Motor control 2 Flashcards
What does the alpha motor neurone do?
Innervate extrafusal muscle fibres of the skeletal muscles
Activation causes muscle contraction
What does a motor neurone pool contain?
all alpha motor neurons innervating a single muscle.
What does stimulation of one motor unit cause?
Contraction of all muscle fibres in that unit
What are the 3 (slow ,fast ,fatiguable) motor unit types classified by?
Amount of tension generated
Speed of contraction
Fatiguability
How does the brain regulate the force a single muscle can produce?
Recruitment
Rate coding
What is recruitment?
Governed by size principle:
smaller units used first, as more force needed more units added
Allows fine control e.g. writing
What is rate coding?
as firing rate increases the force of production by small unit increases
Summation occurs when units fire at frequency too fast to allow muscle to relax between APs
What are neurotrophic factors?
Growth factor preventing neuronal death and promoting growth of neurones after injurty
What are the characteristics of motor unit fibres depended on?
The nerve innervating
Can fibre types change?
Can change properties
Type IIB to IIA most common following training
Type I to II in case of severe decontioning or spinal cord injury
Age associtated loss of Type I + II (more II is lost) leaving a larger proportion of type I hence the slower contraction time
What is a reflex?
An automatic response to a stimulus that involves a nerve impulse passing inward from a receptor to a nerve centre and then outward to an effector (as a muscle or gland) without reaching the level of consciousness.
What is the monosynaptic reflex?
Patella at knee
What is the Jendrassik manoeuvre?
clenching the teeth, making a fist, or pulling against locked fingers when having patellar tendon tapped. The reflex becomes larger
How do supraspinal centres affect reflexes?
CNS inhibitory and exciatory regulation on reflex
Inhibitory control dominates when normal physiology
Decerebration reveals the excitatory control from supraspinal areas
Rigidity and spasticity can result from brain damage giving over-active or tonic stretch reflex.
How does the CNS activate afferent fibres (5)
Activating alpha motor neurons
Activating inhibitory interneurons
Activating propriospinal neurons
Activating gamma motor neurons
Activating terminals of afferent fibres
