Flashcards in 0409 - Cranial Nerves I - BX Deck (20):
Name the 12 cranial nerves
I OlfactoryII OpticIII OculomotorIV TrochlearV TrigeminalVI AbducensVII FacialVIII Vestibulocochlear VIIII GlossopharyngealX VagusXI AccessoryXII Hypoglossal
Categorize the cranial nerves in terms of Sensory only, Motor only, or both.
use the mnemonic: Some Say Money Matters, But My Brother Says Big Brains Matter More. S= sensory onlyM = motor onlyB = both
How are sympathhetic and parasympathetic neurons integrated into cranial nerves?
Sympathetic input: Superior Cervical GanglionParasympathetic output: cranial nerves III, IV, VII, X have parasympathetic output(responsible for everything down to left colic flexure)
What is special about CN II?
Optic nerve not considered part of PNS,considered an extension of the brain.
Where does CN I exit?
Cribriform plate of ethmoid bone.
Name the cranial nerves that control eye movement, where they originate in the brain and where they exit.
III Oculomotor, lateral to mamillary bodies in diencephalonIV Trochlear, dorsal aspect inferior to colliculiVI Abducens, pontomedullary fissure, medial to VIIall exit through the superior orbital fissure.
Describe the route of transmission through the olfactory nerve.
1. Dendrites of Bipolar cells (chemoreceptor cells) ascend2. through cribriform plate (above cribriform is known as olfactory bulb)3. reaches glomerulus 4. mitral cells5. group of mitral cell axons form olfactory tract6. ends in ento-rhinal cortex
List the following for CNII:Location of origin and ending,Exit through skull,Function,Special details
Originates: in diencephalonends at: optic tractExit: through optic canalFunction: sight ONLY (special sensory)Special Details: only half of fibers cross at optic chiasm, only the medial half of the visual field for each eye crosses. mapped projections in occipital cortex, central visual field to back, periphery to anterior, superior projects below calcarine fissure, inferior above fissure.
Describe what happens to vision in the following lesions:Damage to left optic nerveDamage to right optic tractTumour in pituitaryDamage to projections below the calcarine fissure
Left optic nerve lesion: vision in only right eyeDamage to right optic tract: right visual field is goneTumour in pituitary: medial half of visual field is gone, if severe enough complete vision loss. Damage to projections: superior portion of visual field gone.
Where else do optic tract fibers travel to?
Thalamus,Superior colliculi Specifically, Lateral Geniculate Nucleus (LGN) of thalamus
Name the muscles innervated by the cranial nerves that contorl eye movement.
CN III: Superior rectus, inferior rectus, medial rectus, inferior obliqueCN IV: superior obliqueCN VI: lateral rectus
How are pure up and down movements of the eyes completed?
Pure up and down movements require a combination of two movments:UP: superior rectus (up and medial) + superior oblique (down and lateral) Medial and lateral movements cancel out...Down: Inferior rectus (down and medial) + inferior oblique (up and lateral) Note: lateral movements are just the medial and lateral rectus muscles.
What three major sensory signals does the vestibulocochlear nerve receive?
Static vestibular: from saccule and utricles Kinetic vestibular: from semicicular canals (3)Hearing: from cochlea through tectorial membrane
Where does CN VIII exit?
It does not exit, enters skull through internal acoustic meatusstays inside temporal bone
How is kinetic vestibular information conveyed to CN VIII?
semicircular canals move during accelerationendolymph contains jelly-like substanceduring acceleration, the canals move but fluid lags behindhair cells in the cupula detects movement of canal by "brushing" against endolymph signal travels to vestibular ganglion
How is static information conveyed to CN VIII?
through utricles and saccules hair cells in these structures detect which orientation gravity pullsthus telling static head position (continuous signalling) i.e. if a person is lying down, signals continuously tell the person they are lying down.
Which part of the brain receives information from CN VIII?
the posterior two vertical gyri of the insula lobeheschl's gyrus of temporal lobe
Describe the parasympathetic components of CN III
ciliary ganglion receives input from the edinger-westphal nucleus (midbrain strcuture)from ciliar ganglion, short ciliary nerves carry parasympathetic info to the eyes.
What are short ciliary nerves and what information do they carry?
mixed nerve containing sensory, parasympathetic and sympathetic functions. sensory information carried by short ciliary goes to trigeminal V1 (naso ciliary branch) AFFERENT DIRECTIONParasympathetic output from ciliary ganglion (pupil constriction)Sympathetic information from superior cervical ganglion hitchhikes naso-ciliary branch to eye. EFFERENT DIRECTION (pupil dilation)