Anatomy 9a CN1-6 Flashcards
If olfaction a mechanical or chemical receptor?
Chemical
T/F Olfactory receptor cells are neurons in the nasal cavity
True
What bone is the roof of the nasal cavity?
Ethmoid Bone
Which hair system IS neurons:
Olfactory
Cochlea
Vestibular
Olfactory
Describe the olfactory sensory/receptor cells (hair cells) found in the sensory organ olfactory epithelium
(What type of neuron)
Bipolar neurons with cilia (olfactory hairs) on end of dendrite
What are the supporting cells found in the olfactory epithelium?
Mucous membrane lining of nasal cavity that function to support, nourish, insulate, and detoxify olfactory receptor cells (neuroglia)
What are the basal stem cells found in the olfactory epithelium?
Neurons continually undergoing replication to replace olfactory receptor cells which have a life span of 1 month
What are the olfactory glands found in the olfactory epithelium?
Provide mucous to cover surface of olfactory epithelium to dissolve odor molecules so they can interact with receptor cells
T/F: Odor molecules must be dissolved before they can interact with olfactory sensory/receptor cell receptors
True
What is adaption in regard to olfactory apparatus?
Process by which we decrease our sensitivity to continuous exposure to a particular odor (50% adaptation in first second of exposure)
Describe the olfactory pathways starting with an odor ending at olfactory bulb
Odor (molecule in air) -> molecule dissolves in mucous of nasal surface -> molecules binds to combination of olfactory receptors protein (ligand binding) -> Chemical gated channels open (Ca/Cl) -> Depolarize due to graded potential on dendrite/soma in olfactory epithelium (CN 1 not considered ganglia) -> AP down axon CN 1 -> CN 1 goes through cribriform plate to olfactory bulb
T/F: Olfactory bulb is layered for processing signals and is NOT topographically representative of olfactory epithelium for discriminating signals
F:
IS topographically representative of olfactory epithelium for discriminating signals
T/F: Olfactory bulb does not always send signals
False: Olfactory bulb is always sending signals and a new signal changes the pattern of signaling
Olfactory tract carries new pattern of signals from olfactory bulb to:
- Ipsi and contralateral limbic structures (amygdale, entorhinal cortex, hippocampus, prefrontal cortex, Insula (reflex to odor)
- Temporal? either directly or via thalamus for odor discrimination
What are the 5 accessory structures of the eye?
Eye lid Eye brow eye lashes muscles lacrimal apparatus
Eye lid:
Function:
What muscles close lid and what CN?
What is the inner lining of eye lid?
- Function - protect eye
- Orbicularis occuli orbital and palpebral close eye (CN 7)
- Palpebral conjunctiva is the inner lining of eye lid (continuous with sclera)
What is the lacrimal apparatus?
Describe pathway
- Lacrimal glands produce lacrimal fluid (tears) which is released (CN 7)
- Secrete fluid superior/lateral -> flows diagonally to inferior/medial lacrimal canals-> empty into nasal cavity
What are the extrinsic eye muscles? (6)
Superior/inferior rectus
lateral/medial rectus
superior/inferior oblique
What is the sclera of the eye?
Continuous with what?
Avascular/vascular?
- Continuous with the cornea
- Forms an AVASCULAR dense “white” CT covering the eye
The sclera of the eye for an attachment between eye and what 3 structurs?
- Palpebral conjunctiva of eye lid to close off eye socket
- Dural sheath (epineurium) of CN 2
- Tendons of extraoccular muscles
- > Effectively hold eye in place
What is the cornea?
Avascular/vascular?
AVASCULAR area covers anterior surface of eye ball
The vascular middle layer of the eye is called what?
Uveal tract
What is the choroid of the eye?
Middle layer
Contains blood vessels
What is the ciliary body of eye?
Anterior modification of choroid
What is the ciliary processes of ciliary body?
What does it produce?
What does it attach to?
- Form circular ridge
- Contains capillaries
- Produce aqueous humor
- Attach to suspensory ligaments which connect to lens
Ciliary muscle:
What is it?
What CN innervation?
- Circular smooth muscle at base of ciliary process that changes shape of lens by pulling suspensory ligaments (visual accommodation for near/far vision)
- CN3 parasympathetic innervation
Describe what happens when ciliary muscle contracts?
Increase/decrease CN stimulation?
Decrease tension of lense -> convex surface (opening decreases) -> near vision
-Increase CN 3 stimulation
Describe what happens when ciliary muscle relaxes?
Increase/decrease CN stimulation?
Increase tension of lense -> flat surface (opening increases) -> far vision
-Decrease CN 3 stimulation
What is the iris?
- Area of eye color
- Smooth muscle fibers that change size of opening (pupil) through which light enters eye ball
The circular muscle of the iris does what?
Innervated by?
- Constricts pupil
- Parasympathetic CN 3
The radial muscle of the iris does what?
Innervated by?
- Dilate the pupil
- Sympathetic (carotid plexus/sup cervical plexus)
What is the retina?
- Inner layer
- Contains neuron sensor receptor cells and is beginning of visual pathway
What is the pigment epithelium of retina?
Neural/non-neural epithelial cells?
- Outer layer of retina next to choroid
- Composed of non-neural pigmented epithelial cells
What is the photoreceptor layer of retina?
Rods-
Cones-
-Neurons contain sensor receptor processes with photo-pigment
Rods - dim light vision produces gray images (100 million/retina)
Cones - bright light vision produces color images (5 million/retina)
What is the outer nuclear layer of retina?
Soma of rods and cones
The outer synaptic layer of retina is also called?
outer plexiform layer
What is the inner nuclear layer of retina?
Bipolar layer for initial image processing
What is the ganglion cell layer of retina?
- Bodies of ganglia cells (multipolar ganglia cells NOT pseudounipolar)
- Axons of ganglia cells form optic nerve fibers (inner most layer of the retina next to vitrous body)
Which way does light travel?
Inner optic nerve cell layer -> outer pigment epithelium/photoreceptor layer
or vice versa?
Inner optic nerve cell layer -> outer pigment epithelium/photoreceptor layer
Which way do nerve impulses travel?
Inner optic nerve cell layer -> outer pigment epithelium/photoreceptor layer
or vice versa?
Outer pigment epithelium/photoreceptor layer -> Inner optic nerve cell layer
What is the optic disk of the retina?
T/F: Optic disk contains sensory receptor cells
-Blind spot
-Site where optic nerve (CN 2) enters and blood vessels (opthalmic A/V) enter/exit the eye ball
FALSE: Contains no sensory receptor cells (rods/cones)
What is the macula lutea of the retina?
Contains rods or cones?
Visual axis = focal point
-Contains central fovea which is an area of only cones and serves as the area fo highest visual resolution
What is the ora serrata of the retina?
Anterior margin of the neural (photoreceptor) retina
Lens:
Connected by what to what?
Functions?
- Connected by suspensory ligaments to ciliary process/muscles
- Functions to bend light to focus image on retina
- more curved = near, contraction of ciliary
- Less curved = far, relaxation of ciliary
What is the vitreous body (humor)?
- Located between lens and retina
- Contains phagocytes that remove floating debris
What is the anterior cavity of the eye?
What does it contain?
How is the liquid drained?
Between the cornea and the lens
- Contains aqueous humor which is filtered blood plasma secreted by the ciliary body and drained by the canal of Schlemn into the venous system in the anterior chamber
- Nourishes lens and cornea
Refraction:
How are images changed when it gets to retina?
What love corrects images?
Cornea and lens bend light rays to focus them on the retina
- Images are inverted upside down and reversed right to left
- Brain occipital lobe corrects retinal images to give them proper orientation
Accomodation:
What is it?
Describe change for near objects:
Describe change for far objects:
-Process by which curvature of lens is changed to focus light rays on retina
Near objects: curvature becomes greater (ciliary muscles contract and decreases tension on suspensory ligaments)
Far objects: Curvature flattened (CN3 parasympathetic inhibition - ciliary muscles relax and increase tension of suspensory ligaments)
Myopia (nearsightedness):
Distant objects can’t be seen clearly because the image is focused in front of retina
(can only see near objects, use concave lens to fix)
Hypermetropia (farsightedness):
near objects can’t be seen clearly because image is focused behind retina
(can only see far objects, use convex lens to fix)
Presbyopia
Lens becomes less elastic with age and therefore less convex moving the focal point for near vision further away from eyes
Convergence:
Necessary for what type of vision
- Process of moving the eyes medially for near vision so that image of objects hit the equivalent spot in both retinas
- Maintain overlap of visual fields of both eyes for BINOCULAR VISION which allows depth perception and 3 dimensional perception
Light pathway starting with light ending at retina
Light -> object -> reflected light -> cornear -> aqueous humor -> lens -> vitrous body -> retina
Pigment cells
absorb light = quench
photoreceptor cell
transduce light to nerve impulse
Describe nerve signal within retina:
Change pattern of depolarization/hyperpolarization = excitation/inhibition neuron layers within the retina to change pattern of signals on ganglion cell axons/CN2
Where are AP generated in visual pathway?
In ganglion cells
APs exit the eye by?
optic nerve (CN 2)
Where do the two optic nerves meet?
Optic chiasm
Impulses from nasal half of retina go where?
Cross over to opposite side of the brain
Impulses from temporal half of retina go where?
Stay on same side of brain
Where are optic tracts formed?
After the optic chiasm
What does the left optic tract contain?
Left temporal and right nasal retina go to left brain
= right visual field
What does the right optic tract contain?
right temporal and left nasal retina go to the right brain
= left visual field
The optic tracts will send signals to what 3 areas?
- Pretectal area -> pupillary reflex
- Superior colliculus -> horizontal tracing eye movements and head turning
- Lateral geniculate nucleus of thalamus
Spacial relationships of visual/retinal fields are maintained where?
Lateral geniculate nucleus
Where are images processes to be in proper perspective?
Visual cortex
External Eye muscles:
Originate where?
Insert where?
Originate on orbital bone
insert on sclera
Levator Palpebrae superioris
Innervation -
Action -
Innervation - CN 3
Action - elevate eye lid (open)
Orbicularis occuli
Innervation -
Action -
Innervation - CN 7
Action - depress eye lid (close)
Superior oblique
Innervation -
Action -
Innervation - CN 4 trochlear
Action -
1. From near focus (eyes adducted) will further adduct
2. From far focus (eyes abducted) will further abduct
3. Will also depress and medially rotate
Inferior oblique
Innervation -
Action -
Innervation - CN 3
Action -
1. From near focus (eyes adducted) will further adduct
2. From far focus (eyes abducted) will further abduct
3. Will elevate and laterally rotate
Superior rectus
Innervation -
Action -
Innervation - Cn 3
Action - elevate (slight add and medial rotate)
Inferior rectus
Innervation -
Action -
Innervation - CN 3
Action - depress (slight add and lateral rotate)
Medial rectus
Innervation -
Action -
Innervation - CN 3
Action - adduct
Lateral rectus
Innervation -
Action -
Innervation - Cn 6
Action - abduct
Cn3 neuron types: (2)
- Somatomotor to skeletal muscles
2. Visceromotor (parasympathetic) to smooth muscles and glands
The nuclei of CN 3 occulomotor found where in brain stem?
- Somatomotor nuclei
- Visceromotor (parasympathetic) nuclei
- Found at level of midbrain1.
1. Somatomotor nuclei - occulomotor nucleus
2. Visceromotor nuclei - edinger-westphal nucleus
How does CN 3 enter orbital cavity?
Through superior orbital fissure
What muscles does the superior division of CN 3 innervate? (2)
Ipsilateral/Contralateral?
Superior division - ipsilateral
- Superior rectus
- Levator palpebrae
What does the inferior division of CN 3 innervate?
Ipsilateral/Contralateral?
Inferior division - ipsilateral
- Inferior rectus
- medial rectus
- inferior oblique
- Ciliary ganglion (parasympathetic)
How does inferior division of CN 3 affect the
- Ciliary body/ciliary muscles? (describe stimulation/no stimulation)
- Circular muscles of iris?
- Ciliary body/ciliary muscles? accommodation
Stimulation - relax suspensory lig -> increase curvature of lens (near vision)
No stimulation - pull suspensory lig -> decrease curvature of lens (far vision) - Circular muscles of iris? pupil constriction
CN 4 Neuron types: (2)
- Somatomotor to eye muscle
2. Somatosensory proprioception
Pathways of CN4 (trochlear n) start with nucleus Where nucleus located? Where does it cross? How does it enter the orbital cavity? What muscles does it innervate?
- Nucleus = brain stem at level of midbrain
- Cross pretectum
- Cranial foramen = superior orbital fissure
- Contralateral superior oblique (somatomotor and sensory)
CN 6 neuron type (1):
- Somatomotor to lateral rectus m
Describe pathway of CN 6 from brain stem
Where nucleus located in brain stem?
How does it enter the orbital cavity?
What muscle does it innervate?
- Brain stem nuclei at level of open medulla
- Through the superior orbital fissure
- Ipsilateral Lateral rectus m to abduct eye
Describe pathway of sympathetics
Start with preganglionic neuron lateral horn T1 ->
What head structures?
- preganglionic neuron lateral horn T1 ->
- postganglionic neuron in Superior cervical ganglia of paravertebral chain ganglia ->
- Carotid/sympathetic plexus of nerves ->
- Head structures: iris, glands
What is the pupillary light reflex?
Shine light in one eye, both should constrict
Describe 1st part of pathway of pupillary reflex
Start: Light
End: pre-rectal area
- Light
- Ganglion cells
- optic n/optic tract
- pre-tectal area (rostral of superior colliculus
Describe 2nd part of pathway of pupillary reflex
Start: pre-rectal area
End: Pupil constricts
- Pre-tectal area
- Edinger-Westphal nucleus on both sides (bilateral projection via posterior commissure)
- Parasympathetic preganglionic
- Ciliary ganglia
- Parasymp postganglionic
- contract circular m or iris
- pupil constricts
Direct pupillary light reflex
Eye shined light into constricts it’s pupil
Concensual pupillary light reflex
Eye did not shine light into also constricts its pupil
Accommodation reflex -
Accommodation - change focus from far to near object
Accommodation reflex: Describe 1st part of pathway
Start: Motor cortex
end: Activate edinger-westphal
- Motor cortex
- CN 3
- Medial rectus muscles on both sides
- Adduct to facilitate convergence of visual field
- Papillary constriction reflex (pupillary constriction)
- Activate edinger-westphal
Accommodation reflex: Describe pathway
Start: Activate edinger-westphal
end: Near vision
- Activate edinger-westphal
- Ciliary ganglia
- Ciliary muscles contract
- increase curvature lens
- Near vision
