Motor Control #1 Flashcards
Movement disorders are commonly caused by? And what are some examples of this?
Neurological disorders eg) myasthenia gravis, epilepsy, parkinsons
What are the three types of movement?
1) Voluntary
2) Reflexes (somatic)
3) Rhythmic motor patterns
What controls voluntary movement?
The forebrain, the cerebellum, thalamus, basal ganglia
What controls Reflexes and rhythmic motor patterns
The spinal cord and brainstem
What are rhythmic motor patterns?
breathing, locomotion, chewing. Semiautomatic movements that are inbetween reflex and will. We can control to a point.
What are the two subcortical loops that impact our decision making?
CC > Basal ganglia > thalamus
CC > Brain stem > cerebellum > thalamus
Where are the two places you’ll find motoneurons
Motor nuclei in the ventral horns of spinal cord
Motor nuclei in the brain stem (midbrain pons and medulla oblongata) this is done through cranial nerves sending axons to muscles
how many cranial nerves actually send axons
9/12
Two types of motoneurons, and what do they innervate?
alpha motoneurons, innervate extrafusal fibres (the most common muscle fibres)
Gamma motoneurons, innervate intrafusal muscle fibres. this controls the excitability of stretch receptors muscle spindle fibres
Are Alpha and gamma motoneurons independent?
No, a and g motoneurons often have co-activation
Sir John Eccles
studied and characterised motoneurons, lectured in otago, the 1st to measure RMP, AP, synaptic potential.
What was sir John Eccles technique?
Used a glass microelectrode. If you add dye you can see the morphology of nerve cells.
What are the components of motor units
a) Cell body of an a-MN
b) axon
c) all neuromuscular junctions (synapses) formed by a single motoneuron
d) all muscle fibres (extrafusal muscle fibres) innervated by a single motoneuron
what is the innervation ratio?
the amount of muscle fibres a MN can innervate (between 5 to 20,000).
Motor unit types
FF type 11B - fast fatigable S type (type 1) - slow twitch
FF type 11B
Glycolytic, short twitch time (20ms), large, powerful, a few, rapidly fatigue
S type (type 1)
oxidative, slow (50ms+), small, weak, there are many and they are slow to fatigue
What makes S-type a good choice over FF type
There are many, and they are slow to fatigue, unlike FF type
What are S type and FF type useful for?
S type- continuous, weak contractions
FF type - brief, strong contractions
What is the size principle of motor units?
S type recruited first, FF type are recruited only at highlevels of muscle force
What are the physiological consequences of the size principle?
S type MU fire almost always
S type are for sustained, small loads
Weak contractions are graded better then strong
Atrophy of FF will occur without excercise
What motor neurons are activated during REM sleep?
eyes, respiratory, sphinters
How are muscles ‘slaves’ to nerves?
The properties, types of contractions are changed with cross innervation! This is done with experiment between soleus and gastrocnemius
What do gamma MN innervate and what does this do?
They innervate the periphery of intrafusal fibres (muscle spindles) where there are contractile elements. This enhances the ability of the spindle to stretch
What do gamma MN sense?
the changes in muscle length
Whats the difference between somatic and autonomic neurons
Somatic go directly to muscles, whereas autonomic use parasympathetic/sympathetic ganglia as ‘switches’
