L2.2 Motor Control Flashcards
(44 cards)
What are lower motor neurons?
Cranial and spinal nerves
What are upper motor neurons?
Neurons that originate in the cerebral cortex and/or brainstem and descend into the spinal cord or cranial nerve nuclei in the brainstem to control the activity of cranial and spinal nerves
Must be entirely contained within the CNS
Upper motor neuron tracts that go to lower motor neurons in the spinal cord are called?
Corticospinal tracts
Upper motor neuron tracts that go to lower motor neurons in the brainstem are called?
Corticobulbar tracts
What four descending motor tracts originate in the brainstem?
- Vestibulospinal
- Reticulospinal
- Tectospinal
- Rubrospinal (minor in humans)
What upper motor neuron tracts originate within the cortex? (2)
- Corticospinal tract
- Corticobulbar tract
Describe a simplified descending pathway from the cortex
The motor cortex receives information input from what areas? (4)
- Basal ganglia
- Cerebellum
- Somatosensory afferents
- Prefrontal cortex
Which area of the motor cortex has the lowest threshold for action to cause movement?
The primary motor cortex
A lesion to the primary motor cortex would likely impair?
Fractionated finger/facial movements
Skilled hand movements, hand to mouth coordination, lower face
Generally describe the positions of major motor areas in the motor homunculus
What two areas of the brain are responsible for making the decision of which movement to take and predicting the outcome?
- Parietal lobe
- Prefrontal cortex
Parietal receives all the somatosensation of the body, communicates with the higher functions of the prefrontal cortex (will this action help or hurt me, etc).
Information then passed on to the premotor and supplementary motor cortex
If you don’t need sensory input information/sensory cues to do the movement, what motor area of the brain can self-initiate movement?
E.g. decide to shift gaze to the right absent a cue
Supplementary motor cortex
What does the supplementary motor cortex do?
What is a bimanual movement?
What usually controls them?
A movement involving both hands
Usually controlled by the supplementary motor cortex
Unlike the supplementary motor cortex, the premotor cortex organises movements based on?
Sensory information/feedback
Which part of the brain contains ‘mirror motor neurons’? What are they?
Premotor cortex
Become activated seeing another doing a movement and ‘imagining’ us doing the movement ourselves.
What are the important aspects of the premotor cortex? (6)
With regards to planning movement (motor action), what information does the parietal association cortex provide the premotor and supplementary motor cortexes?
Information about the spatial relationships of the body and and its surroundings
The corticospinal tract has ____ fibres in it, which arise from 3 different locations in the cortex. What are they and what % do they contribute?
1 million fibres
30% Precentral gyrus (primary motor)
40% Postcentral gyrus
30% Premotor and supplementary motor
In the corticospinal tract, there are 1 million fibres. Of which,
30% are Precentral gyrus (primary motor)
40% are Postcentral gyrus
30% are Premotor and supplementary motor
Why are there neurons coming from the postcentral gyrus?
These descending neurons inhibit sensory information from coming in at the spinal level they synapse at.
Basically they travel down to a sensory boi and turn him off so he can’t send his signal upwards. Done in times when there is a need for intense motor output
Cerebrospinal tract neurons leave the cortex and descend through?
The posterior limb of the internal capsule
