Unit VI Midbrain (Final Exam)

Where is the tectum of the midbrain located in relation to the cerebral aqueduct?

posterior to cerebral aqueduct

What is the tectum composed of and what does that include?

Quadrigeminal plate; 2 superior and 2 inferior colliculi

Which ventricles does the cerebral aqueduct connect?

Third and fourth

What surrounds the cerebral aqueduct?

periaqueductal gray matter

The nuclei of which cranial nerves are found in/near the periaqueductal gray matter of the tegmentum?

III and IV

Where are the cerebral peduncles located in relation to the cerebral aqueduct?

Ventral to the cerebral aqueduct

Which structures are included in the cerebral peduncles?

Tegmentum, substantia nigra, crus cerebri

What are the four unique characteristics of CN IV?

1) smallest

2) origin on posterior brain stem

3) crossing fibers

4) travels the furthest inside cranial vault

What is another name for CN IV?

Trochlear

Which muscle does CN IV innervate?

superior oblique

What is the origin of CN IV?

Inferior to inferior colliculus on posterior brain stem

What is another name for CN III?

Oculomotor

What is the origin of CN III?

Ventral from interpeduncular fossa

Where are the six nuclei of origin for CN III located?

Periaqueductal gray matter

What reflexes does the superior colliculi deal with?

Visual

What reflexes does the inferior colliculi deal with?

Auditory

What type of tracts do the superior and inferior colliculi use? Which CN does this influence? Which muscles?

Tectospinal; XI; trapezius and SCM

What would a lesion in the tectum impair?

Perception of motion of objects in visual field

Which route will our normal hearing input take?

Lateral lemniscus, medial geniculate body, temporal lobe

Which route do our R hearing reflexes take?

R Lateral lemniscus, R inferior colliculus, R superior colliculus, R tectospinal tract to cross and influence L trapezius and SCM

Which route will our normal sight input take?

Optic tract, lateral geniculate body, occipital lobe

Which route do our R motion (sight) reflexes take?

R Optic tract, SKIP LGB/THALAMUS, R superior colliculus, R tectospinal tract to cross and influence L trapezius and SCM

Which part of the cerebral peduncles is the red nucleus located?

Tegmentum

Which part of the red nucleus does the rubrospinal tract originate?

Magnocellular

Which part of the red nucleus is highly vascular?

Parvocellular

Which structures of the cerebral peduncles extend into the subthalamic region of the diencephalon?

Parvocellular red nucleus and substantia nigra

Where does the red nucleus receive input from?

Central cerebellar nuclei (globose, emboliform, some dentate) and cerebral cortex

What does the red nucleus (rubrospinal tract) have influence over?

Flexor musculature

Where is substantia nigra located?

Between tegmentum and crus cerebri

What makes the substantia nigra black?

Melanin

What does substantia nigra secrete?

Dopamine

What stores dopamine?

Caudate and putamen nuclie

Via which nuclei do the afferent and efferent fibers of the substantia nigra communicate?

Caudate and putamen

What is most likely damaged with Parkinson's?

Substantia nigra not secreting enough dopamine

Where is the crus cerebri located?

Ventrolateral aspect of the cerebral peduncle

What type of tracts dominate the crus cerebri? What do they influence?

Descending pyramidal, cortico-; skilled voluntary movement