Special Senses Part Two (smell, taste, vision, hearing) Flashcards
What is the “hole” in the middle of the iris?
pupil
What “covers” the iris and the pupil?
cornea
clear and transparent
The lens is a derivative of…
Where is the lens?
optic placode
posterior to iris
What is the area responsible for the sharpest vision?
fovea
The optic nerve is connected to neurons that go into where?
retina
coats inner surface of the eye
What’s the name of the place where nerves come off of the retina and turn into the optic nerve?
What does this area NOT contain?
Optic disc “blind spot”
There are NO photoreceptors
2 types of muscle in iris:
pupillary dilator pupillary constrictor (sphincter)
Pupil diameter…
Parasympathetic:
Sympathetic:
Parasympathetic: constricted
Sympathetic: dilated
When the lens is FLAT, it means…
When the lens is THICK, it means…
Flat: object is far away; ciliary muscles are relaxed
Thick: object is close; ciliary muscles are contacted
Accommodation reflex is what?
The autonomic adjustment of the eye to give us clear vision
Nerves and activity associated with…
Distant vision:
Close vision:
Distant: no parasympathetic activity
Close: parasympathetic activity (CN 3)
Functions, activity, and cranial nerves of these muscles…
Sphincter pupillae:
Dilator pupillae:
Ciliary body/muscle:
- Sphincter pupillae: constrict pupil (high light or calm) PARASYMPATHETIC (CN 3)
- Dilator pupillae: dilate pupil (low light, excitement, sex, fear) SYMPATHETIC (CN 3)
- Ciliary body/muscle: change shape of lens; PARASYMPATHETIC (CN 3)
The eye, an extension of the brain, “folded in on itself” and created a double layer. What is the layer that the light hits first after it hits the retina? What is the second layer?
First layer: nerves that consolidate and regulate the information that’s coming from the photoreceptors
Second layer: photoreceptors
What are photoreceptor cells?
rods and cones
*sensory!
Rods:
Cones:
Rods: blacks, grays, motion
Cones: 3 types; colors
What does it mean when someone is colorblind?
They have a defect in a certain kind of cone
Muscles AND nerves associated with…
Blinking:
Winking:
Blinking: levator palpebrae superioris (CN 3) - unconscious
Winking: orbicularis occuli (CN 7) - conscious
Tympanic membrane separates what?
external ear from the middle ear
What does the middle ear house?
malleus, incus, stapes
Sometimes the vibrations going into the ear are too strong. What is the “first” muscle that helps prevent damage by constricting? What is it innervated by?
What is it attached to?
Tensor tympani (CN V3) Malleus
Remember:
What is the stapes derived from?
What is the nerve for it?
Hyoid arch
facial nerve
What is the muscle that attaches to the stapes to prevent damage from strong vibrations?
What is it innervated by?
Stapedius muscle
CN 7
What 2 muscles tense up to reduce the amount of vibrations going into the ear?
Tensor tympani
Stapedius muscle
The vibrations go to the malleus, then the incus, then to the stapes. Where do they go after that?
The stapes footplate sits inside the oval window; it transfers the vibrations to oval window by moving towards, away, towards, away
The vibrations meet the basilar membrane and it moves up and down, which causes the hair cells to move up and down and they end up bending once they hit what?
Tectorial membrane
it DOES NOT move!
What kind of gated channel is involved in hearing?
Mechanically gated channel
Describe the pathway of hearing.
Vibration arrives at tympanum
It vibrates the malleus, then the incus, then the stapes
The stapes vibrates the oval window, causing pressure waves in the cochlea
Pressure waves distort the basilar membrane
Basilar membrane pushed hair cells against tectorial membrane
CN 8 carries signals to the brain
What is the function of the round window?
It acts as a pressure relief
The semicircular canal houses what? And then it houses what?
It houses semicircular ducts which is filled with the fluid that causes us be aware of positional changes
At the base of the semicircular canal, what is responsible for rotational movement?
Ampulla
What is responsible for linear movements, acceleration, and equilibrium?
Macula
Inside an ampulla, there is a gelatinous mass called the _______ which has a base with ________ cells.
cupula
hair
What pushes on the cupula and will move the hair cells?
The fluid around it
Position of the cupula…
Upright:
Bends to left:
Bends to right:
Upright: at rest
Bends to left: move head to right
Bends to right: move head to left
The macula also has a mass of gelatinous material, but unlike the cupula’s gelatinous mass, it is NOT influenced by what?
the fluid movement
What is embedded inside the gelatinous mass of the macula?
minerals called statoconia (or otoliths)
The statoconia is connected to the underlying structures by…
gelatin
*so there is a little delay
The gravity causes the statoconia to do what? Then what happens?
slide slightly
act on the hair cells
*if it’s a strong enough stimulus, it will create an action potential
