motor and neuromuscular control Flashcards
what is meant by hierarchical organisation in motor control
high order areas of hierarch are involved in more complex tasks e.g coordinating muscle movement
lower level areas perform lower level tasks e.g execution of movement
what is meant by functional segregation in motor control
motor system is organised in number of different area that control diff aspects of movement
what are the major descending tracts
pyramidal tracts - corticospinal and corticobulbar
extrapyramidal -
vestibulospinal, tectospinal, reticulospinal,rubrospinal
what makes a tract pyramidal
pass through pyramids of medulla
what is the pathway for pyramidal tracts
motor cortex to spinal cord or cranial nerve nuclei in brainstem
what is the pathway for extrapyramidal tracts
brainstem nuclei to spinal cord
where is primary motor cortex located
precentral gyrus
anterior to central sulcus
what is role of motor cortex
controls fine, discrete, precise voluntary movements
provides descending signals to execute movement
where is premotor cortex located
anterior to primary motor cortex
what is role of premotor cortex
involved in planning movement
regulates externally cued movements e.g seeing picking up object
where is supplementary motor area located
anterior and medial to primary motor cortex
what is role of supplementary motor area
involved in planning complex movements, internally cued e.g speech
what is the pathway in corticospinal tract and what muscles are involved
upper motor neurones in cortex travel down to medulla where 85-90% of fibres decussate and innervate limb muscles = lateral corticospinal tract
10-15% are uncrossed fibres which innervate trunk muscles = anterior corticopinal tract
what is corticobulbar tract responsible for
providing voluntary movements of face mostly and neck muscles too
what is role of vestibulospinal tract
stabilise head during body movements
coordinate head movements with eye movement
mediate postural adjustments
what is the role of reticulospinal tract
= most primitive descending tract, from medulla and pons
responsible for changes in muscle tone associated with voluntary movement and postural stabilty
what is tectospinal tract responsible for
originates from superior colliculus of midbrain
orientation of head and neck during eye movements
what is rubrospinal tract responsible for
originates from red nucleus of midbrain
mainly taken over by corticospinal tract
innervate lmn of flexors of upper limb
* comes into play when lesions to cns
what are the negative (loss of function) signs caused by upper motor neurone lesion
loss of voluntary motor function
paresis - graded weakness of movements
paralyis (plegia) - complete loss of voluntary muscle activity
positve signs (unwanted) sign of umn lesion
increased abnormal motor function due to loss of inhibitory descending inputs spasticity - increased muscle tone hyper-reflexia - exaggerated reflexes clonus - abnormal muscle contractions babinskis sign
what is apraxia
disorder of skilled movement
lesion of inferior parietal lobe and frontal lobe
stroke and dementia are most common causes
what can a lower motor neurone cause
weakness hypotonia hyporeflexia muscle atrophy muscle atrophy fasiculations - twitching fibrillations - spontaneous twitching of individual muscle fibres
what is motor neurone disease
progessive neurodegenerative disorder of motor system
affects both umn and lmn
aka amyotrophic lateral sclerosis
what are the umn signs of mnd
spacticity brisk limb and jaw reflexes babinski sign loss of dexterity dysarthria - difficulty swallowing dysphagia - difficulty swallowing
what are some lmn signs of mnd
weakness muscle wasting tongue fasciculations and wasting nasal speech dysphagia
what structures make up the basal ganglia
caudate nucleus
lentiform nucleus (putamen and external globus pallidus)
nucleus accumbens
subthalamic nuclei
ventral pallidum,claustrum,nucleus basalis
thalamus
amygdala
what is the function of basal ganglia
- decision to move
- elaborating associated movements e.g swinging arms when walking
- moderating and coordinating movement
- performing movements in order
what is parkinsons disease
degeneration of dopiminergic neurones that originate in substantia nigra to striatum
signs/symptoms of parkinsons
bradykinesia - slow movement hypomimic face - emotionless akinesia rigidity tremor at rest
what is huntingtons disease
degeneration of GABAnergic neurones in striatum,caudate and putamen
what does huntingtons disease cause
choreic movemtns - dance
rapid jerky involuntary movements of body,hands and leg first and then rest of body
speech impairment
dysphagia
unsteady gait
later stages - cognitive decline and dementia
what is ballism
usually from stroke affecting subthalamic nucleus
sudden uncontrolled flinging of extremitis
symptoms occur contralaterally
what is cerebellum
located in posterior cranial fossa
separated from cerebrum above by tentorium cerebelli
coordinator and predictor of movement
what is the vestibulocerebellum
part of cerebellum
regulation of gait,posture and equilibrium
coordination of head movements with eye movemt
what can damage to vestibulocerebellum cause
syndrome similar to vestibular disease leading to gait ataxia and tendency to fall
what is the spinocerebellum
responsible for coordination of speech
adjustment of muscle tone
coordination of limb muscles
what can damage to spinocerebellum cause
degeneration and atrophy related with chronic alcoholism
affects mainly legs, causes abnormal gait and stance
what is the cerebrocerebellum
coordination of skilled movements
cognitive function,attention,processing language
emotional control
what can damage to cerebrocerebellum cause
damage to arms/skilled coordinated movements(tremor)and speech
what are the main signs of cerebellar disorders
ataxia - impairments in coordination dysmetria - inappropriate force intentional tremor dysdiadochokinesia - inability to perform rapidly alternating movements scanning speech - staccato
what are alpha motor neurones
- lower motor neurons of brainstem and spinal cord
- occupy anterior/ventral horn of grey matter of spinal cord
- innervate the extrafusal muscle fibres of skeletal muscle
what does activation of alpha motor neurones cause
muscle contraction
what is a motor neurone pool
all the alpha motor neurones which go to an individual muscle
what is a motor unit
a single motor neurone together with all the muscle fibres that it innervates = smallest functional unit
on average how many muscle fibres does each motor neurone supply
600
what does small innervation ratio allow
small fine precise control of that muscle
what are the 3 types of muscle fibres
slow type - s,1
fast, fatigue resistant, - fr,2a
fast, fatiguable - ff, 2b
describe slow motor unit muscle fibres
smallest diameter cell bodies
small dendritic trees
thinnest axons
slowest conduction velocity
describe fast muscle fibres
large diameter cell bodies
large dendritic trees
thicker axons
faster conduction velocity
what are motor unit types classified by
amount of tension generated, speed of contraction and fatiguability
how else can cns regulate force produced
recruitment of number of neurones and rate coding/firing
what is meant by the ‘size principle’
smaller units are recruited first generating small amounts of force and more are recruited if more force is required
what happens when firing rate increases
force produced by unit increases
what are neurotrophic factors
are a type of growth factor
prevent neuronal growth
promote growth of neurons after injury
what is the reason behind plasticity of motor units/muscle fibres
fibre types can change properties under different conditions e.g type of nerve innervating them
what is the most common muscle fibre type change
fast fatiguable to ffr
2b to 2a
when can changes from type 1 to 2 occur
cases of severe deconditioning / spinal cord injury
microgravity during spaceflight can result in shift from slow to fast type muscle fibres
what is ageing associated with
loss of type 1 and 2
more type 1 fibres in aged muscle
what is a reflex function
automatic response to stimulus that involves nerve impulse passing inward from nerve centre then outward to effector without reaching level of consciousness
jendrassik manoevre
larger reflex when patellar tendon tapped
works by reducing inhibition of brain action
what is hyper- reflexia
overactive reflexes
loss of descending inhibition
associated with UMN lesions
what is clonus
involuntary and rhythmic muscle contractions
loss of descending inhibition
what is babinskis sign
stimulate sole of foot with blunt instrument
curling upwards is abnormal
associated with umn lesion
what is hyporeflexia
below normal/ absent reflexes
associated with lmn disease
