Brainstem Flashcards
Longitudinal sections (3)
- where are they located
- what do they contain
- Basilar section: located ANT, mostly MOTOR structures
- descending axons and motor nuclei - Tegmentum - located POST, mostly SENSORY structures
- reticular formation, sensory nuclei & ascending tracts, CN nuclei, MLF - 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
Sensory tracts traveling through brainstem
- 1 not modified
- 2 modified
- Spinothalamic - not modified
- Dorsal column - synapses in INF MED in nucleus cuneatus/gracilis and crosses to form medial lemniscus
- Spinocerebellar - axons leave BS via inf/sup peduncles and enter cerebellum
Motor tracts travelling through brainstem
- 1 not modified
- 1 modified
- Corticospinal - not modified but fibers do cross at INF MED
- Corticobulbar - UMN’s synapse on CN nuclei and exit as LMN for motor control of CN’s
Autonomic Descending pathways traveling through brianstem
- 1 modified
- 1 not modified
- Sympathetic - not modified
2. Parasympathetic - axons synapse w/ BS PS nuclei or cotninue through to the sacral level of spinal cord
Tracts that originate in the BS (4)
- Tectospinal - superior colliculus - SUP MIDBRAIN
- Rubrospinal - red nucleus - SUP MIDBRAIN
- Vestibulospinal - vestibular nuclei
- Reticulospinal - reticular formation
Reticular formation
- what does it do (3 main functions)
- where is it located
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
Medulla
- anatomy
- functions
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
pyramidal decussation
where the corticospinal tracts CROSS in the INFERIOR MEDULLA
Pons
- anatomy
- function
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
Midbrain
- anatomy
- functions
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
Disorders of the Brainstem
- ho will they present
- Four D’s
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
Alternating hemiplegia
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
