor unit?
slow (type 1 ) fast fatigue resistant (type 2A) fast fatigable (type 2B)
What is the difference between slow and fast motor units?
slow
- smallest diameter cell bodies
- smallest dendritic trees
- thinnest axons
- slowest conduction velocity
What is the relation between axon diameter and conduction velocity?
the larger the diameter the faster the conduction speed
How are the 3 types of motor neurones distributed in the muscle?
randomly
On a graph showing response to single motor neurone action potential, what will we see for each motor unit type?
Type 1 (slow) - smallest more shallow bump Type 2A (fatigue resistant) - medium bump, quickly up slowly down Type 2B (fast fatigable) - quickly up, highest bump, longest lasting
How long does the response of each motor neurone type last as a % of its maximum (noting that the maximums different, power produced by FF much greater)
FF - 2 mins
FR - 10s of minutes
S - more than 60
What are the two mechanism by which the CNS can regulate muscle force?
number of neurones (recruitment) - how many are required, more neurones = more muscle fibres
