midbrain (mesencephalon)

Question 1

what is the tectum and what does it contain?

Answer 1

• it is the “posterior” roof of the midbrain

- it contains the quadrigeminal plate- 4 collicular bodies

Question 2

what is the cerebral aqueduct of sylvius?

Answer 2

a channel for CSF exchange between the 3rd and 4th ventricles

Question 3

what surrounds the cerebral aqueduct of slyvius?

Answer 3

periaqueductal gray substance surrounds the aqueduct

Question 4

what important structures are found in the gray substance of the cerebral aqueduct?

Answer 4

nuclei for CN III and IV are found in or near as well as endorphins and enkephalins

Question 5

what is ventral to the cerebral aqueduct?

Answer 5

cerebral peduncles

Question 6

what do the cerebral peduncles contain?

Answer 6

1 tegmentum
2 substantia nigra
3 crus cerebri

Question 7

which is the smallest of the cranial nerves?

Answer 7

CN VI also called the trochlear nerve

Question 8

what does CN IV innervate?

Answer 8

superior oblique muscle of the extraocular eye musculature

Question 9

which cranial nerve travels further inside the cranial vault than any other CN?

Answer 9

CN IV

Question 10

which nerve is ventral from the interpeduncular fossa with its 6 nuclei located in the periaqueductal gray substance?

Answer 10

CN III also called oculomotor

Question 11

what are the functions of CN III?

Answer 11

• 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

Question 12

what does the superior colliculi deal with?

Answer 12

some visual reflexes

Question 13

what does the inferior colliculi deal with?

Answer 13

some auditory reflexes

Question 14

both sets of colliculi use which tract for protective reflexes?

Answer 14

tectospinal tract which allows us to move our head away from loud sounds and objects moving rapidly into our field of vision

Question 15

which tract influences neurons in the upper cervical through CN XI?

Answer 15

tectospinal tract- contracts SCM and trap muscles to prevent head injury

Question 16

lesions in colliculi don’t impair voluntary eyes movements only…

Answer 16

perception of motion of objects in the field of vision

Question 17

where is the tegmentum located?

Answer 17

ventral to the cerebral aqueduct- part of the cerebral peduncles

Question 18

where is the reticular formation of the midbrain located?

Answer 18

tegmentum

Question 19

although the red nucleus is primarily found in the midbrain, the superior part extends?

Answer 19

into the diencephalon’s subthalamic region

Question 20

what are the 2 areas the red nucleus are divided into?

Answer 20

inferior large cell area(magnocellular)

highly vascular superior area (parvocellular)

Question 21

where do most rubrospinal tract fibers originate?

Answer 21

magnocellular area of the midbrain

Question 22

where do inputs come to the red nucleus from?

Answer 22

• central cerebellar nuclei (except fastigial)

- cerebral cortex

Question 23

what is the function of the red nucleus?

Answer 23

contralateral motor responses necessary for postural control and muscle tone primarily in flexor musculature

Question 24

where is the substantia nigra located?

Answer 24

• btw the tegmentum and crus

- also extends into sub thalamus of the diencephalon

Question 25

what gives the substantia nigra its black appearance?

Answer 25

• melanin

- secretes dopamine, melanin part of reaction

Question 26

afferent and efferent fibers of the substantia nigra are exchanged between the telencephalon’s ______ and ______ ______

Answer 26

caudate and putamen nuclei

Question 27

the caudate and putamen nuclei make up most of what?

Answer 27

corpus striatum or basal ganglia of the cerebrum

Question 28

what are some symptoms of parkinson’s disease?

Answer 28

shaking of digits, hands and tongue at rest, odd posture, pain, loss of speech
-evidence points to environmental causes only 5% genetic

Question 29

where is the crus cerebri located?

Answer 29

ventrolateral aspect of the cerebral peduncle

Question 30

what is the crus cerebri composed of?

Answer 30

DESCENDING pyramidal tracts of fibers from cerebral cortex

Question 31

what are examples of the descending tracts in crus cerebri?

Answer 31

1 corticospinal fibers-to cord
2 corticopontine fibers- to pons
3 corticobulbar fibers- to MO
4 corticomesencephalic fibers- CN III and IV

Question 32

magnocellular area

Answer 32

inferior large cell area

Question 33

parvocellular area

Answer 33

highly vascular superior area