Lecture 13 - Corticospinal tract and other

Question 1

What are the three main long tracts of the nervous system?

Answer 1

1. Lateral cortico-spinal tract —-MOTOR
2. Posterior Columns —- sensory (vibration, joint position and fine touch)
3. Anterolateral pathways —- sensory (pain, temperature, crude touch)

Question 2

Where is primary somatosensory area?

Answer 2

Brodmann’s area 3, 1 and 2

post central gyrus

Question 3

Where is the primary motor area?

Answer 3

Brodmann’s area 4

precentral gyrus

Question 4

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.

Answer 4

Lesion in primary cortex - deficits in basic movement and sensation

Lesion in association cortex - deficits in higher order sensory analysis or motor planning

Question 5

Describe the lateral corticospinal tract (the pathway)

Answer 5

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

Question 6

What is the corona radiata

Answer 6

the upper portions of the cerebral white matter

the corticospinal tract goes through this

Question 7

What does the internal capsule look like

Answer 7

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

Question 8

What are the different parts of the internal capsule

Answer 8

Left and right internal capsules each have an anterior limb, genu, and posterior limb.

Question 9

What does the anterior limb of the internal capsule seperate

Answer 9

It seperates the head of caudate (which sits inwards) from the putamen and globus pallidus

Question 10

What does the posterior limb of the internal capsule seperate

Answer 10

It seperates the putamen and globus palladus (outwards) from the thalamus.

Question 11

Where does the corticopsinal tract lie in the internal capsule

Answer 11

in the posterior limb

Question 12

Where does the corticospinal tract go on the spinal cord

Answer 12

Anterior limb

Question 13

Describe the feedback systems

Answer 13

basal ganglia and cerebellum feedback to the cerebral cortex through the thalamus, which go to brainstem and then the lateral and medial motor systems.

Question 14

What NT do the lateral corticospinal tracts use

Answer 14

Ach

Question 15

What can some antipsychotics do?

Answer 15

Older antipsychotics, such as Chlorpromazine, can give a movement disorder due to excess dopamine, causing hyperactivation of the circuits.

Question 16

Where does the lateral corticospinal tract cross over

Answer 16

pyramidal decussation

85% of the neurons - the remaining become the anterior corticospinal tract

Question 17

From the posterior, genu to anterior limb of the intenral capsule, describe what areas of the body are represented on it.

Answer 17

L(i)TAF

leg trunk arm face

Question 18

What are corticobulbar fibers

Answer 18

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

Question 19

What does a lesion in the internal capsule usually produce?

Answer 19

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.

Question 20

Where is the somatotopic arrangement in the midbrain

Answer 20

the middle one-third of the basis pendunculi, on the cerebral peduncles.

goes LTAF, from outside towards middle.

this is on each side/hemisphere.

Question 21

What are the two lateral motor pathways

Answer 21

• lateral corticospinal tract

- rubrospinal tract

Question 22

What tract is made up of the 15% of fibres that do not cross over at the pyramidal decussation

Answer 22

anterior contricospinal tract

• controls bilateral axial and girdle muscles.