Lecture 9a- Cranial Nerves 1,2,3,4,6 Flashcards
OLFACTION (SMELL)
OLFACTION (SMELL)
Olfaction is a _________ interaction between molecules in air with ________ receptors on the membranes olfactory receptor cells (neurons) in the nasal cavity.
- chemical
- chemo
- What makes up the roof of the nasal cavity?
- It has 10-100 million olfaction receptor cells (_______) located in a sensory organ called the __________________.
- ethmoid
- hair cells
- olfactory epithelium
The olfactory epithelium is a sensory organ composed of what 4 main parts?
- olfactory sensory/receptor cells (hair cells)
- supporting cells
- basal stem cells
- olfactory glands
-Olfactory sensory cells (hair cells) are bipolar _______ with what on the end of the dendrite?
- neurons
- cilia (olfactory hairs)
What is different about the hair cells of the olfactory system and the hair cells of the cochlea and vestibular system?
The hair cells of the olfactory system are neurons while the ones for cochlear and vestibular function are not neurons
The supporting cells are _________ since the olfactory cells are neurons. The supporting cells function is to do what?
- neuroglia
- The supporting cells are the mucous membrane lining of the nasal cavity that support, nourish, insulate, and detoxify olfactory receptor cells.
- The basal stem cells of the olfactory epithelium are constantly undergoing what?
- What is the life span of a olfactory receptor cell?
- constantly undergoing replication to replace olfactory receptor cells
- 1 month
What is the function of the olfactory glands?
-dissolve odor molecules so transduction can occur, odor molecules must be dissolved before they can interact with olfactory receptor cells
A relatively small number of olfactory receptors recognize ________ different scents by stimulating unique ________ of receptors.
- 10,000
- combinations
- What is adaptation in regards to the olfactory system?
- When does 50% of adaptation occur?
- process by which we decrease our sensitivity to continuous exposure to a particular odor
- first second of exposure
What are the 9 steps in the olfactory pathway?
- ) odor = molecule in the air
- ) odor molecule dissolves in mucous of nasal surface
- ) odor molecule binds a combination of olfactory receptor proteins
- ) chemical interaction with olfactory receptor opens chemical gated channels (Ca and Cl)
- ) graded potential on dendrite/soma in olfactory epithelium = CN1
- ) AP on axon of the olfactory receptor cell = CN1
- ) CN1 axon goes through cribriform plate to olfactory bulb
- ) signals from olfactory receptor cell activate multiple cells in olfactory bulb which is layered for PROCESSING SIGNALS
- ) olfactory tract carries new pattern of signals from olfactory bulb to ipsi and contralateral limbic structures for the REFLEX RESPONSE TO ODOR, also goes to temporal cortex for odor discrimination
What is the function of the olfactory bulb?
Layered for:
- processing signals
- topographically representative of the olfactory epithelium for discriminating signals
The olfactory tract carries signals from the olfactory bulb to what structures?
Ipsi and Contralateral Limbic Structures
- amygdala, hippocampus, prefrontal cortex
- insula for emotional response to odors = reflex response to odor
Temporal Cortex
-either directly or via thalamus for odor discrimination
ACCESSORY STRUCTURES OF THE EYE
ACCESSORY STRUCTURES OF THE EYE
What are the 5 accessory structures of the eye?
- eye lid
- eye brow
- eye lashes
- muscles
- lacrimal apparatus
What is the function of the eye lid?
protection of the eye
What are the two parts of the orbicularis oculi that function to close the lid? What nerve innervates them?
- palpebral (soft) and orbital (hard)
- CN7
What muscle functions to open the upper eye lid? What nerve innervates it?
- levator palpebral superioris
- CN3
What is the inner lining of the eye lid called?
palpebral conjuctiva
- What is the function of the lacrimal gland?
- Why do we get the sniffles when crying?
- produces lacrimal fluid (tears)
- lacrimal fluid runs from superior/lateral to inferior/medial lacrimal canals which empty into the nasal cavity
What are the extrinsic eye muscles?
- superior and inferior rectus
- lateral and medial rectus
- superior and inferior oblique
ANATOMY OF THE EYE
ANATOMY OF THE EYE
What are the 3 main layers of the eye?
- fibrous outer layer
- vascular middle layer (uveal tract)
- inner layer (retina)
What are the 2 parts of the fibrous outer layer of the eye?
- sclera
- cornea
The sclera is continuous with the ______ and forms an avascular “_____” connective tissue covering of the eye.
- cornea
- white
- The sclera forms an attachment between the eye and what 3 structures?
- What is the function of these 3 structures together?
Structures
- palpebral conjuctiva of eye lid to close off eye socket
- dural sheath of CN2
- tendons of extraoccular muscles
-These 3 structures effectively hold the eye in place
The cornea is an _________ area that covers the ________ surface of the eye ball.
- avascular
- anterior
What are the 2 main parts of the middle layer of the eye?
- choroid
- ciliary body
The choroid is the layer that contains ___________ providing oxygen and nourishment to the outer layer of the retina.
blood vessels
What are the 3 parts of the ciliary body?
- ciliary processes
- ciliary muscle
- iris
What are the functions of the ciliary processes?
- produce aqueous humor
- attach to suspensory ligaments which connect to lens
- The ciliary muscle have CN3 ________ and possible _______ roles.
- The ciliary muscle is a circular smooth muscle at the base of ciliary processes that changes the shape of the lens by pulling on _____________. This provides visual accommodation for what?
- parasympathetic
- sympathetic
- suspensory ligaments
- near and far vision
- Contraction of the ciliary muscles causes a ________ tension on the lense resulting in a _________ surface for ______ vision.
- Relaxation of the ciliary muscles causes a ________ tension on the lense resulting in a _________ surface for ______ vision.
- decreased
- convex (spherical)
- near
- increased
- flattened
- far
The iris is the area of eye ______. It contains _______ muscle fibers that change size of opening (______) through which light enters the eye ball.
- color
- smooth
- pupil
What are the 2 muscles of the iris and what is their function?
- circular m.- constrict pupil; parasympathetic (CN3)
- radial m.- dilate pupil; sympathetic (carotid plexus/ sup cervical plexus)
What is the inner layer of the eye called?
Retina
The retina contains ________ sensor receptor cells and is the beginning of the _____________.
- neuron
- visual pathway
What are the 7 main layers of the retina from outside to inside?
- pigment epithelium
- photoreceptor layer (rods and cones)
- outer nuclear layer
- outer synaptic layer (outer plexiform layer)
- inner nuclear layer
- inner synaptic layer
- ganglion cell layer
The pigment epithelium is the outer layer of the retina next to the ________. It is composed of __________ pigmented epithelial cells.
- choroid
- non-neuronal
The photoreceptor layer of the retina contains both _____ and ______. What are their functions?
- rods- dim light vision produces gray images
- cones- bright light vision produces color images
Are there more rods or cones in the photoreceptor layer?
rods= 100m/retina
cones=5m/retina
What is the outer nucleur layer of the retina?
soma of the rods and cones
The inner nuclear layer is important for what reason?
it is the bipolar layer for initial image processing
- The ganglian cell layer has what type of neuronal structure?
- What forms the optic nerve fibers?
- multipolar, NOT pseudounipolar
- axons of the ganglia cells
- Light travels past inner optic nerve cell layer to _____________/____________.
- Nerve impulses travel from outer photoreceptor layer to ________________.
- outer pigment epithelium/ photoreceptor layer
- inner optic nerve fiber layer
What are 3 specialized areas of the retina?
- optic disc
- macula lutea
- ora serrata
What is the optic disc?
- blind spot; no rods/cones
- area where nerve fibers and blood vessels enter/exit the eye
The macula lutea is the ______=________ and contains the _____________ which is an area of only cones and serves as the area of highest visual resolution.
- visual axis=focal point
- central fovea
The ora serrata is the _______ margin of the neural (photoreceptor) retina.
-anterior
- The lens is connected by ______________ to the ciliary ______/__________.
- What is the function of the lens?
- suspensory ligaments
- processes/muscles
-bend light to focus image on retina
The vitreous body (humor) is located between what structures and has what function? It also contains phagocytes which do what?
- between lens and retina
- holds retina in place
- remove floating debris
The anterior cavity (chamber) is located between the _______ and ______. It also contains __________ which is filtered blood plasma secreted by the __________ and drained by the canal of __________ into the venous system in the anterior chamber.
- cornea and lens
- aqueous humor
- ciliary body
- Schlemn
LIGHT TRANSDUCTION TO NERVE IMPULSE
LIGHT TRANSDUCTION TO NERVE IMPULSE
What are the 3 main processes in light transduction?
- Refraction
- Accomodation
- Convergence
In light refraction, the _______ and ______ bend light rays to focus them on the retina; images are inverted _________ and reversed _______. The ________ lobe corrects retinal images.
- cornea and lens
- upside down, right to left
- occipital
What is accommodation?
The process by which the curvature of the lens is changed to focus light rays on the retina.
- In accommodation, for near objects the curvature becomes ______ and ciliary muscles __________ (CN3 parasympathetic stim).
- In accommodation, for far objects the curvature becomes ______ and ciliary muscles __________ (mostly CN3 parasympathetic inhib).
- greater, contract
- flattened, relax
What are 3 dysfunctions in accomodation?
- myopia (nearsightedness)
- hypermetropia (farsightedness)
- presbyopia
With myopia, the distant objects cannot be seen clearly because the image is focused ________ the retina.
in front of
With hypermetropia, the near objects cannot be seen clearly because the image is focused _________ the retina.
behind
What is presbyopia?
Lens becomes less elastic with age and therefore less convex moving the focal point for near vision further away from the eyes.
What is convergence?
the process of moving the eyes medially for near vision so that image of objects hit the equivalent spot in both retinas.
Convergence is necessary to maintain proper overlap in the visual fields of both eyes for _______________ which allows depth perception and three dimensional perception.
-binocular vision
What are the 8 steps for the light pathway?
- ) Light
- ) Object
- ) Reflected light
- ) Cornea
- ) Aqueous humor
- ) Lens
- ) Vitrous body
- ) Retina
- pigment cells absorb light
- photoreceptor cells transduce light to nerve impulses
Change pattern of depolarization/hyperpolarization=excitation/inhibition of neuron layers within the retina to change pattern of signals on ______________/CN2.
ganglion cell axons
VISUAL PATHWAY
VISUAL PATHWAY
Excitatory and inhibitory impulses generated in ___________ cells move through neurons of other retinal cell layers, where the signal is processed and modified by convergence and divergence, and APs are generated in ____________.
- photoreceptor
- ganglion cells
APs exit the eye by what structure?
Optic nerve/CN2
The optic nerve goes to what structure?
-optic chiasm
- At the optic chiasm, impulses from the _____ half of the retina cross over to the opposite side of the brain.
- At the optic chiasm, impulses from the ________ half of the retina stay on the same side of the brain (ipsilateral)
- nasal
- temporal
When are optic tracts formed?
after the optic chiasma
- Right visual field=_____ temporal and _____ nasal retina go to the left brain via ____ optic tract
- Left visual field=_____ temporal and ____ nasal retina go to the right brain via _____optic tract
- left, right, left
- right, left, right
The optic tracts send signals to what 3 areas?
- pretectal area- pupillary reflex
- superior colliculus- tracing eye movements and head turning
- lateral geniculate nucleus of thalamus
Spacial relationships of the visual/retinal fields are maintained in the ________________.
lateral geniculate nucleus
From the thalamus impulses move on the _______________ to the visual cotex locates in the _________ lobes.
- optic radiations
- medial occipital lobes
EXTERNAL EYE MUSCLES
EXTERNAL EYE MUSCLES
The external eye muscles originate on the _________ bone and insert on the ________.
- orbital
- sclera
What are the 8 external eye muscles and what nerve innervates them?
- Levator palpebrae superioris (CN3)
- Orbicularis oculi (CN7)
- Superior oblique (CN4)
- Inferior oblique (CN3)
- Superior rectus (CN3)
- Inferior rectus (CN3)
- Medial rectus (CN3)
- Lateral rectus (CN6)
What is the function of the Levator palpebrae superioris?
elevate eye lid=open
What is the function of the Orbicularis oculi ?
depress eye lid=close
What is the function of the Superior oblique?
- from near focus (eyes adducted) will further adduct=clinically relevant
- from far focus (eyes abducted) will further abduct=anatomically relevant
- will also depress & medially rotate
What is the function of the Inferior oblique?
- from near focus (eyes adducted) will further adduct=clinically relevant
- from far focus (eyes abducted) will further abduct=anatomically relevant
- will also elevate and laterally rotate
What is the function of the Superior rectus?
elevate (slight adduct and med. rotate)
What is the function of the Inferior rectus?
depress (slight adduct and lat. rotate)
What is the function of the Medial rectus?
adduct
What is the function of the Lateral rectus?
abduct
PATHWAYS OF CN3,4,6 AND SYMPATHETICS
PATHWAYS OF CN3,4,6 AND SYMPATHETICS
CN3 is what nerve?
occulomotor
CN3 (occulomotor) has both ______motor and _______motor neurons.
- somato
- viscero
What is the general pathway of CN3?
- nuclei (somatomotor nuc= occulomotor nuc; parasympathetic nuc= Edinger Westphal nucleus)
- cranial cavity foramen= superior orbital fissure
- superior or inferior division to ipsilateral=uncrossed
- The nuclei of CN3 are locates at the level of the _________.
- What are the 2 nuclei involved in the pathway?
-brainstem
- somatomotor nucleus= occulomotor nucleus
- parasympathetic nucleus= Edinger-Westphal nucleus
The cranial cavity foramen is also known as what?
superior orbital fissure
The superior division goes to the _______ side and contains what muscles?
-ipsilateral
- superior rectus
- levator palpebrae
The inferior division goes to the ________ side and contains what muscles?
-ipsilateral
- inferior rectus
- medial rectus
- inferior oblique
- ciliary ganglion including ciliary body/muscles and circular muscles of iris
CN4 is what nerve?
trochlear
CN4 neurons are _________ to eye muscles as well as ___________ proprioception.
- somatomotor
- somatosensory
What is the pathway of CN4?
- nucleus at midbrain
- cross pre-tectum
- cranial foramen= superior orbital fissure
- contralateral superior oblique muscle
CN6 is what nerve?
abducent
CN6 neurons are ________ to lateral rectus muscle?
-somatomotor
What is the pathway of CN6?
- nucleus at open medulla
- superior orbital fissure
- ipsilateral lateral rectus muscle
What is the pathway of sympathetic neurons?
- preganglionic neuron lateral horn T1
- postganglionic neuron in superior cervical ganglia of paravertebral chain ganglia
- carotid/sympathetic plexus of nerves
- head structures: iris, glands
REFLEXES
REFLEXES
What is the pathway of pupillary light reflex?
- light
- ganglion cells
- optic n/ optic tract
- pre-tectal area
- Edinger-Westphal nucleus on both sides (bilateral projection via posterior commissure)
- parasympathetic preganglionic
- ciliary ganglia
- parasympathetic postganglionic
- contract circular m. of iris
- pupil constricts (direct pupillary light reflex, consensual pupillary light reflex)
What is the difference between direct and consensual pupillary light reflex?
- direct pupillary reflex is pupillary response to light that enters the ipsilateral (same) eye
- consensual pupillary reflex is response of a pupil to light that enters the contralateral (opposite) eye
What is the accomodation reflex pathway?
- changes from far to near objects
1. )motor cortex→CN3→medial rectus muscles both sides→adduct to facilitate convergence of visual field
2. )papillary constriction reflex→pupillary constriction
3. )activate Edinger-Westphal→ciliary ganglia→ciliary m. contract→↑curvature lens→near vision
