Lecture four - Central control of movement Flashcards
What is the difference between the cerebral cortex and the cerebrum?
The cerebral cortex is the outer layer of the cerebrum. It is the outer layer of grey matter. It is primarily involved in consciousness.
The cerebrum is diivided into two halves - the left and right hemisphere. The two halves are connected the corpus collosum.
Is it true the cerebelllum contains 80% of the brains neurons?
Yes.
What are the sulci and gyri of the brain?
The grooves and ridges of the cerebelal cortex respectively.
What are the areas of the brain known to be involved in motor control?
Posterior Parietal Cortex.
Primary Motor Cortex.
The supplementary motor cortex.
The premotor cortex.
The prefrontal cortex.
How were the areas of the brain responsible for motor control discovered?
Through animal experiemtns, such as zapping primate brains when animals were anethetised and seeing what movement was generated.
The Primary Motor Cortex has a somatotopic organisation. What does this mean?
Each area of the M1 corresponds to a different body area.
What determines how big an area for a body part is?
How fine the movement type is. Hands have a relatively large area of the M1. So does the tongue.
Do messages from our different body parts go to the M1?
No. Stimulation of these areas lead to movement of the associated body part, but messages from these body parts go elsewhere.
What is the difference between upper and lower motor neurons?
Upper motor neurons are located in the cerebrum, cerebellum, or brainstem.
Lower motor neurons are located in the spinal chord.
What are the two descending motor tracts?
These descending motor tracts are now information from the brain about movement travel to their target areas, such as limbs. They travel down the white matter of the spinal chord.
1. Pyramidal or lateral tracts - these run down the lateral groves in the spinal chord and carry information about voluntary movement.
2. Medial or ventromedial tracts - these travel down the medial groves of the spinal cord and carry information about involuntary movement, such as balance.
What descending motor tract does not enter the spinal chord?
The corticobulbar tract. This tract sends information about movement to face, neck, tongue etc.
What are the three lateral descending motor tracts discussed in the lecture?
- CORTICOSPINAL TRACT
- RUBROSPINAL TRACT
- CORTICOBULBAR TRACT
Where does the CORTICOSPINAL tract originate, what does it control, and is there crossover (i.e. is the movement controlled contralaterally)?
The corticospinal tract originates in the M1 (primary motor cortex).
It sends messages for movement of the distal parts of the limbs, such as fingers.
There is crossover. This occurs at the MEDULLA (in the brain stem). When the tract enters the spinal chord, it enters on the side opposite to the side of the M1 it originated in, i.e. the left M1 controls the right side fine motor movement.
What does the RUBROSPINAL TRACT control?
Where does it originate?
Is there crossover?
The rubrospinal tract controls arms, forearms and independent movement.
It orginates in the RED NUCLEUS in the mid-brain, BUT it receives information from M1.
There is crossover at the midbrain and so information from the right red nucleus informs movement of the left side of the body.
What does the CORTICOBULBAR TRACT control?
Where does it originate?
Is there crossover?
The corticobulbar tract controls face, neck, tongue and external eye movents.
It originates in the M1.
There is crossover (50% crossover).
The corticobulbar tract does not enter the spinal chord.
What is the significance of M1 for the corticospinal tract, the rubrospinal tract and the corticobulbar tract?
The corticospinal and corticobulbar tract both originate in the M1. The rubrospinal tract originates in the midbrain, but receives information from the M1.
What does the VENTROCORTICOSPINAL TRACT control?
Where does it originate?
Is there any crossover?
The ventrocorticospinal tract is part of the corticospinal tract (makes up about 10%) of this tract.
It controls upper legs and trunk.
It originates in M1.
There is no crossover. That is, it is ipsilaterally controlled.
What does the TECTOSPINAL TRACT control?
Where does it originate?
Is there crossover?
The tectospinal tract controls the coordination of head and trunk movements with the eyes. It is involved in orientating the head toward auditory and visual stimuli. It works in combination with visual and auditory systems.
It originates in the brain stem (superior colliculi), which are in the brain stem.
Movement is controlled ipsilaterally. There is no cross over. This means it informes movement on the same side that it originates from.
What does the VESTIBULOSPINAL TRACT control?
Where does it originate?
Is there crossover?
The vestibulospinal tract controls postural movements.
It originates in the brainstem (vestibular nucleus in the medulla).
There is no crossover. Messages are sent ipsilaterally.
What does the RETICULOSPINAL TRACT control?
Where does it originate?
Is there any crossover?
The reticulospinal tract controls postural movements.
It originates in the pons and medulla.
There is no crossover. Messages are sent ipsilaterally.
The motor cortex has association areas that send messages informing the motor cortex how and well to move/send messages about movement.
One of these areas is the posterior parietal cortex.
What does this area do?
It gives us information about where we are in our environment. It does this by receiving and coordinating information from the vestibular, auditory, visual, and somatosensory systems.
It coordinates this information to give us an understanding of where parts of our body are in relation to other parts of our body as well as to the environment.
Particularly important in movements such as reaching, grasping, and object manipulation.
The Prefrontal cortex is another association area of the motor cortex.
What does it do?
The prefrontal cortex is important for planning movement. Stores and processes information from the posterior parietal cortex and decides appropriate action from there.
Plays a key role in managing impulsive behaviours, concentration, and organization.
What happens to movements when there is damage to the prefrontal cortex?
Movements can become disorganised and impulsive or inappropriate.
When you are at a crossing and you see the green man and automatically start crossing the road, what area of the brain processes this info and sends it to primary motor cortex to insight movement?
The premotor cortex.
