Motor Units, Muscle Spindles and Golgi Tendon Organs Flashcards
What does the neural element of the motor system comprise?
Upper motor neurones and lower motor neurones
The majority of LMNs are what type of neurone?
Alpha motor neurones
What innervates a muscle spindle?
Gamma motor neurones
Axons of LMNs exit the spinal cord via ventral/dorsal roots
Ventral
In what region of the spinal cord are there a greater number of motor neurones?
Cervical enlargement (C3-T1) Lumbar enlargement (L1-S3)
What is a motor unit?
An alpha motor neurone and all the skeletal muscle fibres it innervates
What is a motor neurone pool?
The collection of alpha motor neurones that innervate a single muscle
What can regulate an alpha motor neurone?
Dorsal root ganglion cells
Upper motor neurones
Spinal interneurones
An increased rate of alpha motor neurone firing causes an increase/decrease in muscle force
Increase
Why are smaller motor units recruited more quickly?
As they have smaller cell bodies and are easier to excite
Type I muscle fibres are fast and type II are slow contracting. True/false?
False - type I is slow while type II is fast
What is the Henneman size principle?
That slower motor units are more easily activated by training that activates the muscle
What is the myotatic reflex?
When a skeletal muscle is pulled it pulls back (wouldn’t want to meet it on a night out then lol)
The change in length of a muscle is measured by what?
Muscle spindle
What does a muscle spindle consist of?
Intrafusal muscle fibres
Sensory afferents
Gamma motor neurone efferents
The myotatic reflex can be tested clinically. How?
Striking patellar tendon with a hammer to cause a knee jerk
Outline the myotatic reflex
Muscle spindle stretches Ia afferent activated Synaptic transmission in spinal cord Alpha motor neuone activated Homonymous muscle contracts
What innervates the intrafusal fibres of muscle spindles?
Gamma motor neurones
What are the two types of intrafusal fibres?
Nuclear bag fibres
Chain fibres
Where are golgi tendon organs found?
Junction of muscle and tendon
Group Ib afferents enter the spinal cord and synapse onto what?
Inhibitory interneurones
What do golgi tendon organs measure?
Force generated in a muscle (via tension in tendon)
