Midbrain Anatomy Flashcards

1
Q

Tectum, Tegmentum, and Crus cerebri. Which is where?

A
  • Tectum = dorsal
  • Tegmentum = central
  • crus cerebri = ventral
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2
Q

What is contained in the Tectum?

A

-2 superior and 2 inferior colliculi

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3
Q

What is contained in the Tegmentum?

A
  • Cerebral aqueduct & PAG
  • Red nucleus
  • decussation of superior cerebellar peduncles
  • Substantia nigra (separates tegmentum from the crus cerebri)
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4
Q

What is contained in the crus cerebri?

A

-mostly corticobulbar and corticospinal pathways

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5
Q

What does the substantia nigra divide?

A

-tegmentum and crus cerebri

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6
Q

What are the nuclei of the midbrain separated by colliculus level?

A

Superior colliculus:

  • Red nucleus
  • CN III nucleus

Inferior colliculus:

  • Substantia nigra
  • CN IV nucleus
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7
Q

Where do CN IV fibers leave the midbrain?

A
  • dorsal aspect

- just inferior to inferior colliculus

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8
Q

Where do CN III fibers leave the midbrain?

A
  • ventral aspect

- just medial to crus cerebri

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9
Q

What role does the periaqueductal grey play?

A

-rich in enkephalins for modulation of autonomics and pain

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10
Q

What is contained within the medial longitudinal fasciculus?

A
  • feeds from vestibular nuclei to nucleus of III, IV, and VI
  • think eye movement

(white matter)

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11
Q

What is contained in the central tegmental area of the midbrain?

A

-reticular formation

=serotonin fibers which regulate wakefulness

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12
Q

Where is the location of the decussation of the superior cerebella peduncle?

A

-level of inferior colliculus in midbrain

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13
Q

What runs in the crus cerebri (cerebral peduncle) from medial to lateral?

A

Medial 1/5 = frontopontine fibers

Middle 3/5 = corticobulbar (med) and corticospinal (lat) fibers

Lateral 1/5 = parietal, occipital, and temporal lobes to pontine nuclei

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14
Q

What are the two parts of the substantia nigra?

A
  • pars compacta (medially)

- Pars reticulata (laterally)

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15
Q

What is contained in the two parts of the substantia nigra?

A

Pars compacta = dopamine fibers to basal ganglia – important in Parkinson’s disease

Pars reticulata = GABA fibers to thalamus

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16
Q

You’re at red nucleus. Are you on level of superior or inferior colliculus?

A

Superior colliculus

17
Q

Match visual and auditory pathways to sup/inf colliculus.

A

Visual = superior colliculus

Auditory = inferior colliculus

18
Q

What is the VTA?

A

Important source of DA fibers to forebrain

19
Q

What fibers is the red nucleus receiving?

A

-fibers from superior cerebellar peduncle

20
Q

Where to efferent fibers from the red nucleus go?

A
  • flexor musculature

- inferior olivary nucleus

21
Q

What is contained in the Edinger Westphal nucleus?

A

-presynaptic parasympathetic fibers of III to ciliary ganglion for pupillary constriction of pupillary light reflex as well as accommodation for near vision.

22
Q

What is the posterior commissure important for?

A

-coordinated movement of both eyes

23
Q

What is just dorsal to the medial longitudinal fasciculus?

A

-Nucleus of CN III

24
Q

What is Weber’s syndrome?

A
  • ipsilateral oculomotor paralysis with contralateral upper motor neuron lesion.
  • Results from vascular insufficiency in medial aspect of midbrain at level of superior colliculus.
25
Q

What is Benedikt’s syndrome?

A
  • ipsilateral III paralysis with contralateral tremor and possible contralateral somatosensory loss
  • Vascular lesion to III and red nucleus and superior cerebellar peduncle and medial lemniscus (dorsal columns) and possible spinothalamic tract
26
Q

What is Gaze palsy (Parinaud’s syndrome)?

A

-upward gaze paralysis – vertical gaze – large pupil and abnormal elevation of upper eyelid, and paralysis of accommodation

from pineal tumor which affects pretectal area and posterior commissure