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28 Cards in this Set

  • Front
  • Back

Where do corticospinal tracts arise and which side of the brainstem do they pass?

They arise from neurons in the cerebral cortex.




They pass down the brainstem near its ventral surface(the side of the pons not cerebellum).

What happens to a degenerate corticospinal tract?

It is replaced by astrocytes (glial cells)

Each side of the brain controls the other side of the body. What is this called?

Contralateral control

Upper Midbrain

What level of the midbrain are the red nuclei present at?

Red Nucleus is onlypresent in the midbrain at the level of the superior colliculi.

Where are the corticospinal tracts found at the level of the upper midbrain?

Shown by the 2 red patches (not red circles, these are the red nuclei)

Shown by the 2 red patches (not red circles, these are the red nuclei)

What happens to the superior cerebellar peduncles at the level of the lower midbrain?

They decussate.

What information do corticopontine fibres carry?

Corticopontinefibrestake info from cerebral cortex via the pons to the cerebellum (at least 10x asmany as Corticospinal Tract fibres). These are parts of the cerebral peduncleand crus cerebri that aren’t CST.

At the level of the lower pons, bundles of what are found furthest from the cerebellum?

Bundles of corticospinal fibres

(red) 

Bundles of corticospinal fibres




(red)

Which artery supplies the pons?

Basilar Artery

What happens if a branch of the basilar artery supplying the corticospinal tracts was blocked?

Locked-in Syndrome – meaning they can hear, see, feel (sensory)but cannot move a muscle.

At the level of the open medulla what do the corticospinal tracts form?

They form the pyramids.




Selective damage to the pyramids (rare) tells us about the unique functions of the corticospinal tracts

Name another landmark in the open medulla

Olives

Is the open medulla superior or inferior to the closed medulla?

Superior

What is in the centre of the closed medulla?

The central canal.

What happens at the lowest part of the medulla?

It's where more than a million corticospinal axons cross the midline –Decussation of the pyramids.

There are at least 3 neurons on the pathway from a peripheral receptorto the cerebral cortex; what are they?

1. Primarysensory neurons; have cell bodies in sensory ganglia (e.g. DRG) They carrysensory info to the spinal cord through dorsal roots.


2. Second orderneurons; on same side of the CNS and their axons cross the midline toreach the thalamus.


3. Neurons in thethalamus (third order); send info to the somatosensory cortex.

What does the term "labelled lines" refer to?

Different types of primary afferent axons in peripheral nerves carry different types of sensation.

What are c-Fibres?

C-fibres are associated with nociception. They are thin and unmyelinated (causesslow conduction velocity) and end up in the superficial dorsal horn.

What are Aβ afferents?

Aβ afferents are medium sized and myelinated. They could innervateskin etc. They end in the deep dorsal column.

What are 1a afferents?

Ia afferents (aka primary afferent) with thick myelinated axons are the sensory fibresof stretch receptors aka musclespindles. They monitor the velocity of stretch. End up in the ventral horn.

Describe the spinothalamic tract.

Responsible for pain,temperature and coarse touch information being transmitted from receptors inthe skin up to the thalamus. It is found in the ventral lateral white matter.It is important to note that it decussates in the spinal cord.

Describe the Dorsal Column/Medial Lemniscus

Responsible for light touch, vibrationsensation, conscious proprioception (our position of body in space) anddiscriminative touch. This decussates in the brain not in the spinal cord. Theyascend the dorsal column. The dorsal column nuclei are on the dorsal surface ofthe medulla and this is where the first synapse of the dorsal column pathwayis.

Where are these tracts found in the lumbar cord?

DC/ML Dorsal columns labelled blue. 

Spinothalamic tracts are 2 blue ovals in ventral white matter. 

DC/ML Dorsal columns labelled blue.




Spinothalamic tracts are 2 blue ovals in ventral white matter.

Above the T6 segmentof the cord, the dorsal column splits into 2. What are their names?

Fasciculus gracilisand Fasciculus cuneatus.




The central process of the Aβ fibres travels withinthe FG if it arises from a DRG T7 and below. The central process travels withinFC if it arises from T6 and above. So Gracilis = leg, Cuneatus =arm).

In which part of the brainstem does the Dorsal Column/Medial Lemniscus travel from the dorsal column to the medial lemniscus.

The Upper Medulla.




This is wherethe second order neuron starts.

The PAG is part of what system?

The PAG is part of a descending analgesic system so you can stick electrodes into the PAG and create massive amounts of analgesia (inability to feel pain).

Why are the 2 somatosensory tracts close together in the midbrain?

The 2 somatosensory tracts are close together because they enter thethalamus at very similar places.