Download Brainstem and Cranial Nerves 3

TSM28: BRAINSTEM AND CRANIAL NERVES 3
10/10/08
BACKGROUND: PEDUNCLES
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Peduncles are ‘stalk-like’ connecting structures joining up parts of the brain
There are three pairs of cerebellar peduncles linking the pons to the cerebellum
o The small inferior cerebellar peduncles arise infero-medially in the caudal pons
o The large middle cerebellar peduncles laterally span the caudal and middle pons
o The superior cerebellar peduncles dorso-medially span the whole of the pons
More rostrally there are cerebral peduncles linking the midbrain to the cerebrum, composed of:
o Cerebral crus – ventro-laterally
o Substantia nigra – more dorso-medially; involved in Parkinson’s disease
o Tegmentum – most dorso-medially; covering the reticular formation
QUESTIONS
1.
Which descending motor pathways are present in the cerebral peduncle?
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2.
Which descending motor pathways are present in the pyramids?
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3.
The reticular formation is a dense region of nuclei and nerve fibres in the central brainstem
throughout the midbrain
Which motor pathways originate in the red nucleus?
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6.
The motor decussation is at the level of the caudal medulla so assuming that the lesion would be
rostral to this you would expect contralateral motor deficits below the neck
Where and what is the reticular formation?
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5.
Corticospinal fibres decussate in the caudal medulla and descend the lateral corticospinal tract
What deficits would be seen with a lesion to the left mid-medullary pyramid?
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4.
Corticospinal fibres descend via the cerebral crus
Corticobulbar fibres descend via the cerebral crus or tegmentum
The red nucleus is found in the reticular formation in the midbrain
The rubrobulbar and rubrospinal tracts originate here which facilitate flexion of the contralateral
upper limb
What are the functions of the superior and inferior colliculi?
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The superior and inferior colliculi are found in the tectum of the midbrain
The inferior colliculus relays neurons involved in the central auditory pathway
The superior colliculus receives input from the retina and gives outputs to visual association
areas
7.
What is the neurotransmitter associated with the substantia nigra?
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Dopamine