Motor Pathways Flashcards
(39 cards)
state the broad principles of motor control
Functional segregation and Hierarchical organisation
describe functional segregation
Motor system organised in a number of different areas that control different aspects of movement
describe Hierarchical organisation
high order areas of hierarchy are involved in more complex tasks (programme and decide on movements, coordinate muscle activity)
lower level areas of hierarchy perform lower level tasks (execution of movement)
Motor system hierarchy
(association cortex)
1) Motor Cortex: Receives info from other cortical areas and sends commands to brainstem and thalamus
2) Brainstem and Basal ganglia adjust commands fro other parts of motor system
3) Brainstem passes commands from cortex to spinal cord
(see diagram)
what is the location of Primary motor cortex
Primary motor cortex (M1):
Location: precentral gyrus, anterior to the central sulcus
what is the function of Primary motor cortex
Function: control fine, discrete, precise voluntary movement
Provide descending signals to execute movement
how is Somatotopical Organisation shown
This is called Penfield’s Motor Homunculus
In the motor cortex there is a representation of the muscles of different parts of the body
how is increased muscle use represented in the cortex
the more we use a muscle, the bigger the representation of that muscle in the cortex
The motor homunculus is very distorted because different parts of the body get used more than other parts
This is different in all of us - the cortical representation of the hand in a child is much smaller than that of a pianist
what are types of corticospinal tract
anterior and lateral
They are both composed of upper motor neurones
function of anterior corticospinal tract
The anterior tract is for axial UMNs
Axial: the muscles of the back and spine
Ie, UMNs supplying information to LMNs which will go on to innervate axial muscles
function of lateral corticospinal tract
The lateral tract is for appendicular UMNs
Appendicular: Muscles of the limbs
which neurones exit via the ventral root
Somatic and autonomic motor neurones
what order of neuornes exist in the corticospinal tract
Upper motor neurone
Cell body in the motor cortex in lamina V, betz cells
Axons travel in the lateral/ ventral corticospinal tracts to synapse with LMN.
Lower motor neurone
Cell body in the ventral horn
Axon travels out of the ventral root
describe the general path of upper and lower motor neurones before decussation
UMNs start in the motor cortex:
Path: corona radiata - internal capsule - peduncles at the midbrain
describe lateral corticospinal tract path
decussate in medullary pyramids
descend contralaterally in the lateral corticospinal tract
synapse with contralateral LMNs in the ventral horn
describe anterior corticospinal tract path
continue to descend ipsilaterally in the anterior corticospinal tract
decussate in the spinal cord at the anterior white commissure
Only then will they synapse with a LMN cell body in the ventral horn
what percentage of neurones decussate in medulla and what type of neurones are they
90% (UMNs of lateral corticospinal tract)
10% that don’t cross over are of anterior corticospinal tract
which other descending pathway is there and what does it do
Corticobulbar Tract - starts in the cortex, then exits and innervates the muscles in the face
describe corticobulbar pathway
arise from the lateral aspect of the primary motor cortex - internal capsule - brainstem
neurones terminate on the motor nuclei of the cranial nerves (hypoglossal nucleus)
Here, they synapse with LMN (hypoglossal nerve), which carry motor signals to muscles of face and neck
describe the location of the premotor cortex
frontal lobe anterior to M1
describe the function of the premotor cortex
Function: planning of movements
Regulates externally cued movements
e.g. reaching out for an object:
moving a body part relative to another body part (intra-personal space)
movement of the body in the environment (extra-personal space)
describe the location of the Supplementary motor area
frontal lobe anterior to M1, medially
describe the function of the Supplementary motor area
Function: planning complex movements; programming sequencing of movements
Regulates internally driven movements (e.g. speech)
SMA becomes active when thinking about a movement before executing that movement
briefly describe the association cortex and its constituants
Brain areas not strictly motor areas as their activity does not correlate with motor output/act
(Posterior parietal cortex and Prefrontal cortex)
