Motor Control Flashcards
What is the highest level in the motor system?
The primary cortex
What does the primary motor cortex do?
It projects directly into the spinal cord via the corticospinal tract
It regulates the motor tracts that originate in the brainstem
What is the middle level in the motor system?
The brainstem
What does the brainstem do?
It is a laterally descending system which controls distal limbs and is important for goal-directed movements of the hand and arm
What is the lowest level of the motor system?
The spinal cord
What does the spinal cord do?
It controls neuronal circuits that mediate reflexes automatisms such as walking as well as many other actions
What is the symplest reflex?
mono-synaptic
Only involves one sensory neuron and one motor neuron
What haooens if you artificially stimulate the motor cortex, brainstem and spinal cord?
You only get twitches
What do lateral brainstem pathways control?
The hands and the arm
What do direct spinal cord pathways control?
Muscles and reflexes
What does the basal ganglia ‘loop’ back to and via what pathway?
It only feeds back to the motor cortex via the subcortical loop
What is the role of the basal ganglia and the cerebelllum?
They receive information from many different areas of the cortex and they project to the motor cortex
They are aware of situations a person is in and they monitor commands to the muscle to make sure they are appropriate for the situation
If commands are not appropriate then they calculate correct signals and send this to the motor cortex
What does the cerebellum feed back to?
Mainly the motor cortex but it can send signals down the brainstem and the spinal cord
When was the motor cortex discovered?
1870
In the mid 20th century electrical stimulation of the frontal lobes showed what?
There are specific motor effects depending on which site is stimulated in humans and primates
How have motor maps been produced?
They are correlated with anatomical and clinical observations on effects of lesions
Where is brodmanns area 4 located?
It is found to be in an area in which the lowest intensity stimulus elicited a movement
It is the primary motor cortex and is found infront of the central sulcus (can be called the pre central gyrus)
Are the control areas for different parts of the body proportional to the size of the body part?
No because some small areas such as the hands and lips need fine motor control so their control area is disproportionally big
What happens to the spinal cord as a result of lesions in the primary motor cortex?
There is degeneration in the associated spinal cord area
What are the motor cortex’s first neurons called?
Upper motor neurons
What is the role of upper motor neurons?
They carry motor commands down the brain, brainstem and to the spinal cord
They are involved in planning, initiating and directing movements
What is the red nucleus/ nucleus ruber?
Mainly controls gait and crawling in babies
It relays information from the motor cortex to the cerebellum
What is the vestibular nuclei?
Cranial nuclei for the vestibular nerve
They are grouped by the pons and the medulla in the brainstem
Function in the maintenance of equilibrium and posture, perception of the head position and acceleration as well as general muscle tone
What is the superior colliculus?
Paired structure in the midbrain
Directs behavioural responses toward specific points in egocentric space eg head turning and eye movements
What is reticular formation?
Has projections to the thalamus and cerebral cortex
Allows some control over which sensory signals reach the cerebrum and come to our conscious attention
Has a role in states of consciousness like sleep and alertness
What has to be controlled by the motor system?
Muscle tone
Postural muscles
Maintained balance
Orientation of the head and body
Describe the upper motor neurons direct pathway
The neurons input to lower motor neurons from axons extending directly from the cerebral cortex
Describe the upper motor neurons indirect pathways
Input to lower motor neurons from motor centres in the brainstem
What do both of the upper motor neuron pathways do?
Both pathways govern the production of action potentials in the lower motor neurons, the final common pathway, that leads to muscle contraction/movement
Why are lower motor neurons called the final common pathway?
These are the neurons which innervate the muscle
What are the 4 sub areas of the basal ganglia?
The caudate, putamen, substantia nigra and subthalamic nuclei
What is Gilles de la Tourette’s syndrome?
Causes tics and vocal tics
Caused by a dysfunction in the cortical and subcortical regions and the basal ganglia
What is the role of the cerebellum?
Control activity of the upper motor neurons
It connects to the cortex via the thalamus and the brainstem
It monitors movements for differences between intended and actual movements
If there are any discrepancies it sends an error signal and tries to reduce the discrepancy
