Lecture 13 - Corticospinal tract and other Flashcards
What are the three main long tracts of the nervous system?
- Lateral cortico-spinal tract —-MOTOR
- Posterior Columns —- sensory (vibration, joint position and fine touch)
- Anterolateral pathways —- sensory (pain, temperature, crude touch)
Where is primary somatosensory area?
Brodmann’s area 3, 1 and 2
post central gyrus
Where is the primary motor area?
Brodmann’s area 4
precentral gyrus
How does the presentation of a lesion in a primary motor or sensory cortex differ from a lesion in an association cortex of sensory and motor.
Lesion in primary cortex - deficits in basic movement and sensation
Lesion in association cortex - deficits in higher order sensory analysis or motor planning
Describe the lateral corticospinal tract (the pathway)
over half of fibres originate in PRIMARY MOTOR CORTEX, others from the premotor and supplementary motor, or parietal.
- includes GIANT BETZ cells, which are the largest neurons all the way from cortex to brainstem.
- cerebral cortex > corona radiata > internal capsule, where white matter pathways converge and funnel, condensing down to fewer and fewer fibers, as connections to different subcortical structures are made
What is the corona radiata
the upper portions of the cerebral white matter
the corticospinal tract goes through this
What does the internal capsule look like
there is a right and left one
theyre little ‘v’ shape arrowheads pointing inwards, towads each other.
thalamus sits between then
and putamen on the other sides of them
What are the different parts of the internal capsule
Left and right internal capsules each have an anterior limb, genu, and posterior limb.
What does the anterior limb of the internal capsule seperate
It seperates the head of caudate (which sits inwards) from the putamen and globus pallidus
What does the posterior limb of the internal capsule seperate
It seperates the putamen and globus palladus (outwards) from the thalamus.
Where does the corticopsinal tract lie in the internal capsule
in the posterior limb
Where does the corticospinal tract go on the spinal cord
Anterior limb
Describe the feedback systems
basal ganglia and cerebellum feedback to the cerebral cortex through the thalamus, which go to brainstem and then the lateral and medial motor systems.
What NT do the lateral corticospinal tracts use
Ach
What can some antipsychotics do?
Older antipsychotics, such as Chlorpromazine, can give a movement disorder due to excess dopamine, causing hyperactivation of the circuits.
Where does the lateral corticospinal tract cross over
pyramidal decussation
85% of the neurons - the remaining become the anterior corticospinal tract
From the posterior, genu to anterior limb of the intenral capsule, describe what areas of the body are represented on it.
L(i)TAF
leg trunk arm face
What are corticobulbar fibers
these are fibers that go from cortex to brainstem
eg. motor fibers for the face
because they dont go to the spine, so not corticospinal
What does a lesion in the internal capsule usually produce?
despite the somatotopic arrangement, lesions usually produce weakness in ENTIRE CONTRALATERAL BODY, because of how compact it is.
however, can sometimes create more selective motor deficits.
Where is the somatotopic arrangement in the midbrain
the middle one-third of the basis pendunculi, on the cerebral peduncles.
goes LTAF, from outside towards middle.
this is on each side/hemisphere.
What are the two lateral motor pathways
- lateral corticospinal tract
- rubrospinal tract
What tract is made up of the 15% of fibres that do not cross over at the pyramidal decussation
anterior contricospinal tract
- controls bilateral axial and girdle muscles.
