Brainstem Flashcards
Abducens nuclei
- caudal pons
- CN VI
- motor
Abducens nucleus
•pons, 4th floor of ventricle –> lateral rectus
Basal pons
•longitudinally oriented nerve fibers, transversely oriented nerve fibers and scattered clumps of grey matter called pontine nuclei •the longitudinal fibers are coming from the cerebral cortex; some of them continue caudal through the CST but most of them are corticpontine fibers that end on the ipsilateral pontine nuclei, then they cross the midline and project through the middle cerebellar peduncle to all areas of the cerebellum
Blink Reflex
•CN V in, CN VII out
Caudal edge of the pyramidal decussation
•the formal boundary between the brainstem and the spinal cord
Caudal medulla
- no 4th ventricle, just a vestigial central canal •posterior columns (FG and FC) end by synapse in posterior column nuclei (NC and NG) •pyramid on each side contains the CST •STT
- midline structures - anterior spinal artery & verterbral arteries
- lateral - PICA
Caudal midbrain
- the 4th ventricle is all gone, replaced by the aqueduct (surrounded by the periaqueductal grey) •inferior colliculus above each side of the aqueduct (major component of the auditory pathway) •basal pons is mostly gone, replaced on each side by a cerebral peduncle •STT •ML •superior cerebellar peduncles decussate on their way to the thalamus
- midline - posterior cerebral artery (some from basilar)
- lateral - superior cerebellar artery (some from posterior communicating)
Caudal pons
- the 4th ventricle continues •basal pons •middle cerebellum peduncle •STT •ML •CST
- midline structures - basilar
- lateral - AICA
Cerebellopontine angle
- triangular area formed by the cerebellum, upper medulla and MCP
- CN VII and VII emerge from the brainstem here
Cerebral peduncle
•big collection of fibers from the cerebral cortex on their way to the pontine nuclei (in the caudal pons —> MCP —-> to the cerebellum), the spinal cord (via the CST) and to some cranial nerve nuclei (via the corticobulbar tract)
Cochlear nucleus
•spiral ganglia–> cochlear nucleus in pons/medulla cerebellopontine angle
Corticopontine fibers
- transversely oriented fibers in the rostral pons that cross the midline and project through the middle cerebellar peduncle to all araeas of the cerebellum
- travel along the cerebral peduncle from the cerebreal cortex to the cerebellum
Corticospinal fibers
- fibers that travel downstream from the cerebral cortex and will continue caudally into the pyramid
- travel along the cerebral peduncle from the cerebreal cortex to the pyramids
- longitudinally oriented in basal pons
Corticospinal tract
•The corticospinal tract is a white matter motor pathway starting at the cerebral cortex that terminates on lower motor neurons and interneurons in the spinal cord, controlling movements of the limbs and trunk. •the LCST and ACST decussate in the pyramids and form the CST and travel up through the brainstem •represents the contralateral side of the body
Dorsal motor nucleus
- DMN X
- rostral medulla
- CN X
- parasympathetic cardiovascular functions, breathing, food, digestion etc…
dorsal motor nucleus of teh vagus
- rostral medulla
- thoracic and abdominal viscera
- CN X
Edinger - Westphal nucleus
- CN III
- parasympathetic to ciliary ganglion –> sphincter pupillae, ciliary muscle
Facial motor nucleus
- brainstem near STT
- LMN facial expression and stapedius
- damage = paralysis ipsilateral face, unnatural sounds in ipsilateral ear
facial nuclei
- pontomedullary junction/caudal pons
- CN VII
- motor
- the axons wrap around the abducens nuclei and form the internal genu of the facial nerve before they leave the brainstem
- damage causes paralysis of the entire ipsilateral face and things can also sound unnaturally loud (stapedius)
Gag Reflex
•CN IX in, CN X out
nu
•rostral medulla
•
hypoglossal nuclei
- several rootlets front of medulla
- all extrinsic and instrinsic muscles of the tongue except palatoglossus (CN X)
Hypoglossal nuclei
- rostral medulla
- CN XII
- motor
Hypoglossal nucleus
- rostral medulla
- CN IX
- exits at groove between olive and pyramids
Inferior cerebellar peduncle
•rostral medulla •inferior olivary nucleus outputs cross the midline and form the ICP
Inferior colliculus
•above each side of the aqueduct in the caudal midbrain •major component in the auditory pathway
Inferior olivary nucleus
•rostral medulla •a large nucleus related to the cerebellum •outputs cross the midline and form most of the inferior cerebellum peduncle •the olive!
inferior salivary nuclei
- rostral medulla
- scattered in RF
- CN IX
- parasympathetic
interpeduncle fossa
The interpeduncular fossa is a somewhat rhomboid-shaped area of the base of the brain, limited in front by the optic chiasma, behind by the antero-superior surface of the pons, antero-laterally by the converging optic tracts, and postero-laterally by the diverging cerebral peduncles.
Jaw Jerk Reflex
•CN V in, CN V out
Main sensory nuclei
- mid pons
- CN V
- sensory
- touch and proprioception synapse here and cross the midline, joining the ML
- the main sensory nuleus then merges with the spinal nucleus
Medial Lemniscus
•The medial lemniscus, also known as Reil’s band or Reil’s ribbon, is a pathway in the brainstem that carries sensory information from the gracile and cuneate nuclei to the thalamus. The fibers of the medial lemniscus take origin in the gracile and cuneate nuclei of the medulla oblongata, and as internal arcuate fibers they cross to the opposite side in the sensory decussation. •at the level of the brainstem,represent the contralateral side of the body
Medial longitudinal fasiculus
•rostral medulla •a small tract important in eye and head movements •can be seen at this and all subsequent brainstem levels
mesenphilic nucleus
- starts at midpons, extends rostrally from the main sensory nucleus, reaching the rostral midbrain
- CN V
- sensory
- collection of pseudounipolar afferents that contain cell bodies of masseter muscle spindle afferents and other mechanoreceptors in the mouth and around the tempromandibular joint
Middle cerebellar peduncle
•caudal pons •fibers from the pontine nuclei enter and go to all areas of the cerebellum •major route through which the cerebral cortex sends messages to the cerebellum
Motor nucleus
- mid pons
- CN V
- motor
- UMN and LMN synapse here
nucleus ambiguus
- rostral medulla
- CN IX motor stylopharyngeus
- CN X motor larynx and pharynx
Oculomotor nucleus
•ventral to aqueduct -PAG, superior colliculus midbrain —> superior oblique muscle crosses over therefore lesion on nucleus = contralateral
Oculomotor nucleus
- caudal midbrain
- CN III
- motor and preganglionic parasympathetics
Pontine nuclei
•scattered clumps of grey matter found in basal pons
Pontine nuclei
•caudal pons •scattered clumps of grey matter where the cortiopontine fibers (longitudinal fibers coming from the cerebral cortex) end •then they cross the midline and enter the middle cerebellar peduncle
Posterior column nuclei
•where FG and FC synapse •contain the second order neurons for the major touch/position pathway, their axons cross the midline to form the medial lemniscus
Posterior Commissure
•the formal boundary between the brainstem and the diencephalon
posterior spinocerebellar tract
•The dorsal spinocerebellar tract (posterior spinocerebellar tract, Flechsig’s fasciculus, Flechsig’s tract) conveys proprioceptive information from proprioceptors in the skeletal muscles and joints to the cerebellum.
Rectus
•neural tissue dorsal to the ventricular system in the midbrain •contains the colliculi
Red nucleus
- rostral midbrain
- involved in motor coordination
Reticular formation
•The reticular formation is a matrix of nerve fibres and nerve cell bodies that form much of the core of the brainstem, extending from the medulla, indeed from the spinal cord, to the intra-laminate nuclei of the thalamus.
Rostral medulla
- the 4th ventricle opens up
- medial lemniscus is medial an ribbon shaped
- inferior olivary nucleus —> the olive!
- MLF is visible here and at all subsequent levels of the brainstem
- midline structures - anterior spinal artery & verterbral arteries
- lateral - PICA
Rostral midbrain
•the aqueduct continues on its way to the 3rd ventricle •above the aqueduct on each side is a superior colliculus (a component of the visual system) •superior peduncles have crossed and now barrel right around or through the red nucleus (mostly without synapsing) on their way to the nucleus •cerebral peduncle still contains corticopontine, corticospinal and corticobulbar fibers •STT and ML are now a continuous band of fibers getting ready to terminate in the thalamus
Rostral pons
- the 4th ventricle narrows and funnels down into the aqueduct of the midbrain •the basal pons is still obvious •superior cerebellar peduncle leaves the cerebellum and enters the brainstem on its way to the contralateral thalamus
- midline structures - basilar
- lateral - AICA
salivary nuclei
- RF of rostral medulla
- CN IX
solitary tract
- pontomedullary nucleus
- CN VII, CN IX, CN X
- The solitary tract (Latin: tractus solitarius, or fasciculus solitarius) is a compact fiber bundle that extends longitudinally through the posterolateral region of the medulla. The solitary tract is surrounded by the nucleus of the solitary tract, and descends to the upper cervical segments of the spinal cord.
Solitary Tract
- rostral medulla
- CN VII, IX, X
Solitary Tract and Solitary Nucleus
- caudal pons - VII sensory
- rostral medulla - CN IX (sensory - taste, parasympathetic - carotid body and sinus) and X (parasympathetic- primary afferents from thoracic and abdominal viscera)
- visceral dorsal column
- synpase here and then project to varous places
Spinal trigeminal nucleus
- starts at mid pons as part of the main sensory nuclei, where primary afferents enter the brainstem and extends caudally all the way to the upper cervical cord
- CN V sensory
- pain and tempertature synapse at the caudal part of the spinal nucleus, cross the mid line and merge with the STT
Spinothalmic Tract
•The spinothalamic tract (part of the anterolateral system or the ventrolateral system) is a sensory pathway from the skin to the thalamus. From the ventral posterolateral nucleus in the thalamus, sensory information is relayed upward to the somatosensory cortex of the postcentral gyrus. •at the level of the brainstem,represent the contralateral side of the body
Superior cerebellar peduncle
- fibers from the cerebellum to the thalamus
- decussate in the caudal midbrain
- enters at the level of the pons
Superior Colliculus
- above the aqueduct in the rostral midbrain - tectum
- component of the visual system CN III
superior salivary nucleus
- rostral medulla
- CN VII
- all gland except parotid
Superior salivary nucleus
- caudal pons
- CN VII
- parasympathetic
- glands
Tegementum
•the area between the ventral structures and the floor of the ventricular system •this is a generic term for a part of the cross-sectional area that contains various tracts and nuclei embedded in the reticular formation
Trigeminal ganglion
- pons
- main sensory, spinal and mesencephalic nuclei
- CN V
Trochlear nucleus
- caudal midbrain
- CN IV
- motor
Pupillary Light Reflex
•CN II in, CN III out (bilaterally)
