Midbrain Flashcards
(28 cards)
Some landmarks for the midbrain on myelin sections include…
- The cerebral aqueduct
- the tectum (sup and inf colliculi, dorsal to the aqueduct)
- The tegmentum (ventral to the aqueduct)
The inferior colliculi are part of the auditory system and _____
The superior colliculi are part of the visual system and are involved in ____
Convey info from the ipsilateral lateral lemniscus (bilateral info) to the MGN via the brachium of the inf colliculus
Vision
The crus cerebri contain axons from the _____. They, along with the ____ and the _____, make up the cerebral peduncles.
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
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
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
The pretectal area, on either side of the posterior commissure…
Computes and controls the total amount of light entering each eye
The rostral end of the mlf is referred to as the ____ because it controls _____
A lesion here would present as….
Interstitial nucleus/nucleus of cajal/ vertical gaze center Vertical gaze (up and down) An inability to look up or down
In the midbrain, the medial lemniscus carries _____ and the anterolateral tract carries ______
Epicritic info for the contralateral side of the body, head to toe
Protopathic info for the contralateral side, head to toe
The decussation of the superior cerebellar peduncle occurs in the ______ midbrain. Axons ______ and head to the _____ or the _____ where they synapse.
Caudal/Middle
leave the cerebellum
contralateral red nucleus or the thalamus
The rubrospinal tract begins at the ____ and travels downward, ending in the _____. It is involved in ____
Red nuclei
Cervical enlargment
Distal fine motor control
The cerebral cortex projects to the red nucleus which then projects to the ____ with info that is destined for the cerebellum via the _____
Inferior olivary complex
ICP
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….
In a red nucleus in the midbrain
Ipsilateral Cr 3 signs
Dysdiadochokinesia, dysmetria, intention tremor (lateral cerebellar deficits)
Nuclei for Cr __ and ___ are in the midbrain. Cr ___ is located more caudally and Cr. ___ is more rostrally
3 and 4
4= caudal
3= rostral
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
Periaqueductal gray
Dorsal
Hypothalamus
Controlling the perception of pain
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…
Dopamine
Striatum
Motor control
Parkinson’s disease
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 ____
reticular formation
thalamus
regulating arousal and the sleep-wake cycle (Ach promotes wakefulness)
Coma
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
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)
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…
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
The midbrain is supplied mainly by the _____ with the tectum receiving some blood from the ____
Posterior cerebral
Superior cerebellar artery
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 ___
Between the sup and inf colliculi
near midline, ventral to the PAG
Conveys auditory info from the inf colliculus to the MGN
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 ____
Ventral to the PAG, dorsal to the MLF, near midline
Cerebral peduncle
Even more laterally
PAG, ventral to the aqueduct
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 ____
Posterior commisure
Pupillary accommodation (i.e. constriction) and convergence
mlf
Mydriasis means…
Miosis means…
Dilation (d) of the pupils
Constriction of the pupils
The only cr that emerge on the ventral aspect of the brainstem are…
Cr 2, 3 and 6
2 x 3 = 6
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
2
Edinger-wesphal nucleus
3 (bilaterally)
