motor pathways and cortical motor function Flashcards
motor system hierachy DIAGRAM
motor cortex receives info from other cortical areas, and sends info to basal ganglia to thalamus and brainstem brainstem sends info from cortex to spinal cortex basal ganglia and cerebellum refine movement
location of primary motor cortex DIAGRAM
primary motor cortex in pre-central gyrus- central sulcus separates frontal and parietal lobes, so motor cortex in frontal lobe
motor pathways DIAGRAM
from betz cells (long soc) in motor cortex , UPPER motor neurone go through basal ganglia via internal capsule to midbrain where it goes via cerebral peduncle through pons (peduncle hidden by transverse fibres) to medulla where it goes to pyramids at medulla it crosses over to other side via lateral corticospinal tract, then lower motor neuron goes via ventral root to muscles some fibres (on right) decussate at level of spinal cord rather than medulla, and are part of anterior corticospinal tract- needed for muscles in thorax eg intercostals
corticobulbar pathway DIAGRAM
motor neurons in brainstem to cranial nerve nuclei- pass from eg head (lateral part of cortex) down internal capsule to brainstem, where it synapses, and then goes to muscles eg tongue
premotor cortex location and function
in frontal lobe anterior to motor cortex needed for planning of movements- if you want to pick an apple, you need to know where you are in space (intra-personal space), and how you will move in space (extra-personal space)
supplementary motor area- location and function
frontal lobe anterior to M1, but more medial than pre motor cortex plans complex movements eg speech and sequence of movements- when thinking about movement before actually moving, this area active
association cortex
not strictly motor areas but involved in motor function posterior parietal function- ensures movements are targeted accurate to objects prefrontal cortex- appropriate movements based on previous experience (eg not touching a hot plate like before)
define lower motor neuron
neurons projecting out from ventral horn of spinal cord, or from brainstem from cranial nerve nuclei
define upper motor neuron
betz cells projecting to spinal cord (corticospinal) or to cranial nerve nuclei (corticobulbar)
define pyramidal symptoms vs extrapyramidal
those symptoms involving damage to lateral corticospinal tract vs damage to basal ganglia/cerebellum
upper motor neuron lesion
loss of function, either paresis (weakness or movement) or paralysis/plegia (complete loss of movement) also have increased abnormal motor function on other hand due to fewer inhibitory descending inputs- can lead to spasticity (more muscle tone ie rigidity), hyper-flexia (bigger reflexes), clonus (repeated muscle contraction) and babinski’s sign (abnormal response of toe)
define apraxia and causes
cannot perform skilled movement (not weak) due to lesion of parietal lobe or frontal lobe (premotor or supplementary area) most commonly due to stroke/dementia
lower motor neuron lesions
causes weakness, hypotonia (less muscle tone), hyporeflexia and muscle atrophy (muscle that’s lost innervation shrinks) also leads to fasciculations (damaged motor units cause sudden A.P’s= twitch) and fibrillations (twitches for EMG exam)
motor neurone disease
damage to both upper and motor neurons- most common type is ALS has wide range of causes- tends to progress from legs up leads to dysphagia (both upper and motor neurons) and dysarthria (problem breathing- upper motor neuron signs)
fasciculations vs fibrillation
both symptoms of LMN disease- fibrilllations are contractions of muscle fibre vs motor unit
fibrillations NOT visible through skin vs visible
fibrillations shorter and less powerful
