Neuron

• highly specialized cells
• compartmentalized and polarized (because one axon, not symetrical)
• soma (cell body), axon, dendrite (recieve info), axon terminal (send info)

Nissl body/ substance

• unique to neurons
• high density of rough ER
• neurons are highly active in protein synthesis

Axon 

• only in neurons( 1 per neuron)
• uniform diameter(mm to > 1m)
• each axon usually has collaterals to multiple targets
• terminal synapses
• contains microtubules(tubulin) and neuofilaments(intermediate only in neurons)
• no ribosomes in axon(all proteins from cell body 

Axonal (axoplasmic) transport

anterograde transport

• microtubles
• kinesin: ATPase provides energy for microtubules
• fast transport (100-400mm/day) for proteins in secretory vesicles, neutrotransmitters in synaptic vessicles and mitochondria
• slow transport (1mm/day) of cytoskeleton proteins, proteins for regeneration, enzymes for transmitter production

Axonal (axoplasmic) transport

retrograde transport

• uses the ATPase dynein
• fast transport(20-250mm/day)
• growth factors and materials for recycle
• retrograde transport of toxins, rabies virus
• can be used as research tool

Dendrites

• spines: bud like extension of dendrite membrane: increase in communication sites, relatively independent
• not all neurons have spines on dendrites
• synapses form on spines as well as dendritic shafts
• microtubles, neurofilaments and mitochondria
• no myelin (axons have it) and ribosomes in dendrites(not enough to be independent of soma protein production

Dendritic (dendroplasmic) transport 

• both anterograde and retrograde transport
• both kinesin and dynein superfamily proteins
• more complicated than in axons
• microtubules in axons are oriented uniformly
• microtubules in dendrites: mixed in orientation

Bipolar Cell

• two neurites: dendrite vs axon
• dendrite at top recieving information, soma in middle and axon at bottom sending it
• special senses: bipolar cells in retina, olfactory, sensory neurons, vestibular ganglion cells, auditory ganglion cells

pseudounipolar neuron

• cell body off to the side
• its single neurite bifurcated: peripheral axon vs central axon
• primary sensory systems
• pain, touch, temperature
• dorsalroot ganglion (DRG) neurons
• neurons in sensory ganglia of cranial nerves (V, VII, IX, X)

Multipolar Neurons

• most common( >99%)
• three or more neurites(one axon, many dendrites)
• motor neuron of spinal chord, pyramidal cell of hippocampus, perkinje cell of cerebellum
• other classifications: spiny vs aspinous; sensory vs motor neurons; glutamatergic, GABAergic, etc

Glia: Differences from neurons

• three main types
• non-polarized
• electrical synapses
• most have no action potentials
• outbumber neurons
• able to divide after birth

Astrocytes

• star shaped glia
• protoplasmic  (grey matter)
• fibrous(fibrillar) (where the axons are, white matter)
• physical support, transport of nutrients, scavengers, regulate extracellular content

Microglia and Oligodendrocyte

• two types of glia cells
• microglia are immune effector cells or scavengers
• oligodendrocytes provide myelin to CNS neurons

Oligodendrocyte-CNS Myelination

• myelin: a membranous wrapping
• one oligodendrocyte~ multiple axons
• Nodes of Ranvier: unmyelinated parts
• most axons are myelinated

Nodes of Ranvier

• cluster of voltage-gated Na, and K channels
• essential for propagation of action potentials 

Anatomical Planes

• coronal(frontal)-parallel to the face
• sagittal(median)-seperating left and right halves of the body. Also called midsagittal; planes off to one side of the midline are parasagittal.
• horizontal-plane parallel to the ground
• transverse- plane is perpendicular to the long axis of the structure under study

Ipsilateral vs contralateral

• ipsilateral: on the same side 
• contralateral: on the opposite side

Decussation

• point where a pathway crosses the midline

CNS subdivisions

• Cerebrum-conscious perception, thought, volition
• diencephalon
• brainstem-basic life support, hearing, balance: midbrain, pons and medulla
• cerebellum: nonconscious motor control: aspects of motor control of which we are not consciously aware/do not require conscious thought
• spinal chord: sensory and motor control, reflexes

Spinal Chord

• connects brain to periphery
• connects with spinal nerves to coordinate many activities: sensation, muslce control, reflexes, autonomic nervous system

Brainstem

• basic life support: cardio-resp centers, maintain consciousness
• cranial nerves: balance, hearing, taste, sensorya nd motor to face
• connects spinal cord with higher centers 
• superior: midbrain, pons, medulla
• CN III-XII are attached to brainstem

Cerebellum

• non-conscious contributions to motor coordination
• connects brainstem via: superior cerebellar pedunce(scp), middle crebellar peduncle(mcp), inferior cerebellar peduncle(icp)

Forebrain

• diencephalon+telencephalon
• conected to brainstem by the cerebral peduncles
• covered largely by cerebral cortex: gyrus(gyri)-the bumps, sulcus(sulci)-the grooves

Diencephalon

• thalamus: gateway to cerebral cortex, sensory, motor and other functions
• hypothalamus: autonomics, endocrine systems for homeostasis, powerful association with emotions

Telencephalon

• cerebral hemispheres, cerebrum
• conscious perception, thought, volition
• surface: cerebral cortex
• deep: white matter and nuclei

Telencephalon: lobes

• frontal lobe, parietal lobe, occipital lobe, temporal lobe
• lateral fissure(slyvian) seperates the temporal lobe from the frontal and parietal lobe
• central sulcus sepraters the frontal lobe from parietal lobe (line btw motor and sensory function)
• parieto-occipital sulcus is self explanatory 

Proprioception

• ability to view our body in time and space
• crosses midline in a decussation in the medulla
• lesion in brain would be contralateral, lesion in lumbar spinal chord would be ipsilateral 

CSF/ventricular System

• reduction of tractions of the nerves and blood vessels connected with the C S
• cushioning effect on the CNS and dampens the effects of trauma
• removing of metabolites from the CNS
• maintaining a stable ionic environment for the CNS

Ventricular system subdivisions

• lateral ventricles
• third ventricle
• cerebral aqueduct
• fourth ventricle
• atrium

Lateral Ventricles 

• C shape structure with a short tail
• anterior horn, body, posterior and inferior horns, intraventricular foramina(of monro), atrium

Third Ventricle

• narrow space between two thalami
• it is connected rostrally with the lateral ventricles and caudally with the cerebral aqueduct

Cerebral Aqueduct

• small canal connecting third and fourth ventricles
• because of narrow diameter, cerebral aqueduct especially susceptible to occlusion (hydrocephalus)

Fourth Ventricle

• a pyramid-shaped space
• dosally it extends into the cerebellum and caudally it continues into the central canal of the spinal cord
• has three openings into the subarachnoid space: 2 foramina of luschka and a foramen of magendie

Atrium

• space where the body of the lateral ventricles, posterior horn and temporal horn converge

CSF Composition

• very little amount of protein present, no blood cells in the CSF
• glucose, Ca and K less than in blood serum
• Na, Cl and Mg is greater than in blood serum

CSF circulation

• produced by the choroid plexus(lateral and fourth vent)
• from the lateral ventricles flows into third ventricle via foramina of monro
• third ventricle flows into fourth via the cerebral aqueduct
• leaves fourth through the foramina of luschka and magendie into the cerebellomedullary cistern(cisterna magna)
• travels within the subarachnoid space into the venous sinuses through the arachnoid vili
• pressure in subarachnoid space is higher than in venous sinuses so no flow back

Blockage of CSF flow

• typically occures in cerebral aqueduct
• results in swelling or enlargement of the lateral ventricles(hydrocephalus)
• hydrocephalus can also be a result of choroid plexus tumor leading to CSF overproduction-the amount of CSF exceeds the flow capacity 

Meninges

• located internal to the skull and the vertebral colum
• meninges consist of fibroblasts and connective tissue
• human meninges: dura mater, arachnoid mater, pia mater
• protect underlying brain and spinal chord, support framework for arteries, veins and sinuses, enclose a fluid-filled cavity, the subarachnoid space

Dura Mater

• contains blood vessels and nerves
• has great strength(large amounts of collagen)
• has two layers periosteal and meningeal (cannot seperate)
• meningeal layer during development forms the dura infoldings(falx cerebri, falx cerebelli and tentorium)
• the tentorium divides the cranial cavity into supratentorial and infratentorial compartments

Arachnoid mater

• arachnoid barrier cell layer and spindly cells(arachnoid trabeculae)
• separated from pia mater by the subarachnoid space containing CSF
• enlarged regions of subarachnoid space are called cisterns(pontine, interpeduncular, chiasmatic, superior, cerebellomedullary and lumbar)

Herniation Syndromes

• supratentoral or infratentorial herniations
• a shift of the brain through or across regions due to mass effect(tumor, trauma, or infection

Supratentorial herniation

• most common is uncal herniation
• a hematoma forces the uncus to push on the midbrain
• major deficits are decreased levels of consciousness, dilation of the pupil and loss of most eye movement, paralysis of one side of the body

Infratentorial herniation

• most common is tonsillar herniation
• a cerebellar tumor increases intracranial pressure and pushes tonsil to compress the medulla(cardivascular and respiratory centers, reticular formation-coma)

Epidural (extradural) hemorrhage

• bleeding between skull and dura mater
• most common cause is an injury to the head, with or without skull fracture
• blood from damaged arteries detarch the dura from the skull and form an epidural (extradural) hematoma
• lessions tend to be short and wide because they do not cross the dural skull attachments

Subdural hemmorrhage

• bleeding between the dura and arachnoid
• blood from damaged veins, passing through the subarachnoid space to enter venous sinuses, detach the junction between dura and arachnoid
• looks long and thin on MRI(no attachment to skull)

Subarachnoid hemmorrhage

• bleeding in the subarachnoid space
• blood vessels(usually arteries) may be damaged from trauma or may rupture spontaneously in the subarachnoid space
• blood will be present in CSF obtained by cisternal puncture(lumbar cistern)
• blood appears on MRIs around the brain, including the major CSF cisterns

General Brain information

• 50% of all brain probelms are vascular
• the brain has 2% of total body wieght and recieves 15-17% of total body blood supply
• brain consumes 20% of the oxygen used by the body
• 10-12 seconds of brain blood deprivation results in loss of consciousness
• brain damage may occur after 3-5 minutes without blood supply

Branches of internal carotid artery

• ophthalmic artery(eye)
• posterior communicating artery: connects internal carotid and ventrobasilar systems
• anterior choroidal artery: suplies infer horn of the lateral ventricle, choroid plexus and optic tract
• anterior cerebral artery(ACA) supplies the medial surface of the cerebral cortex up to the parieto-occipital sulcus
• anterior communicating artery: connencts the two ACAs
• middle cerebral artery(MCA) supplies the lateral surface of the hemisphere, except for the superior, occipital and inferolateral aspects

Branches of Middle Cerebral Artery

• venticulostriate arteries
• supply the basal ganglia, thalamus and internal capsule
• if dammaged, cause classic stroke

Branches of the vertebral Artery

• 2 posterior spinal arteries: arise from either vertebral arteries(25%) or posterior inferior cerebellar arteries(75%)
• anterior spinal artery: formed from 2 vertebral arter
• posterior inferior cerebellar arteries: supplies deep cerebellar, inferior cerebellum and medulla
• basilar artery: formed by the union of the two vertebral arteries
• anterior inferior cerebellar arteries: suply ant and inf cerebellum and parts of medulla and pons
• superior cerebellar arteris: supply part of the midbrain, superior surface of the cerebellum
• posterior cerebral arteries: supply occipital lobe and medial surface of temporal lobe, midbrain and thalmus

Great Arterial Circle (of Willis)

• formed b the anastomosis of the internal carotid and vertebrobasilar blood systems
• multiple branches of the circle penetrate the ventral surface to form anterior and posterior perforated substances
• consists of: anterior communicating
• anterior cerebral artery
• internal carotid arteries
• posterior communicating arteries
• posterior cerebral arteries
• basilar artery 

Watershed Areas

• where two major cerebral arteries terminate
• anterior border zone: btw anterior and middle cerebral arteries
• posterior border zone: btw middle and posterior cerebral arteries

Need to know:

Deep Cerebral Veins

• Internal Cerebral Vein
• Great cerebral vein of Galen

Major Venous Sinuses

• cavernous sinus drains into the sigmoid sinus through superior and inferior petrosal sinuses
• superior and inferior sagital sinuses and straight sinus drain into the confluence of sinuses
• confluence of sinuses drains into the transverse sinuses, which drain into the sigmoid sinuses
• sigmoid sinuses drain into the internal jugular veins to the heart

ophthalmic vein

• accepts drainage of blood from the medial angle of the eye, nose, lips 
• this drains into the cavernous sinus where the internal carotid arteries and CN III, IV, V, and VI are passing through
• therefore, an infection from this part of the face may spread into the cavernous sinus with severe consequences

Blood supply

• anterior spinal artery: supplies anterior 2/3 of spinal cord
• posterior spinal arteries: supply dorsal 1/3 of spinal cord
• extra blood supply comes from branches of large internal arteries(medullary arteries)
• largest medullar arteries are artery of Adamkiewicz
• radicular arteries supply blood but do not make connections with spinal arteires
• radicular-medullary arteries

Artery of Adamkiewicz

• medullary artery
• appears at the level of T12-L2
• accidental tied off during an abdominal surgery will cause paralysis in the lower half of body including legs

Cells surrounding the brain

microvessels

• endothelial cells
• pericytes
• astrocytes

Endothelial cells of BBB

• lack fenestrations
• instead have tight junctions-provide continuous physical barrier
• lack pinocytotic vessicles
• increased mitochondria and transport proteins for energy dependent transport

Pericytes of the BBB

• connective tissue cells with smooth muscle-like properties
• stabilize BBB
• influence endothelial cell proliferation
• regulate permeability to water and some other molecules
• attracts and organizes astrocyte process

Astrocytes of the BBB

• astrocyte processes(end feet) cover 95% of brain microvessel surface
• support other cell types
• facilitate cell-cell communication in and out of the BBB
• modulates permeability of certain substances

Circumventricular Organs

• parts of the brain require direct access to the bloodstream
• for sensing blood levels or releasing substances into the blood
• posterior pituitary, median eminance(hypothalmus), area postrema(vomiting center), OVLT(fluid and electrolyte balance), subfornical organ(fluid and elec balance), pineal cland(cicardian rhythm, melatonin), subcommissural orgain(secretes proteins into csf)

Compromise of  BBB

• trauma (injury, radiation, chemicals)
• ischemia/hemorrhage
• tumors
• inflammation
• neurodegenerative diseases
• some metabolic and congenital disorders
• epilepsy
• demyelinating disease

BBB and Drug delivery

• increase permeability/disrupt BBB
• modify drug to make it more likely to pass BBB
• trojan horse-package drugs in something that does pass BBB
• avoid the BBB

Increasing BBB permeability

• osmolarity
• chemical
• focused ultrasound

Drug modification for BBB

• reduce Pglycoprotein efflux 
• reduce H-bonds
• increase lipophilicity
• reduce molecular weight
• replace carboxylic groups
• add intramolecular H-bond
• modify/select for transporters

Permeable Precursors

• L=Dopa-uses amino acid transporters to cross BBB(dopamine is not permeable)
• chlorambucil esters-more lipophilic
• estredox-more liophilic than other estrogen

Trojan Horse, BBB

• exploitation of receptor mediated transcytosis system
• transferrin or insulin receptors are present in BBB
• coupling of drug to protein or peptid like insulin, transferrin via sulfur bond

Drugs Avoiding BBB

• inject into brain
• inject into CSF
• transnasal

Reflexes

• triceps C7, 8
• Biceps C5, 6
• Knee L3, 4
• Ankle S1, 2

Parts of the spinal chord

• midian fisure
• dorsal and ventral column
• lateral column
• dorsal horn( laminae I-VI)
• ventral horn (laminae VII-IX)
• laminae X is area around central canal 
• white mater: funiculus to fasciculus to tract to pathway

Ascending (Sensory) Pathway

• posterior colums: fasciculus gracillis (lower body) and cuneatus (upper body)
• posterior spinocerebellar tract
• Anterior spinocerebellar tract(both on lateral side)
• lateral spinothalamic tract (anterolateral system)
• anterior spinothalamic tract (anterolateral system)

Descending (motor) Pathways

• primarily in anterior(ventral); some lateral contribution
• lateral corticospinal tract
• rubrospinal tract (flexion, extension)
• rest are posture and balance(body in space)
• anterior corticospinal tract
• tectospinal tract
• reticulospinal tract
• vestibulospinal tract

Dorsal Intermediate Sulcus

• separates fasciculus cuneatus(FC) from fasciculus gracilis
• start to see fasciculus cuneatus around T6

Spinal Accessory Nucleus (ACC)

• C1-C5
• motor component for trapezius and sternocledomastor muscles
• origin of Cranial nerve XI (Accessory nerve
• only CN with origin in spinal cord

Phrenic Nerve Nucleus (P)

• C3 to C5
• motor component for diaphragm
• most medial portion of ventral horn

Intermediolatefal Column (IML)

• T1 to L2
• sympathetic pre-ganglionic neurons 
• juts out from the grey matter and is also known as lateral horn

Dorsal Nucleus of Clark(DN)

• C8/T1 to L2/3
• sensory component for unconscious proprioception of hindlimb and cerebellum
• looks like tight little circle

Sacral Parasympathetic Nucleus 

• S2 to S4
• parasympathetic preganglionic neurons for pelvic viscera

Spinal cord blood supply

• vertebral arteries come off the ascending aorta
• vertebral arteries contribute to anterior spinal artery that runs near anterior fissure and the posterior spinal arteries that run on the dorsal cord near the dorsal intermediate sulcus
• redicular arteries come off the descending aorta and provide blood near the spinal cord but dont attach
• sulcal artery comes off the anterior spinal arterior and goes into the anterior firsure and dives into the spinal cord
• both the ASA and PSA have arterial vasocorona that circle around the spinal cord (AVC)
• Anterior spinal artery does all of the grey matter and all of the lateral and ventral white matter 
• posterior spinal artery does the dorsal column

Brainstem Nuclei Functions

• Essential life-support (cardiorespiratory)
• consciousness and arousal(sleep)
• motor and sensory (most major tracts pass through)
• modulate internal state (emotions)
• modulate higher functions (attention and cognition)

Fiber tracts through brainstem

• major motor and sensory tracts pass through
• corticospinal-pyramidal system: volitional movement
• posterior column-medial lemniscus system: carries sensory info from body to the cortex(touch)
• trigeminal nuclei: carries sensory of touch, pain, itch and some proprioception
• anterolateral system: carries sensory information from the body, pain, temp, itch, no touch

Ventral view of brainstem

• caudal border of medulla is the pyramidal decessation(cross over in middle)
• rostral border of medulla is the caudal border of the middle cerebellar peduncle 

Dorsal View of Brainstem and Thalamus

• striae medullares is the rostral border of the medulla, caudal bodrer of pons 
• CN IV(trochlear nerve) is the rostral border of pons or caudal border of mid brain 

Arterial Supply of Brainstem

Ventral View

• vertebral arteries come together to form the basilar artery
• posterior spinal arteries normally come off the vertebral and wrap around the anterior surface
• anterior spinal arteries come off the vertebral
• posterior inferior cerebellar artery(PICA) come off vertebral
• Anterior inferior cerebellar artery(AICA) come off the basilar artery
• superior cerebellar artery comes off the rostral portion of basilar artery

Intrinsic brainstem organization

• following from ventral to dorsal
• base: all three levels have a base
• tegmentum: all three levels have a tegmentum in btw the base and ventricular system
• tectum(small right about the cerebellum): above ventricular system and is only in midbrain

Medulla-Spinal Cord Transition

Decussation of the pyramids

• new things: spinal nucleus CN V, and spinal tract CN V around it (recieves fibers from VII, IX, and X too)
• Changing things Pyramid at the ventral(anterior portion) and the decussation of pyramids

Medulla

Level of the Obex

• changeing: inferior cerebellar peduncelw ith dorsal sphocerebellar tract, and the obex
• New things: external(lateral cuneate nuclease, nucleus cuneatus, nucleus gracilis, nucleus soliterius, tractus solitarius, dorsal motor nucleus of X, nucleus CN XII(most medial with fibers running), internal arcuate fibers, medial longitudinal fasciculus, tectorspinal tract, medial lemniscus, inferior olivary nucleus(squigly), CN XII, and nucleus ambiguus

Medulla

Level of the inferior Olive

• changing: external cuneate nucleus, inferior cerebellar peduncle, nucleus cuneatus, fourth ventricle(big space)
• new: choroid plexus(in fourth ventricle), and CN X(coming off the posterior lateral part) 

Medulla

Level of CN X and Vestibular Nuclei

• changing: inferior cerebellar peduncle(getting larger)
• new: inferior vestibular nucleus and medial vestibular nucleus
• reticular formation is a big space of a large number nuclei

Medullo-Pontine Junction

Level of Cochlear Nerve

• changing: inferior olivary nucleus, corticospinal tract(moved up some), and inferior cerebellar peduncle
• new: pontine nuclei(displaced corticospinal tract), middle cerebellar peduncle, central tegmental tract, CN IX, CN VII, ventral cochlear nucleus, dorsal cochlear nucleas(cochlears cover dorsal horn), and nucleus prepositus
• raphe nuclei(obscurus pallidus) midline nuclei: source of serotonin 

Arterial Supply to Lower Medulla(caudal)

• posterior spinal artery does the posterior 50%
• vertebral artery does the next 25% when moving anteriorly except the very midline
• anterior spinal artery does the rest

Arterial Supply to the middle medulla

• anterior spinal does the entire medial portion 
• vertebral artery does the lateral ventral portion
• Posterior inferior cerebellar artery does the dorsal lateral portion 

Arterial Supply to the Rostral Medulla

• anterior spinal artery does the medial portion
• vertebral artery does the rest of the lateral ventral portion
• Posterior inferior cerebellar artery does most of the lateral dorsal portion
• the very most lateral dorsal portion is done by the anterior inferior cerebellar artery
• knocking out AICA effects hearing because it supplies to choclear stuff

Pons

Level of the Facial Nucleus

• change: middle cerebellar peduncle (massive), inferior cerebellar pedunce, and medial lemniscus(shifting)
• newP dentate nucleus surrounding the superior cerebellar peduncle, superior vestibular nucleus, lateral vestibular nucleus, nucleus CN VI, superior olivary nucleus, CN VI (way ventral to nucleus), trapezoid body, CN VII, nucleus CN VII, fibers of CN VII

Pons

Level of Genu of Facial Nerve

• changing: CN VI, fibers of CN VI, and fibers of CN VII(wrap around nucleus of CN VI)
• New: medial vestibular nucleus, globose and emboliform nuclei, facial colliculus

Pons

Level of Trigeminal Motor and Main Sensory Neclei

• changing: fourth ventricle is starting to narrow
• new: superior medullar veium(thin sheet of white matter btw brain stem and cerebellum), locus coeruleus, medial parabrachial nucleus, lateral parabrachial nucleus(these are on either side of the sup cerebellar peduncle), mesencephalic nucleus CN V, CN V(runs through medial cerbellar peduncle), main(chief) sensory nucleus CN V, motor nucleus  of CN V(mastication)

Pons-Midbrain Junction

Level of Cranial Nerve IV and Locus Coeruleus

• changing: superior cerebellar peduncle becomes more elongated, and the fourth ventricle is not the aqueduct
• new: Periaqueductal grey matter(around the aqueduct), CN IV exiting at the very dorsal lateral parts, and lateral lemniscus

Arterial Supply to the Lower Pons

• all branches off the basilar artery
• paramedian branches cover the entire median portion
• short circumferential branches cover the rest of the ventral lateral portion
• long circumferential branches cover the dorsal lateral portions

Arterial supply to the upper pons

• superior cerebellar artery does the very dorsal portion that is on the sides of the fourth ventricle
• long circumferential branchs do the lateral dorsal portion before the ventricle
• short circumferential branchs do the lateral ventral portion
• and paramedian branches do all the median to the ventricle

Arterial Supply at the pons-midbrain transition

• superior cerebellar artery does all the lateral dorsal part 
• short circumferential  branches do the lateral ventral party
• paramedian branches do the whole median part

Midbrain

• tectum
• corpora quadrigemina(superior and inferior colliculus)
• trochlear nerve
• brachium of inferior (auditory) and superior colliculus (visual)
• two colliculus help make up border of midbrain
• optic tract forms lateral and some rostral border of midbrain
• very rostral border is mamillary bodies

Interpeduncular fossa

• also interpeduncular cistern
• space formed by the cerebral peduncles and mamillary bodies
• roof known as the posterior porforated substance(holes for blood vessels)

Mid Brain

Level of Inferior Colliculus

• changing: pontine nuclei(displaced by cerebral peduncle), cerebral aqueduct, and lateral lemniscus
• newL substantia nigra, cerebral peduncle, brachium of inferior colliculs, inferior colliculs, periaqueductal grey matter, nucleus of CN IV, superior cerebellar peduncle(decussation, interpeduncular nuclei (only unpaired, right in middle nucleus)

Midbrain

Level of superior colliculus

• changing: periaqueductal grey matter gains nuclei, and brachium of inferior colliculus gets very samll and might dissapear
• New: red nucleus, CNII, ventral tegmental area (behaviors), ventral tegmental decussation, nucleus CN III, nucleus of edinger-westphal, mesencephalic nucleus CN V, suuperior colliculus

Vascular Supply

Mid Brain

• paramedian branches off the basilar and posterior cerebral artery, supplies median portion back to the aqueduct
• quadrigerminal artery(Branch of PCA) and superior cerebellar artery supply all of the dorsal part
• quadrigeminal supplys the lateral part of the ventral part only

Cerebellum

Mid-sagital View

• Primary fissure seperates the anterior and posterior lobe
• posterolateral fissure seperates the large posterior lobe from the flucculonodular lobe(sort of anterior)
• flucculonodular lobe made up of nodulus in center and flocculi on either side(flocculus)

Cerebellar peduncles

• superior cerebellar peduncle(scp): connects cerebellum iwth midbrain and thalamus
• middle cerebellar peduncle(mcp): connects cerebellum with pons
• inferior cerebellar peduncle(icp): connects cerebellum with medulla and spinal chord

Cerebellum Internal Structure

• cerebellar cortex(grey matter)
• white matter
• deep nuclei (grey matter)

Clinical Considerations -CN I

• anosmia-totoal loss of ability to smell. Hyposmia or olfactory hypesthesia-decreased sensitivities to odorants
• patient complaints of loss of taste are oftentimes due to olfactory dysfunction
• olfactory deficits are associated w/ alzheimer disease, parkinson disease, huntington chorea, and kallman's syndrome
• when testing for olfaction a nontrigeminal stimuli should be use- taht is, one that does not activate trigeminal receptos(amonia)

CN II Targets

• Optic Nerve
•  superior colliculus and lateral geniculate nucleus

CN III

• occulomotor Nerve
• inferior oblique muscle, inferior, medial and superior rectus muscle
• also levator palpebrae and parasym for cilliary ganglion
• nucleus of CN III and edinger-westphat nucleus (aqueduct in this level)
• paralysis of eye muscles(deviation), pupil dilation, ptosis(drooping of eyelid)

CN IV

• trochlear Nerve (smallest cranial nerve)
• innervates superior oblique
• a lesion at the level of the trochlear nerve nucleus will impair the contralateral superior oblique muscle
• a lesion after decussation will impair the ipsilateral superior oblique muscle

CN V-Trigeminal Nerve

• exit from pons and has ophtlamic (sensory), maxillary(sensory) and mandibular(sensory and motor) branches
• sensory(main), motor, and mesencephalic(proprioception) nuclei located in dorsolateral pons
• spinal nucleus and spinal tract in most of brainstem
• facial paralysis, loss of sensation or pain

CN VI

• Abducens Nerve
• innervates lateral rectus muscle(abduction)
• since Nucleus CN VI in pons (do not cross over)
• lesion results in flaccid paralysis of ipsilateral lateral recus muscle- eye deviation towards the middle

CN VII

• Facial Nerve
• exits at border of medulla and pons
• motors all muscles of face except muslces of mastication
• sensory is front 2/3 of tounge
• Nucleus that sends fibers out that wrap around the Nucleus of VI (abduccens)
• lesions result in paralysis of facial muscles on the affected side and loss of taste sensation from the anterior 2/3 of tounge(smile, frown ect)

CN VIII

• Vestibulocochlear Nerve
• sensory nerve to the inner ear(balance and hearing)
• butterfly shape has central and dorsal cochlear nuclei, as well as multiple vestibular nuclei
• vestibular: vertigo, movement disorders or nystagmus
• cochlear: hearing loss and tinnitus

CN IX

• Glossopharyngeal Nerve
• exits lateral to the olive
• innervates parotid, posterior 1/3 tounge and senses O2/CO2 levels in common carotid
• nucleus ambiguus
• lesion result in loss of taste and gag reflex
• neuralgia-pain in pharynx, caudal tongue and tonsil

CN X

• vagus nerve, exits lateral to the olive
• resp and digestion
• level with choroid plexus
• spinal, trachus sollitarus and nucleus solitarius and dorsal motor nucleus and nucleus ambiguus(IX and X)
• lesion can reulst in paralysis of pharyngeal and laryngeal muscles

CN XI

• accessory nerve from spinal and some medulla(motor)
• shoulder movement(paralysis causes drooping): Trapezius and sternocleidomastoid

CN XII

• hypoglossal nerve
• motor for the tounge
• can be seen in a level with the choroid plexus and nucleus found just ventral to fourth ventricle
• lesion reults in toungue deviation towards side of lesion