Motor Control Flashcards
what type of motor neurons have direct control of muscles in the spinal cord ?
alpha motoneurones
what are the four systems which provide information for movement?
basal ganglia
cerebellum
local spinal cord
brain stem circuits
what would be the result of a lower motor neuron lesion?
flaccid paralysis and muscle atrophy
what would be the result of a upper motor neuron lesion?
spasticity
rigidity
- as the reflex arcs aren’t affected so the involuntary reflexes would still occur
- there are many synapses, including inhibitory synapses so rigidity is possible
what does corticospinal lesions result in?
weakness
- rather than paralysis
what muscles correlate with the medial motor neurons ?
shoulder muscles
what muscles correlate with the lateral motor neurons ?
finger muscles
is sensory input required for motor neurons to function properly?
yes
what is another name for the corticospinal tract?
pyramidal tract
what sensory information does the brain stem receive?
information about balance form the vestibular system
what sensory information does the cortex receive ?
visual auditory emotional smell intellectual cues
what sensory information does the spinal cord receive ?
touch
pain
proprioceptors
what are the three levels of hierarchy for motor control?
cortex
brain stem
spinal cord
how does the spinal cord receive information from descending tracts?
from direct cortical input via the brain stem where tracts travel through the pyramidal tract
what does DRG stand for?
dorsal root ganglia
what would be the result if a patient lost all their proprioception?
loose the sense of where your body was in space and motor control
what would cause a patient to loss their proprioception?
lose of sensory neurons in the dorsal root ganglia
how do reflexes help to determine where the problem/damage is?
reflexes are related to certain cord segments so-
if one reflex is present but another one is absent then you can determine what level the problem is present at
what are nociceptors ?
pain receptors
what is the pain reflex called?
flexor reflex
are nociceptive fibres confined to a single spinal level?
no
which neurons do nociceptive fibres activate?
alpha motor neurons
flexor reflex
- as well as contracted and relaxing ipsilateral muscles, what other mechanisms are done?
excitatory interneurones cross the spinal cord and excite the contralateral extensors
inhibitory interneurones also cross over and there is inhibition of the contralateral flexors
flexor reflex
- as well as changing the muscles on the ipsilateral side, why are the muscles affected on the contralateral side ?
to maintain balance and posture
where does sensory information ascend to from the spinal cord?
contralateral spinothalamic tract to the thalamus
what is the flexor reflex called when the contralateral side is also involved ?
flexor-crossed extensor reflex
which reflex is faster ?
- stretch reflex
- flexor crossed extensor reflex
stretch reflex
- less synapses
- muscle spindles have thicker diameter than nociceptors
what is the golgi body reflex?
when there is a stretch on the muscle, the golgi tend bodies are stretched and cause the motor neurons to relax and the muscle relaxes
- this prevents the muscle from ripping
can reflexes be over ridden ? (such as golgi tendon reflex of relaxing your arm)
yes
descending voluntary excitation of motoneurones can override the inhibition from the GTOs and maintain contraction.
what reflex is occurring when holding something heavy in your hands with your elbow at 90 degrees?
stretch reflex
does one alpha motor neuron synapse with one other neuron ?
no
- more than 10,000 synapses mostly from cortical excitatory or inhibitory inputs (sensory inputs)
what pathways do gamma motor neurons depend on?
activity of gamma-motoneurones depends entirely on descending pathways
what is the difference between the alpha and gamma motor neurons ?
alpha motor neurons = innervate extrafusal muscle fibres
gamma motor neurons = innervate intrafusal muscle fibres
if the pain area is large enough can the pain fibres spread through several spinal levels?
yes
what is facilitation of sensory input?
the enhancement of the response of a neuron to a stimulus following prior stimulation
- for example, finger on hot plate will result in hand being pulled away but may also cause the contralateral arm to extend as well
what is the sign when their is plantar extension instead of flexion?
babinski sign
what is spinal shock?
combination of hyporeflexia (lose of reflexes) and autonomic dysfunction that accompanies spinal cord injury.
- the reflexes gradually start to come back as other pathways are formed
what is clonus ?
stretch causes oscillatory muscle contraction/relaxation
