Class 1 - Motor and Action 1 Flashcards
Acetocholine
Neurotransmitter important for pereferal motor activity two important receptors: Nicotenic, Muscrenic
Nicotenic Receptors are
Ionotropic
Muscuringic
binds to receptor, sends G protien to do other things inc. opening a seperate ion chanel
Cell bodies that generate acetroline pathways are in
ponds, midbrain, and baisal forbrain
Lots of acetocoline
maintains normal cortical excitability
Acetocholine when anestatised
decreased levels
Acetocholine is involved in
selective attention, motavation, reward
Acetocholine is active in
neuromuscular junction - where PNS stimilates activity
motor unit
where neurons (alfa) activates mussles (is both neuron and mussle fiber where it actavates)
motor units are medated by ____ and binds with ___
Acetocholine , Nicotenic receptors (in membrane of skelatal muscle)
opening of ion chanels in motor unit causes
mussle contraction
Reflux circiut
reflex - movments gnerated without cortical imput
alfa motor neurons - innnervate musles - recieve signal from spinal interneuron (in spinal cord)
two pathways where information from brain desends to spinal cord and out
lateral cortical spinal tract
medial tract
lateral cortical spinal tract
- fine motor movement, more distal lymbs
projects contralaterally
medial tract
walking, posture, standing, more procximal parts of lymbs and the trunk
is the extraperamital tracks
project not only contralaterally but also ipsolaterally
cerebellum
from video - “makes movements smooth”
“little brain” 3/4 of neurons of the brain 1/10 of the space - smaller neurons
imputs from all over the brain - visual, proceptrive, vestibular, somatosensory, autory
two hemispheres
prjects ipsolaterally
Functontal dividson of the cerebellum
Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum
Vestibulocerebellum
balance, eye movement
Spinocerebellum
smooth control of movement, coordination in walking, running
Lateral regions control more distal muscles, more medial regions control more proximal muscles
Cerebrocerebellum
highly skilled movements (requiring sensorimotor learning)
writing and speaking
Basala gangla
group of nucil
though to select what canadate plan of action is vs other alternitives
impotant in initation of action
dopamean
recepter subtypes (main)
D1 - excitatory
D2 - inhibitory
three differnt pathways in which can act
- Nigrostriatal system
- others involved in reward learning + motivation
• Useful for producing actions that have rewarding consequences!
doubble inhibiton circult
lowers baceline level of activity
makes certine signal stand out (by disinhibiting it, or not inhibiting it)
Nigrostriatal system
housed in substantra nigra - wheere cell bodies for DA activirt is highjlighted/housed
primartly in control of movement
Basal gangla - orgnaization
organixation of different patheays
green- exitory
red - inhibitory
How basal gangla influence cortical activity
two wats
direct root
indirect root
direct root
Does:
activated by:
Pathway:
Cortical excitation:
facilate movement - alows for initation of movment
activated by D1 receptors
DOrsal striatum is activated - inhibits internal segment of globus palatas
inhibatory done by gabergernic
net level of higher cortical excitation
substantia nigra sends __
can send both excityory and inhibtory
globus palatas internal segment normaly
(GPi) inhibits the thalamus
Thalamus connections to the cortex are
excitatory
indirect root
does:
activated by:
pathway:
cortical excitation:
in generally, supressing unwanted movments
D2 receptors
Normaly dorsal straitum (actavation) is inhibiting external segment of the GP
and the GPe normaly inhibits the subthalamic nuclis (STN)
subthalmic nucleis activates GPi (which inhibits the thalamus)
net level of lower cortixal excitation
Supplementary motor cortex
areas:
does:
supplementary motor area, supplementary eye field, presupplementary motor area
help code motor plan
motor plan
representation of intended movement
general - what is goal of movement want to do
specific - muscular control needed
Information contained in motor plan
- Which effectors to use
- Which order to use them
- Direction and force of individual effectors
- Timing between movements
- Commands for motor neurons
What are effectors
muscles, areas of body that move
most activity in SMA
is leading up to action
neuron in SMA sensitive to
order that things are done (Push pull vs pull push)
Pre SMA order
(order) does not matter
increased activity prior to third movement
Mirror Neurons
Not only to doing action but to someone else doing that action.
can be specific or broad
- coding for intent of action (can fire even if not see)
Anterior cingulate cortex
where:
implicated in:
(ACC) above CC
implicated in motor activity, attention, and emotion
motor - more activity in control and planning of new (untrained) movements
selecting for movement among compeeting alternatives (clasic word vs color)
Bimodal neurons in parietal cortex
proprioceptive, kinesthetic, somatosensory and visual info
- modulate receptive fields
damage to parietal regions
(dorso-dorsal stream) causes optic ataxia
optic ataxia
imparments to reach and grasp baised on visual information
Primary Motor Cortex
Organization:
Mapping:
M1
Parts of body with fine motor control are bigger
Organized around specific body area for specific region
distortion of size of region compared to size on body
Mapping is upside down, more dorsal regions (lower parts of body) more ventral (face)
cortical motor neurons synapse directly onto
alpha motor neurons (instead of onto spinal interneurons)
cortical motor neurons more responsive to
fine control, precision (small changes) (vs power gripping)
each motor neuron cell has ____ (movement preferences)
different preferences for movement
direction vector
combine activity of motor neurons: summation of direction moving towards
Direction: cell’s preferred direction
Length: firing rate of cell at a given moment
population vector
summation of direction vector
D1 is
excitatory
D2 is
inhibitory
basal ganglia uses ___ and acts on ___
uses double inhibiton circuit
act on dopameane
MPTP
A drug that is selectively toxic for DA cells
(overview of) Motor pathways
Between the association areas and the spinal cord sit the primary motor cortex and brainsem strustures which, with the assistance of the cerabellum and the basal gangla, convert these patterns into commands to the muscless.
alfa motor neurons
- innnervate musles - recieve signal from spinal interneuron (in spinal cord)
Gamma motor neurons
part of properseptive system, important for sensing and regulating length of mussle fibers
alfa Motor neurons originate in the
spinal cord
exit through the ventral root
terminate in muscle fibers
alfa motor neurons recceive preferfy imput from
muscle spindles
musle spindles axons enter dorsal root of spinal cord and synapse on
spinal internurons
that project to alfa motor neurons
strech reflex
if unexpected strech, alfa motor neurons are activated, returnign to origonal state
Extrapramidal tracts are a priamry sourse of
indirect control over spinal activry modulating posture, musle tone, and movement speed
recieve imput from subcortical and cortical structres
ataxia(s) result from
damage to the cerabellum
Basala gangla includes
caudate nucleus and putamen (both = stratum)
globus pallidus
subthamic nuclea STN
substantantia nigra
Basala gangla imput is
restructed to mainly the two nucli forming the stratium
Basala gangla output is
alsmost excultivly by way of the internal segment of the GP and part of the substantra nigra (SNr)
Corticospinal tract is also known as
the pyramidal tract (and CST)
Brodman area 4
M1
M1 divisions
evolutonaraly older - rostal region
more resentyl evolved - caudal regon
CST neurons that orgionate in the rostral region terminate on
spinal interneurons
CST neurons that origonate in the caudal region terminate on
(are also called)
spinal interneurons or directly stimulate alfa motor neurons.
corticomoterneurons (or CM neurons)
CM neurons include prominate projections to
mussles of the upper limbs and suport dexterous control of fingersand hands (inc. ability to manipulate tools)
Distance between represntaions in M1 is closely related to
how often (two fingers) are used togehter
CM neurons are preferntal active durring ___ comapired to ___
Pinch, power grip
lesions in M1 primaraly result in
hemiplegia
hemiplegia usally effects
most distal effectors (ex. fingers on hand
reflexes absent immedatly affter a stroke often
return and oftern produce hyperactive or spacic reflexes
Lateral and medial aspects of brodman area 6
premotor cortex (lateral) and suplementart moter (medial) cortex (SMA)
disingwshemnt in premotrot cortex
ventral (cPMC) and dorsal (dPMC)
somatosensory cortex provides a
representation of the body and how it is situated in space
critical info to move effectivly
Paretal cortex provides
anatomical substrate for sensory guided actions
SMA provides
stronger connections with medial frontal cortex, areas assocated with prefrences and goals
might help decide which object to choose or help plan a sequence of learned actions
divisio of doral stream
dorsol dorsal and ventro-dorsal
dorsal dorsal stream has a role in
reaching
lesions in dorsal dorsal stream have
optic ataxia
ventral dorsal stream has a role in
producing both transitive grestures (manitpulte object) and intranstivie gestures (singify intention, wave goodbye)
Lesios in ventral dorsal stream have
apraxia
apraxia
loss of praxis, or skilled action
affects motor planing, knowlege of which actions are possible with a given object.
Insular corex and brocha’s area are involved in
production of speach movements
frontal eye fieds are involved in
contreol of eye movements
anterior cingulat corex is involved in
selestion and control of actions, evaluation the effort or cost requited to produce a movment.
Activity of cells in M1 corrilates much bettwe with ___ than __
movement direction, target location
Simmilar tuning (prefered direction) are found in cells in
premotor and paretical cortextes
also cerebellum and basal gangla
___ is an excellent predictor of movement direction
population vectors
Before movement is produced the population vector
shifts in the direction of the upcmoming movement
sugessting some cells are involved in movement planning
SCn to the striatum is known as
the dopamine pathway
GPi and SNr have __ baseline firing rates producing
high, strong tonic inhibition of the motor system by the inhibitory projection to the thalamus and superior coliculi
basal gnaglia can act as a __ and play a critical role in the
gaitkeeper of cortical activity, initation of actions
As a specitic motor plan gains strength the inhibitory signaling __
is decresed for selective neurons.
