Motor Flashcards
circuits that drive movement
voluntary movement and reflexes
proprioception
knowing position and movement of body
muscle length
muscle tension/movement
True or false: Voluntary movements are made up of different
combinations/speeds of reflexes.
FALSE
reflexes are different processes than voluntary movement
spinal reflex
simple, varying and unlearned responses
don’t require brain inputs to the spinal cord
voluntary movement
require brain inputs to the spinal cord
motor plan, or motor program, is established before action occurs
ex. adjust. balance before reaching out to hold a door knob
voluntary motor systems
sensing the outside world guides action selection
ex. approach reward/reinforcer or withdraw from negative
central nervous system produces specific patterns of muscle contractions that lead to specific actions
systems involved in voluntary motor movement
primary motor cortex
non-primary motor cortex
cerebellum/basal ganglia
brainstem
spinal cord
skeletal muscle system
primary motor cortex
initiate main commands
non-primary motor cortex
additional motor commands
cerebellum/basal ganglia
modulate motor control systems
brainstem
integrates motor commands from higher brain regions
spinal cord
implements commands from brain
formed by axons of M1 neurons in primary motor cortex
skeletal muscle system
determine possible movements
Which brain region is responsible for initiating most motor
commands?
A. Brainstem
B. Primary motor cortex
C. Cerebellum
D. Basal ganglia
B. primary motor cortex
skeletal muscles
can be synergists or antagonists
synergists
contract together
antagonists
contract opposing each other
how to muscles contract?
alpha motoneuron sends an axon that branches
each axonal branch/terminal opposes a separate muscle fiber at a motor end plate- individual muscle fiber- can widely spread axon terminals- different muscle fibers
synapse of muscles
neuromuscular junctions
neuromuscular junction
alpha motoneuron releases acetylcholine (ACh) to the motor end plates from the axon terminal
ACh binds to ___ in the neuromuscular junction
nicotinic acetylcholine receptors (nAChR) in the motor end plate to allow Na+ influx
Na+ influx from neuromuscular junction creates
EPP (end plate potential) which triggers muscle fiber contraction
What is an end plate potential most similar to?
A. Action potential
B. Postsynaptic potential
B. Postsynaptic potential
When you step on a
nail, why don’t you fall
down? How do you
balance while walking?
having reflex on one side bringing it back- other leg tightens and balances
cross extensor system
cross extensor system
specific to spinal cord & legs
info from one side switches to the other side
not just used for reflexes- used when we walk
stimulus of stepping on a nail on the right side
stimulus goes up sensory into spinal cord- goes into right dorsal side- synapse on neuron-interneuron- shuttles info on right dorsal spinal cord to right ventral spinal cord- alpha motoneuron controls foot- crosses spinal cord- ventral left side motoneurons- give information to appropriately control their muscles
walking
central pattern generator
antagonistic muscles
right hamstring contracts, quadricep stretches
left hamstring relaxes, quadricep contracts
What are the quadricep and hamstring examples of?
A. Integrative muscles
B. Antagonistic muscles
C. Synergistic muscles
B. antagonistic muscles
pyramidal motor system
primary motor cortex
nonprimary motor cortex
primary motor cortex M1
homunculus- somatosensory and M1 don’t line up the same
Betz cells (pyramidal neurons) form the homunculus
pyramidal system- voluntary movements
M1 pyramidal neurons form axon bundles
crosses in the medulla
descends caudally in spinal cord via corticospinal tract
synapse onto ventral spinal cord alpha-motoneurons
muscle fiber contracts
M1 simple movements
contraction of simple muscle “units” leads to simple movements
SMA/premotor cortices
SMA and premotor cortex control subsets of M1 neurons
coordinated activity of muscle units to produce complex movements
SMA
planning movement that is internally generated, rehearse
premotor
directs movement based on external stimuli
ex. gripping closer to the water bottle rather than farther away
mirror neurons in premotor cortex
neurons active when performing a task
same neurons also active when watching someone else perform same/similar task
understand/imitate another person’s actions- maybe for learning? or for cooperation
empathy?
language?
autism spectrum disorder?
motor deficits
paralysis
spasticity
neurological problems- where the problem is permanent or can be. partially healed
spasticity
motorneurons
spinal cord
primary cortex
primary cortex deficit
stroke in primary motor cortex- due to plasticity of motorneurons can be partially healed
spinal cord deficit
often persistent- lesion of spinal cord- message is not traveling down spinal cord
motorneuron deficit
often partial recovery
lesions in motor cortex- due to plasticity can be healed over time
motor deficits
apraxia (non-primary motor cortex)
ideomotor apraxia
ideational apraxia
apraxia (non-primary motor cortex)
impairment in beginning/executing voluntary even though no muscle paralysis
ideomotor apraxia
the inability to carry out a simple motor activity in response to verbal command, even though this same activity is readily performed spontaneously
cannot generate when they are asked to- cannot start the movement
ideational apraxia
the inability to carry out a sequence of actions, even though each element can be done correctly
capable of each task in the sequence but cannot do them together
extrapyramidal motor systems connects
with motor cortices to form a closed loop
cortex to EMS to cortex
extrapyramidal motor systems
basal gangli and cerebellum
EMS: basal ganglia
initiation of motor action (related to motivational systems and cognition)
EMS: cerebellum
coordination, precision, and accurate timing
alcohol can inhibit the activity of the cerebellum: causing them to slur their words or stumble losing coordination
basal ganglia and primary motor cortex synchronicity
activity in the basal ganglia looks similar to the activity in the primary motor cortex
cerebellum and non-primary motor cortex synchronicity
cerebellum forms closed loop with non-primary motor cortex
similar patterns of neuron activity
Which part of the central nervous system would you expect to be
more active in a very talented piano player compared to a beginner
piano player?
A. Spinal cord
B. Cerebellum
C. Medulla
D. Basal ganglia
B. cerebellum
ability to move fingers in a precise accurate flow
basal ganglia / go/stop pathways
D1 and D2 are dopamine receptors
Two BG circuits
excitatory
inhibitory
“excitatory” D1 receptors
GO/DIRECT pathway
excitatory postsynaptic potential- fires an action potential
“inhibitory” D2 receptors
STOP/INDIRECT pathway
inhibitory postsynaptic potential- neurons will not fire action potentials
dopamine turns on the
D1 GO pathways, which leads to reward-seeking & initiation of movement
dopamine turns off the
D2 STOP pathways, which leads to reward-seeking & initiation of movement
DIRECT/GO
cerebral cortex/primary motor cortex -> caudate -> globus pallidus internal-> thalamus
basal ganglia regions
globus pallidus internal/external
caudate
GO PATHWAY
cerebral cortex -> sends info (glutamate) to caudate -> excitatory-> caudate is receiving info from substantia nigra-> dopamine is released from SN-> dopamine binds D1 receptor EPSP-> glutamate receptor EPSP-> D1 releases NT GABA into globus pallidus internal-> cells in GPe are inhibited and do not release action potentials-> cells in thalamus are excited because of lack of GABA release and release glutamate-> cerebral cortex-> permission to move has been granted-> M1 motoneurons send action potentials down axon
INDIRECT PATHWAY
cerebral cortex-> D2 receptors in caudate-> GPe-> subthalamic nucleus-> GP1-> thalamus-> cerebral cortex
STOP PATHWAY
glutamate from cerebral cortex to caudate-> SN releases dopamine to D2 receptors-> glutamate EPSP, dopamine IPSP, cancels each other out-> neuron that has D2 receptor does not fire action potential-> subthalamic does not release glutamate to GPi-> GPi does not release GABA-> thalamus fires glutamate-> cerebral cortex-> permission to move is granted
when dopamine is present
triggers movement both pathways
turn on go and turn off stop
when dopamine is not present
blocks movement
basal ganglia does not grant permission
Parkinson’s Disease
resting tremor, impaired gait, difficulty initiating movements
unknown etiology (partially genetic, partially environmental)
loss of substantia nigra dopamine neurons
pharmacological therapy involves dopamine replacement
caudate does not receive dopamine- cannot permit movement
Huntington’s Disease
chorea (writhing movements of limbs, head)
genetic; caused by single allele: trinucleotide expansion in huntington gene (>40 repeats)
longer repeat sequences, earlier onset
permission granted excessively-> more difficult to do the movement that is wanted
If Parkinson’s disease can be treated by enhancing dopamine
transmission (via L-dopa replacement), what might be a good strategy
for treating Huntington’s disease?
A. Enhancing dopamine transmission
B. Reducing dopamine transmission
C. Enhancing serotonin transmission
D. Reducing serotonin transmission
B. Reducing dopamine transmission
