29/ motor control Flashcards
(30 cards)
what are all movements produced by the skeletal musculature initiated by
lower motor neurons (final neurons in motor pathway)
spine contains central pattern generators, what do these do
generate complex behaviours w/o input from the brain, although the brain does influence these systems
simulation of what area of the brain elicits contralateral muscle movement
primary motor cortex
what are neurons found in the brain that control motor function called
upper motor neurons
how does the motor cortex somatotopic map compare to the somatosensory system map
- similar but not identical
- area dedicated to ears smaller - we don’t move our ears
what type of striated muscle controls: trunk movement/ shoulder, elbow, pelvis, knee/ hands, feet, digits
- axial muscles
- proximal muscles
- distal muscles
how many lower alpha neurons does each muscle fibre receive input from
1
how many muscles does each lower motor neuron innervate
1
what is a motor unit
motor neuron and all the muscle fibres it innervates
motor neuron pool
all the motor neurons that innervate a single muscle
how are motor neurons organised in the spinal cord
- spatially
- motor pool for a muscle grouped in rod shaped clusters within the spinal cord extending over several vertebral segments
how did we find out how motor neurons are organised in the spinal cord
- tracers injected into spec muscles, then transport back along motor axons to cell bodies in spinal cord
- injection into the gastrocnemius activates dif set of motor neurons to soleus
what does the medio-lateral position of a motor pool refelct
whether its motor neurons innervate a proximal or distal muscle
how are motor pools organised
- somatotopic
- both medio-laterally and a-p
what does somatotopy in the motor cortex reflect
the location of upper motor neurons that innervate lower motor neurons in the spinal cord
what 2 inputs do lower motor neurons receive
- local spinal cord inputs
- direct inputs from upper motor neurons
what tracts do upper motor neurons project to lower motor neurons through
descending tracts
what is the corticospinal tract cst
- for control of voluntary movement
- one of the lateral pathways of the spinal cord
- position of the cst neurons in the cortex reflects where they project to in the spinal cord
pyramidal cells of the motor cortex project axons in the corticospinal tract
- 90% of cortex is a 6 layered structure
- main inputs to cortex are to stellate cells in layer 4
- main outputs are from layers 3, 5 and 6
- axons of corticospinal tract derive from large pyramidal cells in layer 5 which project down sc
dif sets of upper motor neurons control dif functions
- axons of corticospinal tract cross the midline in the pyramidal decussation in the medulla and project contralaterally in the spinal cord to synapse on laterally located lower motor neuron circuits that control distal muscles
- cst is one of lateral pathways
where do brainstem upper motor neurons project to
- project to medial motor pools primarily concerned w postural movement
- axons from brainstem project ipsilaterally in vestibulospinal and reticulospinal tracts
- project medially in spinal cord
- synapse on medially located lower motor neuron circuits that control axial muscles
- these are ventromedial pathways
what do motor cortex upper motor neurons do
- primarily concerned w fine voluntary control of more distal structures
- anticipation - feeds into brainstem upper motor neurons
what tracts make up ventromedial pathway, what does it control
- vestibulospinal tract: head balance and turning
- tectospinal: orienting response
- reticulospinal tract: antigravity reflexes
- posture
- mainly ipsilateral
dif between where upper and lower neurons synapse onto
- upper: lower or interneuron
- lower: directly on muscle fibres
