Midbrain - more detail

Question 1

locus ceruleus - location, function?

Answer 1

• rostral pons at midbrain junction
• medial

-supplies entire CNS with noradrenergics –> attention, vigilance

Question 2

trochlear nucleus - location, function?

Answer 2

• caudal 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

Question 3

occulomotor nucleus - location, function?

Answer 3

• caudal midbrain
• medial

-innervates levator palpebrae superioris, inf./sup./medial rectus, inf oblique (somatic motor)

Lesion:

• lateral gaze (MLF)
• ptosis

Question 4

Edinger-Westphal Nucleus

Answer 4

• caudal midbrain
• medial
• parasympathetic preganglionic cells
• innervates sphincter pupillae, ciliary muscle (visceral motor)

Lesion:
-dilated pupil, unresponsive to light

Question 5

nigra striata

Answer 5

• rostral midbrain
• lateral
• contains dopamine neurons
• lose 80% = Parkinson’s Disease

Question 6

reticular formation in midbrain

Answer 6

• reticular activating system: arousal/consciousness

- descending pain pathways

Question 7

axons of reticular formation

Answer 7

• gigantocellular neurons
• highly bifurcating
• goes throughout entire NS
• integrates

Question 8

raphe nuclei

Answer 8

• in all levels of brainstem
• along midline/”seam”
• produce serotonin
• serotonin projects to all CNS

-involved in descending pain pathways, arousal

Question 9

coma is caused by

Answer 9

-dysfunction of upper brainstem reticular formation
OR
-dysfunction of extensive bilateral regions of cerebral cortex

Question 10

reticular activating system

Answer 10

pons –> thalamus –> cortex all over

• arousal
• essential for consciousness

Question 11

descending motor pathways

Answer 11

• originate in reticular formation in brainstem
• target lower motor neurons
• can take over corticospinal pathway if damaged
• decerebrated cat can still run on treadmill

Question 12

descending pain pathways

Answer 12

• receive input from hypothalamus
• supresses spinothalamic pathway
• stimulation: stop pain from reaching consciousness

periaquductal gray –> [raphe nucleus] –> [spinal cord] –> suppress spinothalamic neurons

Question 13

periaqueductal gray contains lots of __________ receptors

Answer 13

periaqueductal gray contains lots of OPIATE receptors

-target for pain drugs

Question 14

where does the descending pain pathway synapse?

Answer 14

raphe nuclei

Question 15

mesencephalic nucleus - location, function?

Answer 15

• midbrain
• cannot see it

moderates muscles of mastication

Question 16

inferior colliculus

Answer 16

-part of hearing pathway

IC –> thalamus –> auditory cortex

Question 17

relative location of trochlear nucleus in relation to MLF

Answer 17

trochlear nucleus sits in/above MLF

Question 18

tectum

Answer 18

• above the cerebral aqueduct
• top of brainstem
• has superior/inferior colliculi

Question 19

what is the only cranial nerve that exits on the dorsal side?

Answer 19

CN IV

Question 20

superior colliculus

Answer 20

• auxillary vision in humans
• input from retina
• orient head/eyes to light/sound

-NOT part of primary visual system

Question 21

red nucleus

Answer 21

• target for fibers exiting cerebellum
• start of rubrospinal pathway
• influences LMNs

Question 22

substantia nigra

Answer 22

• dopinergic neurons located here

- supplies DA to basal ganglion

Question 23

MLF connects ______ and _____

Answer 23

MLF connects VI and III

Question 24

mesolimbic/mesocortical pathways

Answer 24

involved in addiction pathways

Question 25

symptoms of Parkinson’s disease occurs when ~__% of _________ producing cells are damaged

Answer 25

symptoms of Parkinson’s disease occurs when ~80% of DOPAMINE producing cells are damaged

Question 26

medial midbrain syndrome - what structures affected?

Answer 26

CST/CBT: contralateral deficits

CN III: dilated pupil, ptosis, lateral gaze (all ipsilateral)