BMS11004 WEEK 11 - WEDNESDAY Flashcards
upper and lower motor neurons, MS, somatopy
what do simple reflexes involve
local circuit control of spinal motor neurons by spinal sensory neurons
what motor neuron initiates all movements from skeletal muscles
lower motor neurons
what neurons control upper motor functions
upper motor neurons
what does somatotopically mapped mean in motor cortex
correlate site of stimulation with location of muscle contraction, showing topographic maps
how is lower and upper body represented on somatotopic map
lower body = medially
upper body = laterally
proportions reflect density of innervation, behavioural signif
what do axial muscles control
trunk movement
what do proximal muscles control
shoulder, elbow, pelvis, knee movement
what do distal muscles control
hands, feet, digits movement
what do lower motor neurons in ventral horn of spinal cord do
innervate striated muscle to control movement
define motor unit
motor neuron and all muscle fibres it innervates
define motor neuron pool
all motor neurons that innervate single muscle
explain the organisation of motor pools in spinal cord
grouped in rod-shaped clusters, extends over several vertebrae segments
what is corticospinal tract (CST) important for
control of voluntary movement
position of CST neurons in cortex reflex where it projects to in SC
what are main inputs of cortex
to stellate cells in layer IV
what are main outputs to cortex
layers III, V, VI
explain the projections of corticospinal tract axons controlling distal muscles
axons cross midline in “pyramidal decussation” in medulla, project contralaterally in spinal cord and synapse onto lateral lower motor neuron circuits
what do ventromedial pathways control
controls posture
what do vestibulospinal, tectospinal and reticulospinal tracts (part of ventromedial pathway) control
vestibulospinal= head balance, turning, input from vestibular systems
tectospinal= orientating response, input from visual system via superior colliculus
reticulospinal= antigravity reflex
name the 3 tracts making up ventromedial pathway
vestibulospinal, tectospinal, reticulospinal
what is role of upper motor neurons of motor cortex when projecting contralaterally via corticospinal tract
initiate complex voluntary movement, muscles for precise limb movement (mostly hands)
what is role of upper motor neurons of motor cortex when projecting via corticobulbar tract to the hypoglossal nucleus in brainstem
movement of tongue
name an overall function of upper motor neurons in brainstem
maintain posture and balance
where are upper motor neurons in brianstem mostly located
reticular formation, vestibular nucleus, superior colliculi
what does ipsilaterally mean?
on same side of body
where do upper or lower motor neurons synapse onto?
upper= onto lower motor neurons
lower= onto muscle fibres
explain anticipatory feedforward mechanism
adjust body posture to compensate for generated forces when lever is lifted
apply feedforward mechanism to indirect cortical control of lower motor neurons for voluntary movement
anticipation of movement activate indirect projections to axial muscle, via reticular formation
direct to spinal cord via corticospinal tract
how does mirror therapy work for phantom limb pain
reorganise/integrate the mismatch between proprioception and visual feedback of non-limb
mirror neurons in somatosensory and motor cortex fire when act and observe an action
what can mirror therapy be used in aside from phantom limb pain
complex regional pain syndrome, post-stroke
give another name for motor neuron disease
amyotrophic lateral sclerosis
define motor neuron disease
degenerative disease of motor neurons, muscle atrophy, sclerosis (hardening) of lateral spinal cord (degeneration in axons in CST)
name symptoms of lower MND
muscle paresis, weakness, paralysis
lost muscle tone, lost stretch reflex
severe muscle atrophy
what do individuals with lower MND die from
lung dysfunction from atrophy of intercostal muscles
name symptoms of upper MND
muscle weakness
spasticity -increase muscle tone, failed modulation of stretch reflex
hyperactive reflex
lost fine movement
what do individuals with upper MND die from
loss of input to bulbar muscles- tongue, pharynx via corticobulbar tract
what could MND potentially be due to?
excitoxicity (overstimulated by glutamate = cell deaths)
vicious cycle of glutamate release in hypoxia (post-cardiac arrest, stroke or trauma)
what drug could work for MND but give issues of this
glutamate blocker, but only delays by few months
explain the 10% link of MND to genetics
mutation in genetic encoding of SOD1- enzyme picking up free radicals accumulating in metabolically active cells.
