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