midbrain (mesencephalon) Flashcards
what is the tectum and what does it contain?
- it is the “posterior” roof of the midbrain
- it contains the quadrigeminal plate- 4 collicular bodies
what is the cerebral aqueduct of sylvius?
a channel for CSF exchange between the 3rd and 4th ventricles
what surrounds the cerebral aqueduct of slyvius?
periaqueductal gray substance surrounds the aqueduct
what important structures are found in the gray substance of the cerebral aqueduct?
nuclei for CN III and IV are found in or near as well as endorphins and enkephalins
what is ventral to the cerebral aqueduct?
cerebral peduncles
what do the cerebral peduncles contain?
1 tegmentum
2 substantia nigra
3 crus cerebri
which is the smallest of the cranial nerves?
CN VI also called the trochlear nerve
what does CN IV innervate?
superior oblique muscle of the extraocular eye musculature
which cranial nerve travels further inside the cranial vault than any other CN?
CN IV
which nerve is ventral from the interpeduncular fossa with its 6 nuclei located in the periaqueductal gray substance?
CN III also called oculomotor
what are the functions of CN III?
- innervates 4 of the 6 extraocular muscles
- raises upper eyelids
- carries preganglionic parasympathetic axons from accessory oculomotor nucleus to the ciliaris and sphincter pupillae muscles of the eye
what does the superior colliculi deal with?
some visual reflexes
what does the inferior colliculi deal with?
some auditory reflexes
both sets of colliculi use which tract for protective reflexes?
tectospinal tract which allows us to move our head away from loud sounds and objects moving rapidly into our field of vision
which tract influences neurons in the upper cervical through CN XI?
tectospinal tract- contracts SCM and trap muscles to prevent head injury
lesions in colliculi don’t impair voluntary eyes movements only…
perception of motion of objects in the field of vision
where is the tegmentum located?
ventral to the cerebral aqueduct- part of the cerebral peduncles
where is the reticular formation of the midbrain located?
tegmentum
although the red nucleus is primarily found in the midbrain, the superior part extends?
into the diencephalon’s subthalamic region
what are the 2 areas the red nucleus are divided into?
inferior large cell area(magnocellular)
highly vascular superior area (parvocellular)
where do most rubrospinal tract fibers originate?
magnocellular area of the midbrain
where do inputs come to the red nucleus from?
- central cerebellar nuclei (except fastigial)
- cerebral cortex
what is the function of the red nucleus?
contralateral motor responses necessary for postural control and muscle tone primarily in flexor musculature
where is the substantia nigra located?
- btw the tegmentum and crus
- also extends into sub thalamus of the diencephalon
what gives the substantia nigra its black appearance?
- melanin
- secretes dopamine, melanin part of reaction
afferent and efferent fibers of the substantia nigra are exchanged between the telencephalon’s ______ and ______ ______
caudate and putamen nuclei
the caudate and putamen nuclei make up most of what?
corpus striatum or basal ganglia of the cerebrum
what are some symptoms of parkinson’s disease?
shaking of digits, hands and tongue at rest, odd posture, pain, loss of speech
-evidence points to environmental causes only 5% genetic
where is the crus cerebri located?
ventrolateral aspect of the cerebral peduncle
what is the crus cerebri composed of?
DESCENDING pyramidal tracts of fibers from cerebral cortex
what are examples of the descending tracts in crus cerebri?
1 corticospinal fibers-to cord
2 corticopontine fibers- to pons
3 corticobulbar fibers- to MO
4 corticomesencephalic fibers- CN III and IV
magnocellular area
inferior large cell area
parvocellular area
highly vascular superior area
