Download The Internal Structure of Brainstem

The Internal Structure
of Brainstem
OUTLINE
▪ Gray Matter
- Cranial Nerve Nuclei
- Relay Nuclei
▪ White Matter
- Ascending Tracts
- Descending Tracts
▪ Reticular Formation
▪ Transverse Sections
Ventral View
▪ Medulla Oblongata
- anterior medial fissure
- pyramid
- olive
- pyramidal decussation
▪ Pons
- basilar sulcus
- basilar part
- middle cerebellar peduncle
▪ Midbrain
- cerebral peduncle
- interpeduncular fossa
- posterior perforated substance
External Features of Brainstem
▪ Midbrain
Dorsal View
▪ Rhomboid Fossa
- dorsal median sulcus - striae medullares
- sulcus limitans
- medial eminence
- facial colliculus
- vestibular area
- hypoglossal trigone
- vagal trigone
- corpora quadrigemina
- pineal body
▪ Medulla Oblongata
- gracile tubercle
- cuneate tubercle
- trigeminal tubercle
The Continuation of Brainstem & Spinal Cord
(Rhomboid Fossa & Fourth Ventricle)
Grey Matter of Brainstem: Cranial Nerve Nuclei
Development of Spinal Cord & Brainstem
Sulcus Limitans
▪ GSE column (SE column)
▪ SVE column (branchial efferent column)
▪ GVE column – parasympathicus
▪ GVA column – subconscious sensation
▪ SVA column – taste sense
▪ GSA column – conscious sensation
▪ SSA column – audition & posture
Motor & Sensory Columns
of Spinal Cord & Brainstem
SE
SVE
GVE
SVA
GVA
GSA
SSA
Brainstem
Spinal cord
SE
VE
VA
SA
Arrangement of Cranial Nerve Nuclei in Brainstem
GSE(SE)
GVE
VA (GVA & SVA)
SSA
Medial
Lateral
SVE (branchial motor)
GSA
▪ GSE: oculmotor, trochlear &
hypoglossal nuclei
▪ SVE: trigeminal motor, facial
motor, ambiguus & accessory
spinal nuclei
▪ GVE: accessory oculmotor, sup.
& inf. salivatory & dorsal motor
vagus nuclei
▪ VA: solitary nuclei
▪ GSA: trigeminal sensory (mesencephalic,
principal / main & spinal) nuclei
▪ SSA: vestibular & cochlear nuclei
Motor Cranial Nerve Nuclei
▪ GSE: oculmotor, trochlear & hypoglossal nuclei
▪ SVE: trigeminal motor, facial motor, ambiguus nuclei (& accessory spinal)
▪ GVE: accessory oculmotor, sup. & inf. salivatory & dorsal motor vagus nuclei
Sensory Cranial Nerve Nuclei
▪ VA: solitary nuclei
▪ GSA: trigeminal sensory (mesencephalic, principal / main & spinal) nuclei
▪ SSA: vestibular & cochlear nuclei
Location of the Cranial Nerve Nuclei
▪ superior colliculus
▪ inferior colliculus ▪ facial colliculus ▪ hypoglossal
triangle
▪ vagal triangle ▪ striae medullares ▪ sulcus limitans ▪ vestibular area
GSE: Oculomotor Nucleus – at the level of the superior colliculus of midbrain
Trochlear Nucleus – at the level of the inferior colliculus of the midbrain
Abducent Nucleus – beneath the fascial colliculus
Hypoglossal Nucleus – beneath the hypoglossal trigone
SVE: Trigeminal Motor Nucleus – at mid-pons
Facial Motor Nucleus – at the caudal pons
Accessory Spinal Nucleus – at caudal medulla & C1-C6 segments of spinal cord
Ambiguus Nucleus – at the rostral medulla
GVE: Accessory Oculomotor Nucleus – dorsal-medial to the Oculomotor Nucleus
Superior & Inferior Salivatory nuclei – at the caudal of pons
Dorsal Motor Vagus nucleus – at the rostral medulla, beneath the vagus trigone
GVA & SVA: Solitary Tract Nuclei – in the medulla
GSA: Trigeminal Sensory Nuclei – runs whole length of brainstem
SSA: Vestibular Nucleus – beneath the vestibular area
Cochlear Nuclei – beneath the lateral recess of rhomboid fossa
The Relation between Cranial Nerves & Cranial Nerve Nuclei
▪ Solitary Tract Nuclei (Ⅶ,Ⅸ,Ⅹ)
- gustatory nucleus
- cardiorespiratory (baroreceptor &
dorsal respirator nuclei)
- commissural nucleus
▪ Ambiguus Nucleus (Ⅸ,Ⅹ,Ⅺ)
Oculomotor N.
Trochlear N. — GSE
- oculomotor nuc. – GSE
- accessory oculomotor nuc. – GVE – dilator pupillae
Abducent N. — GSE
Trigeminal N.
- trigeminal sensory nuc. – GSA
- trigeminal motor nuc. – SVE
SVE
(masticatory mm.)
GSA
Facial N. —— GVE, SVA, SVE, GSA
- facial motor nuc. – SVE
- sup. salivatory nuc. – GVE
- solitary tract nuc. – SVA
GVE & SVA
SVE (muscles of facial expression)
GSA (part of skin of external ear & proprioception of muscles
of facial expression)
- Internediate nerve — Trigeminal Sensory Nuclei (principal)
Glossopharyngeal N.
- ambiguus nuc. – SVE
- inf. salivatory nuc. – GVE
- solitary nuc. – GVA & SVA
- spinal nuc. of trigeminal n. – GSA
SVE
GVA
GVE
GVA
SVA
&
GSA
GSA
Vagus N.
- dorsal vagal nuc. – GVE
- ambiguus nuc. – SVE
- solitary nuc. – GVA
- spinal nuc. of trigeminal n. – GSA
SVE
GVE
GVA
GSA
Accessory N.
- ambiguus nuc. (SVE) – vagus nerve
- accessory spinal nuc.
Hypoglossal N. – GSE
Vestibulocochlear N. – SSA
▪ sup. & inf. colliculus nuc.
▪ red nuc. & substantia nigra
▪ pontine nuc.
▪ inf. olivary nuc.
▪ gracile & cuneate nuc.
The Relay Nuclei in Brainstem
Red Nucleus & Substantis Nigra
Pontocerebellar Fibers
Olivocerebellar Tract
The White Matter: Ascending Tracts
▪ medial lemniscus
- continuation of gracilis & cuneatus
▪ spinal lemniscus
- continuation of spinothalamic tract
Gracilis & Cuneatus Nuclei
▪ trigeminothalamic tract (GSA)
▪ lateral lemniscus (audition)
▪ trigeminothalamic tract
Cerebral Cortex
VPM of Thalamus (3rd neuron)
Decussation
Trigeminal Sensory Nuc. (2nd neuron)
Trigeminal Ganglion (1st neuron)
GSA Information
▪ lateral lemniscus
- conveys the auditory sensation
(special somatic) from corti organ
of both sides.
Superior Olivary Nucleus
Inferior Colliculus Nucleus
▪ pyramidal system
- corticospinal tract
- corticonuclear tract
▪ extrapyramidal system
The White Matter: Descending Tracts
The Pyramidal System
▪ corticospinal tract
- anterior corticospinal tract – uncrossed fibers
- lateral corticospinal tract – crossed fibers
▪ corticonuclear / corticobulbar tract
Hypoglossal Nucleus
Facial Motor Nncleus
The Extrapyramidal System
Medial Longitudinal Fasciculus
▪ interconnects the oculomotor, trochlear,
abducens, accessory oculomotor, vestibular,
reticular & spinal accessory nuclei, coordinating
conjugate eye movements & associated
movements of the head and neck.
The Reticular Formation
▪ 3 zones (columns)
- median, medial & lateral
▪ median zone – nuclei raphe & paramedian
reticular nuclei (project to cerebellum)
▪ medial zone – ―effector‖ area
▪ lateral zone – ―sensory‖ area
Reticular Activating System
Pontine,
Ventral & Dorsal
Respiratory
Centers
Cardioinhibitory &
Cardioacceleratory
Centers
Pons
▪ respiratory centers
(pneumotaxic & apneustic)
Medulla
▪ cadiovascular centers
Oblongata ▪ respiratory rhythmicity centers
Locations of
Cardiovascular
& Respiratory
Centers
Ascending
Tracts
Descending Tracts
Tracts of the Brainstem
To Cerebellum
Level of Decussation of the Pyramids
- decussation of pyramids
- fasciculi gracilis & cuneatus
- spinal lemniscus
Level of C1~2
- nucleus & spinal tract of trigeminal nerve
- accessory nucleus
Level of Decussation of medial Lemnisci
(Great Sensory Decussation)
- gracile & cuneate nuclei
- medial lemniscus
- internal arcuate fibers
- external arcuate fibers
- dorsal motor nucleus of vagus
- pyramid
- spinal lemniscus
- nucleus & spinal tract of trigeminal n.
Level of Inferior Olivary Nucleus
- hypoglossal nucleus & nerve
- dorsal nucleus of vagus
- vestibular nuclei
- inferior olivary nucleus
- solitary tract & nucleus
- inf. cerebellar peduncle
- ambiguus nucleus
Reticular Formation
▪ 3 zones (columns)
- median, medial & lateral
- pyramid
- nucleus & spinal tract
of trigeminal n.
- spinal lemniscus
- medial lemniscus
Level of Caudal Pons
- abducens nucleus
- motor nucleus of CNⅦ
- transverse pontine fibers
- middle cerebellar peduncle
- corticospinal tract
- spinal lemniscus
- nucleus & spinal tract of trigeminal n.
- medial lemniscus
Level of Trochlear Nerve
Level of Trigeminal Nerve
- decending fibers
of pyramidal system
Dorsal
- superior cerebellar peduncle
Ventral
lateral lemniscus
spinal lemniscus
trigeminothalamic tract
medial lemniscus
- superior cerebellar peduncles & their decussation
- corticonuclear & corticospinal fibers
- trochlear nucleus
- cerebral aqueduct
Levels of Pontine-mesencephalic Junction &
Inferior Colliculus
spinal lemniscus
trigeminothalamic tract
Ventral
Inferior colliculus
medial lemniscus
lateral lemniscus
Dorsal
- red nucleus
- substantia nigra
- corticonuclear & corticospinal fibers
- cerebral aqueduct
Level of Superior Colliculus
Dorsal
Ventral
spinal lemniscus
medial lemniscus
trigeminothalamic tract
Online Resource:
Atlas of the Brainstem
http://www.dartmouth.edu/~rswenson/Atlas/BrainStem/