Neuroscience Week 5: The Pons

Question 1

The pontine basis comprises

Answer 1

• Pontine nuclei
• Pontocerebellar fiber tracts cross the pons and pass into the middle cerebellar peduncle as an important step in the corticopontocerebellar pathway. Clinical Correlation: central pontine myelinolysis
• Corticonuclear (aka corticobulbar) tracts
• Corticospinal tracts (lateral to them)
• The middle cerebellar peduncle (aka brachium pontis) in the dorsal pons.
• The pontine nuclei project pontocerebellar fibers via the middle cerebellar peduncle as part of the corticopontocerebellar pathway.
• The inferior cerebellar peduncle.
• The superior cerebellar peduncle (aka brachium conjunctivum).
• -The middle and inferior cerebellar peduncles are the main inflow pathwaysinto the cerebellum and that the superior cerebellar peduncle is the main outflow pathway from the cerebellum.

Question 2

Pontocerebellar fiber tracts cross the pons and pass into?

Answer 2

middle cerebellar peduncle as an important step in the corticopontocerebellar pathway.

Question 3

central pontine myelinolysis

Answer 3

• Central pontine myelinolysis (CPM) was first described in 1959 in alcoholics and the malnourished and later determined to be due to a rapid correction of sodium in hyponatremic patients.
• In short: if the rate of rise of tonicity (from correction of hyponatremia) is too fast, the cell will shrink, and oligodendrocytes are vulnerable to cell death.
• The pons has a great deal of white matter and thus the disorder localizes foremost to the pons, but, as expected, it encompasses other areas, as well, thus the disorder now describes both central & extra-pontine myelinolysis.

Question 4

The pontine nuclei project pontocerebellar fibers via the

Answer 4

middle cerebellar peduncle as part of the corticopontocerebellar pathway.

Question 5

The middle and inferior cerebellar peduncles are the main

Answer 5

inflow pathways into the cerebellum and that the superior cerebellar peduncle is the main outflow pathway from the cerebellum.

Question 6

The inferior cerebellar peduncle comprises the

Answer 6

restiform and juxtarestiform bodies

Question 7

Spinocerebellar, reticulocerebellar, and olivocerebellar fibers pass through the

Answer 7

restiform body, whereas the juxtarestiform body primarily comprises fibers that pass between the vestibular nucleus and vestibulocerebellum.

Question 8

The superior cerebellar peduncles attach to the

Answer 8

upper pons and midbrain; the middle cerebellar peduncle attaches to the pons and extends to the pontomedullary junction; and the inferior cerebellar peduncle attaches to the lower pons and medulla.

Question 9

In the Pons The medial lemniscus lies _________

Answer 9

Medially, (unlike in the midbrain, where the red nuclei push the medial lemniscus out laterally).

Question 10

In the pons The spinothalamic tract lies lateral to

Answer 10

The medial lemniscus

Question 11

In the pons The anterior trigeminothalamic tract (TTT) lies along the

Answer 11

posterior wall of the medial lemniscus

Question 12

In the Pons Anterior spinocerebellar tract lies

Answer 12

far lateral from posterior wall of the medial lemniscus

Question 13

The medial longitudinal fasciculus descends through the

Answer 13

dorsal midline tegmentum (as it does throughout the brainstem)

Question 14

The locus coeruleus lies in

Answer 14

the posterior tegmentum.

Question 15

Locus coeruleus nuclei are most heavily concentrated in the

Answer 15

pons and are concentrated most significantly with noradrenalin (aka norepinephrine)

Question 16

Given their noradrenergic make-up and widespread connections, the locus coeruleus most likely plays a role in

Answer 16

attention and arousal.

Question 17

Note that although most heavily concentrated in the pons, the locus coeruleus actually spans from the

Answer 17

caudal end of the periaqueductal gray area in the lower midbrain to the facial nucleus in the mid-pons.

Question 18

The reticular formation most notably functions in

Answer 18

• wakefulness. It divides into lateral, medial, and median zones. The raphe nuclei populate the median zone.
• They are primarily serotinergic and are modulated by psychotropic medications.

Question 19

CRANIAL NERVE NUCLEI Medially, the motor nuclei:

Answer 19

• In midline, the abducens nucleus of CN 6.
• Lateral to it, the motor trigeminal nucleus of CN 5.
• The facial nucleus of CN 7.
• The superior salivatory nucleus of CN 7.

Question 20

CRANIAL NERVE NUCLEI Laterally, the sensory nuclei:

Answer 20

The principal sensory nucleus of CN 5.

The vestibulocochlear nucleus of CN 8.

Question 21

The tectospinal tract continues to descend through the

Answer 21

dorsal midline tegmentum; it produces contralateral head turn

Question 22

The tectospinal tract originates in the

Answer 22

superior colliculus of the midbrain, decussates in the dorsal midbrain tegmentum, and innervates the upper cervical spinal segments

Question 23

The central tegmental tract descends through the

Answer 23

• dorsal, central tegmentum.
• It carries ascending reticular fibers to the rostral intralaminar nuclei of the thalamus as part of the ascending arousal system and descending fibers from the red nucleus to the inferior olive as part of the triangle of Guillain-Mollaret, which is a network involved in movement

Question 24

Oculopalatal Myoclonus

Answer 24

• Oculopalatal myoclonus is a segmental myoclonus with continuous, pendular oscillations most commonly in the vertical plane. Rhythmic movement of the platysma muscle in conjunction with the palate. It is distinguished from pendular nystagmus because of the presence of myoclonus of non-ocular structures, such as the palate.
• In the clinical syndrome of oculopalatal myoclonus, hypertrophy of the inferior olivary nucleus exists in association with dysfunction of the dentato-rubro-olivary pathway (Guillain Mollaret triangle). Hypertrophy of the inferior olivary nucleus exists in association with dysfunction of the dentato-rubro-olivary pathway (Guillain Mollaret triangle).

Question 25

The rubrospinal tract lies just

Answer 25

posterior to the anterolateral system

Question 26

The rubrospinal tract Function

Answer 26

It produces upper extremity flexion.

Question 27

The rubrospinal tract originates

Answer 27

from the red nucleus in the midbrain, crosses in the ventral tegmental area of the brainstem, and innervates the upper cervical spinal cord.

Question 28

Pontine components of the auditory system

Answer 28

• The lateral lemniscus tract in the lateral tegmentum.
• The trapezoid body: a conglomeration of auditory fibers that lie between the lateral and medial leminscuses.
• The superior olivary complex in the anterolateral tegmentum. It comprises three separate nuclei:
• The nucleus of the trapezoid body.
• The medial superior olivary nucleus.
• The lateral superior olivary nucleus.

Question 29

Identify

Answer 29

Question 30

Identify

Answer 30

Question 31

Identify