Motor Flashcards
What does the cortex send to the spinal cord?
Direct and indirect projections
-Corticospinal and corticovulbar/bulbospinal
How is movement initiated?
In the basal ganglia which projects to the motor cortex
What is movement regulated by?
The cerebellum which projects to the motor cortex
What does the cerebral cortex consist of?
Primary motor cortex, premotor cortex, Broca’s area, Frontal eye field
Describe the frontal eye field.
Number 8
Voluntary movements of the eyes
Describe Broca’s area.
Numbers 44 and 45
One side only- typically the left
motor speech area
Think Broca Broadcasting
Describe the premotor cortex.
Anterior to precentral gyrus (6)
Coordinates simultaneous movement of many muscle groups
Describe the primary motor cortex.
Precentral gyrus (4) of the frontal lobe
Related to the somatosensory cortex (3,2,1)
What region of the brain activates as we think about movement?
Example: When I think about getting up to pee while laying in bed
The supplementary motor
WWhat is the purpose of descending motor pathways?
Descending tracts deliver efferent impulses from the brain to the spinal cord
What are the two groups of descending tracts?
Direct pathways aka pyramidal tracts
Indirect pathways aka any other tract
How many neurons do motor pathways involve? What are they?
Two- One upper in the motor cortex and one lower that is a spinal/cranial nerve motor neuron
How many neurons do motor pathways involve? What are they?
Two- One upper in the motor cortex and one lower that is a spinal/cranial nerve motor neuron
Where do direct pathways originate?
In the precentral gyri with pyramidal neurons
Where are impulses sent in the direct system?
Through the corticospinal tracts and synapse in the anterior horn
What activates skeletal muscles?
Stimulation of anterior horn neurons
What part of the direct pathway innervates the cranial nerve nuclei
Corticobulbar tracts
What does the direct pathway regulate?
Fast and fine skilled movents
What does a motor unit consist of?
The efferent branches of the axon of a spinal/cranial motor neurons and all the muscle fibers that it innervates
Where does innervation of skeletal muscle take place?
Neuromuscular junction
What role does acetylcholine have in the innervation of skeletal muscle?
Acetylcholine is the NT that diffuses across the synaptic cleft
Binds to receptors causing ions to move, depolarization of cell and end plate potential that results in an action potential
Which cranial nerve nuclei innervate extraocular muscles?
CN III - Oculomotor
CN VI- Abducens
CN IV - Trochlear
OAT
Which cranial nerve nuclei innervate the muscles of mastication (chewing)?
CN V -Trigeminal
Which cranial nerve nuclei innervates the muscles of facial expression?
CN VII- Facial
Which cranial nerve nuclei innervates the muscles of the tongue?
CN XII- Hypoglossal
How does paralysis occur?
Cross sectioning of the spinal cord at any level causes motor and sensory loss in regions inferior to the cut
What is paraplegia? Which sections of the spinal cord must be affected for paraplegia to occur?
Paralysis of the legs but not the arms
Transection between T1 and L1
What is quadriplegia? Which sections of the spinal cord must be affected for quadriplegia to occur?
Paralysis of all limbs from the neck down
Transection in the cervical region
What is paralysis?
Loss of motor function
What is flaccid paralysis?
Severe damage to the ventral root or anterior horn cells
Lower motor neuron damage therefore impulses do not reach muscles
Results in no voluntary or involuntary control of muscles
What is Spastic Paralysis?
Only upper motor neurons of the primary motor cortex are damaged
Spinal neurons remain intact and muscles are irregularly stimulated
No voluntary control of muscles
What does the indirect descending motor system include?
Brain stem, motor nuclei and all motor pathways not part of the pyramidal system
Also vestibulospinal, reticulospinal, and tectospinal tracts
What is another name for the indirect descending system?
Extrapyramidal system
True or false: Motor pathways are complex and multisynaptic?
True
What do axial muscles maintain?
Balance and posture
What do motor pathways regulate?
Axial muscles
muscles controlled coarse movements of the proximal portions of limbs
Head neck and eye movement
What do reticulospinal tracts do?
Maintain balance
What do rubrospinal tracts do?
Control flexor muscles
What do the superior colliculi and tectospinal tracts mediate?
Head movements
What does the cerebellar cortex do?
Calculates the best way to perform a movement
What is the role of the cerebellum?
data reception from the cortex with the intent to initiate voluntary movement
What do proprioceptors and visual signals do?
Inform the cerebellum of the body’s condition
True or false: In cerebellar processing, a blueprint of coordinated movement is sent to the cerebral motor cortex?
True
What is the neocerebellum?
The lateral lobes/dentate nucleus connections to and from the cerebral cortex dysmetria and ataxia (Intention tremor)
What does the midline cerebellum do?
Responsible for spinal inputs, posture and balance
What does the vestibulocerebellum responsible for?
Flocculonodular lobe/fastigial nucleus
Vertigo nystagmus
What happens in the final common pathway?
Lower motor neurons recieve signals from both direct and indirect upper motor neurons
Sum of all inhibitory and excitatory signals determine the final response of the lower motor neuron and skeletal muscles
What happens if the cortex or corticospinal tract is damaged?
The normal plantar flexion response to stroking the sole is replaced by dorsiflexion
*Note the dorsiflexion response is only appropriate in infants 0-1 years old
What can result after a spinal cord injury?
Muscle spasms- Normal flow of signals is disrupted and the message does not reach he brain instead they are sent back to the motor cells in the spinal cord
