Midbrain - more detail Flashcards
locus ceruleus - location, function?
- rostral pons at midbrain junction
- medial
-supplies entire CNS with noradrenergics (NE) –> attention, vigilance
trochlear nucleus - location, function?
- rostral midbrain
- medial
- only nerve that exits dorsally
-innervates superior oblique (somatic motor)
Lesion:
- no dramatic loss
- may have trouble descending stairs
- may have slight diplopia while reading
occulomotor nucleus - location, function?
- rostral midbrain
- medial
-innervates levator palpebrae superioris, inf./sup./medial rectus, inf oblique (somatic motor)
Lesion:
- lateral gaze (MLF)
- ptosis
Edinger-Westphal Nucleus
- rostral midbrain
- medial
- parasympathetic preganglionic cells
- innervates sphincter pupillae, ciliary muscle (visceral motor)
Lesion:
-dilated pupil, unresponsive to light
nigra striata
- rostral midbrain
- lateral
- contains dopamine neurons
- lose 80% = Parkinson’s Disease
reticular formation in midbrain
- reticular activating system: arousal/consciousness
- descending pain pathways
axons of reticular formation
- gigantocellular neurons
- highly bifurcating
- goes throughout entire NS
- involved in modulating the level of neural activity in the cerebral cortex
raphe nuclei
- in all levels of brainstem
- along midline/”seam”
- produce serotonin
- serotonin projects to all CNS
-involved in descending pain pathways, arousal
coma is caused by
-dysfunction of upper brainstem reticular formation
OR
-dysfunction of extensive bilateral regions of cerebral cortex
reticular activating system
pons –> thalamus –> cortex all over
- arousal
- essential for consciousness
descending motor pathways
- originate in reticular formation in brainstem
- target lower motor neurons
- can take over corticospinal pathway if damaged
- decerebrated cat can still run on treadmill
descending pain pathways
- receive input from hypothalamus
- supresses spinothalamic pathway
- stimulation: stop pain from reaching consciousness
periaquductal gray –> [raphe nucleus] –> [spinal cord] –> suppress spinothalamic neurons
periaqueductal gray contains lots of __________ receptors
periaqueductal gray contains lots of OPIATE receptors
-target for pain drugs
where does the descending pain pathway synapse?
raphe nuclei
mesencephalic nucleus - location, function?
- midbrain
- cannot see it
moderates muscles of mastication
inferior colliculus
-part of hearing pathway
IC –> thalamus –> auditory cortex
relative location of trochlear nucleus in relation to MLF
trochlear nucleus sits in/above MLF
tectum
- above the cerebral aqueduct
- top of brainstem
- has superior/inferior colliculi
what is the only cranial nerve that exits on the dorsal side?
CN IV
superior colliculus
- auxillary vision in humans
- input from retina
- orient head/eyes to light/sound
-NOT part of primary visual system
red nucleus
- motor coordination
- target for fibers exiting cerebellum
- start of rubrospinal pathway
- influences LMNs
substantia nigra
- dopinergic neurons located here
- supplies DA to basal ganglion
MLF connects ______ and _____
MLF connects VI and III
mesolimbic/mesocortical pathways
involved in addiction pathways
symptoms of Parkinson’s disease occurs when ~__% of _________ producing cells are damaged
symptoms of Parkinson’s disease occurs when ~80% of DOPAMINE producing cells are damaged
medial midbrain syndrome - what structures affected?
CST/CBT: contralateral deficits
CN III: dilated pupil, ptosis, lateral gaze (all ipsilateral)
