Voluntary Motion Flashcards
What are the 4 main cortical areas associated with production of voluntary motion?
primary motor cortex
supplementary motor cortex
premotor cortex
parietal cortex areas
How does your brain get input to enable motor actions based on visual input?
V2 –> dorsal visual pathway to parietal/frontal cortex
What is the first part of reaching motion (creating a rough map of space around you)?
info from visual cortex –> V6a, PEc, MIP and VIP in parietal cortex –> VIP (ventral intraparietal area) makes rough map of space around you
Where do signals go after the VIP in the reaching process?
VIP –> F4 in premotor cortex = detailed map of space around you
(neurons are excited by proximity - closer the object is, the more they fire)
What pathway in reaching gets visual information about where your arm is in space (NOT where the bowl is)?
Superior parietal cortex (V6a, etc) –> F2 in the premotor cortex –> map of your arm in relationship to your body and things around you is constructed
What are the visual cues of grasping related to?
the goal of what you intend to do
pay attention to the features of the item you’re interested in picking up
What does the anterior intraparietal area and PFG respond to?
seeing and object to grasp = visually dominant neurons
grasping an object = motor dominant
both seeing and grasping an object = visuomotor neurons
What is the Voluntary grasping path?
PFG/AIP –> F5 –> neurons fire w/ goal of the action
What does the premotor cortex do?
receives sensory info required to move (particularly F4 and F5)
dorsal - applies rules that det whether it is appropriate to move
IDs the intent of the motion and decides what to produce
What are the 2 divisions of the supplementary motor cortex and what do they do?
supplementary motor area (SMA): postural control during mvt
Pre-supplementary area (Pre-SMA): plans the motor program required to make the action occur
If you are going to get candy from a bowl, what has your pre-SMA done?
identified the sequence of how to do the movements
Where is the primary motor cortex?
What does it do?
precentral gyrus
controls specific movements
regions of body that do fine motions have proportionally high representation
How are the columns of the primary motor cortex arranged?
each column produces a specific movement (not a specific muscle)
What cerebral layer are Betz cells located?
V
What layer of the primary motor cortex receives sensory input?
layer IV
relatively small here compared to other parts of the brain
What characterizes layer V of the primary motor cortex?
output for the corticospinal (pyramidal) pathway
How many sets of neurons are in each column of the primary motor cortex?
appear to be 2 sets:
one to start the motion
one to maintain it as long as necessary
How are neighboring columns of the primary motor cortex related?
neighboring columns control related motions, not neighboring muscles
What are the 2 types of columns of the primary motor cortex?
- on/off for agonist muscles
- off/on for the antagonist muscle
What is the cerebellum’s role in voluntary motion?
sequence complex actions
correct force/direction
balance and eye movements
learning of complex actions
What are the 2 parts of the spinocerebellum and what do they do?
central = postural control
either side of vermis = force and direction of motion
Where is the cerebrocerebellum and what does it do?
lateral regions of the cerebellum
plan complex motions
sequence of motions
Where is the vestibulocerebellum and what does it do?
flocculonodulus
balance/ eye movements
future - not current
What part of the cerebellum does outputs?
deep cerebellar nuclei:
dentate nucleus (most lateral)
fastigial nucleus
interpositus (most medial): globose, emboliformis
How are postural adjustments to ongoing motions accomplished?
Inputs: vestibular, visual and auditory, efferent copy –> to spinocerebellum
outputs: interpositus n, fastigial n –> rubrospinal tract
How are ballistic motions controlled via the cerebellum?
inputs: muscle afferent, efferent copy –> lateral spinocerebellum
outputs: interpositis –> rubrospinal tract
What is an efferent copy?
what brain sends to muscle of the expected motion
sent to cerebellum so it can mediate/alter motion
How is the sequencing of rapid movements and the planning of complex motions accomplished via the cerebellum?
inputs: all regions of cerebral cortex –> cerebrocerebellum
outputs: dentate –> back to cortex
How is the control fo eye movement and balance, particularly in the future accomplished via the cerebellum?
input: vestibular apparatus (direct or indirect) –> vestibulocerebellum
output: fastigial nucleus –> vestibular nuclei –> ascend or descend
Without the basal ganglia, how is voluntary motion affected?
won’t be able to initiate motion or
will get stuck at start and can only repeat starting action
How do the basal ganglia work?
inhibition and withdrawal of that inhibition –> to start movement
excess of GABA
What is the nigrostriatal path?
from SNPC –> to striatum = caudate and putamen
tonically active
dopaminergic
What type of receptor is used in the direct and indirect pathways?
D1 = direct
D2 = indirect
What is the basic direct path?
SNPC – dopamine D1 –> striatum – GABA –> SNPR and GPi – GABA –> Thalamus
* allows motion when active
What is the indirect pathway?
SNPC –Dopamine D2 –> striatum –GABA –> GPe – GABA –> subthalamic nucleus – EAA –> SNPR and GPi – GABA –> Thalamus
*opposes motion when active
What is the intrastriatal cholinergic system?
btw the nuclei of the striatum
effects: excitatory, in particular to indirect path
What do you need to activate the indirect path?
intrastriatal cholinergic pathway
EAA inputs from the cortex
How does the brain get around muscles spindle reflexes?
if the brain activates the alpha motoneuron, also activates gamma-motoneuron for spindles in contracting muscle
if it inhibits alpha motoneuron, will also inhibit gamma motoneuron in antagonist muscle
