Intro To Neuroanatomy - Lecture 1 Flashcards
Where are the upper motor neurones located?
Cerebral cortex
Motor areas
How do the cerebellum and basal ganglia act upon the cerebral cortex?
Indirectly via the thalamus(the only direct input to the cerebral cortex)
What is the hierarchy of motor control within the brain?
Motor cortex
Cerebellum
Basal ganglia
How does the motor cortex connect to the spinal cord? What occurs with injury of this area?
Motor cortex has direct link with spinal cord via the corticospinal tract (upper motor neurons)
Damage to this area causes spasticity/paralysis
What information does the cerebellum receive and from where?
Afferent information from the spinal cord (spinocerebellum) and also information from the cerebral cortex (cerebrocerebellum) also argument for info from brain stem (vestibulocerebellum)
What occurs with injury at the cerebellum?
Inaccurate / poorly timed movement can be observed (looks like person is drunk)
What occurs with damage to basal ganglia?
Can result in difficulty initiating/terminating movement e.g. Parkinson’s and Huntingtons
What does the gray and white matter of the spinal cord contain?
Gray matter contains all the cell bodies of the neurons(sensory, motor and interneurons)
White matter contains the axonal tracts
The motor neurons exhibit ‘somatotopy’, what does this mean?
The proximal and distal muscles are represented in the proximal and distal spinal cord.
Motor neurones for distal muscles (hand) lay in the dorsolateral part of the spinal gray
Motor neurones for more medial muscles lay at progressively more medial (the ventromedial cell group) parts of the spinal gray
Which side is the dorsal side of the spinal cord, and what is the dorsal side typically associated with?
Dorsal means the back side, and is concerned with the entering of sensory information.
Sensory info from muscles such as spindles or GTO enters via this dorsal route
What are the 2 lateral and 2 medial spinal tracts?
Lateral - corticospinal, rubrospinal
Medial -vestibulospinal, reticulospinal
What are the 4 key spinal descending tracts point of origin?
Corticospinal - originates in the motor cortex
Rubrospinal - originates in the red nucleus (midbrain)
Vestibulospinal - originates in the vestibular nuclei
Reticulospinal - orginates in the reticular formation (pontine+medullary)
Does the CS cord make direct or indirect connections to the motor neurons?
Both, indirect is via the brain stem pathways.
What is pyramidal decussation?
This is where the CS tract crosses over to the other side of the body. 90% of the tract crosses over (lateral CS tract), 8% is the ventral CS tract and 2% does not cross over
How does the number of direct connections to the spinal cord change In species?
Higher animals have more direct connections, which correlates with manual dexterity. However this reliance means humans are less able to cope with spinal damage
What is the babinski sign?
When sole of foot is stroked along a path, the toes will fan out and big toe will extend. In infants smaller toes will fan out and big toe will dorsiflex - as CS pathways are not fully myelinated
The rubrospinal tract receives a large input from where?
The contralateral cerebellum and the ipsilateral motor cortex
What is the ‘journey’ of the rubrospinal fibres?
The fibres originating in the red nucleus cross the midline the instant they exit the nucleus. They then course in the ventrolateral part of the brain stem to the cord, ending in occupation of the same part of the white matter that CS fibres occupy.
Which part of the spinal cord contains the motor neurones responsible for muscles in the fore and hind limbs?
Fore - cervical
Hind limbs - lumbar
What does recording data tell us about the function of the RS tract?
Controls the shaping of the hand during a reach to grasp movement
What did Lawrence and Kuipers (1968) find about the rubrospinal tract?
It can compensate for damage to the CS tract, severed the CS of monkeys and after a few weeks they were fine apart from not being able to use their fingers individually
What is the main function of the vestibulospinal tract?
Descending VS information contracts and relaxes muscles to maintain postural stability when the head moves.
Where does the vestibular nuclei reside?
The mid and lower pons and the brain stem
What is the route of the reticulospinal fibers?
They run caudally to the spinal cord where they terminate in the same part of the spinal gray matter as vestibulospinal fibres do
Alongside having a role in postural control and balance, what else does the reticulospinal system do?
They carry information from a variety of other sensory modalities and mediate postural adjustments in response to startling stimuli
What are the occipital and temporal lobes involved in?
Occipital - visual processing
Temporal - hearing/speech comprehension
What is the innervation number equation?
Innervation number = fibres/motor neurons
A lower innervation number = more control
