Autonomic Nervous System Flashcards
Lens
A transparent, biconcave structure located behind the iris
Attached to the ciliary body by suspensory ligaments, layers of protein fiber arranged like a onion layered skin
Cataracts
Opacity of the lens; Opaque, Cloudy, not transparent
Causes of Cataracts
Idiopathic, don’t know what caused it
Senile as you get older
Radiation
Long time usage of certain druges
Focal Point
Light passing through the lens is bent or refracted to a specific point
Focal Distance
Distance from the middle of the lens to the focal point
Accomodation
ability of the lens to flatten or bulge, or bending of the lens to place focal point on the retina to allow the object to be focused
What is the function of the lens
To bend or flatten to refract the light rays to place on the retina
Visual Acuity is based on what chart?
Snellen’s Chart
20/20 Vision
Normal Vision
Standing 20 feet away and being able to see the 2nd to bottom line
20/15 Vision
Better vision than 20/20
Standing 20 feet away and being able to see the last line
20/30
Worse than Normal Vision
Standing 20 feet away and being able to see the 3rd line from the bottom line
Normal person can see what a 20/30 person can see 30 feet away instead of 20, which is what the 20/30 person can see
20/200
Legally Blind
Albino’s are legally blind because they don’t have enough pigment in the back of the eye to absorb scattered photons of light.
This person stands 20 feet away and can see what a 20/20 vision person can see at 200 feet away.
What refracts light more than anything?
Cornea
As we allow light rays to pass through the eyeball, is light rays traveling through different densities of tissue?
Yes they are traveling through many different densities of tissue. The first thing they travel through is the cornea, then the aqueous humor, then through the lens, then through the vitreous humor.
What is the only thing that has the ability to adapt to change the refraction?
Lens
Emmetropia
Normal Vision
When ciliary muscles are relaxed the lens flattens, placing a distant image in focus on retina
Myopia
Near Sighted
Can see normal at close range but blurs at distance.
Characteristics of Myopia
Elastic bulging lens
The eyeball could be too deep
It places the focal point in front of the retina then diverge the light rays behind it, on the central fovea, but if you can’t get it on the central fovea it decreases visual acuity
Hyperopia
Far Sighted. What you’re good at
Short and Flat lens
Cannot refract light rays as well
Can see at normal distance, but not close up.
Less elastic lens and shallow eyeball.
Focal point is behind the retina.
Flatter lens, less refraction allows it to hopefully place that focal point, especially distant vision on the back of the retina
Focal Point is behind the Retina.
Presbyopia
Farsightedness in older people
Can’t see up close
Doesn’t bend the light as well due to loss of elasticity of the lens
Single Binocular Vision
Humans, both eyes focus on one object
Object is refracted to identical spots on both retinas
Eye Dominance
Use one eye basically to see and one eye to judge depth perception
Diplopia
Double vision
The perception of 2 images of a single object
The brain is adaptable. Orbital Fracture, restrict eye movement. That’s relatively an acute condition because the brain hasn’t had a chance to accomodate for it. But if you leave it, you will eventually suppress the bad eye image and you will eventually see the one image again
Strabismus
Cross eyed
Usually don’t have double vision because brain learns to suppress one image
Astigmatism
Imperfections in the cornea disrupting clarity of vision;
Certain parts of the visual field will be fuzzy
Two Types of Photoreceptors
Rods
Cones
Rods
High Sensitive to minimal light. Allows us to see at night (shapes and movement)
More dense away from the center
Sensitive to light in general not color
Work better in low light
Discs contain what?
Rhodopsin
Also known as visual purple; Reddish purplish pigment
Rhodopsin
The presence of photon of light that is broken down into Opsin and Retinene
How does Opsin and Retinene get converted back to Rhodopsin
By ATP and ADP + Pi
Dissection of Rods?
Discs, Nucleus, and Synaptic Endings
Specialized receptors for light up on top, rest supports the structure
Where does Retinene comes from?
Vitamin A
It is important in Night Vision
When can you actually see or perceive that flash of light?
When the photon of light breaks up Rhodopsin into the two structures.
It takes awhile to bring the two back together, it requires ATP, as Rhodopsin
When we reform rhodopsin we can no longer see the sensation of light
Ghost Images
Look at the lights, close our eyes and perceive an after image, it will be there for awhile until we reform the rhodopsin
Cones
Receptors for color and visual acuity (sharp vision)
Do not work in low light. Work in bright light. That is why we go from normal day to dusk, we start to lose color, because the cones cannot pick up enough light to perceive the color to fire the cone, so the Rods work
Found in greater numbers towards the center of the retina
Where is the highest concentration of Cones?
Macula Lutea
Fovea Centralis
Cones contain 3 types of photopigments that require bright light for breakdown. Much more complex than Rhodopsin
Amount of Red Cones in the eye?
74%
Amount of Blue cones in the eye?
16%
Amount of Green cones in the eye?
10%
When will you get White Light?
When all the cones are firing
What is the Pigmented Layers job?
Job is to absorb any scattered photons of light so that they don’t bounce up and hit something that they shouldn’t hit. It would create a decrease in visual acuity
What is involved in adjusting the sensitivity of light that the brain receives?
Amacrine and Horizontal Cells
What does the Amacrine and Horizontal Cells do?
They help to adjust the amount of information that goes from here (Dark and Light Adaptation) to the brain.
For example: Start out in dark lodge, walk out to start skiing, it’s painful to look at the snow because it’s too bright, but after awhile the brightness decreases it’s not as painful. Then you go back inside the lodge you can’t see because it’s so dark, you’re adjusting the sensitivity over a period of time to what you’re obviously visually seeing.
Dark Adaptation
An increase in sensitivity to light while in the dark.
Direct Pupillary Reflex
Pupils constrict when light is shined directly into the one eye
Indirect Pupillary Reflex
Pupil constrict in the opposite eye when light is shined directly into one eye
Light Adaptation
a decrease in sensitivity to light after exposure
100 fold difference
Purpose of Direct and Indirect Pupillary Reflex
Decrease light when entering the eye
Protects the retina from overexposure
Increases depth of field of focus
Improves image sharpness
Optic Fibers From Lateral Retina
They are ipsilateral
Medial Retina goes to which side?
Opposite side
Does Optic Chiasm have crossing fibers?
Yes
If you have a pituitary tumor and it sets on the back, it affect what?
Crossing Fibers, the part of the visual field that you would have a problem with
What part of the visual field would you lose if you had the lesion on the back of the medial side of the optic chiasma?
You would have a problem seeing laterally
If the medial retina is effected what would it effect?
It would effect the lateral visual field creating tunnel vision.
Palpebra
Upper Eye lid
Palpebral Fissure
Where eye lid comes into contact with the eyeball itself
Lateral Canthus
Lateral angle of the eye
Medial Canthus
Medial angle of the eye
Lacrimal Caruncle
fleshy part (pink and round) in the medial or nasal corner of your eye where you get the eye gunk
Lacrimal Puncta
Little holes in the Lacrimal Caruncle
Drain fluid into the nasal cavity
Meibomian Glands
Sebaceous glands located along the inner eyelid
Produces mucous
Lipid like substance that reduces surface tension between the eyelids
Chalazion
Infected meibomian gland
Not painful
Stye
Infected eyelash hair follicle
Painful
Tarsal Plate
Thick fold of connective tissue lining each eyelid, providing support
Upper eyelid, levator palpebra, allows eyelid to move up as one unit instead of accordian like
Conjuctiva
A protective specialized epithelial tissue that covers the eyelids and eye ball
Two Parts
Palpebral
Bulbar
Bulbar
Lines outside the eyeball
Fornix
Area where the palpebral meets the bulbar
Superior Oblique
Down and In
C4 Trochlear Nerve
Inferior Oblique
Up and In
C3 Oculomotor Nerve
Lateral Rectus
Abducens
Abducts the pupil and pulls it laterally
Superior Rectus
Medial Rectus
Inferior Rectus
Oculomotor nerve
Pinna
Entire structure of the ear
Job is funnel or channel the sound into the external ear canal
Ear Lobe
the bottom portion of the pinna (ear)
where you get your ears pierced
External Auditory Meatus
Black area in the ear
Tragus
Flap on in the middle of the ear
Deflects air away from ear. It deflects turbulence so you can hear better when facing the wind
Turbulence
Creates sound
Ceruminous Glands
Produces ear wax (sterile)
Ear Divisions
External, Middle, and Inner Ear
External Ear
Pinna - directs sound waves towards Tympanic Membrane
External Auditory Canal - conducts vibrations
Divider between External and Middle Ear
Tympanic Membrane
Tympanic Membrane
Divider
Has the middle ear
6 Ossicles - 3 on each side
MIS
Malleus
Incus
Stapes
Functions of MIS
Transmits sound waves generated at the Tympanic Membrane to the oval window
Eustachian Tube
Connect the little ear to the nasal pharanyx
Middle ear and outside air
Equalizes pressure
Vestibular Apparatus
Balance and equilibrium
Cochlea
Hearing
Tensor Tympani
1 of 2 muscles that attaches to the Tympanic Membrane and it will contract when we anticipate loud sounds
Ossicles
Transmit sound
Two Components of Inner Ear
Controlled by the Vestibular Cochlear Nerve
- Vestibular Portion involved in balance and equilibrium
- Cochlear Portion involved in hearing
Mechanism of Hearing
Housed in Cochlea
O. R.
Oval Window before Round Window
Scala Vestibuli and Scala Tympani
Connected to each other
Organ of Corti
Tectorial Membrane
Sterocilia
Basilar Membrane
Steps for hearing
Sound waves come into the scala vestibuli causethe vestibular membrane to vibrate
Causing endolymph to transmit sound waves to the tectorial membrane which vibrates causing the stereocilia to move
Movement of the hair cells or sterocilia cause a nerve impulse
Sound waves
The distance of sound wave travels down the membrane depends on the frequency of the soundwave.
High Frequency
Perceived close to the oval window
Travel short distance along the stereocilia
Low Frequency
Travels further away from the oval window
Travel a longer distance along the stereocilia
Neural Deafness
Caused by breaking the stereocilia.
Conduction Deafness
Caused by blocking the canals, etc. thus preventing the sound waves from reaching the stereocilia
Tempanic Membrane
Is the ear drum
Static Equilibrium
Your Heads position relative to gravity
Balance problems Tilting your head
Macula
Receptors inside the utricle and sacculethat perceive changes in head position relative to gravity
Otoliths
Ear stones
Crystals of Calcium set on top of the gelatinous mass
Gelatinous Mass
Changes in head position relative to gravity cause a shift in the position of the gelatinous mass causing hair cells to fire
Dynamic Equilibrium
Detect rotational acceleration/deceleration movement
Accelerate and feel that sense of acceleration
Deceleration feel when you stop
Semicircular Canal
all at right angles to each other to detect the relative movement of Acceleration and Deceleration movement in any plane
Ampulla
The opening
Swelling at the end of the canal
Crista
Raised structure with hairs embedded into the cupula
Inertia
Short lived
As we takeoff, we accelerate, forward movement
Fluid in the semicircular canal lags behind causing the cupula bending backward or in one direction
Semicircular Canal
Filled with Fluid
Initial Rotation of the head
When head rotates - cupula bends due to movement of endolymph against the cupula
Stimulates hair cells to fire
Nystagmus
Movement of the eyes until the cupula is no longer bent (causes rapid lateral repetitive eye movement
Inertia is overcome
Now the endolymph is moving at the same speed as the cupula and the cupula does not bend and the nerve does not fire
After Inertia
Head stops rotating and the endolymph continues to rotate and the cupula is displaced in the opposite direction
Nerve fires again
