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Photoreception Accessory Structures Eyebrows Eyelids Lacrimal caruncle Sebaceous & sweat glands; Sandman’s eye sand. Epicanthic fold Eyelashes Innervated with many nerves. Conjuctiva—transparent membrane—over eyelids and sclera. Important in lubrication of the eye.

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Presentation Transcript
the eye
Photoreception

Accessory Structures

Eyebrows

Eyelids

Lacrimal caruncle

Sebaceous & sweat glands; Sandman’s eye sand. Epicanthic fold

Eyelashes

Innervated with many nerves.

Conjuctiva—transparent membrane—over eyelids and sclera. Important in lubrication of the eye.

Conjuctivitis—Pinkeye.

Lacrimal Apparatus

Lacrimal gland

Nasolacrimal duct

Tears contain antibodies and lysozyme.

The Eye
the human eye
The Human Eye
  • Cornea—contains many nerve endings.—transplantation and repair.
  • pupil
  • iris
  • Lens--convex
  • suspensory ligaments
  • ciliary bodies
  • Extrinsic muscles
  • retina
  • cones and rods
  • optic nerve
  • Choroid coat—Why is it dark colored?
light and image formation
Electromagnetic Radiation

Visible light

Reflection

Refraction

Real image

Convex lens

Upside down and reversed form left to right.

Light and Image Formation
image formation
Focal point

Focal length

Retina

Photoreceptors

Optic disc

Blind spot

Optic nerve

Rods

cones

Macula lutea

Fovea centralis

Forms a pathway for light to get to the photoreceptors.

Most cones are in the fovea.

This is where important area for hard focusing.

Small portion of our field of view.

Image Formation
human eye defects
Human Eye Defects
  • Myopia
  • Causes
  • Eye too long or lens too convex
  • Effects
  • Correction—concave lens.
  • Hyperopia
  • Causes
  • Eye too short or lens too flat
  • Effects
  • Correction—convex lens.
  • Presbyopia
eye disorders
Diplopia—movements of the extrinsic muscles of the 2 eyes are not coordinated. Leads to double vision.

Strabismus—”cross-eyed” Affected eye rotates either medially or laterally. Treatments and effects.

Retinal Detachment

Glaucoma—excessive aqueous humor—Intraocular pressure.

Cataract—clouding of the lens. May be caused by sunlight, diabetes, smoking, vitamin deficiencies,, etc…

Astigmatism

Color blindness

Night blindness

Eye Disorders
visual pathways to the brain
Visual Pathways to the Brain
  • From the retina, visual impulses travel to:
    • Optic nerve
    • Optic chiasma
    • Optic tracts
    • Thalamus
    • Optic radiation tract
    • Primary visual cortex in the optic lobe.
hearing
What is sound?

Wavelength

Frequency

Pitch

Intensity

Amplitude

Loudness

Decibels

Above 90 db is dangerous

Hearing range—20 to 20000 Hz

Hearing
hearing14
Mechanoreceptors

Fluids

Outer, middle, and inner ear

Outer ear

Pinna or auricle

Are bigger ears better?

External auditory canal

Ceruminous glands

Tympanic membrane

Middle Ear

Pharyngotympanic tube

Eustachian tube

How does this structure function?

Ossicles

Malleus, incus, stapes

Malleus is attached to the eardrum.

Stapes is attached to the oval window of the inner ear.

Sound amplification

Hearing
hearing15
Transmit vibrations of the eardrum to the middle ear.

Inner ear

Bony labyrinth

Semicircular canals

Vestibule

Cochlea

Membranous labyrinth

Inside the bony labyrinth

Filled with fluid

Vestibule—oval window is attached to this structure.

Contains equilibrium receptors.

Semicircular canals—poster and lateral to the vestibule. Ampulla—equilibrium receptors.

Hearing
hearing18
Cochlea—anterior to the vestibule.

Cochlear duct

Basilar membrane

Organ of Corti

Hair cells

Cochlear nerve

Thalamus

Auditory cortex in temporal lobes

Disorders of the Ear

Otitis Media

Deafness

Conduction Deafness

Otosclerosis—stapes becomes fused to oval window.

Sensorineural deafness—damage to hair cells or neural pathways.

Cochlear implants

Tinnitus

Hearing
equilibrium
Importance of head movements.

Inputs from the inner ear, eyes, and stretch receptors

Vestibular apparatus

Vestibule—static equilibrium

Semicircular canals—dynamic equilibrium

Maculae—respond to straight line changes in speed and direction, not to rotation

Hairs cells

Vestibular nerve

Respond only to changes in velocity or acceleration.

Equilibrium
equilibrium20
Equilibrium
  • Crista ampullaris
  • Semicircular canals
  • Respond to rotation
  • Changes in rotation
  • Hair cells
  • To balance centers in the brain stem or the cerebellum
  • Motion sickness
  • Sensory input mismatch
taste
Chemoreceptors

Aqueous chemicals

Taste buds

Most on the tongue

Papillae—projections of the surface of the tongue.

Gustatory and taste cells—taste receptors

Taste pore

Gustatory hairs

Replaced every 7 to 10 days—taste buds

4 basic tastes

Sweet, salty, bitter, sour

Sweet—sugars, alcohols, amino acids

Sour—acids

Salty—metal ions

Bitter—alkaloids; poisons

Taste
taste23
Taste
  • Impulses travel from taste receptors to:
    • Either the facial nerve or glossopharyngeal nerve or vagus nerve to:
    • Medulla to:
    • Thalamus to:
    • Gustatory cortex in the parietal lobes
    • There are also branches to the limbic system
    • Triggers digestive reflexes.
smell
Olfaction

Olfactory epithelium in the roof of the nasal cavity.

Olfactory receptor cells

Olfactory cilia

Mucous covered

Life span of 60 days.

Olfactory receptors to:

Olfactory nerves to:

Olfactory bulbs to:

Olfactory tract to:

Thalamus to the olfactory cortex and the frontal lobe and to the hypothalamus, amygdala, and other parts of the limbic system.

Anosmias

Zinc deficiencies

Smell
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