Midterm 2 - Unit 5 Lecture 1 Flashcards
How do we produce voluntary movement?
Motor plan – an abstract representation of an intended movement
what are the components of motor plan
specify a goal for the action
create the plan
initiate and execute the movement
compare executed movement with the plan on-line
How does the brain communicate with the motor neurons in the spinal cord?
Axons from the brain descend through the spinal cord along two major group of path-ways:
lateral and ventromedial pathways
Some originate from the cerebral cortex and others from the brain stem
what are the other names for Lower motor Neuron
“Final common pathway”
Alpha motor neuron
where does the Lower motor Neuron originate
Spinal cord and Brainstem
what muscles do Lower motor Neuron innervate
skeletal muscle
Lower motor Neurons are affected by….
descending motor neurons, sensory neurons, and interneurons
where do Upper Motor Neuron originate
the cerebral cortex and travel down to the brain stem or spinal cord
where do the Upper Motor Neuron terminate
Spinal cord and Brainstem
Descending motor pathways are organized into two major groups:
Lateral pathways
Medial pathways
what do the Lateral pathways control
control both proximal and distal muscles and are responsible for most voluntary movements of arms and legs
what do Medial pathways control
control axial muscles and are responsible for posture, balance, and coarse control of axial and proximal muscles.
what is the one lateral motor pathway called
rubrospinal tract
what are the 3 medial motor system
vestibulospinal tract
reticulospinal tract
tectospinal tract
The lateral corticospinal tract contains over _____ of the ________ present in the corticospinal tract and runs the ___________________
90%, fibres, length off the spinal cord
what is the primary responsibility of the lateral corticospinal tract
control the voluntary movement of distal muscles on contralateral limbs.
where does the lateral corticospinal tract originate
the primary motor cortex which lies in the precentral gyrus
what happens when a when a stimulus is engaged in the lateral corticospinal tract
cell body of the lateral corticospinal tract will send an impulse through the tract that will eventually travel to the anterior horn of the spinal cord
from where it will transmit the impulse via lower motor neurons into the muscle fibers
what happens when a motor act is planned to move the leg
an impulse generated from the primary motor cortex will be conducted through the lateral corticospinal tract ipsilaterally
It passes through the posterior limb of the internal capsule
decussates(cross) at the caudal medulla (pyramidal decussation), and then continues to descend contralaterally into the spinal cord
what is the anterior corticospinal tract
is a small bundle of descending fibers that connect the cerebral cortex to the spinal cord.
where does the anterior corticospinal tract originate
primary motor and premotor areas
where do the impulses cross in the anterior corticospinal tract
Remains uncrossed until spinal cord
what is the function of the anterior corticospinal tract
Bilaterally activates interneurons and motor neurons of proximal & axial muscles
what are the two pathways that are considered these direct connections(Cortex directly to spinal cord) with the spinal cord
Lateral Corticospinal Tract
Anterior (Ventral) Corticospinal Tract
where do Brainstem Pathways originate
Originate from Brainstem nuclei to spinal motor neurons
Both Medial and Lateral motor system are involved in these brainstem pathways. True or false
true
where do Vestibulospinal Tracts originate from
Vestibular nuclei
what are the two vestibulospinal tracts
Lateral Vestibulospinal Tract
Medial Vestibulospinal Tract
where does the Lateral Vestibulospinal Tract project to
projects ipsilaterally down to the lumbar region of the spinal cord
function of Lateral Vestibulospinal Tract
helps to maintain an upright and balanced posture by stimulating extensor motor neurons in the legs
where does the Medial Vestibulospinal Tract project to
projects bilaterally down the spinal cord and triggers the ventral horn of the cervical spinal circuits
function of Medial Vestibulospinal Tract
Positioning of head and neck
where does the Rubrospinal Tract originate from
Originates from red nucleus
where does the Rubrospinal Tract cross the midline
in brainstem
what column does the Rubrospinal Tract travel in
lateral column
function of Rubrospinal Tract
Involved in Goal-directed limb movements,
e.g., reaching, manipulation
Influences distal muscles
Reticulospinal Tract origin
reticular formation
Reticulospinal Tract function
Involved in stabilizing posture
Tectospinal Tract origin
superior colliculus
Tectospinal Tract function
Thought to pay a role in coordination of head and eye movement
Reticulospinal Tract travels in
anterior column to entire cord
Tectospinal Tract travels to
travel to cervical spinal cord
Cerebral Cortex – Motor Areas
Primary Motor Cortex (M1)
Supplementary Motor Area (SMA)
Premotor cortex (PMC)
Primary Motor Cortex (M1) location
Pre-central Gyrus
Primary Motor Cortex (M1) Function
Initiation and execution of movement
Specify how actions are to be carried out
Primary Motor Cortex (M1) Direct connection go through…
lateral cortical spinal and anterior cortical spinal
Primary Motor Cortex (M1) indirect connection go through…
these brain stem pathways
Neurons in M1 fire…
immediately before and during voluntary movement
Primary Motor Cortex (M1) encodes two aspects of the movement
direction and force
what is somatopically mapped
Motor cortices
Major Inputs for M1
Premotor and Supplementary motor areas
Primary Somatosensory
Parietal (area 5)
Basal ganglia and cerebellum through thalamus
Major Outputs for M1
Basal Ganglia
Cerebellum
Motor nuclei in brainstem and spinal cord
what do the (Association) Motor Areas consist of
Premotor area/cortex (PMA)
supplementary motor area (SMA)
Premotor area/cortex (PMA) located more
lateral
supplementary motor area (SMA) located more
medial and superior
(Association) Motor Areas Receive inputs from?
thalamus and other cortical areas
Function of Motor Association Areas
PMA and SMA Involved in planning movements
Neurons fire well before the movement occurs (as soon as goal is set) and continue to fire during the movement
Premotor cortex encodes
what actions are desired
M1 encodes
how the actions will be carried out
what is a major difference between Motor Association Areas and M1
Doesn’t code for movement force the way M1 does
how does the Premotor Area/Cortex (PMA) receive inputs
Receives multisensory inputs
Externally cued to generate or activate the plan
especially visual signals, used to guide movements
Ex: when you realize the change of light from red to green on a stoplight then proceed to let go of brake and press the gas
Sequencing motor synergies using sensory cues
Involved in preparation for voluntary movements
Stimulation causes muscle contractions at multiple joints (same limb)
Affects contralateral limbs
Influenced by cerebellum via thalamus
Affects contralteral limbs
is Supplementary Motor Area (SMA) internally or externally initiated
Used in internally initiated (self-motivated) movements
Same sequencing role but based more on internal than on external sensory cues, e.g. learned sequences
Associated with bimanual control
Inter-hemispheric connections between SMAs
Influenced by basal ganglia via thalamus
mirror neurons
Some PMA neurons fire not only when producing an action but also when seeing someone else make a similar an action.
