Special Senses

EAR

• Receptor types

  • Mechanoreceptors - detect mechanical or physical changes

    • ex. touch, muscle tension, hearing, equilibrium, vibration, itch, pressure

  • Thermoreceptors - detect changes in temperature

    • receptors for hot and cold

  • Nociceptors - detect tissue damage

  • Photoreceptors - detect changes in the amount of light

  • Chemoreceptors - detect chemicals dissolved in fluids

    • ex. stomach can detect differences between sugars and proteins

• Olfactory nerve drops into nasal cavity to be able to perceive chemicals

• Nerves to detect taste

  • CN IX (9) - Glossopharyngeal - gag reflex

  • CN X (10) - Vagus

  • CN VII (7) - Facial nerve

• Hear through : Gases →Solids → Liquids

• Parts of the ear

  • External Auditory Canal

    • contains ear wax: helps with moisture

  • Ossicles : Malleus, Incus, Stapes

    • works together like a megaphone which help sound travel better (through solids)

      • Oval and round window help hold in the liquid

  • Cochlea

    • 2 tubes (grey and brown)

      • grey tube is filled with perilymph

      • brown tube is filled with endolymph

        • endocochlear nerve for hearing - nerve has extensions

• After Stapes vibrates the sound transfers to liquids

• Tonotopic Organization

  • in the cochlea there are spaces for high pitch (high frequency - harder to bend) & for low pitch (low frequency - easier to bend @ the apex)

  • first nerve endings are first to be damaged (high frequency damages first)

• Eustachian Tube

  • tube from nose to ear

• Static Equilibrium

  • Otoliths - rocks inside the ear (made of calcium carbonate (limestone))

  • Vestibular branch is connected to the otoliths by gelatines mass

• Dynamic Equilibrium

  • 3 semicircular canals filled with endolymph

    • fluid moves and bends hair mass to tell the brain that you are spinning

EYE

• Lacrimal Apparatus

  • Nasal lacrimal duct - connects the corner of the eye (tears) to the nose, producing too many tears can produce more snot

• Tarsal glands / Meiobian glands

  • tunnels inside the eyelid

  • make oil (good lubricant)

    • floats on the water of the tears - prevents scratching on the eye

• Extraocular Muscles - help tract movement

  • Superior Rectus - look up

  • Lateral Rectus - look towards sides

  • Inferior Rectus - look down

  • Inferior Oblique - looks up and out

  • Superior Oblique - looks down and out

  • Medial Rectus - look toward nose

• Cranial Nerves

  • CN III - superior rectus, inferior rectus, medial rectus, inferior oblique

    • also controls raising of upperlid

    • controls pupil

  • CN IV - superior oblique

  • CN VI - lateral rectus

• Iris

  • colored area of the eye

  • melanin gives the color

    • if the melanin if flat it is dark, if it is angled there is a different color (green, blue, etc)

    • other colors besides brown is a mutation

    • without melanin the eyes would be red (blood vessels)

  • CN III (oculomotor nerve) - sphincter pupillae muscle - circular muscle - closes and opening

  • SNS - dilator pupillae muscle - dilates pupils

    • ex. used in dim light

• Sclera

  • majority of the eye is white stuff *sclera*

  • hard

• Cornea is fixed (first lens light hits)

• Lens - helps focus from near → far vision (layers of transparent tissue)

• Anterior cavity contains aqueous humor (liquid)

  • helps cornea and lens

  • carries away waste back to the blood

  • scleral venous sinuses (drain) - carry waste from eye to the blood

• For close vision the ciliary muscles contract & the lens becomes globular (circular)

• For far vision the ciliary muscle relax & the lens becomes long/thin

• Choroid - vascular layer, part at the retina where the blood vessels are

  • pigmented with melanin

  • tupedum lucidum - shows in some animals

• Retina - nothing attaches it to the eye except for the fluid in the back of the eye (vitreous humor)

  • place in retina where there are no nerves - blind spot (always in peripheral)

    • in a region called optic disc

    • blood vessels and nerves can’t be in the same space together

• Macula lutea - light focuses on this “target”

  • fovea centralis (back most part of the eye)

    • middle spot of the macula

    • helps give the best visualization/if not focused vision is blurry

• Eemmetropic

  • closest to perfect eye vision (focal point on macula)

• Myopic

  • light scatters because the eye is too long (nearsighted)

  • light rays converge too soon

  • lenses help rays converge later

    • concave lens - spread light outwards

    • convex lens - cause focal point to start before it gets to the eye, allows eye to focus

• Hyperopic

  • socket wasn’t deep enough (farsighted)

• Presbyopia

  • hardening of the lens

• Astigmatism

  • imperfect cornea (not domed shaped)

• If prescription is (-) nearsighted if (+) farsighted

• Central Dogma

  • pigments = proteins

    • erythrolabe = red

    • chlorolabe = green

    • cyanolabe = blue

  • DNA only makes 3 ways to see color

• Rods and Cones face the wall