Brain stem & Cerebellum

The brain Telencephalon Diencephalon Cerebellum Brain stem

The brain stem Consists of Midbrain Pons Medulla oblongata 1 2 3

Ventral surface Pyramid: contain pyramidal tract (corticospinal tract ) Decussation of pyramid: formed by crossing fibers of corticospinal tract Olive: produced by underlying inferior olivary nucleus Anterolateral sulcus: rootlets of hypoglossal nerve emerge from it Retroolivary sulcus: rootlets of glossopharyngeal, vagus and accessory nerves emerge from it XII IX X XI

Medulla oblongata Dorsal surface Lower portion  Gracile tubercle : produced by underlying gracile nucleus  Cuneate tubercle : marks the site of cuneate nucleus  Inferior cerebellar peduncle  Obex Upper portion: forms the lower half of rhomboid fossa

Pons Ventral surface Basilar part Basilar sulcus Bulbopontine sulcus: from medial to lateral, the abducent, facial and vestibulocochlear nerves appear Middle cerebellar peduncle Trigeminal nerve Pontocerebellar trigone: the junction of medulla, pons and cerebellum V VI VII VIII

Pons Dorsal surface Superior cerebellar peduncle Superior medullary velum Trochlear nerve 1 3 2

Midbrain Ventral surface Crus cerebri Interpeduncular fossa oculomotor nerves emerge from medial of crus cerebri Posterior perforated substance III VI

Midbrain Dorsal surface Superior colliculus constitute centers for visual reflexes Inferior colliculus associated with auditory pathway Brachium of superior colliculi Brachium of inferior colliculi IV

Fourth ventricle Position Situated ventral to cerebellum, and dorsal to pons and cranial half of medulla Central canal →fourth ventricle →mesencephalic aqueduct→third ventricle

Boundaries Inferolateral: gracile and cuneate tubercles, inferior cerebellar peduncle Superolateral: superior cerebellar peduncle Lateral recess

Features Median sulcus Sulcus limitans Vestibular area overlies vestibular nuclei Acoustic tubercle overlying dorsal cochlear nucleus Medial eminence Striae medullares

Facial colliculus: overlies nucleus of abducent n. and genu of facial nerve Hypoglossal triangle: verlying hypoglossal nucleus Vagal triangle: overlies dorsal nucleus of vagus nerve Inferior Fovea Area postrema

Roof Anterior part: formed by superior cerebellar peduncle and superior medullary velum Posterior part: formed by inferior medullary velum and choroid plexus of fourth ventricle Three apertures  Median aperture of fourth ventricle  Two lateral apertures of fourth ventricle

Internal structures Gray matter Cranial nerve nuclei Relay nuclei

Names of cranial nerves Ⅰ Olfactory nerve Ⅱ Optic nerve Ⅲ Oculomotor nerve Ⅳ Trochlear nerve Ⅴ Trigeminal nerve Ⅵ Abducent nerve Ⅶ Facial nerve Ⅷ Vestibulocochlear nerve Ⅸ Glossopharyngeal nerve Ⅹ Vagus nerve Ⅺ Accessory nerve Ⅻ Hypoglossal nerve

Functional components General somatic afferent fibers (GSA): transmit exteroceptive and proprioceptive impulses from head and face to somatic sensory nuclei Special somatic afferent fibers (SSA): transmit sensory impulses from special sense organs of vision, equilibrium and hearing to the brain General visceral afferent fibers (GVA): transmit interoceptive impulses from the viscera to the visceral sensory nuclei Special visceral afferent fibers (SVA): transmit sensory impulses from special sense organs of smell and taste to the brain General somatic efferent fibers (GSE): innervate skeletal muscles of eye and tongue Special visceral efferent fibers (SVE): transmit motor impulses from the brain to skeletal muscles derived from brachial (gill) arches of embryo. These include the muscles of mastication, facial expression and swallowing General visceral efferent fibers (GVE): transmit motor impulses from the general visceral motor nuclei and relayed in parasympathetic ganglions. The postganglionic fibers supply cardiac muscles ， smooth muscles and glands

Classification of cranial nerves Sensory cranial nerves: contain only afferent (sensory) fibers  Ⅰ Olfactory nerve  Ⅱ Optic nerve  Ⅷ Vestibulocochlear nerve Motor cranial nerves: contain only efferent (motor) fibers  Ⅲ Oculomotor nerve  Ⅳ Trochlear nerve  Ⅵ Abducent nerve  Ⅺ Accessory nerv  Ⅻ Hypoglossal nerve Mixed nerves: contain both sensory and motor fibers---  Ⅴ Trigeminal nerve,  Ⅶ Facial nerve,  Ⅸ Glossopharyngeal nerve  Ⅹ Vagus nerve

Sensory cranial nerves N.Location of cell body and axon categories Cranial exit Terminal nuclei Main action Ⅰ Olfactory cells (SVA) Cribrifom foramina Olfactory bulb Smell Ⅱ Ganglion cells (SSA) Optic canal Lateral geniculate body Vision Ⅷ Vestibular ganglion(SSA) Internal acoustic meatus Vestibular nuclei Equilibri um Cochlear ganglion (SSA) Cochlear nuclei Hearing

Motor cranial nerves N.Nucleus of origin and axon categories Cranial exitMain action Ⅲ Nucleus of oculomotor (GSE) Superior orbital fissure Motor to superior, inferior and medial recti; inferior oblique; levator palpebrae superioris Accessory nucleus of oculomotor (GVE) Parasympathetic to sphincter pupillea and ciliary muscles Ⅳ Nucleus of trochlear nerve (GSE) Superior orbital fissure Motor to superior oblique Ⅵ Nucleus of abducent nerve (GSE) Superior orbital fissure Motor to lateral rectus Ⅺ Nucleus of accessory nerve (SVE) Jugular foramenMotor to sternocleidomastoid and trapezius Ⅻ Nucleus of hypoglossal nerve( GSE) Hypoglossal canalMotor to muscles of tongue except palatoglossus

General somatic efferent nuclei Nucleus of oculomotor n. Nucleus of trochlear n. Nucleus of abducent n. Nucleus of hypoglossal n.

Special visceral motor nuclei Motor nucleus of trigeminal n. Nucleus of facial n. Nucleus ambiguous Accessory nucleus

Special visceral efferent nuclei NucleusSiteCranial n.Function Motor nucleus of trigeminal n. Pons Ⅴ Masticatory muscles, tensor palati & t. tympani Nucleus of facial n.Pons Ⅶ Facial m., platysma, posterior belly of digastric, stylohyoid, stapedius Nucleus ambiguusMedulla Ⅸ,Ⅹ.ⅪⅨ,Ⅹ.Ⅺ Skeletal m. of pharynx, larynx and upper part of esophagus Accessory nucleusMedulla- cervical cord Ⅺ Sternocleidomastoid, trapezius

General visceral motor nuclei Accessory oculomotor nucleus Superior salivatory nucleus Inferior salivertory nucleus Dorsal nucleus of vagus n.

General visceral efferent nuclei NucleusSiteCranial nerve Function Accessory oculomotor nucleus Midbrain Ⅲ Sphincter pupillae and ciliary m. Superior salivatory nucleus Pons Ⅶ Submandibular, sublingual and lacrimal glands Inferior salivertory nucleus Medulla Ⅸ Parotid gland Dorsal nucleus of vagus n. medulla Ⅹ Many cervical, thoracic and abdominal viscera

Visceral sensory nuclei ( general and special ) Nucleus of solitary tract

Visceral sensory nuclei ( general and special ) NucleusSiteCranial n.Function Nucleus of solitary tract Medulla Ⅶ,Ⅸ,ⅩⅦ,Ⅸ,Ⅹ Taste and visceral sensation

General somatic afferent nuclei Mesencephalic nucleus of trigeminal n. Main sensory nucleus of trigeminal n. Spinal nucleus of trigeminal n.

General somatic sensory nuclei NucleusSiteCranial n.Function Mesencephalic nucleus of trigeminal n. Midbrain Ⅴ Proprioception of head Main sensory nucleus of trigeminal n. Pons Ⅴ Tactile sensation of face Spinal nucleus of trigeminal n. Medulla upto 2 nd cx. seg. Ⅴ Pain and temperature sense of face

Special somatic afferent nuclei Cochlear nuclei 2 - Dorsal - Ventral Vestibular nuclei 4 - Superior - Inferior - Medial - Lateral

Special somatic afferent nuclei NucleusSiteCranial n.Function Cochlear nuclei Pons and medulla Ⅷ Sense of hearing Vestibular nuclei Pons and medulla Ⅷ Sense of equilibrium

Non-cranial nerve nuclei NucleusSite Gracile nucleusMedulla (underneath gracile tubercle) Cuneate nucleusMedulla (underneath cuneate tubercle) Superior olivery nucleusPons Pontine nucleuspons Nucleus of inferior colliculusMidbrain Gray matter layers of superior colliculus Midbrain Red nucleusMidbrain Substantia nigraMidbrain Pretectal areaMidbrain

Cerebellum Site: Posterior cranial fossa, behind pons & medulla oblongata. 2 Surfaces: Superior & Inferior. 3 Parts: * Vermis - Superior: indistinct from sup. surface. - Inferior: lodged in the vallecula. * 2 Lobes

Cerebellum 3 Fissures: * Primary * Horizontal * Posterolateral Functional Divisions: * Archi-cerebellum: vestibulo-cerebellum. * Paleo-cerebellum: spino-cerebellum. * Neo-cerebellum: ponto-cerebellum.

Cerebellum