motor pathways W3 Flashcards
what structures does the motor system incorporate
cerebral hemispheres
basal ganglia
cerebellum
thalamus
brain stem
spinal cord
peripheral nerve
NMJ/skeletal muscle
where are cell bodies of lower motor neurons located
lamina 9 of Rexeds laminae in the ventral horn of spinal cord
A-alpha fibre function
motor to skeletal muscle
A-beta fibre function
sensory - touch, pressure, vibration
A-gamma fibre function
muscle spindles (stetch detection)
A-delta fibres function
sensory - pain (localised), temperature, touch
B fibres function?
pre-ganglionic autonomic
C fibres function
sensory - pain (diffuse), temperature, post-ganglionic autonomic
neuromuscular junctions size number and variation
size - 50um across
number - one per muscle fibre
variation - all cholinergic (acetylcholine, excitatory)
what can regulate the firing pattern of lower motor neurons?
upper motor neurons
are upper motor neurons always excitatory?
no!!!!!!
structures upper motor neurons are influenced by or reside in?
cerebral cortex (motor and sensory)
basal ganglia
thalamus
red nucleus
reticular formation
vestibular system
visual system
cerebellum
inferior olivary complex
what motor function is the corticospinal pathway
control of voluntary and precise movement
where are upper motor neuron cell bodies found
primary motor cortex
pre-motor cortex
supplementary motor cortex
cingulate motor cortex
somatic sensory cortex
what is the corticospinal pathway from the cortex to brainstem?
cortical grey matter
corona radiata (axons)
internal capsule (axons)
parts of internal capsule and function?
anterior limb = ascending
genu
posterior limb = descending
external features of brain stem - anterior view - midbrain?
mammillary body
crus cerebri
external features of brain stem - anterior view - pons?
middle cerebellar peduncle
external features of brain stem - anterior view - medulla?
olive lateral to pyramid
decussation of pyramids at caudal end
external features of brain stem - posterior view - midbrain?
thalamus
superior colliculus
inferior colliculus
external features of brain stem - posterior view - pons?
superior cerebellar peduncle
middle cerebellar peduncle
floor of 4th ventricle
inferior cerebellar peduncle
external features of brain stem - posterior view - medulla?
cuneate tubercle
gracile tubercle
fasciculus cuneatus
fasciculus gracilis
where does the corticospinal pass after the internal capsule
crus cerebri of midbrain
where does the corticospinal pass after the crus cerebri
pontine corticospinal tracts
where does the corticospinal pass after pontine corticospinal tracts
pyramid of medulla
where does the corticospinal pass after pyramid of medulla
lateral and ventral corticospinal tracts of spinal cord
what occurs to upper motor neurons in pyramids?
75-90% decussate
10-25% remain ipsilateral (and decussate at level of their LMN synapse)
where do axons run in the lateral corticospinal tract?
contralateral
where do axons run in the ventral corticospinal tract?
ipsilateral
extra-pyramidal motor pathways? contra/ipsilateral?
rubrospinal tract - contralateral
vestibulospinal tract - ipsilateral
tectospinal tract - contralateral
reticulospinal tract - ipsilateral
where does the rubrospinal tract come from
red nucleus in midbrain
where does the vestibulospinal tract come from
vestibular nuclei in pons and medulla
where does the tectospinal tract come from
superior colliculus in midbrain
upper motor neuron loss causes what?
weak voluntary movements of affected muscles
slow wasting muscle atrophy
spasticity
positive Babinski reflex
lower motor neuron loss causes what?
weak or paralysed affected muscles
profound muscle atrophy
tendon reflexes weak/absent
fibrillation potentials can be recorded from denervated muscle
fasciculation occurs
what are the basal ganglia?
group of subcortical nuclei that interact with each other
parts of the basal ganglia?
caudate
putamen
globus pallidus external
globus pallidus internal
subthalamic nucleus
substantial nigra
