Spinal Cord and Periphery Flashcards
where motor neuron crosses?
at the medulla
what do all the axons of motor neurons pass through after beginning at the gyrus?
the internal capsule
what part of the internal capsule do motor fibres pass through?
the posterior limb
after passing through the internal capsule what do motor fibres enter?
the midbrain
what is the crus cerebri?
the cerebral peduncle in the anterior part of the midbrain that is the motor fibres bypassing the thalamus from the midbrain.
where do motor fibres sit in the pons?
the front part
describe the course of an upper motor neuron from the gyrus to its synapse in the grey matter of the spinal cord
gyrus > posterior limb of the internal capsule > midbrain > cerebral peduncles to pons > medulla (decussation) > spinal cord grey matter synapse at level it exits
what do ascending spinal tracts carry?
sensory information
how many neurons are in the ascending spinal tracts?
3 (1st, 2nd and 3rd order neuron)
in a sensory spinal tract which neuron will cross the spinal tract?
the 2nd neuron
what sort of information does the dorsal column pathway carry?
> fine touch, tactile localisation, vibration sense and proprioception
where does the 1st sensory neuron synapse in the dorsal column tract?
gracile and cuneate nuclei at the bottom of the medulla
what sensory neuron crosses to the opposite side in the dorsal column tract?
the second sensory neuron
what is the medial lemiscus?
sensory fibres from the posterior spinal cord that have synapsed in the medulla
where does the 2nd order neuron take the sensory information in the dorsal column tract?
to the thalamus
where does the 3rd order neuron take the sensation to and from in the dorsal column tract?
from the thalamus to the post central gyrus
what is the thalamus?
a group of nuclei involved in the processing of sensory information through which all sensory information passes.
sensory relay station.
what groups of nuclei make up the thalamus?
anterior
medial
lateral
what sort of sensation is carried by the lateral spinothalamic tract?
pain and temperature
where does the 1st order neuron synapse in the lateral spinothalamic tract end?
at the level it enters the spinal cord in the grey matter
at what level does the lateral spinal tract cross the spinal cord?
at the level it enters
if the lesion is above the level of the crossing is the deficit on the opposite or the same side?
the opposite
if the lesion is below the level of crossing is the deficit on the same side or the opposite side?
the same side as the lesion
someone has a paralysis of their right side with touch deficit but pain sensation is lost on their left. why?
this is because the lateral spinal tract crosses as it enters the spinal cord at a different level so the lesion is above the level of crossing but below the level of crossing for the dorsal spinal tract carrying touch sensation
what is a reflex?
an involuntary stereotyped pattern of response brought about by a sensory stimulus.
is the stretch reflex mono or polysynaptic?
monosynaptic to the muscle that is contracted but polysynaptic to an inhibitory neuron to the antagonist muscle causing it to flex (peciprocal innervation)
how that the stretch reflex be affected if the upper motor neuron was damaged?
it would be present and exaggerated
what would the affect of an upper motor neuron lesion be on the muscle?
spastic paralysis with hyperreflexia
what would be effect be of a lesion of the upper motor neuron above the decussation?
contralateral spastic paralysis and hyperreflexia
what would the effect be of a lesion of the upper motor neuron below the decussation?
ipsilateral spastic paralysis and hypereflexia
what is the effect of a lower motor neuron lesion?
ipsilateral flaccid paralysis and areeflexia
