Neuroanatomy Dr Najeeb Descending tracts 1
What are the 3 grooves in the brain (lobe?) called?
Central and pre and post central sulcus
What are the two horizontal front sulci called?
Superior and inferior frontal sulcus respectively.
What are the 3 brain areas above, inbetween and below the superior and inferior frontal sulci called?
superior, middle and inferior frontal gyrus
What are the brain areas inbetween the pre and central and post and central sulci called?
Pre and post central gyrus
The post central gyrus is responsible for?
The pre central gyrus is responsible for?
Primary motor area
The area in front of the pre central sulcus is?
The pre motor area and above it the supplementary motor area.
What is the Homunculus?
The diagram with areas of the brain matched to body parts responsible for those body parts therefore oversized hands and lips.
In the pre motor area list from top to bottom 4 areas of responsibilty.
frontal eye field
forming words (Broker's Area)
If right frontal eye field area is irritated which way does the eye look?
If the frontal eye field area of the pre motor cortex is destroyed the eyes look where?
Towards the damaged lobe.
The descending tract is known as ?
The cortical spinal tract
What % of fibres come from the primary motor area (pre central gyrus)?
What % of fibres come from the pre motor area and supplementary area (in front of the pre central sulcus)
What % of fibres come from the sensory cortex? (post central gyrus)
There are how many layers of neuron are there in the cortex and from what layer does these motor messages come from?
They come from layer 5 of 6
Which area also has the large neuron cell bodies in?
The Primary cortex
What are the large Primary cortex neurons called? Size? myelin?speed?Target neuron?
Cells of Betz, 60 microns (7 times RBC), heavily myelinated, 70m/s, alpha neuron directly to stimulate muscle. (no interneuron - internuntial)
In total how many fibres descending? How many are Betz?
One million either side (30,000 Betz)
Converge from the corona radiata to be very compact where?
in the posterior limb of the internal capsule.
What problem with the posterior limb of the internal capsule can be seen in the elderly?
Compromise of it's artery the lenticle striate artery.
Blockage causes a massive problem of hemi-plagia (lose contra-lateral sensory and motor control)
From the internal capsule the descent is to?
Substantia nigra of the mid-brain
In the mid brain what is between the tegmentum and the substantia nigra?
Visual spinal reflexes are controlled by?
Spyria colliculus (tectum) ??
The spinal cortical tract crosses where?
Midbrain the crus cerebrai
How many sections does the crus cerebrai have and where do the cortial spinal tract descending fibres cross?
The central 3 of 5 (they are anterior mid brain so damage to the posterior spares these fibres.
What areas of grey matter reside in the pons? Connected with what brain area?
Pontive nucleii linked to the cerebellum
What happens to the cortical spinal tract fibres when it reaches the pons?
They become scattered due to the laterality of the pontive nucleii to the cerbellum.
Damage to the pons causes what extent of damage to the cortical spinal tract and why?
Smaller damage because of the dispersed nature of the tract at this point.
The Medulla has what regions? What happens to the cortical spinal tract as it descends into the medulla from the pons?
Pyramids and Olives, they converge again and compact through the pyramids (the central sections) known now as the pyramidal tract. (lateral damage spares the tract fibres)
What do 90% of the fibres do after the pyramidal tract of medulla?
They cross (major motor crossing- pyramidal dessucation?)
Where do the crossed fibres go (90%)? and the 10% of straight down ones?
Crossed = contra lateral lateral column
uncrossed = anterior column
Do the anterior fibres cross at all? Originated where? Responsible for ?
Yes, at their destination level attach to the medial part of grey matter. Came from supplementary area responsible for axial control (trunk movements)
The many descending fibres (90%) are responsible for what movements?
Fine hand movement .......+
As they leave the cortex what do they do?
Collateral connections Inform neighbouring cells what they are doing.
As they descend through the internal capsule they connect with what? and for what purpose?
Lentiform nucleus (basal ganglia? - have motor plans here)
Collaterally connect with what in the mid brain? Why?
Red nucleus to coordinate the wrist which is essential for hand movement.
Colaterally connecting with the reticular formation does what?
Keeps all the cerebrum alert
The vestibular nuclei do what?
Control the anti gravity muscles
How many levels are there to the cerebellum?