Midbrain

Question 1

Some landmarks for the midbrain on myelin sections include…

Answer 1

• The cerebral aqueduct
• the tectum (sup and inf colliculi, dorsal to the aqueduct)
• The tegmentum (ventral to the aqueduct)

Question 2

The inferior colliculi are part of the auditory system and _____
The superior colliculi are part of the visual system and are involved in ____

Answer 2

Convey info from the ipsilateral lateral lemniscus (bilateral info) to the MGN via the brachium of the inf colliculus
Vision

Question 3

The crus cerebri contain axons from the _____. They, along with the ____ and the _____, make up the cerebral peduncles.

Answer 3

Descending motor axons from the cortex (corticospinal tract, corticobulbar tract, corticopontine tract- UMNs of the brainstem-spinal tracts)
the substantial nigra and the red nuclei

Question 4

The ____ is the boundary b/wn the midbrain and the diencephalon. The pineal body is in close proximity and a tumor here may present as

Answer 4

posterior commisure (impt in the pupillary light reflex)
A paralysis of upward eye mvts and fixed, dilated pupils (no pupillary light reflex), possible hydrocephalus if cerebral aqueduct is obstructed

Question 5

The pretectal area, on either side of the posterior commissure…

Answer 5

Computes and controls the total amount of light entering each eye

Question 6

The rostral end of the mlf is referred to as the ____ because it controls _____
A lesion here would present as….

Answer 6

Interstitial nucleus/nucleus of cajal/ vertical gaze center
Vertical gaze (up and down)
An inability to look up or down

Question 7

In the midbrain, the medial lemniscus carries _____ and the anterolateral tract carries ______

Answer 7

Epicritic info for the contralateral side of the body, head to toe
Protopathic info for the contralateral side, head to toe

Question 8

The decussation of the superior cerebellar peduncle occurs in the ______ midbrain. Axons ______ and head to the _____ or the _____ where they synapse.

Answer 8

Caudal/Middle
leave the cerebellum
contralateral red nucleus or the thalamus

Question 9

The rubrospinal tract begins at the ____ and travels downward, ending in the _____. It is involved in ____

Answer 9

Red nuclei
Cervical enlargment
Distal fine motor control

Question 10

The cerebral cortex projects to the red nucleus which then projects to the ____ with info that is destined for the cerebellum via the _____

Answer 10

Inferior olivary complex

ICP

Question 11

The only place in the brain where you can have a lesion that gives you contralateral cerebellar signs is….
This would also present with ____ and the cerebellar signs present are….

Answer 11

In a red nucleus in the midbrain
Ipsilateral Cr 3 signs
Dysdiadochokinesia, dysmetria, intention tremor (lateral cerebellar deficits)

Question 12

Nuclei for Cr __ and ___ are in the midbrain. Cr ___ is located more caudally and Cr. ___ is more rostrally

Answer 12

3 and 4
4= caudal
3= rostral

Question 13

The ____ surrounds the cerebral aqueduct and is ___ to the cranial nerve nuclei. It receives input from the ____ and is important in ____ thus it receives projections from the ALS

Answer 13

Periaqueductal gray
Dorsal
Hypothalamus
Controlling the perception of pain

Question 14

The substantia nigra appears black because the neurons that produce ____ also produce melanin. These neurons project to the ___ and are involved in ____ via the basal ganglia system. A lesion here would cause…

Answer 14

Dopamine
Striatum
Motor control
Parkinson’s disease

Question 15

Cholinergic neurons at the pons-medulla junction project to the ____ (descending) and the _____ (ascending). These projections are impt for the ____. A lesion here can cause ____

Answer 15

reticular formation
thalamus
regulating arousal and the sleep-wake cycle (Ach promotes wakefulness)
Coma

Question 16

Cr 4 is the only Cr nerve to ____. It innervates the _____ of the eye. It is located _____ on a caudal midbrain myelin. A lesion here will affect ___ and may cause diplopia

Answer 16

originate on the dorsal aspect of the brainstem
Superior oblique muscle
Lateral to the mlf and ventral to the PAG
The ability to look down (esp from a nasal position)

Question 17

Cr 3 contains _____ and _____ fibers. It controls _________ muscles of the eye and the _____ as well. It is involved in both the ___ and ____ reflexes. A lesion here would present as…

Answer 17

Somatic motor and prarasympathetic fibers
Medial, superior and inferior rectus and inferior oblique and levator palpebrae
Convergence and accommodation reflexes via the parasymps
A down and out eye with a droopy eyelid (ptosis), dilated pupil, and no response to light shined in either eye

Question 18

The midbrain is supplied mainly by the _____ with the tectum receiving some blood from the ____

Answer 18

Posterior cerebral

Superior cerebellar artery

Question 19

The middle midbrain is the area _____. In a myelin section here, you can see Cr 4 which is located ____ and the brachium of the inferior colliculus which ___

Answer 19

Between the sup and inf colliculi
near midline, ventral to the PAG
Conveys auditory info from the inf colliculus to the MGN

Question 20

In a myelin section of the rostral midbrain, you can see the Cr. 3 nucleus located _____ and its fibers which exit the brainstem at the level of the ____. The ALS is located ____ as it approaches the VPL/VPM of the thalamus. And the raphe nucleus can be seen in the ____

Answer 20

Ventral to the PAG, dorsal to the MLF, near midline
Cerebral peduncle
Even more laterally
PAG, ventral to the aqueduct

Question 21

in the rostral-most midbrain, the pretectal areas (connected by the ____) are visible. Each one contains an edinger-westphal nucleus which is important in _____. The vertical gaze center is also located here, at the rostral end of the ____

Answer 21

Posterior commisure
Pupillary accommodation (i.e. constriction) and convergence
mlf

Question 22

Mydriasis means…

Miosis means…

Answer 22

Dilation (d) of the pupils

Constriction of the pupils

Question 23

The only cr that emerge on the ventral aspect of the brainstem are…

Answer 23

Cr 2, 3 and 6

2 x 3 = 6

Question 24

In the pupillary light reflex, Cr ____ is the afferent branch. Once light hits the cornea, it conveys this signal to the ____ which then activates the efferent limb, Cr. _____, which causes the sphincter muscles in both eyes to contract, constricting the pupil

Answer 24

2
Edinger-wesphal nucleus
3 (bilaterally)

Question 25

The rostral part of the mlf is the _____ aka the vertical gaze center. This functions to ______. Axons from here travel through the ____ to the ____ to innervate this Cr nerve

Answer 25

interstitial nucleus (of Cajal)
Coordinate conjugate vertical gaze
posterior commisure
contralateral Cr 3 nucleus

Question 26

Increased intracranial pressure such as that from noncommunicating hydrocephalus or a tumor presents with what general symptoms?

Answer 26

Papilledema, headaches, vomiting

Question 27

The ONLY place where a lesion can give you crossed cerebellar signs is the ___ because…

Answer 27

Red nucleus
Cerebellar outflow goes through the superior cerebellar peduncle, which decussates in the middle midbrain and send fibers to the contralateral red nucleus (i.e. a lesion would give contralateral cerebellar signs)

Question 28

A lesion to the edinger-wesphal nucleus would cause…

Answer 28

a dilated pupil, loss of accommodation (problem with parasympathetic innervation of the eye)