intro to brainstem

Question 1

The cerebellum is attached to the brainstem by what?

Answer 1

peduncles: inferior, middle and superior

Question 2

function of inferior cerebellar peduncle

Answer 2

conveys spinal cord information to the cerebellum and interconnects the cerebellum
with the vestibular nuc. and inferior oliveconveys spinal cord information to the cerebellum and interconnects the cerebellum
with the vestibular nuc. and inferior olive

Question 3

function of middle cerebellar peduncle

Answer 3

route by which information from the cerebral cortex gets to the cerebellum via the pontine nuclei

Question 4

function of superior cerebellar peduncle

Answer 4

route by which the cerebellum gets information back to the cerebral cortex (via the thalamus).

Question 5

1. Locate and identify the attachment points of all the brainstem cranial nerves (CNIII – CNXII) {Fig. 2-17 to Fig. 2-22}

Answer 5

ok

Question 6

Describe how the brainstem is divided into sensory and motor regions/ visceral and non visceral regions

Answer 6

The alar plate is located laterally and contains sensory nuclei and the basal plate is located medially and contains motor nuclei. These two plates are separated by the sulcus limitans. Additionally, within each plate, there is a visceral portion closest to the sulcans limitans and a non visceral portion farthest away from the sulcans.

Question 7

What is the reticular formation

Answer 7

the core of the brainstem - performs diffuse functions such as keeping you awake and breathing

Question 8

What do nuclei in the somatic motor zone innervate?

Answer 8

aka near midline in basal plate: They innervate extraocular muscles (III, IV, VI) or tongue (XII)

Question 9

What is the medial longitudinal fasciculus

Answer 9

tract of the pons and upper medulla that connects motorneurons for extraocular muscles.

Question 10

List the branches of the trigeminal nerve and their general functioins

Answer 10

ophthalmic: somatosensory. Maxillary: somatosensory. Mandibular: somatosensory and motor

Question 11

where is the trigeminal nucleus?

Answer 11

There are two: trigeminal motor nucleus(aka spinal/descending trigeminal nucleus) and the principal (main) sensory nucleus. Both are in the midpons. Mesencephalic is a third nucleus with little importance

Question 12

What kind of info does the principal sensory nucleus deal with and where do axons project from it

Answer 12

touch, vibration and position (analogous to dorsal column). Projects to the VPL in the contralateral thalamus

Question 13

Where do the C and Ad fibers of trigeminal nerve project to

Answer 13

They turn caudally after entering the brainstem to form the descending root of the trigeminal nerve which terminate at the spinal trigeminal nucleus (which extends from the pons to the spinal cord). Carries pain and temp info

Question 14

functions of lower and upper spinal trigeminal nucleus

Answer 14

lower: deals with pain and temp info (like the substantia gelatinosa of the spinal cord) Upper: trigeminally mediated reflexes (ie. Eye blink reflex)

Question 15

What/where is the mesencephalic nucleus- what does it do and what happens if it is severed

Answer 15

This is a trigeminal nucleus that exists in the brainstem (pons) as a result of neural crest cells which become trapped in the brain during embryogenesis. It has one process that extends peripherally to proprioceptors of gums or jaw and a central process that terminates in the main sensory trigeminal nucleus. There are no deficits if it is severed

Question 16

Which nuclei are in the branchiomotor nuclei group and what do they have in common

Answer 16

trigeminal motor nucleus, the facial (motor) nucleus and the nuc. ambiguus. What these have in common is that they innervate striate muscles derived from the branchial mesenchyme (of neural crest origin). (6-2)

Question 17

Which nuclei are in the viscerosensory and autonomic nuclei

Answer 17

solitary nuc. and solitary tr. and the preganglionic
parasympathetic nuclei: dorsal motor nuc. of the vagus, superior and inferior salivatory nuc., and the Edinger-Westphal nuc., part of the oculomotor nuc.

Question 18

What is the function of the dorsal motor nucleus of the vagus and where is it located

Answer 18

located in medulla (dosrally). Contains preganglionic parasympathetic neurons of the vagus nerve

Question 19

where is the hypoglossal nucleus and what is its function

Answer 19

in medulla next to the dorsal motor nucleus of vagus and nucleus of solitary tract. Contains motor neurons that innervate the tongue.

Question 20

Where is the nucleus of the solitary tract and what does it do

Answer 20

in medulla next to hypoglossal nucleus and dorsal motor nucleus of vagus. visceral sensory nucleus; farther rostrally, it would also deal with taste information

Question 21

Which nuclei are included in the auditory system nuclei

Answer 21

including the cochlear nuc. and the ascending relay nuclei for audition including: Trapezoid body, superior olive, lateral lemniscus, inferior colliculus and medial geniculate nuc.

Question 22

Which nuclei are in the vestibular system and what do they do

Answer 22

vestibular nuclear complex- connect with motorneurons via the MLF to innervate the extraocular muscles and vestibular nuclei send long descending axons to the spinal cord to trigger postural reflexes to changes in perceived direction of gravity.

Question 23

where is the cochlear nucelus located

Answer 23

medulla

Question 24

list the cerebellum associated tracts and nuclei

Answer 24

pontine nuclei, inferior olivary nuc. (= Principal olivary nuc.), red nuc., and superior cerebellar peduncle

Question 25

Where is the dentate nucleus and what does it do

Answer 25

squiggly lines in the cerebellum- send axons out the superior cerebellar peduncle to end in the contralateral VA/VL nucleus of the thalamus

Question 26

Where is the vestibular nucleus located

Answer 26

medulla- just medial to the inferior cerebellar peduncle

Question 27

where is the middle cerebellar peduncle and where do its fibers originate

Answer 27

pons- axons from the contralateral pontine nuclei project to the deep cerebellar nuclei and to granule cells of the cerebellar cortex through the midde cerebellar peduncle

Question 28

where is the facialnucleus, what is its function, route of axons

Answer 28

innervates muscles of facial expression. Axons go up towards abducens, around in front of abducens then back past the facial nucleus to exit the brainstem

Question 29

where is the abducens nucleus and where do fibers project

Answer 29

pons- motor neurons and interneurons that project via the MLF to nuc III and innervate the lateral rectus

Question 30

Where is the superior olivary nucleus, function and fiber paths

Answer 30

auditory- input from both ipsilateral and contralateral cochlear nucleus. Projects to inferior colliculus

Question 31

2. Locate and identify the following features on the intact brainstem: approximate dividing lines between medulla, pons and midbrain; optic chiasm, mammillary body, superior and inferior colliculi; crus cerebri (cerebral peduncle), basal pons, superior, middle and inferior cerebellar peduncles, pyramid and olive. {Figs. 2-17, 2-20, 2-21; 2-31; 2-33}

Answer 31

ok

Question 32

What symptoms occur when the pyramidal tract is cut, where do these tracts cross midline? Where are they located throughout the brainstem

Answer 32

spastic paralysis- located anteriorly in medulla/ pons, then anterior-lateral in midbrain. Fibers cross at the pyramidal decussation in the medulla

Question 33

What symptoms occur when the anterolateral/ spinothalamic tract is cut- where do these tracts cross midline?

Answer 33

loss of pain and temperature- tracts are located laterally in medulla, lateral and more posterior in pons, then even more posterior in the midbrain. The fibers cross in spinal cord at the level of enrty

Question 34

What symptoms occur when the dorsal column/medial lemniscus tract is cut, where do these tracts cross midline?

Answer 34

loss of 2-pt discrimination, fine touch, and concious proprioception. Tracts are located dorsally until mid-medulla, then they cross as the internal arcuate in the medulla are located medially as the medial lemniscus in the medulla, cental but more lateral in the pons, anterior/lateral in the midbrain

Question 35

What symptoms occur when the spinal trigeminal tract and nucleus is cut, where do these tracts cross midline?

Answer 35

loss of pain and temp for the head. Tract fibers are located just dorsal to the anterolateral tract in the medulla (dorso-lateral), CNV is located btw the pons and the medulla, the fibers become the trigeminothalamic tract just dorsal to the medial lemniscus in the pons and midbrain

Question 36

damage to the brainstem and cerebellum show up on which side of the body

Answer 36

ipsilateral side (as opposed to the cerebrum)

Question 37

Where is the inferior olive located and what fibers does it carry

Answer 37

in the medulla (anterior)- squiggly lines. These cells project via the contralateral inferior cerebellar peduncle to the cerebellar cortex where they end as climbing fibers.

Question 38

Give location of cell bodies of origin and destination of fibers from the pyramids

Answer 38

originates from ipsilateral motor and premotor cortex; terminates in the contralateral spinal cord

Question 39

Give location of cell bodies of origin and destination of fibers from the medial lemniscus

Answer 39

originates from the contralateral nuc. gracilis and cuneatus; terminates in the ipsilateral VPL.

Question 40

Give location of cell bodies of origin and destination of fibers from the inferior cerebellar peduncle

Answer 40

originates from the contralateral inferior olive and from neurons of the ipsilateral Clarke’s column (spiinocerebellar tr.). More rostrally, the peduncle also will contain fibers from the ipsilateral vestibular nerve and nuclei. These axons end in the ipsilateral cerebellum.