UNIT 3 - Handout (Anatomy of Special Senses) [2] Flashcards
clear tissue behind iris and pupil
lens
__________: proteins within the lens arranged like the layers of an onion that make up the refractive media of the lens
- Perfectly transparent and lacks blood vessels enclosed by a clear ____________ and held in position by encircling ________, which attach to the ciliary processes.
- Focus images on the retina to facilitate clear vision
- lens divides the interior of the eyeball into 2 cavities:
- crystallins
- connective tissue capsule
- zonular fibers
2 cavities
1. anterior cavity
2. posterior cavity
o space anterior to the lens —consists of two chambers.
o Anterior chamber lies between the cornea and the iris
o Posterior chamber lies behind the iris and in front of the zonular fibers and lens
anterior cavity
o Also called __________
o Lies between the lens and the retina.
o Within it is the ________, a transparent jellylike substance that holds the retina flush against the choroid, giving the retina an even surface for the reception of clear images
POSTERIOR CAVITY
- vitreous chamber
- vitreous body
When light passes through the eye, it gets bent at the cornea, so the light gets focused.
The light then passes through the lens, another area of bending, focusing it to the area of the ________ (area of most acute vision).
The image perceived at the retina is inverted, the image becomes upright/erect when it is perceived at the brain.
Each cell of the retina has an electrical connection to the ______, which carries the image from the retina to optic nerves then optic chiasm passing to the optic tract and Lateral Geniculate Body sending it to optic radiations into the visual cortex or the calcarine fissure of the occipital lobe: where the image will be formed, viewed & understood, & perceived as upright.
- fovea centralis
- optic nerve
retina –> optic nerve –> optic chiasm –> optic tract –> lateral geniculate body
The first step in visual transduction is absorption of light by a __________, a colored protein that undergoes structural changes when it absorbs light, in the outer segment of a photoreceptor.
Light absorption initiates the events that lead to the production of a receptor potential.
The single type of photopigment in rods is ________.
Three different _________ are present in the retina, one in each of the three types of cones.
- photopigment
- rhodopsin
- cone photopigments
Color vision results from different colors of light selectively activating the different cone photopigments.
All photopigments associated with vision contain two parts:
1. ________ (____)
2. ________ (____)
__________: formed from carotene, the plant pigment that gives carrots their orange color.
- glycoprotein (opsin)
- derivative of vitamin A (retinal)
- Vitamin A derivatives
________: the light-absorbing part of all visual photopigments.
In the human retina, there are four different ______, ____ in the cones and ___ in the rods (_______).
Small variations in the amino acid sequences of the different opsins permit the rods and cones to absorb different colors (___________) of incoming light.
- Retinal
- 4 diff opsins: three in the cones, one in the rods (rhodopsin)
- wavelengths
PROCESS OF PHOTOTRANSDUCTION
- In darkness, retinal has a bent shape, called _______, which fits snugly into the opsin portion of the photopigment.
When cis-retinal absorbs a photon of light, it straightens out to a shape called _______. This cis-to-trans conversion is called _________ and is the first step in ___________.
After retinal isomerizes, several unstable chemical intermediates form and disappear. These chemical changes lead to production of a receptor potential.
- cis-retinal
- trans-retinal
- isomerization
- visual transduction
- cis-retinal
PROCESS OF PHOTOTRANSDUCTION
- In about a minute, ________ completely separates from opsin.
The final products look colorless, so this part of the cycle is termed ___________.
- An enzyme called _________ converts trans-retinal back to cis-retinal.
- trans-retinal
- bleaching of photopigment
- trans-retinal
3.- retinal isomerase
PROCESS OF PHOTOTRANSDUCTION
- The cis-retinal then can bind to ______, reforming a functional _________. This part of the cycle—___________— is called ________.
- opsin
- photopigment
- resynthesis of a pigment
- regeneration
STRUCTURE INVOLVED
- ciliary muscles
- zonules
- lens
VIEWING DISTANT OBJECTS
1. rest
2. stretch
3. flat
VIEWING NEAR OBJECTS
1. contract
2. relax
3. round/convex
________: may occur due to trauma, such as a blow to the head, in various eye disorders, or as a result of age-related degeneration.
The detachment occurs between the neural portion of the retina and the pigmented epithelium.
Fluid accumulates between these layers, forcing the thin, pliable retina to billow outward.
The result is distorted vision and blindness in the corresponding field of vision.
The retina may be reattached by laser surgery or cryosurgery (localized application of extreme cold), and reattachment must be accomplished quickly to avoid permanent damage to the retina.
detached retina
With aging, the lens loses elasticity and thus its ability to curve to focus on objects that are close.
Therefore, older people cannot read print at the same close range as can younger people. This condition is called ______________.
By age 40 the near point of vision may have increased to 20 cm (8 in.), and at age 60 it may be as much as 80 cm (31 in.).
- usually begins in the mid-forties. At about that age, people who have not previously worn glasses begin to need them for reading.
Those who already wear glasses typically start to need bifocals, lenses that can focus for both distant and close vision.
presbyopia
3 main regions of ear
- external ear
- auricle
- external auditory canal
- tympanic membrane - middle ear
- malleus (hammer)
- incus (anvil)
- stapes (stirrups) - internal ear
- outer bony labyrinth
- inner membranous labyrinth
collects sound waves and channels them inward
external ear
conveys sound vibrations to the oval window
middle ear
houses the receptors for hearing and equilibrium
internal ear
3 parts of external ear
- auricle
- External Auditory Canal
- Tympanic membrane
a flap of elastic cartilage shaped like the flared end of a trumpet and covered by skin
auricle
a curved tube about 2.5 cm (1 in.) long that lies in the temporal bone and leads to the eardrum
External Auditory Canal
- or the eardrum, a thin, semitransparent partition between the external auditory canal and middle ear
- Covered by epidermis and lined by simple cuboidal epithelium
- Between the epithelial layers is connective tissue composed of collagen, elastic fibers, and fibroblasts
Tympanic membrane
o A small, air-filled cavity in the petrous portion of the temporal bone that is lined by epithelium
o It is separated from the external ear by the tympanic membrane and from the internal ear by a thin bony partition that contains two small openings: the oval window and the round window
middle ear
3 auditory aussicles
- malleus (hammer)
- Incus (Anvil)
- Stapes (Stirrups)
- attaches to the internal surface of the tympanic membrane.
- Head of the malleus articulates with the body of the incus
Malleus (Hammer)
middle bone in the series, articulates with the head of the stapes
Incus (Anvil)
- Base or footplate fits into the oval window
- Between the epithelial layers is connective tissue composed of collagen, elastic fibers, and fibroblasts
Stapes (Stirrups)
2 MUSCLES ATTACHED TO OSSICLES
- Tensor tympani
- Stapedius
- muscle supplied by the mandibular branch of the trigeminal (V) nerve
- Limits movement and increases tension on the eardrum to prevent damage to the inner ear from loud noises
Tensor tympani
- muscle supplied by the facial (VII) nerve
- Smallest skeletal muscle in the human body. By dampening large vibrations of the stapes due to loud noises, it protects the oval window, but it also decreases the sensitivity of hearing.
stapedius
- commonly known as the eustachian tube
- Its opening is found at the anterior wall of the middle ear
- Consists of both bone and elastic cartilage, connects the middle ear with the nasopharynx (superior portion of the throat)
- It is normally closed at its medial (pharyngeal) end.
- During swallowing and yawning, it opens, allowing air to enter or leave the middle ear until the pressure in the middle ear equals the atmospheric pressure.
Auditory tube or pharyngotympanic tube
TWO MAIN DIVISIONS OF INTERNAL EAR
1) Outer bony labyrinth
2) Inner membranous labyrinth
Lined with periosteum and contains perilymph
Outer bony labyrinth
3 areas of Outer bony labyrinth
a. Semicircular canals
b. Vestibule
c. Cochlea
- projecting superiorly and posteriorly from the vestibule, named the anterior, posterior, and lateral based on their positions
- Anterior and posterior semicircular canals are vertically oriented
- Lateral one is horizontally oriented.
- At one end of each canal is a swollen enlargement called the ampulla
a. Semicircular canals
- oval central portion of the bony labyrinth
b. Vestibule
- a bony spiral canal that resembles a snail’s shell and makes almost three turns around a central bony core called the _______
- _________: above cochlear duct and ends at the oval window filled with perilymph
- _________: aka. Cochlear duct is a continuation of the membranous labyrinth into the cochlea; it is filled with endolymph
- _________: below scala vestibuli ends at the round window filled with perilymph
c. Cochlea
- modiolus
- Scala vestibuli
- Scala media
- Scala tympani
__________ - separates the cochlear duct from the scala vestibuli
__________ - separates the cochlear duct from the scala tympani
- Vestibular membrane
- Basilar membrane
o a coiled sheet of epithelial cells, including supporting cells and about 16,000 hair cells, which are the receptors for hearing.
Spiral organ or organ of Corti
2 Groups of Hair cells:
o ________: arranged in a single row
o________: are arranged in three rows.
At the apical tip of each hair cell are 40–80 ______ and a _______ (cilium) that extend into the endolymph of the cochlear duct.
- Inner hair cells
- Outer hair cells
- stereocilia; kinocilium
- a flexible gelatinous membrane, covers the hair cells of the spiral organ
- In fact, the ends of the stereocilia of the hair cells are embedded in the tectorial membrane while the bodies of the hair cells rest on the basilar membrane.
Tectorial membrane
At their basal ends, inner and outer hair cells synapse both with first-order sensory neurons and with motor neurons from the cochlear branch of the vestibulocochlear (VIII) nerve.
Cell bodies of the sensory neurons are located in the ___________
Innervation of hair cells
- spiral ganglion
- Surrounded by ______ and contains _______
- A series of epithelial sacs and tubes inside the bony labyrinth that have the same general form as the bony labyrinth and house the receptors for hearing and equilibrium
- Two sacs in the vestibule called the _____ (little bag) and the _____ (little sac)
- The portions of the membranous labyrinth that lie inside the bony semicircular canals are called the ____________
2) Inner membranous labyrinth
- perilymph; endolymph
- utricle; saccule
- semicircular ducts
_________: device that translates sounds into electrical signals that can be interpreted by the brain.
The external parts of a cochlear implant consist of
(1) a microphone worn around the ear (picks up sound waves)
(2) a sound processor (converts sound waves into electrical signals)
(3) a transmitter(worn behind the ear, receives signals from the sound processor and passes them to an internal receiver)
The internal parts of a cochlear implant are the
(1) internal receiver (relays signals to –>)
(2) electrodes implanted in the cochlea (trigger nerve impulses in sensory neurons in the cochlear branch of the vestibulocochlear (VIII) nerve)
cochlear implant
two types of equilibrium or balance
- Static equilibrium
- Dynamic equilibrium
- refers to the maintenance of the position of the body (mainly the head) relative to the force of gravity.
- Body movements that stimulate the receptors for this include tilting the head and linear acceleration or deceleration, such as when the body is being moved in an elevator or in a car that is speeding up or slowing down
Static equilibrium
- maintenance of body position (mainly the head) in response to sudden movements such as rotational acceleration or deceleration.
Dynamic equilibrium
the receptor organs for equilibrium are called the _____________; these include the saccule, utricle, and semicircular ducts
- vestibular apparatus
________: the sensory apparatus that helps body maintain its postural equilibrium.
it provides an individual with sense of balance and awareness of spatial orientation – making one aware of relationship with the surroundings (e.g. standing, sitting down)
vestibular system of the ear
As head rotates, the duct moves but the endolymph lags behind owing to inertia.
Exerts pressure deflecting the cupula and bends the stereocilia to the opposite direction.
When the stereocilia moves toward the kinocilia, it produce _______ thus, it is ______ or _______.
And when the stereocilia moves away from the kinocilia, it ________ thus, it is _______ or ________.
This stimulates the hair cells producing electric signals and transmitting to the brain through vestibular nerve fibers.
With constant motion, endolymph catches up with the movement of the duct.
No more deflection of the cupula stopping sensation of acceleration.
For example, when a person turns his/her head to the right.
This will be detected by horizontal semicircular canals.
When one is excited, the other is inhibited.
The Right semicircular canal will turn to the right, due to inertia the endolymph goes the opposite direction.
The movement of the fluid will push the hair cells towards the kinocilium, thereby depolarizing the hair cells.
This will detect the motion.
On the other hand, the Left semicircular canal will turn to the right but the endolymph will turn to the left, pushing the stereocilia away from the kinocilium, which will produce hyperpolarization of the hair cells.
Thus, left side is inhibited.
___________: condition that results when there is a conflict among the senses with regard to motion.
For example, the vestibular apparatus senses angular and vertical motion, while the eyes and proprioceptors in muscles and joints determine the position of the body in space.
If you are in the cabin of a moving ship, your vestibular apparatus informs the brain that there is movement from waves.
But your eyes don’t see any movement. This leads to the conflict among the senses. Symptoms of motion sickness include paleness, restlessness, excess salivation, nausea, dizziness, cold sweats, headache, and malaise that may progress to vomiting. Once the motion is stopped, the symptoms disappear.
If it is not possible to stop the motion, you might try sitting in the front seat of a car, the forward car of a train, the upper deck on a boat, or the wing seats in a plane.
Looking at the horizon and not reading also help. Medications for motion sickness are usually taken in advance of travel and include scopolamine in time release patches or tablets.
MOTION SICKNESS
