Motor System Part 1 Flashcards
Is motor function an isolated process?
No it is integrated with sensory
What is the motor system?
Allows normal movements to occur
Smooth accurate movement, suppression of unwanted movements
Requires communication between brain
What are the 4 components of the motor system?
From first to most deep:
UMN
LMN
Basal ganglia
Cerebellum
What are the upper motor neurons?
Pyramidal tracts
What are the lower motor neurons?
Receives input from the UMN to innervate the muscle
What is the basal ganglia?
Refines the movement so that it is neither excessive or inadequate
What is the cerebellum?
Programs and coordinate the movement
Describe the pathway of UMN?
Begins in frontal lobe’s motor areas
UMN influence LMN in brainstem (cranial nerves) or spinal cord (spinal nerves)
2 different muscle control pathways one cranial (head) one spinal (below head)
What are the 2 UMN pathways called?
Corticospinal
Corticobulbar
Describe the corticospinal pathway.
Descends to spinal cord to influence the ventral roots of spinal nerves
Describe the corticobulbar pathway.
Descends to the brainstem to influence cranial nerves
Not all cranial nerves have motor functions
What commands do LMN carry? What do they include in the somatic motor system?
Carry commands to the contractile units of voluntary muscles so that movement occur
Spinal nerves and their nuclei
Cranial Nerves and their nuclei
From where do the UMN and LMN receive additional input?
Basal ganglia, cerebellar, and brainstem motor centers
Describe the basal ganglia motor center.
Located in deep cerebrum
Allow desired movements
Postural adjeustments
Prevents undesired movements
Describe the cerebellar motor center.
Fine tunes via connection to cortex and brainstem motor centers
Describe the brainstem motor centers.
Integrates movements of eye and head structures
Can movement ever just involve on muscle pathway?
NO!!!
What system plays a large role in integrating movements (balance)?
Vestibular system
How does fine tuning of movement occur during integration?
Via connections from cerebellum with motor cortex and brainstem motor centers which influence LMNs
How are movements integrated in UMN and LMN?
Muscle receptors send info back to LMN and cerebellum during movement to fine tune and coordinate movement as it proceeds
Where do UMN (aka the pyramidal system) begin?
In the primary motor cortex (aka area 4, M1)
Describe the pathways of UMN after beginning in primary motor cortex.
Projection pathways carry info to brainstem and spinal cord where they synapse with LMN
Corticobulbar and corticospinal pathways carry info to cell bodies of LMNs
Where do UMN and LMN synapse?
Brainstem and spinal cord
What two pathways allow for UMN to reach the cell bodies of LMN?
Corticobulbar (face/head)
Corticospinal (below face/head)
What pathways carry UMN to area where they synapse with LNN?
Projection pathways
Where is the primary motor cortex located?
Precentral gyrus of the frontal lobe (M1 or area 4)
What occurs in the primary motor cortex?
Motor execution
Marks start of UMN pathway
How did Brodmann develop the Brodmann Map?
Mapped out how brain cells are laid out across the cortex paying no mind to function
Ended up correlating with brain function just based on cells
What is the motor homunculus (little man)?
Neurons in the primary motor cortex are organized by body part
Size of body part is related to the number of neurons
Hands and mouth are heavily populated
Describe the somatotopic representation of the primary motor cortex?
From lateral to medial, head to toe
Describe the organization of the sensory cortex.
Parallel organization
Describe the process within the primary motor cortex when movement is desired.
UMN begin pathway (pyramidal cells in the primary motor cortex)
Output is made from appropriate part of primary motor cortex depending on body part that wants to move
What type of info does the motor system use to determine its actions?
Sensory info
What information programs everything that the motor system does?
Cerebellar information
What questions are asked to direct the motor system and other parts of the brain to end info to motor areas?
What is the purpose of the movement? Simple or complex?
Which muscle has to move? How much? How fast?
Is more than one muscle needed? How are movements coordinated?
What are commissural fibers?
Connect right and left halves of the brain
Corpus callosum
Anterior commissure
What are association fibers?
Connect different areas within the same hemisphere
What are projection fibers?
Connect the cortex with deeper underlying region of the brain, brainstem and spinal cord
What is important when processing info and planning movement?
Communication between all parts of the brain
Describe the function and shape of pyramidal cells.
Chief output neurons (projection fibers)
Pyramid cell body
Describe granule cells
Main interneurons of the cortex
Short axons arborize (branch freely and repeatedly) with neighboring neurons
What are cortical columns?
Perpendicularly oriented columns of functional activity
Contains thousands of interconnected neurons
What is the function of the internal granular layer of the cortical columns?
Chief input layer
Receives afferent fibers from the thalamic nuclei
Describe the infragranular layer 5 and 6 of the cortical columns. To where do they project?
Chief output layers
5 projects to striatum, brainstem and spinal cord
6 projects to the thalamus
Describe the suprgranular layers 1 through 3 of the cortical columns.
Associative
Connect to other parts of the cortex
The layers of the cortical columns that have functions are:
Input (granule)
Output (pyramidal)
Association
To where do the functions of the cortical columns facilitate communication?
Input and output with other parts of CNS, with adjacent and distance parts of the cortex
Describe the pathway of signals through the cortical columns.
Sensory info comes into the motor association areas, gets processed and then is sent out to the cerebellum and deep nuclei for proper programing
Info then comes back into the association areas and is shared with the primary motor cortex which executes the movement.
What is the function of the primary motor cortex?
Motor execution
Start of the UMN pathway
What parts of the motor cortex are involved in planning motor processes?
Premotor cortex and supplemental motor cortex (SMA)
