EENT Flashcards
The process whereby light rays are bent when they pass from a medium of one density into a medium of a different density - except when they strike perpendicular to the surface
Refraction
Any light that enters from a point more than 20 feet away is considered ________
Parallel
Any light that enters from a point less than 20 feet away is considered _______
Diverging
If the light enters parallel, it is refracted to a point known as the ____________ behind the lens. It is the line that passes through the center of the curvature of the lens (____________)
Principle focus; principle axis
The process whereby the zonular fibers tighten (contract) and pull the lens to “__________” going from a far focus to a near focus
Accommodation
Zonular fibers ________ as the lens flattens for distance vision
Relax
A visual problem that is usually caused by your eyeball being a little too short; problems reading or seeing closer objects clearly; AKA foresightedness
Hyperopia
Hyperopia aka foresightedness can be corrected with what type of lenses?
Convex
The clinical opposite of hyperopia, aka nearsightedness. The result of the eye being a little too long; trouble seeing things in the distance
Myopia
Myopia aka nearsightedness is corrected with what type of lenses?
Biconcave
A defect in the curvature in the cornea. The cornea is not uniform in shape and this causes light to be refracted to different areas of focus so that part of the image is blurred
Astigmatism
Astigmatism can be corrected with what type of lenses
Cylindrical - they equalize the refraction in all meridians
Result of loss of accommodation; considered a normal aging process. This generally occurs in individuals by about the age of 40. Makes reading and close work difficult
Presbyopia
What type of lenses correct presbyopia?
Convex lenses that magnify close objects
Defect caused when the visual images do not fall on the same corresponding areas of each retina; causes a wandering eye otherwise known as being “cross-eyed.” This misalignment can occur in one or both eyes and results in them turning either inward, outward, upward, or downward.
Strabismus
A second-order neuron in the visual pathway which transmits signals from photoreceptors to ganglion cells; hyperpolarizing, depolarizing
Bipolar cells
Third-order neurons in the visual pathway; converge to exit the eye as the optic nerve
Ganglion cells
Connect receptor cells to the other receptor cells; hyperpolarizing
Horizontal cells
These cells connect ganglion cells to one another; depolarizing
Amacrine cells
Refers to clarity of vision or sharpness of vision; a person’s ability to see small details
Visual acuity
Color vision is mediated by __________ cells
Ganglion
Ipsilateral contraction; when light enters a pupil it constricts
(Direct) pupillary light reflex
Constriction of the pupil on the opposite side (contralateral constriction)
Consensual light reflex
Double vision
Diplopia
Half-blindness
Hemianopia
Same side of both visual fields
Homonymous
Opposite sides of the visual fields
Heteronymous
Gradual hearing loss associated with aging. Likely due to gradual cumulative loss of hair cells and neurons
Presbycusis
Impaired sound transmission in the external or middle ear and impacts all sound frequencies
Conductive Hearing Loss
Problems arise in the middle ear; most commonly the result of loss of cochlear hair cells but can also be due to problems with cranial nerve 8 or within the central auditory pathway; impairs the ability to hear certain pitches, while other pitches can be heard
Sensorineural Hearing Loss
Conductive and sensorineural hearing loss can be differentiated in the clinic by using a combination of the _______ & ______ tests.
Weber & Rinne
Test that measures bone conduction
Weber
Test that measures the ratio of air to bone conduction
Rinne
What is the function of the auditory cortex?
to process sound, volume, and pitch
Orientation in space depends on input from….(4 answers)
- Vestibular receptors
- Visual cues
- Proprioceptor impulses from joint capsules
- Impulses from cutaneous exteroceptors
What type of receptors are taste and smell?
Chemoreceptors and Exteroceptors
Small area located in the roof of the nasal cavity containing 10-20 million bipolar olfactory neurons interspersed with sustentacular and basal stem cells
Olfactory epithelium
Where the axons of olfactory sensory neurons contact the primary dendrites of the mitral and tufted cells to form synaptic units called olfactory glomeruli; also contains periglomerular cells
Olfactory bulbs
Inhibitory neurons connecting one glomerulus to another
Periglomerular cells
Where are taste buds located? (4)
Taste buds are ovoid bodies located in the mucosa of the epiglottis, palate, and pharynx, and in the walls of the papillae of the tongue.
What are the 4 distinct types of cells located within each taste bud?
Basal cells, dark cells, light cells, intermediate cells
Activated by G protein linked receptors; natural sugars such as sucrose in synthetic sweeteners act via different receptors on gustducin
Sweet
Triggered by H+ ions; ENaCs permit the entry of protons and may contribute to the sensation of this taste. H+ ions can also bind to and block a potassium sensitive channel - the fall in potassium permeability can depolarize the membrane
Sour
Produced by a variety of unrelated compounds; many are poisons and this taste serves as a warning to avoid them. Some compounds bind to and block potassium selective channels. G protein linked receptors also play a role with _____ substances such as strychnine
Bitter
Triggered by NaCl; mediated by a sodium selective channel known as ENaC. Entry of sodium into the receptor depolarizes the membrane generating the receptor potential
Salt
Taste due to activation of a truncated glutamate receptor MgluR4. It’s unclear how activation of the receptor produces depolarization. Glutamate in food may also activate ionotropic glutamate receptors to depolarize the umami receptors
Umami
What is the stimulus for the labyrinth righting reflex?
Tilting of the head
What is the response of the labyrinth righting reflex?
Compensatory contraction of the neck muscles to keep the head level
What is the response of the labyrinth righting reflex?
Compensatory contraction of the neck muscles to keep the head level
Sudden jerky movements that occur as the gaze shifts from one object to another
Saccades
Tracking movements of the eye as they following moving objects
Smooth pursuit movement
Adjustments that occur in response to stimuli initiated in the semicircular canals, maintain visual sensation as the head moves
Vestibular movements
Bring the visual axes toward each other as attention is focused on objects near the observer
Convergence movements
Acute bacterial conjunctivitis is often caused by
Gram-positive bacteria such as staph, haemophilus, strep, and moraxella
