Motor Systems l Flashcards
What function does the motor system have?
Functions to move the body
What are the parts of the motor system? (6)
- Motor Cortex
–Spinal Cord
–Brainstem
–Motor Nerves (CN &
spinal)
–Basal Ganglia
–Cerebellum
What is the function of the posterior motor cortex?
Provides sensory information to the frontal cortex
What is the function of the prefrontal cortex?
Plans movements
What is the function of the premotor cortex?
Organize movement sequences
What is the function of the motor cortex?
Produces specific movements
What is the order of the motor signal on the cortex? (4)
How many homunculi do the primary motor and premotor cortices contain?
10 homunculi
What do the disproportionate sizes of the homunculi represent?
The complexity of movements that they can perform
Larger are in the homunculi = greater ____________
motor control
Which parts of the homunculi are especially large?
Hand and Face
What would happen if we would electrically stimulate a certain area in the motor cortex?
It would elicit movements of body parts corresponding to the map of the body
Is the motor system responsible for:
a) Control of individual muscles
b) Specialized control of muscle combinations (movement)
c) Information processing of our sensory information
b) Specialized control of muscle combinations (movement)
Different homunculi represent different classes of ____________ specified by ____________, __________________ and ___________.
movement
body part
movement location
function
Different homunculi represent different classes of ____________ specified by ____________, __________________ and ___________.
movement
body part
movement location
function
What are the two main motor pathways?
Direct Pathway
Indirect Pathway
What is another name for the direct pathways in motor systems?
Pyramid Pathway
What is another name for the indirect pathways in motor systems?
Extrapyramidal Pathway
Where do Pyramidal neurons (upper motor neurons) originate from?
Motor cortex
Upper motor neurons are part of which nervous system?
CNS
Lower motor neurons are part of which nervous system?
PNS
Pyramidal neurons (i.e., upper
motor neurons) originating in motor
cortex project directly to: (2)
–Brainstem as Corticobulbar tract
–Spinal cord as Corticospinal tract
(aka Pyramidal tract)
The pyramidal neurons from the motor cortex projection to the brainstem is called the ___________________ tract
Corticobulbar Tract
The pyramidal neurons projection to the Spinal is called the ___________________ tract
Corticospinal Tract
The corticobulbar Tract Synapses on which cranial nerves (lower motor neurons)? (6)
CN 5 7 9 10 11 12
Why does the corticobulbar tract synapse specifically with the CN 5 7 9 10 11 12?
Because they are motor nerves (or mixed) that control face, head and neck.
Corticobulbar regulation of MOST cranial nerves is _________________
Bilateral
Give an example of the fact that Corticobulbar regulation of most cranial nerves is bilateral.
E.g., fibers from left motor cx
innervate left & right cranial nerve
motor nuclei in brainstem
What is the clinical implication of the fact that Corticobulbar regulation of most cranial nerves is bilateral?
Unilateral lesions to upper motor
neurons have mild effects on motor
control of speech, but bilateral lesions
can cause severe dysarthria
In the corticospinal tract, the primary motor cortex projects to the ___________
Spinal Cord
____% of fibers from each
hemisphere CROSS in
brainstem (i.e., pyramidal
decussation) and descend
in the spinal cord as the
LATERAL corticospinal tract
95%
95% of fibers from each
hemisphere cross in
brainstem (i.e., pyramidal
decussation) and descend
in the spinal cord as the
_____________________________
lateral corticospinal tract
What is another name for the crossing of fibers in each hemispheres?
Decussation
What does the lateral corticospinal tract control?
movements of limbs/digits
____% of fibers from each
hemisphere DO NOT CROSS
in brainstem and descend
in the spinal cord as the
VENTRAL (or anterior)
corticospinal tract
5%
What is Dysarthria?
difficulty speaking caused by brain damage, which results in an inability to control the muscles used in speech.
5% of fibers from each
hemisphere do not cross
in brainstem and descend
in the spinal cord as the
________________________________________
ventral (or anterior)
corticospinal tract
What does the ventral (or anterior)
corticospinal tract control?
Movements of trunk
Where do corticospinal axons terminate?
On spinal cord motor nerves (i.e., lower motor neurons)
_____________________ terminate on spinal cord
motor nerves (i.e., lower motor neurons)
Corticospinal axons
Where are the corticospinal axons located?
Located in the ventrolateral spinal cord and
jut out to form the ventral horns
Lateral corticospinal tract synapses with interneurons and motor neurons that innervate ________________________________.
muscles of the limbs and digits
Interneurons project to__________________
Motor neurons
Motor neurons project to ___________________________
muscles of the body
Ventral corticospinal tract synapses with _____________________ and _______________ neurons that innervate the trunk
interneurons and motor neurons
The interneurons and motor neurons of the spinal cord are envisioned as a ____________________ that representing the muscles that they innervate
homunculus
Since the corticospinal tract is mostly
crossed (i.e., contralateral), unilateral
lesions to upper motor neurons affect limb
movement ________________________________
on the opposite side of body
What are clinical implications from unilateral
lesions to upper motor neurons affect limb
movement?
Since the corticospinal tract is mostly
crossed (i.e., contralateral) it unilateral lesions can cause:
Hemiplegia
Hemiparesis
What is hemiplegia?
one-sided paralysis
What is hemiparesis?
weakness or the inability to move on one side of the body
