BRAINSTEM. Structural Overview of Brainstem Midbrain, pons, medulla functions.
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Transcript of BRAINSTEM. Structural Overview of Brainstem Midbrain, pons, medulla functions.
BRAINSTEM
Structural Overviewof Brainstem
• Midbrain, pons, medulla
• functions
BRAINSTEM
VENTRAL SURFACE DORSAL SURFACE
medulla
• Connects pons superiorly with spinal cord inferiorly
• Conical in shape
• The Central canal continues upward into the lower half of medulla, in the upper half of medulla it expands as the cavity of fourth ventricle
• two parts: open and closed
• an open part (close to the pons)
• a closed part (further down towards the spinal cord).
Gross Anatomy Review Medulla - ventral
Anterior median fissurePyramidsPyramidal decussationOliveInferior cerebellar peduncle
Gross Anatomy ReviewDorsal medulla• Posterior median
sulcus• Gracile tubercle• Cuneate tubercle.
Brainstem X-sections
• Caudal medulla• Rostral medulla• Caudal pons• Rostral pons• Caudal midbrain• Rostral midbrain
medulla
• 3 sections inside the medulla:
I. Pyramidal decussation
II.Sensory decussation
III.Level of olive
Caudal medulla pyramidal decussation
CAUDAL MEDULLA(LEVEL OF PYRAMIDAL DECUSSATION)
DMS
GN
CN
SN5
PD
P
DSC
VSC
VMF
FGFC
ST5Central grey
matter
Central canal
CAUDAL MEDULLA(LEVEL OF PYRAMIDAL DECUSSATION)• DMS: Dorsal median sulcus• FG: fasciculus gracilis• GN: Gracile nucleus• FC: Fasciculus cuneatus• CN: Cuneate nucleus• SN5: Spinal nucleus of trigeminal nerve• ST5: Spinal tract of trigeminal nerve• P: Pyramid• PD: Pyramidal decussation• DSC: Dorsal spinocerebellar tract• VSC: Ventral spinocerebellar tract• VMF: Ventral median fissure
CAUDAL MEDULLA(LEVEL OF PYRAMIDAL DECUSSATION)• GREY MATTER: • Sensory nuclei: Gracile, cuneate, spinal
nucleus of trigeminal• WHITE MATTER:
1. Ascending tracts: Gracile, cuneate, spinal tract of trigeminal, dorsal & ventral spinocerebellar, spinal leminiscus
2. Descending tracts: Pyramidal & extrapyramidal tracts
CAUDAL MEDULLA(LEVEL OF PYRAMIDAL DECUSSATION)
• Pyramidal decussation: Most of the fibers of pyramid decussate then pass laterally & dorsally to form the lateral corticospinal tract that descend in the lateral white column of spinal & terminate in ventral horn cells of opposite side
• Spinal nucleus of trigeminal: It lies in the lower part of pons, the whole medulla & extends to the 2nd cervical segment of spinal cord where it is continuous with substantia gelatinosa. It receives pain & temperature sensations from the face along trigeminal nerve
CAUDAL MEDULLA(LEVEL OF PYRAMIDAL DECUSSATION)
• Dorsal & ventral spinocerebellar tracts: They carry proprioceptive fibers to the cerebellum through inferior cerebellar peduncle (dorsal) & superior cerebellar peduncle (ventral)
• Gracile &Cuneate tracts: They carry proprioceptive sensations & end in Gracile & Cuneate nuclei (2nd order neurones in dorsal column tract)
MID MEDULLA(LEVEL OF SENSORY DECUSSATION)
DMS
VMF
P
GN
CN
SN5
FG
FC
ST5
DSC
VSC
ML
SensoryDecussation
Internal Arcuate Fibers
Central canal
Central grey matter
MID MEDULLA(LEVEL OF SENSORY DECUSSATION)
• Gracile & cuneate nuclei: They are more prominent. Axons of cells of gracile & cuneate nuclei curve around the central canal as internal arcuate fibers then decussate forming the sensory decussation & ascend in the brain stem as medial leminiscus that end in the ventral posterolateral nucleus of thalamus
• Pyramid: They are more prominent
MID MEDULLA(LEVEL OF SENSORY DECUSSATION)
• GREY MATTER: • Sensory nuclei: Gracile, cuneate, spinal
nucleus of trigeminal• WHITE MATTER:
1. Ascending tracts: gracile, cuneate, spinal tract of trigeminal, dorsal & ventral spinocerebellar, spinal leminiscus
2. Descending tracts: Pyramidal & extrapyramidal tracts
•gracile & cuneate nuc & fasc•Int arcuate fibers – ML•MLF•Nucleus of spinal tract of trigeminal nerve•Inferior olivary nuc•Pyramids •Hypoglossal nuclei
Caudal medullaint arcuate fibers
Rostral medullainf olivary nuc• olivary nuclear complex• Vestibulocochlear nuclei• Nucleus ambiguus• Hypoglossal nerve, dorsal
nucleus of vagus, vestibulocochlear, glossopharyngeal and accessory nuclei
ROSTRAL MEDULLA
4TH VMV
LV
ICPMLF
ML
P
I.O.
HVS
A
DCN
VCN
VagusNerve
HypoglossalNerve
VMF
D
M
ROSTRAL MEDULLA• H: Hypoglossal nucleus • V: Dorsal vagal nucleus• S: Nucleus solitarius• A: nucleus ambiguus• MV: Medial vestibular nucleus• LV: Lateral vestibular nucleus• DCN: Dorsal cochlear nucleus• VCN: Ventral cochlear nucleus• ICP: Inferior cerebellar peduncle• I.O.: Inferior olive• D: Dorsal accessory olive• M: Medial accessory olive• MLF: Medial longitudinal fascisulus• ML: Medial leminiscus• P: Pyramid• VMF: Ventral median fissure
ROSTRAL MEDULLA
• GREY MATTER:1.Motor nuclei: Hypoglossal, dorsal
vagal, nucleus ambiguus2.Sensory nuclei: Nucleus solitarius,
medial & lateral vestibular nuclei, dorsal & ventral cochlear nuclei, spinal nucleus of trigeminal
3.Extrapyramidal nuclei: Inferior olive, medial & dorsal accessory olive
ROSTRAL MEDULLA
• WHITE MATTER:1.Ascending tracts: Medial leminiscus,
spinal leminiscus, spinal tract of trigeminal, ventral spinocerebellar tract
2.Descending tracts: Pyramidal & extrapyramidal tracts
3.Both ascending & descending tract: Medial longitudinal fasciculus
4.Inferior cerebellar peduncle: fibers connecting medulla to cerebellum
ROSTRAL MEDULLA
• Hypoglossal nucleus: It lies in the medial part of floor of 4th ventricle. It contains motor neurones innervating muscles of tongue (except palatoglossus) through hypoglossal nerve
• Dorsal vagal nucleus: It lies in the floor of 4th ventricle , lateral to hypoglossal nucleus. It contains preganglionic parasympathetic neurones running in the vagus nerve
• Nucleus Solitarius: It lies ventrolateral to dorsal vagal nucleus. It receive taste fibers from facial, glossopharyngeal & vagus nerves
ROSTRAL MEDULLA
• Nucleus ambiguus: It lies dorsal to inferior olivary nucleus. It contains motor neurones innervating muscles of pharynx, palate & larynx through glossopharyngeal, vagus & cranial part of accessory nerves
• Medial & lateral vestibular nuclei: They lie in the floor of 4th ventricle, lateral to dorsal vagal nucleus. They receive afferent fibers from vestibular nerve
• Dorsal & ventral cochlear nuclei: They lie dorsal (dorsal nucleus) & lateral (ventral nucleus) to ICP. They receive afferent fibers from cochlear nerve
ROSTRAL MEDULLA
• Olivary nuclear complex: It is formed of a large nucleus (inferior olive) & 2 smaller nuclei (medial & dorsal accessory olive).
1. Afferents: From cerebral and cerebellar cortex & spinal cord
2. Efferents: To cerebellum through ICP3. Function: They are concerned with
control of movement
ROSTRAL MEDULLA
• Medial longitudinal fasciculus: It consists of both ascending & descending fibers:
1. Ascending fibers: connect vestibular nuclei to nuclei supplying extraoccular muscles (occulomotor, trochlear & abducent nuclei). It coordinates movements of head & eyes
2. Descending fibers: connect vestibular nuclei to nuclei of ventral horn of spinal cord (medial vestibulospinal tract). It control body posture & balance
ROSTRAL MEDULLA
• Spinal leminiscus: It carries pain, temperature & touch sensations from the opposite side of body to ventral posterolateral nucleus of thalamus
• Inferior cerebellar peduncle: It is formed of fibers connecting medulla to cerebellum
Level of Inferior Olives
Inferior cerebellar peduncle = Restiform body
Inferior olivary nuclei
MLF
Vestibular nuclei
Medial InferiorHypoglossal nucleus CN XII
Arcuate nuclei pontine nuclei
Rostral medulla
N. ambiguus
Motor nucleus for CN IX, X & XI
N. solitarious
Sensory nucleus for CN VII, IX, X
Spinal trigeminal tract
CN V, VII, IX, X
Dorsal motor nucleus of X
Cranial Nerves of the Medulla
Vestibular nuclei
CN XII
Cranial Nuclei of the Medulla
N. solitarious
Sensory nucleus for CN VII, IX, X
Cranial Nuclei of the Medulla
N. solitarious
Sensory nucleus for CN VII, IX, X
Spinal trigeminal tract
Cranial Nuclei of the Medulla
N. ambiguus
Motor nucleus for CN IX, X & XI
N. solitarious
Sensory nucleus for CN VII, IX, X
Spinal trigeminal tract
Cranial Nuclei of the Medulla
N. ambiguus
Motor nucleus for CN IX, X & XI
N. solitarious
Sensory nucleus for CN VII, IX, X
Spinal trigeminal tract
CN V, VII, IX, X
Dorsal motor nucleus of X
CN IX: Glossopharyngeal Nerve
N. ambiguus
Motor nucleus for CN IX, X & XI
N. solitarious
Sensory nucleus for CN VII, IX, X
Spinal trigeminal tract
CN V, VII, IX, X
CN IX: Glossopharyngeal Nerve
N. ambiguus
Motor nucleus for CN IX, X & XI
N. solitarious
Sensory nucleus for CN VII, IX, X
Posterior 1/3 of the tongue
Spinal trigeminal tract
CN V, VII, IX, X
CN IX: Glossopharyngeal Nerve
N. ambiguus
Motor nucleus for CN IX, X & XI
N. solitarious
Sensory nucleus for CN VII, IX, X
Posterior 1/3 of the tongue
Spinal trigeminal tract
CN V, VII, IX, X
Sensation behind ear
CN IX: Glossopharyngeal Nerve
N. ambiguus
Motor nucleus for CN IX, X & XI
Stylopharyngeus (lifts pharynx)
N. solitarious
Sensory nucleus for CN VII, IX, X
Posterior 1/3 of the tongue
Spinal trigeminal tract
CN V, VII, IX, X
Sensation behind ear
CN IX: Glossopharyngeal Nerve
N. ambiguus
Motor nucleus for CN IX, X & XI
Stylopharyngeus (lifts pharynx)
N. solitarious
Sensory nucleus for CN VII, IX, X
Posterior 1/3 of the tongue
Inf. salivatory nucleus
Parotid gland, parasympathetic
Spinal trigeminal tract
CN V, VII, IX, X
Sensation behind ear
CN X: Vagus Nerve
N. ambiguus
Motor nucleus for CN IX, X & XI
N. solitarious
Sensory nucleus for CN VII, IX, X
Spinal trigeminal tract
CN V, VII, IX, X
CN X: Vagus Nerve
N. ambiguus
Motor nucleus for CN IX, X & XI
N. solitarious
Sensory nucleus for CN VII, IX, X
Taste, epiglottis Cardiorespiratory
Spinal trigeminal tract
CN V, VII, IX, X
CN X: Vagus Nerve
N. ambiguus
Motor nucleus for CN IX, X & XI
N. solitarious
Sensory nucleus for CN VII, IX, X
Taste, epiglottis Cardiorespiratory
Spinal trigeminal tract
CN V, VII, IX, X
Ear
CN X: Vagus Nerve
N. ambiguus
Motor nucleus for CN IX, X & XI
Pharynx Larynx
N. solitarious
Sensory nucleus for CN VII, IX, X
Taste, epiglottis Cardiorespiratory
Spinal trigeminal tract
CN V, VII, IX, X
Ear
CN X: Vagus Nerve
N. ambiguus
Motor nucleus for CN IX, X & XI
Pharynx Larynx
N. solitarious
Sensory nucleus for CN VII, IX, X
Taste, epiglottis Cardiorespiratory
Dorsal motor nucleus of X
Spinal trigeminal tract
CN V, VII, IX, X
Ear
CN X: Vagus Nerve
N. ambiguus
Motor nucleus for CN IX, X & XI
Pharynx Larynx
N. solitarious
Sensory nucleus for CN VII, IX, X
Taste, epiglottis Cardiorespiratory
Dorsal motor nucleus of X
Parasympathetic, preganglionic
Spinal trigeminal tract
CN V, VII, IX, X
Ear
Pons
• Lies anterior to cerebellum
• Connects medulla to midbrain
• 1 inch long
Pons
Landmarks
4th ventricle Cerebellum and Middle cerebellar peduncle Basilar groove
Cranial Nerves
Abducent, facial, vestibulocochlear, Trigeminal nerves
Ventral – Lateral View
Midbrain
Cerebral peduncles
Pons
Basis pontis
Medulla
Pyramid Olive
Pons
Posterior view• Median sulcus• Medial eminence• Sulcus limitans• Facial colliculus• Area vestibuli
Pons
• It is commonly divided into anterior part(basal part) and posterior part (tegmentum) by transversely running fibers of trapezoid body
Internal Structure of the Pons
Cross section at two levels
• Level of facial nucleus (CN VII)
• Level of trigeminal nuclei
Level of facial colliculus
Pons
Descending upper motor neurons
Connection of pons to cerebellum
(inf. cerebellar peduncle)
Middle cerebellar peduncle
Medial lemniscus Ascending 2nd order sensory neurons
4th Ventricle
Cranial Nerves of Lower Pons
CN VIII – Vestibular Nuclei Pure sensory lateral location Balance
Posterior view: Cerebullum cut away
Cranial Nerves of Lower Pons
CN VIII –
Vestibular Nuclei
(Cochlear Nuclei)
Cranial Nerves of Lower Pons
CN VII nucleus – Facial nerve
Muscles of face
At a slightly higher level
CN VI nucleus – Abducens nerve
Abduction of eye
Longest, most vulnerable CN
Cranial Nerves of Lower Pons
CN VII nucleus - Facial nerve
Muscles of face
Cranial Nerves of Lower Pons
CN VI nucleus – Abducens nerve
Abduction of eye
level of Upper Pons
Upper Pons4th Ventricle
Middle cerebellar peduncle
Corticospinal tract, corticobulbar tract, corticopontine fibers
Descending fibers
Upper Pons4th Ventricle
Middle cerebellar peduncle
Pontine nuclei in basis
Upper Pons
Pontine nuclei
Trapezoid body – transverse fibers in pontine tegmentum
Lateral lemniscus
Lower Pons
Pontine nuclei
Lateral lemniscus
Medial lemniscus fibers from dorsal column (position and vibration)
Trigeminal tract pain, temperature, touch from contralateral face
Lemniscal sensory system – in tegmentum of the pons
Cranial Nerve of the upper Pons
4th Ventricle
CN V
Motor trigeminal nucleus
Cranial Nerve of the upper Pons
4th Ventricle
CN V
Motor trigeminal nucleus
Principal trigeminal sensory nucleus
Cranial Nerve of the upper Pons
4th Ventricle
CN V
Motor trigeminal nucleus
Principal trigeminal sensory nucleus
Trigeminal fascicles
Trigeminal nerve
Upper Pons4th ventricle cerebral aqueduct
Superior cerebellar peduncle
Descending upper motor neurons
Transverse ponto-cerebellar fibers
Upper Pons4th ventricle cerebral aqueduct
MLF
Midbrain
• 0.8 inch in length
• Connects Pons and cerebellum with the forebrain
cerebral aqueductcerebral aqueduct
EXTERNAL MORPHOLOGY
superior colliculussuperior colliculus
EXTERNAL MORPHOLOGY
inferior colliculusinferior colliculus
EXTERNAL MORPHOLOGY
CN.IVCN.IV
EXTERNAL MORPHOLOGY
crus cerebricrus cerebri
EXTERNAL MORPHOLOGY
interpeduncular fossa
interpeduncular fossa
EXTERNAL MORPHOLOGY
CN.IIICN.III
INTERNAL MORPHOLOGY-slide 16INTERNAL MORPHOLOGY-slide 16
cerebral aqueductcerebral aqueduct
External Structure of Midbrain
1. Optic chiasm
2. Interpeduncular fossa
3. Oculomotor nerve (CN III)
4. Trochlear nerve (CN IV)
5. Pons
6. crus cerebri
Ventral surface
(anterior)
Posterior view
Patterning of the Midbrain
Internal Structure of Midbrain
Cross section at two levels
• Level of inferior colliculus
• Level of superior colliculus
Lower MidbrainInferior colliculus
hearing
cerebral aqueduct
DORSAL
VENTRAL
Crus cerebri
Lower MidbrainInferior colliculus
Substantia nigra
Melanin-containing cells that produce dopamine Project to the basal ganglia, cerebral cortex, cerebellum, hypothalamus
Lower MidbrainInferior colliculus
Substantia nigra
Crus cerebri
Crus cerebri
Lower MidbrainInferior colliculus
CN IV Trochlear nerve
Lower MidbrainInferior colliculus
CN IV Trochlear nerve
MLF
Lower MidbrainInferior colliculus
CN IV
MLF
Lower MidbrainInferior colliculus
hearing Mesencephalic nucleus of V
Internal Structure of Midbrain
Cross section at two
Levels:• Level of inferior colliculus
• Level of superior colliculus
Upper Midbrain
Superior colliculus
vision
Substantia nigra Crus cerebri
Upper Midbrain
Vision
Superior colliculus Lateral geniculate body
Hearing
Inferior colliculus Medial geniculate body
Upper Midbrain
Superior colliculus
vision
Red nucleus – relay from cortex and cerebellum to spinal cord, thalamus, reticular formation, substsantia nigra
Cranial Nerves of Upper Midbrain
Superior colliculus
vision
Red nucleus
Edinger Westfal nucleus
MLF
CN III Oculomotor nucleus