Brainstem

Question 1

Longitudinal sections (3)

• where are they located
• what do they contain

Answer 1

1. Basilar section: located ANT, mostly MOTOR structures
   - descending axons and motor nuclei
2. Tegmentum - located POST, mostly SENSORY structures
   - reticular formation, sensory nuclei & ascending tracts, CN nuclei, MLF
3. Tectum - only in MIDBRAIN
   - structures involved w/ reflexive control of the eye and movements of the head
   - contains superior & inferior colliculi (tectospinal & aud/visual info)

• Pretectal area –> optic reflexes

Question 2

Sensory tracts traveling through brainstem

• 1 not modified
• 2 modified

Answer 2

1. Spinothalamic - not modified
2. Dorsal column - synapses in INF MED in nucleus cuneatus/gracilis and crosses to form medial lemniscus
3. Spinocerebellar - axons leave BS via inf/sup peduncles and enter cerebellum

Question 3

Motor tracts travelling through brainstem

• 1 not modified
• 1 modified

Answer 3

1. Corticospinal - not modified but fibers do cross at INF MED
2. Corticobulbar - UMN’s synapse on CN nuclei and exit as LMN for motor control of CN’s

Question 4

Autonomic Descending pathways traveling through brianstem

• 1 modified
• 1 not modified

Answer 4

1. Sympathetic - not modified

2. Parasympathetic - axons synapse w/ BS PS nuclei or cotninue through to the sacral level of spinal cord

Question 5

Tracts that originate in the BS (4)

Answer 5

1. Tectospinal - superior colliculus - SUP MIDBRAIN
2. Rubrospinal - red nucleus - SUP MIDBRAIN
3. Vestibulospinal - vestibular nuclei
4. Reticulospinal - reticular formation

Question 6

Reticular formation

• what does it do (3 main functions)
• where is it located

Answer 6

Adjusts general activity of the NS - alerting & arousal
3 main functions:
1. integrate sensory & cortical info
2. regulate somatic motor activity, ANS and consciousness
3. Modulate nocicpetive informatoin

Located along entire length of brainstem

Major nuclei:

• ventral tegmental area
• pedunculopontine nucleus
• raphe nucleus
• locus cereleus and medial reticular area

Question 7

Medulla

• anatomy
• functions

Answer 7

ANT surface - pyramides, olives
POST surface - inferior cerebellar peduncle, central canal

Functions (CN VII through X, and XII)

• contributes to control of eye and head movements
• coordinates swallowing
• helps regulate CV, respiratory and visceral activity

Question 8

pyramidal decussation

Answer 8

where the corticospinal tracts CROSS in the INFERIOR MEDULLA

Question 9

Pons

• anatomy
• function

Answer 9

Posterior pons border is on the 4th ventricle

Most vertical tracts remain unchanged through pons EXCEPT
- corticopontine & corticobulbar (trigeminal & facial nucleus)

Functions:

• nuclei for CN V - VII (facial sensation, lateral mvmts of the eye, facial expression & chewing muscles)
• process motor info from cerebral cortex & relay to cerebellum

Question 10

Midbrain

• anatomy
• functions

Answer 10

Most superior part of the brainstem, connects the diencephalon to the pons
- contains cerebral aqueduct that joints the 3rd and 4th ventricle and is surrounded by periaqueductal gray

• 3 longitudinal sections

Question 11

Disorders of the Brainstem

• ho will they present
• Four D’s

Answer 11

Present as a mix of UMN and LMN sympttoms, and ipsilateral and contralateral
- in general, the L CN supplies the L side

Four D’s:
dysphagia, dysarthria, diplopia, dysmetria

Question 12

Alternating hemiplegia

Answer 12

Lesion to ONE side of the BS and can only occur @ 3 levels, but not at the same time
- CN III, VI, or XII

These are LMN’s which will cause flaccid paralysis on the SAME side of the lesion
–> it will also damage the corticospinal tract nearby, which are UMN’s and will cause spastic paralysis on the OPPOSITE side