Unit 2: Brain & Some CNs

telencephalon

- cerebrum, includes:

+ frontal lobes (primary motor cortex)

+ parietal lobes (primary sensory cortex)

+ temporal lobes

+ occipital lobes

corpus callosum

- component of telencephalon

- connects the right and left hemispheres at inferior edge of longitudinal fissure

diencephalon

- thalamus, epithalamus, & hypothalamus

mesencephalon

- also called midbrain

- includes corpora quadrigemina, cerebral peduncles

- connects the cerebellum & brainsteam to the cerebrum

metencephalon

- pons (middle cerebellar peduncles)

- cerebellum

myelencephalon

- medulla oblongata

brainstem components

- mesencephalon, pons, medulla oblongata

central sulcus

- separates frontal and parietal lobes

- precentral gyrus (primary motor cortex)

postcentral gyrus (primary sensory)

longitudinal fissure

- between right and left hemispheres of brain

transverse fissure

- between cerebrum and cerebellum

lateral sulcus

- separates parietal and frontal lobes from temporal lobe

choroid plexus

- produces CSF

-looks like cottage cheese

- line select areas of the walls of the ventricles

lateral ventricles

- paired spaces in the cerebrum with body, anterior, posterior, and inferior horns

- connect to third ventricle via the interventricular foramen

third ventricle

- single space on midline between the right and left thalamus

- receives CSF from lateral ventricles

- drains into cerebral aqueduct through the midbrain

fourth ventricle

- single pyramid shaped space between pons and cerebellum

- receives CSF from cerebral aqueduct

- drains into subarachnoid space of spinal cord

cervical portion of ICA

- remains in the carotid sheath and has no branches in the neck

petrous portion of ICA

- enters the carotid canal to first run superior and then anteromedially through the petrous portion of the temporal bone

cavernous portion of ICA

- emerges from carotid canal to cover (but not pass through) foramen lacerum

- artery turns anteriorly and then runs superiorly in the carotid grooves of the sphenoid bone

supraclinoid portion of ICA

- emerges above the anterior clinoid process

- gives off ophthalmic artery as this portion goes by the optic canal

ICA final branches

- gives off the middle and anterior cerebral arteries of the cerebral arterial circle

- an anastomosis between the right and left anterior cerebral arteries is via the anterior communicating artery

basilar artery

- right and left vertebral arteries merge together to form the basilar artery, which runs along the midline of the anterior surface of the brainstem

branches off vertebral artery

- gives off posterior inferior cerebellar arteries which wind around the cerebellum

basilar artery branches

- anterior inferior cerebellar arteries : run around inferior portion of cerebellum

- pontine branches : come off both sides of basilar a.

- superior cerebellar arteries : wind around superior portion of cerebellum

- posterior cerebral arteries : terminal branches of basilar, wind around posterior part of the cerebrum

posterior communicating arteries

- connect the posterior cerebal arteries and internal carotids

all arteries in Cerebral Arterial Circle / Circle of Willis

- ICAs

- anterior cerebral arteries

- anterior communicating artery

- posterior cerebral arteries

- posterior communicating arteries

ciliary ganglion

- preganglionic fibers from CN III

- postganglionic fibers via short ciliary nerves to eye for constrictor pupillae and ciliary muscles

pterygopalatine ganglion preganglionic fibers

- preganglionic fibers from CN VII via greater petrosal nerve, which exits a hiatus in the anterior petrous portion, passes through foramen to meet the deep petrosal nerve (sympathetic fibers) to make the nerve of the pterygoid canal

pterygopalatine ganglion postganglionic fibers

- fibers via the zygomatic nerve to lacrimal nerve (CN V1 branch) to lacrimal gland

nasal and palatine mucous glands,

taste buds in palatal mucosa

submandibular ganglion

- preganglionic fibers from CN VII via chorda tympani nerve along the lingual nerve

- postganglionic fibers travel to submandibular and sublingual salivary glands

otic ganglion preganglionic fibers

- from CN IX via lesser petrosal nerve (exits skull via foramen ovale)

- lesser petrosal nerve receives sympathetic fibers from the tympanic nerve (CN IX branch)

- tympanic nerve re-enters the skull through a hiatus just posterior to the carotid canal to join the lesser petrosal nerve

otic ganglion postganglionic fibers

- fibers travel via auriculotemporal nerve to parotid gland

trigeminal nerve

- leaves the cranial vault and enters trigeminal (Meckel's) cave, which is an extension of the subarachnoid space

- trigeminal ganglion lies in the cave

ophthlamic nerve

- somatic sensory only

- divides in cavernous sinus and branches pass anteriorly via the superior orbital fissure into the orbit and anterior scalp

branches off ophthalmic nerve

- frontal

- lacrimal

- nasociliary

frontal nerve

- divides into the supraorbital and supratrochlear nerves, innervating the anterior scalp

lacrimal nerve

- sensory to conjunctiva, upper lid

carries parasympathetic postganglionic fibers of CN VII to lacrimal gland

nasociliary nerve

- sensory to nasal cavity (ethmoidal nerve) and cornea (long ciliary nerve)

- carries parasympathetic postganglionics of CN III to ciliary and constrictor pupillae muscles via short ciliary nerve

maxillary nerve

- somatic sensory only

- passes via foramen rotundum into the pterygopalatine fossa

- branches pass from the fossa to all parts of the maxilla, nasal cavity, and palate

maxillary nerve branches

- zygomatic nerve

- infraorbital nerve

- posterior and middle superior alveolar nerves

- anterior superior alveolar nerve

- greater & lesser palatine nerves

- nasopalatine nerve

zygomatic nerve

- divides into zygomaticofacial and zygomaticotemporal nerves which are cutaneous to cheek and temporal region

infraorbital nerve

- passes via the inferior orbital fissure, infraorbital groove, canal, and foramen to innnervate nose, cheek, lower eyelid, and upper lip

posterior and middle superior alveolar nerves

- innervate the upper premolars and molars

anterior superior alveolar nerve

- innervates the upper incisors

nasopalatine nerves

- from the greater palatine nerve or pterygopalatine ganglion

- passes via the sphenopalatine foramen into the nasal cavity and incisive canals, foramina, and fossa to mucosa of anterior hard palate

greater and lesser palatine nerves

- innervate mucosa of the hard and soft palates and nasal mucosa via the nasal branches

- pass through the greater and lesser palatine foramen

mandibular nerve

- somatic sensory and somatic motor

- enters infratemporal fossa via the foramen ovale

branches of mandibular nerve

- inferior alveolar nerve

- lingual nerve

- buccal nerve

- auriculotemporal nerve

inferior alveolar nerve

- mainly sensory

- passes through the mandibular foramen to innervate the lower teeth

- gives off nerve to mylohyoid that innervates the mylohyoid muscle and anterior belly of digastric

- passes out of the mental foramen as mental nerve to innervate skin over mental region

lingual nerve

- somatic sensory to anterior 2/3 of tongue

buccal nerve

- sensory to cheek

auriculotemporal nerve

- sensory nerve which ascends anterior to the ear to innervate the scalp

facial nerve

- transverses the facial canal in temporal bone

- divided into intermediate nerve and motor root

intermediate nerve

- smaller root

- responsible for somatic sensory (to skin of external acoustic meatus), parasympathetics, taste

motor root

- larger or 'proper' branch of CN VII responsible for somatic motor to muscles of facial expression

geniculate ganglion of facial nerve

- contains bodies of sensory nerve fibers

intermediate nerve branches

- greater petrosal nerve

- nerve of the pterygoid canal

greater petrosal nerve

- preganglionic parasympathetics join the deep petrosal nerve (sympathetic fibers from spinal cord) to become the nerve of the pterygoid canal

nerve of the pterygoid canal

- travels through the pterygoid canal to the pterygopalatine fossa

- preganglionic parasympathetics synapse at pterygopalatine ganglion

- postganglionic fibers then travel to lacrimal gland on branches of CN V1 & CN V2

chorda tympani

- preganglionic parasympathetics and taste from anterior 2/3 of tongue

- crosses deep surface of tympanic membrane

- leaves temporal bone through the petrotympanic fissure (just posterior to the mandibular fossa)

- joins the lingual nerve carrying parasympathetics to the submandibular and sublingual salivary glands (synapse in submandibular ganglion) and taste from anterior 2/3 of tongue

- also does small somatic sensory to skin of the external acoustic meatus, fibers through stylomastoid foramen

motor root branches

- leave the temporal bone via the stylomastoid foramen and divide within the parotid gland into 5 branches

- innervate the muscles of facial expression (and occipitalis)

- includes: temporal, zygomatic, buccal, mandibular, and cervical branches

cranial nerve nuclei

- cranial nerve fibers connect to cranial nerve nuclei

- sensory neurons terminate here; motor neurones originate

- all CNs except CN I, II, and XI have nuclei in the brain stem

- CN I & CN II are extensions of forebrain

- CN CI nucleii are in C1-3 spinal cord

olfactory foramina contains

- in cribriform plate of ethmoid

- axons of CN I traverse the foramina and synpase with the olfactory bulb

optic canal contains

- CN II

- ophthalamic artery/vein

superior orbital fissure contains

- CN III, IV, VI, and ophthalmic nerve (CN V1) enter orbit after passing through cavernous sinus

foramen rotundum contains

- maxillary nerve which traverse the foramen to enter the pterygopalatine fossa

foramen ovale contains

- mandibular nerve traverses foramen to enter infratemporal fossa

internal acoustic meatus contains

- CN VII and CN VIII enter temporal bone through this meatus

stylomastoid foramen contains

- somatic motor portion of CN VII passes out to the facial muscles

foramen lacerum contains

- greater petrosal nerve (CN VII fibers) passes through to meet the deep petrosal nerve

jugular foramen

- CN IX, X, XI leave skull to enter neck

- venous blood from sigmoid sinus enters jugular vein

hypoglossal canals

- CN XII leave skull to enter neck

foramen magnum

- CN XI (spinal portion) enters skull