Brainstem (Unit 2)

Gross anatomy of Brainstem

  • Thalamus

    • Anterior nucleus

    • Pulvinar

    • Medial Geniculate Nucleus

    • Lateral Geniculate Nucleus

  • Epithalamus

    • Pineal gland

  • Hypothalamus

    • Optic chiasm

    • Optic tract (CN 2)

    • Mammillary bodies

    • Pituitary stalk

(Midbrain)

  • Superior Colliculus

  • Inferior Colliculus

  • Brachium of the Inferior Colliculus

  • Cerebral Peduncles

  • Interpeduncular fossa

(Pons)

  • Cerebellar peduncles

    • Superior

    • Middle

    • Inferior

  • Transverse fibers of pons

  • Facial colliculus

(Medulla)

  • Pyramids

  • Olives

  • Cuneate and gracilis tubercles

  • Obex

  • Area postrema

3rd Ventricle

Cerebral aqueduct

4th Ventricle

Interpeduncular cistern

Cranial nerves 1-12

Cranial Nerves

  • 1 - Olfactory (sensory)

  • 2 - Optic (sensory)

  • 3 - Oculomotor (motor)

  • 4 - Trochlear (motor)

  • 5 - Trigeminal (sensory/motor)

  • 6 - Abducens (motor)

  • 7 - Facial (sensory/motor)

  • 8 - Vestibulocochlear (sensory)

  • 9 - Glossopharyngeal (sensory/motor)

  • 10 - Vagus (sensory/motor)

  • 11 - Accessory (motor)

  • 12 - Hypoglossal (motor)

CN 3, 4, 6 are associated with the eye

  • 3 - somatic motor - oculomotor nucleus

    • medial rectus, inferior rectus, inferior oblique, superior rectus

    • levator palpebrae superioris

  • 3 - parasympathetic motor - Endinger-Wastphal nucleus

    • contains the cell bodies of parasympathetic preganglionic neurons of eye

    • smooth muscle of pupil constrictor

    • ciliary body (lens accommodation)

  • 4 (trochlear) - somatic motor - trochlear nucleus (level of inferior colliculi)

    • superior oblique

    • looking down

    • (the only cranial nerve to exit dorsally and decussate before exiting)

  • 6 (abducens) - somatic motor - abducens nucleus (level of the facial colliculus)

    • lateral rectus

    • eye abduction

5 - trigeminal nerve

  • Voluntary motor (voluntary movement of jaw)

    • motor nucleus of trigeminal nerve

      • muscle of mastication (chewing)

  • Somatic sensation (face, dura, head, jaw)

    • mesencephalic nucleus

      • mediates jaw reflexes

      • afferents from GTO and muscle spindles in muscles of mastication

      • midbrain

    • principle nucleus

      • rostral pons

      • touch and vibration

    • spinal nucleus

      • pain, temperature, crude touch

  • Three main branches: V1, V2, V3

    • ophthalmic division

      • upper 1/3 of face (forehead)

    • maxillary division

      • middle 1/3 (cheeks and upper jaw)

    • mandibular division

      • lower 1/3 (chin)

7 - facial nerve

  1. Voluntary motor

    • Facial nucleus efferents

    • muscles for facial expression

  2. Special sensory

    • Taste (anterior 2/3s of tongue)

    • afferents into the solitary nucleus

  3. Parasympathetic preganglionic

    • Salivatory glands and tear glands (salivation and lacrimation)

    • efferent from superior salivatory nucleus

  4. Somatic sensation

    • small area behind/within the ear

    • afferents to trigeminal sensory nuclei (shares these nuclei with 5)

8 - Vestibulocochlear nerve

  • Sensory - hearing and balance

    • Cochlear nerve + Vestibular nerve converge into vestibulocochlear nerve

    • Cochlear detects sound

    • Vestibular organs detect acceleration and orientation of the head

  • Vestibular Schwannoma aka cerebellopontine angle (CPA) tumor is common pathology of CN 8 (and as grows can impact CN 7 and cause Bell’s Palsy)

Solitary nucleus

  • aka Nucleus Tractus Soltarius (NTS) - like “nucleus of tasting stuff)

  • Sensory nucleus with afferents from CN 7, 9, 10

  • Rostral

    • Taste from 7, 9, 10

  • Caudal

    • Digestive feedback from 10

    • Cardiovascular feedback from 9, 10

    • Respiratory feedback from 9, 10

Nucleus ambiguous

  • motor nucleus of 9 and 10

  • Speech and swallowing

9 and 10

9 - Glossopharyngeal

  • Voluntary motor

    • Swallowing (stylopharyngeus muscle)

    • nucleus ambiguous

  • Special sensory

    • taste, from posterior 1/3 of tongue

    • rostral solitary nucleus

  • Somatic sensory

    • back of tongue and throat

    • spinal trigeminal nucleus

  • Visceral sensory

    • from baroreceptors

  • Parasympathetic ganglionic

    • Salivary gland

    • Efferents from inferior salivatory nucleus

10 - Vagus

  1. Voluntary motor

    • Swallowing and speech

    • nucleus ambiguous

  2. Special sensory

    • taste, from epiglottis/back of throat

    • rostral solitary nucleus

  3. Somatic sensory

    • throat

    • spinal trigeminal nucleus

  4. Visceral sensory

    • baroreceptors and organs

    • caudal solitary nucleus

  5. Parasympathetic ganglionic

    • glands, cardiac and smooth muscles in organs of neck, thorax, abdomen

    • efferents from dorsal motor nucleus of vagus (DMX or DMV).



11 - Accessory nerve

  • Motor to trapezius and sternocleidomastoid

  • does not originate from the brainstem

12 - hypoglossal

  • motor to intrinsic tongue muscles

Cross-sectional anatomy

  • Rostral midbrain (Superior colliculus)

    • Superior colliculus

    • Cerebral aqueduct

    • Periaqueductal gray

    • Red nucleus

    • Oculomotor nucleus

    • Edinger-Westphal nucleus

    • Substantia nigra

    • Cerebral penducles

    • Interpeduncular fossa

    • Cranial nerve 3 (Oculomotor)

  • Caudal midbrain (Inferior Colliculus)

    • Inferior colliculi

    • Cranial nerve 4 (trochlear)

    • Cerebral aqueduct

    • Periaqueductal Gray

    • Decussation of the superior cerebellar peduncles (X/SCP)

    • Substantia nigra

    • Cerebral peduncles

    • Ventral pons (some sections)

  • Rostral Pons (Trigeminal Nerve)

    • Superior cerebellar peduncle

    • Middle cerebellar peduncle

    • Fourth ventricle

    • Motor trigeminal nucleus

    • Principal sensory trigeminal nucleus

    • Cranial nerve V (Trigeminal)

    • Longitudinal fibers of the pons

    • Transverse fibers of the pons

    • Pontine nuclei

  • Caudal Pons (Facial colliculus)

    • Superior cerebellar peduncle

    • Middle cerebellar peduncle

    • Fourth ventricle

    • Facial colliculus

    • Abducens nucleus, CN 6

    • Facial nucleus, CN 7

    • Vestibulocochlear complex, CN 8

    • Longitudinal fibers of the pons

    • Transverse fibers of the pons

  • Rostral Medulla (Olive)

    • Fourth ventricle

    • Hypoglossal, CN 12

    • Dorsal motor nucleus of the vagus (DMX)

    • Solitary nucleus (NTS)

    • Vestibulocochlear complex

    • Inferior cerebellar peduncle

    • Inferior olivary nucleus

    • Pyramid

    • CN 9, CN 10

  • Caudal Medulla (Cuneate and Gracile Tubercles)

    • Gracile nucleus

    • Cuneate fasciculus

    • Cuneate nucleus

    • Internal arcuate fibers

    • Spinal trigeminal nucleus

    • Pyramids

  • Motor Decussation

    • Gracile fasciculus

    • Gracile nucleus

    • Cuneate fasciculus

    • Cuneate nucleus

    • Spinal trigeminal nucleus

    • Pyramids/motor decussation (corticospinal tract

Somatosensory tracts

  • Dorsal spinocerebellar tract

  • Anterolateral tract

  • DC-Medial Lemniscus tract

Motor tracts

  • Corticospinal tract

    • Anterior

    • Lateral

  • Corticobulbar tract

  • Corticopontine tract

    • Pontine nuclei

    • Transverse fibers of pons

    • Middle cerebellar peduncles

    • Cerebellum

    • VPL?????