Unit II: Cranial Nerves I, II, III Flashcards
The olfactory epithelium lining is specifically located in what part of the nasal cavity?
Superior nasal concha
What type of neurons are olfactory neurons?
Bipolar
About how many olfactory nerves convey information to the olfactory bulbs?
10 to 20
What are the olfactory receptors called that are found in the PNS?
Olfactory hairs
What is another term for olfactory nerves?
Fila olfactoria
Are olfactory neuron axons myelinated?
No, but they are covered by Schwann cells (PNS)
Olfactory nerves pass through what specific part of which bone?
Cribriform plate of ethmoid bone
In the olfactory bulb, the olfactory nerves synapse on the dendrites of which cells?
Mitral cells
What is formed at the olfactory synapse?
Synaptic glomerulus
What are the secondary sensory neurons of the olfactory pathway?
Mitral cells
Where are the cell bodies of mitral cells located?
Olfactory bulb
Mitral cells relay information in which direction and through what?
Posteriorly through the olfactory tract
Where do the olfactory tract fibers split into medial and lateral olfactory striae?
Anterior perforated substance
Where do medial stria fibers travel to and how do they get there?
They travel to the opposite olfactory bulb via the anterior commissure
Lateral stria fibers of the olfactory tract carry formation to which location?
Primary olfactory cortex (Bdmn. Area 34)
Where is the primary olfactory cortex?
Periamygdaloid and prepiriform area, including the uncus on the medial aspect of the temporal lobe
Where is the secondary olfactory cortex?
Bdmn. Area 28: entorhinal area in the parahippocampal gyrus
What is unique about the neurons of the olfactory sensory pathway?
Only made up of 2 total neurons (instead of the typical 3 for most sensory pathways
Olfaction is an exception among senses for what reason?
It is the only sensory pathway that does not synapse in the thalamus
What is the term meaning a total loss of smell (rare condition)?
Anosmia
What can CSF leakage in the form of a runny nose be indicative of?
Skull fracture
In Alzheimer’s Disease, what is typically the location of some of the first neurons to be destroyed?
Olfactory cortex (asymmetric lost of smell)
What layer of the eye is the only complete layer?
Fibrous tunic
What two things make up the fibrous tunic (outermost layer) of the eye?
Sclera and cornea
What is the name of the middle layer of the eye?
Vascular layer
What three things make up the vascular layer of the eye?
Ciliary body, iris, and choroid
What is the innermost layer of the eye?
Retina (with ten total layers)
What is another name for the pigmented layer of the retina?
Cementing layer
The pigmented layer of the retina is adjacent to what part of the eye?
Choroid
What layer of the retina contains rod and cone cell bodies?
Outer nuclear layer
In which layer of the retina do the rods and cones synapse with bipolar cells?
Outer plexiform layer
What layer of the retina contains cell bodies of bipolar cells?
Inner nuclear layer
In which layer of the retina do bipolar cells synapse with ganglion cells?
Inner plexiform layer
In which layer of the retina do ganglion cell bodies lie?
Ganglion cell layer
What type of neurons ultimately give rise to the optic nerve?
Ganglion cells
Which layer of the retina contains retinal ganglion cell axons?
Nerve fiber layer
What is the name of the glial boundary separating the retina from the vitreous body?
Internal limiting membrane
Are retinal ganglion cell axons myelinated?
No
What are the three layers of the retina that contain neurons?
Ganglion cell layer, inner nuclear layer, and outer nuclear layer
What are the three types of cones that receive color information?
Red, green, and blue
What do cones require to function best?
Adequate light
Where is the point of clearest vision & area of highest concentration of cones?
Fovea centralis (center of the retina)
Are rods located in the fovea?
No
Where are the rods located?
Periphery of the retina
What is the only thing that rods sense?
Light vs dark
When do the optic nerve axons become myelinated?
When they leave the eyeball and enter the actual optic nerve
What forms the myelin on the optic nerve axons?
Interfascicular oligodendrocytes
Which fibers cross in the optic chiasma?
Fibers from the medial (nasal) side of each retina
The optic tract travels around what structures?
Cerebral peduncles
Where do the majority of optic nerve tract fibers synapse?
Lateral geniculate body to be relayed to the cerebral cortex in the occipital lobe (Bdmn. Area 17)
If there is a lesion in the optic nerve, what is the result?
Blindness in one eye
If there is a lesion in the decussating fibers of the optic chiasma, what is the result?
Tunnel vision
If there is a lesion in the optic tract, what is the result?
Loss of half of the visual field
If a flashlight is shined directly in the right eye, what is the result & reflex shown?
Right pupil constriction (direct light reflex)
What are the two muscles influenced by the tectospinal tract?
Trapezius and sternocleidomastoid
When a flashlight is shown into the right eye, what happens to the left pupil and what reflex is demonstrated?
Left pupil constricts, as well, but less; consensual light reflex
How many neurons make up the optic pathway to get from receptor to arrive at the occipital lobe?
Four
What does the accommodation reflex enable us to do?
Allows the shape of the lens to change for focus
When focusing on closer objects, does the lens appear more concave or convex by way of the accommodation reflex?
Convex
What is the name of the reflex that makes up blink and retract when our cornea is touched?
Corneal reflex
What is the term to describe the contraction of the medial rectus muscles to see objects moving closer to us?
Convergence
Do the visual reflexes we discussed test for cranial nerve II only?
No; it tests multiple cranial nerves
Cranial nerve II accounts only for what portion of the visual reflexes?
Afferent component only
Which spinal tract originates in the superior colliculus?
Tectospinal
Cranial nerve III carries what types of fibers?
Somatic and parasympathetic
What are the nuclei of origin of cranial nerve III?
Oculomotor nuclei
Where are the oculomotor nuclei located?
Periaqueductal gray matter, anterior to cerebral aqueduct, at the level of the superior colliculi
Which part of the cerebral cortex sends axons to the oculomotor nuclei?
Bdmn. Area 8
In addition to the cerebral cortex, the oculomotor nuclei receive fibers from which locations?
Superior colliculus and medial longitudinal fasciculus
Oculomotor axons travel through which structure as they exit the CNS?
Red nucleus
The oculomotor axons ultimately exit the CNS in what structure?
Interpeduncular fossa (into the cistern)
When the oculomotor nerve exits the CNS, what covers it?
Neural fascia (epi, peri, and endoneurium then deeply with myelin formed from Schwann cells)
Oculomotor nerves penetrate what substance while traveling along the cavernous sinus on its way to exit the skull?
Dura mater
Cranial nerve III exits the skull via what opening?
Superior orbital fissure
When does the oculomotor nerve split into superior and inferior rami?
Once in the eye socket
What muscles are supplied by the superior ramus of the oculomotor nerve?
Superior rectus (inferior aspect of it is pierced) and levator palpebra superioris
What are the three branches of the inferior ramus of the oculomotor nerve?
Medial, central, and lateral branches
What does the medial branch of the inferior ramus of the oculomotor nerve supply?
Medial rectus
What does the central branch of the inferior ramus of the oculomotor nerve supply?
Inferior rectus
What does the lateral branch of the inferior ramus of the oculomotor nerve supply?
Inferior oblique
What is another name of the accessory oculomotor nucleus?
Edinger-Westphal nucleus
The accessory oculomotor nucleus contains what type of neurons?
Preganglionic parasympathetic
Where do the preganglionic parasympathetic neurons from the accessory oculomotor nucleus synapse?
In the ciliary ganglion
Where is the ciliary ganglion located?
Posterior to the eyeball about 1 cm anterior to the superior orbital fissure
Postganglionic parasympathetic axons from the ciliary ganglion follow the course of which structures?
Ciliary arteries
Postganglionic parasympathetic axons from the ciliary ganglion pierce what structure of the eye?
Sclera
What do the postganglionic parasympathetic axons of the ciliary ganglion supply?
Ciliaris and sphincter papillae muscles
What is the action of the ciliaris muscle when contracted?
Lens becomes more convex for focusing
What is the action of the pupillary constrictor muscle (sphincter pupillae)?
Constricts the pupil
What nerve involved in another olfactory pathway is poorly developed in humans but important in other species for tracking prey?
Vomeronasal nerve
What nerve in another olfactory pathway is from the nasal septum and serves an autonomic function?
Terminal nerve
What is the purpose of the medial stria fibers of cranial nerve I to cross midline and travel to the opposite olfactory bulb?
To ensure that each cerebral hemisphere receives information from both nostrils
Axons from ganglion cells are conveyed in the nerve fiber layer to what location?
Optic disc
What are the three nuclei of termination of cranial nerve II?
Lateral geniculate bodies, superior colliculus, pretectal nucleus of the midbrain
What is the function of the fibers of cranial nerve II that synapse in the pretectal nucleus of the midbrain?
Light reflexes
