Special Senses Flashcards
What components make up the periorbital region?
Superior and Inferior Palpebra - eyelids
Eyelashes
Supraorbital ridge - diverts fluids
Lacrimal caruncle - directs tears into opening to drain
Extrinsic Eye muscles
What is the lacrimal apparatus and what are the components?
Produces and brings tears to surface of eye and reabsorbs tears
Components
- Lacrimal Gland - produce tears
- Lacrimal Ducts - bring tears to eye
- Lacrimal Puncta - entry into lacrimal canals
- Lacrimal Canals - brings tears to nasolarcimal duct
- Nasolacrimal Duct - takes tears to nasal cavity
How does the eyelid blink and what is the purpose?
Blink from lateral to medial and helps spread tears
What kind of antimicrobial is contained in tears?
Lysozyme
What are the components of the fibrous tunic?
Continuous w/ dura mater of brain
- Cornea - clear part of eye
- Sclera - white of eye
- conjuctiva is the mucous membrane of sclera
- Canals of Schlemm - edge of cornea/sclera
- where you drain fluid from eye
What are the components of the vascular tunic?
- Choroid
- blood vessels provide nutrients for retina
- Ciliary Body
- ciliary muscle - connects to lens to change shape
- ciliary processes - make aqueous fluid
- Iris
- sphinctor pupillae - constrict pupil
- dilator pupillae - dilate pupil
How is the lens held in place?
With suspensory ligaments
What is the accommodation reflex?
The lens changes shape for near/far vision
- Near vision lens = more biconvex (round)
- Far vision lens = less biconvex
What makes up the nervous tunic or retina?
- Pigmented Layer - absorbs light to prevent from bouncing
- Nervous Layer - photoreceptors, bipolar and ganglion cells
- Optic Disk - blind spot where retina connects to optic nerve
- Ora Serrata - where retina connects to ciliary body
What are the different nervous layers of the retina or nervous tunic?
- Photoreceptor layer
- rods - dim light and black/white
- cones - color vision
- Bipolar layer
- bipolar cells
- Ganglion layer
- axons that compose optic nerve
What is the central fovea?
Central fovea - only photoreceptors=sharpest vision
-100% cones in central fovea and more rods as you move away
What are the characteristics of the lens?
- biconvex
- made of crystallin proteins
- suspensory ligaments
- change shape with accomodation reflex
- focuses light on the retina
How does the ciliary body and suspensory ligaments interact with eachother to change shape of lens?
Ciliary body relaxes = more tension on suspensory ligaments
-lens is less biconvex for far vision
Ciliary body contracts = less tension on suspensory ligaments
-lens is more biconvex for near vision
What are the different cavities and chambers of the eye?
Anterior Cavity
- posterior chamber
- anterior chamber
Posterior Cavity
What fluids fill up the different cavities of the eye? How is intraocular pressure and turgor maintained?
Anterior Cavity = aqueous humor
-constanty produced and reabsorbed
Posterior Cavity = vitreous humor
-not continuously produced/reabsorbed
Intraocular pressure maintained with aqueous humor
Turgor (shape) maintained with vitreous humor
What three processes are involved in formation of images on the retina?
- Refraction of light rays
- accomodation of lens
- constriction of pupil
How much light is refracted by the cornea and lens?
cornes = 60%
lens = 40%
How does accomodation work for lens?
Biconvex lens
Far object = less convex
Near object = more convex
ciliary muscles change shape of lens
How does constriction of the pupil affect vision?
Part of the accomodation reflex that limits peripheral light
-near vision = pupillary constriction
How do photoreceptors act as neurons in different light conditions?
What are the characteristics of rod cells?
- not present in central fovea
- increase in concentration to ora serrata
- dim light and peripheral vision
- 6 – 600 rod cells converge on 1 bipolar cell, as well as amacrine and
- horizontal cells.
What are the characteristics of cone cells?
- 100% cone cells in central fovea
- diminish in number toward ora serrata
- three different types: blue, red, green cone cells
- bright light required to break pigments
- 1:1 relationship with bipolar cells
- visual acuity and color vision
Walk through the visual pathway.
Begin when bipolar neurons initiate action potential after receiving signal from photoreceptors
-Ganglion cell axons converge in blind spot = optice nerve
Optic Chiasma = some crossing over
- medial retina pathway = contralateral
- lateral retina pathway = ipsilateral
What is the anatomy of the external ear?
What are ceruminous glands?
Located in external ear and produce cerumin, ear wax.
-antimicrobial
What is the anatomy of the middle ear?
What do mastoid air cell do?
packets of air in temporal bone that drain fluid from middle ear
What are the three ossicles and why have three?
Malleus, Incus, Stapes
-can modulate amount of vibration reaching middle ear
What are the protective muscles around ossicles and what is tehir function?
Stapedius and Tensor tympani
-prevent ossicles from vibrating too hard w/ loud sustained sounds
What is the anatomy of the border betwen outer/middle ear?
What is the outer anatomy of the internal ear?
Bony Labyrinth filled with perilymph
- 3 semicircular canals
- frontal, horizontal, sagittal
- vestibule - equilibrium
- cochlea
What is the inner anatomy of the internal ear?
Membranous Labyrinth filled w/ endolymph
- 3 semicircular ducts
- frontal, horizontal, sagittal
- vestibule - equilibrium
- utricle and saccule filled with fluid
- cochlea
- cochlear duct also known as scala media
What is the anatomy of the cochlea cross section?
Scala vestibuli - has perilymph
Scala tympani - has perilymph
Scala media - has endolymph
Vestibular membrane - move w/ sound
Basilar membrane - move w/ sound
Tectorial membrane - does not move w/ sound
Spiral organ of Corti - organ used in hearing
How does stiffness of the vestibular/basilar membrane correlate w/ sound?
The beginning of the cochlea near round window = more stiff
-more stiff = high frequency = high pitch
End of cochlea = more flexible
-more flexible = low frequency = low pitch
Explain the physiology of hearing
What is static equilibrium?
Accomplished with saccule and utricle in vestibule
-filled w/ endolymph
Hair cells inside saccule and utricle sense changes in the gelatinous otolithic membrane
-as otoliths move they move hair cells
What does static equilirbium monitor?
- perception of head orientation when body is stationary
- perception of linear acceleration/deceleration
How is dynamic equilibrium monitored?
- Semicircular ducts
- the three positions of the ducts monitor equilibrium in that plane
- hair cells
- monitor changes in gel that fills cupula in the ampulla
- cupulla in the ampulla
What does dynamic equilibrium monitor?
perception of rotational movements
