Motor control Flashcards
(21 cards)
What are Alpha motor neurons
The lower motor neurons of the brainstem and the spinal cord
What type of muscles are innervated by Alpha motor neurons
Extrafusal muscle
What does a motor neuron pool contain
All alpha motor neurons innervating a single muscle
What is a motor unit
A single motor neuron together with all the msucle fibers it innervates
What is a motor unit
A single motor neuron together with all the msucle fibers it innervates
What is the smallest functional unit to produce force
A motor unit
How many muscle fibers does each motor unit innervate
600
What are the three types of motor units,
How are they distributed
Slow (S, Type 1)
Fast, fatigue-resistant (FR, Type IIA)
Fast fatigueable (FF, Type IIB)
Distributed throughout the muscle
describe Slow (S, Type I ) motor units
Smallest in diameter
Small dendritic trees
Thinnest Axons
slowest conduction velocity
Describe Fast muscle fibers (both FR Type IIA, FF Type IIB)
Larger diameter cell bodies
Larger dendritic trees
Thicker axons
Faster conduction velocity
How are motor units classified
Amount of tension generated
Speed of contraction
Fatiguablity
(look at graph when revising)
what are the two mechanisms which are used to regulate the force produced by a muscle
Recruitment and Rate coding
Describe how motor units are recruited
They are not recruited randomly, there is an order
Smaller muscles are recruited first by the “size principle”
This allows fine control
describe how rate coding controls muscle force
Motor units can fire at a range of frequencies
e.g: slow units fire at lower frequencies
frequency increases = force increases
summation is when the frequency is so fast it doesnt allow the muscle to relax between AP
What are neurotrophic factors
A type of growth factor that prevents neuronal death, promotes growth of neurons after injury
When is it common for type IIB to Switch to IIA
After training
When is it possible for type I to change to type II
Following severe deconditioning or spinal cord injury
Also can be caused by microgravity during space flights
What type of muscle fiber loss is associated with aging
A loss of both type I and II, with a preferential loss of type II
this leads to a greater proportion of type I muscles, evident from slower contraction times
what is a reflex
An automatic response to a stimulus that involves a nerve impulse passing inward from a nerve > nerve center > an effector, without reaching consciousness
How are the magnitude and timing of a reflex determined
Intensity and onset of peripheral stimulus
how do reflexes differ from voluntary movements
Once a reflex is released, it can’t be stopped
