Control of Movement Flashcards
Without the cerebellum, movements would be…?
ataxic.
Motor neurons are mainly located where?
In the anterior horn of spinal cord.
How many cranial nerves are engaged in motor functions?
9/12 (not 1, 2 and 8)
Where are alpha MN’s? What do they do?
ventral (anterior) horn. They innervate extrafusal muscles.
Where are gamma MN’S? What do they do?
In ventral horn. Innervate intrafusal muscle fibers.
Contractile elements of spindles are innervated by gamma MN’s in which part?
Distal part.
What is a motor unit?
anatomical and functional unit of motor system.
consists of muscle fibers and alpha MN’s.
Which neuron type is recruited first?
S type (slow twitch) - Type I. They are active in weak contractions. S type do NOT fire in REM. Required to prevent atrophy of FF units (Type IIB) in exercise.
Type Ia fibers release what neurotransmitter?
Glutamate (then alpha MN efferent stimulated)
What are interneurons?
Inhibitory neurons that act upon the antagonist muscle.
Golgi Tendon Organs have what afferent fiber?
Ib (slower than Ia). The inhibitory neuron releases glycine as the neurotransmitter which inhibits the alpha MN acting on muscle. The effector is the SAME muscle. Maintains tension in the optimal range.
In the pain reflex, what interneurons are activated?
Excitatory interneurons. Alpha MN’s to flexor muscles are stimulated.
Which neuron type is best for sustained but small loads?
Type I or S type.
Alpha motor neurons have inputs from what 3 paths?
- descending tracts (cortico-spinal, vestibulao-spinal…)
- Spinal interneurons (inhibitory/excitatory)
- Afferent fibres (Ia) - muslce spindles.
What are the 3 main reflexes?
Stretch, golgi-tendon and the flexion (or pain) reflex.
In the stretch reflex, what neurotransmitter is released from the sensory fibres?
Glutamate
What does ‘reciprocal inhibition’ mean?
The Ia afferent also excites an interneuron which inhibits the alpha-MN that innervates the anatgonist to the muscle targeted.
In the stretch reflex, what neurotransmitter is released from the interneuron?
Glycine.
What type of sensory neuron is in the golgi-tendon relfex?
Ib afferent neurons (slower than Ia).
In the golgi-tendon organ reflex, what is the inhibitory neuron and what neurotransmitter does it release?
Ib inhibitory neuron
Glycine
Is the golgi-tendon organ parallel with the muscle?
No, it’s in series.
What is the effector in the golgi-tendon organ reflex?
The SAME muscle.
What is the purpose of the golgi-tendon organ reflex?
It protects the muscle from extreme overload. It maintains tension in the optimal range.
