Brain stem. The brain stem Consists of Midbrain Pons Medulla oblongata 1 2 3.
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Transcript of Brain stem. The brain stem Consists of Midbrain Pons Medulla oblongata 1 2 3.
Medulla oblongata
Ventral surface Pyramid: contains pyramida
l tract (corticospinal tract) Decussation of pyramid: f
ormed 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
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2
3
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XIIIX
XXI
Medulla oblongata
Dorsal surface Lower portion
Gracile tubercle: produced by und
erlying gracile nucleus Cuneate tubercle: marks the site
of cuneate nucleus Inferior cerebellar peduncle Obex
Upper portion: forms the lower half of rhomboid fossa
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3
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Pons
Ventral surface Basilar part (1)
Basilar sulcus (2)
Bulbopontine sulcus (3): from medial to lateral, the abducent, facial and vestibulocochlear nerves appear
Middle cerebellar peduncle (4)
Trigeminal nerve (5)
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2
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5VVI
VIIVIII
Pons
Dorsal surface Superior cerebellar pedu
ncle (1) Superior medullary velu
m (2) Forms the upper half of r
homboid fossa
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2
Midbrain
Ventral surface Crus cerebri (1)
Interpeduncular fossa (2) oculomotor nerves emerge from medial of crus cerebri
Posterior perforated substance (3)
Oculomotor nerve
123III
VI
Midbrain
Dorsal surface Superior colliculus (1) consti
tute centers for visual reflexes Inferior colliculus (2) associ
ated with auditory pathway Brachium of superior colliculi Brachium of inferior colliculi Trochlear nerve (IV) Medial geniculate body (3) Lateral geniculate body (4)
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2IV
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Fourth ventricle
Position Situated ventral to
cerebellum, and dorsal to pons and cranial half of medulla
Central canal →fourth ventricle →mesencephalic aqueduct→third ventricle
Fourth ventricle
Boundaries Inferolateral: gracile an
d cuneate tubercles, inferior cerebellar peduncle
Superolateral: superior cerebellar peduncle
Lateral recess
Fourth ventricle
FloorUpper pontine and lower medullary se
parated by Striae medullares (1) Median sulcus divided it into right and
left halves (2 Medial eminences) (2)
Upper part: Facial colliculus (3): overlies nucleus
of abducent n. and fibers of facial nerve
Upper Vestibular area (4): overlies vestibular nuclei
Superior fovea (5)
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2
3
4 5Sulcus Limitans
Fourth ventricle
Lower part: Hypoglossal triangle (1): overlying h
ypoglossal nucleus Lower Vestibular area (2) Vagal triangle (3): overlies dorsal nu
cleus of vagus nerve Inferior Fovea ( Inverted Y ). 22 12
3
Roof Upper part: formed by superio
r cerebellar peduncle and superior medullary velum
Lower part: formed by inferior medullary velum and choroid plexus of fourth ventricle
Three apertures Median aperture of fourth ve
ntricle Two lateral apertures of fourt
h ventricle
Fourth ventricle
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 an
d 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
ⅠOlfactory nerve ⅡOptic nerve Ⅷ Vestibulocochlear nerve
Motor cranial nerves: contain only efferent (motor) fibers Ⅲ Oculomotor nerve Ⅳ Trochlear nerve ⅥAbducent nerve Ⅺ Accessory nerv Ⅻ Hypoglossal nerve
Mixed nerves: contain both sensory and motor fibers--- ⅤTrigeminal nerve, Ⅶ Facial nerve, ⅨGlossopharyngeal nerve ⅩVagus nerve
Sensory cranial nervesN. Location of cell
body and axon categories
Cranial exit
Terminal nuclei
Main action
Ⅰ Olfactory cells (SVA)
Cribrifomforamina
Olfactory bulb
Smell
Ⅱ Ganglion cells (SSA)
Optic canal
Lateral geniculate body
Vision
Ⅷ Vestibular ganglion(SSA)
Internal acoustic meatus
Vestibular nuclei
Equilibrium
Cochlear ganglion (SSA)
Cochlear nuclei
Hearing
Motor cranial nervesN. Nucleus of origin and
axon categoriesCranial exit Main 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 foramen Motor to sternocleidomastoid and trapezius
Ⅻ Nucleus of hypoglossal nerve( GSE)
Hypoglossal canal Motor 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
Nucleus Site Cranial 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 ambiguus Medulla Ⅸ, .Ⅹ Ⅺ Skeletal m. of pharynx, larynx and upper part of esophagus
Accessory nucleus Medulla-cervical cord
Ⅺ Sternocleidomastoid, trapezius
General visceral motor nuclei
Accessory oculomotor nucleus
Superior salivatory nucleus
Inferior salivertory nucleus
Dorsal nucleus of vagus n.
Visceral sensory nuclei ( general and special )
Nucleus Site Cranial n. Function
Nucleus of solitary tract
Medulla Ⅶ, ,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 nucleiNucleus Site Cranial
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 2nd 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
Nucleus Site Cranial n. Function
Cochlear nuclei
Pons and medulla
Ⅷ Sense of hearing
Vestibular nuclei
Pons and medulla
Ⅷ Sense of equilibrium
Non-cranial nerve nuclei Nucleus Site
Gracile nucleus Medulla (underneath gracile tubercle)
Cuneate nucleus Medulla (underneath cuneate tubercle)
Superior olivery nucleus Pons
Pontine nucleus pons
Nucleus of inferior colliculus Midbrain
Gray matter layers of superior colliculus
Midbrain
Red nucleus Midbrain
Substantia nigra Midbrain
Pretectal area Midbrain