Unit 5 - Special Senses Flashcards
How are receptors categorized?
By the type of energy required to activate them
What is perception?
The organization, identification and interpretation of sensory information in order to represent and understand the environment
Vision involves ________ striking the retina of the eye; and hearing involves _________.
Light, pressure waves
What is the adequate stimulus?
Sensory endings respond to a particular type of energy applied to them or near them
Energy must be converted to electrochemical energy. This conversion is called:
Primary transduction process
What is the primary transduction process for the visual system?
Converting photons of light into a change in membrane potential
What is the primary transduction process for hearing?
Converting pressure waves in air to pressure waves in a fluid which then bend a hair
What is a receptor potential
A type of graded transmembrane potential difference produced by activation of a sensory receptor
How are receptor potentials most often produced?
Sensory transduction by depolarization
True or false: receptor potentials can be caused by hyper polarization if K+ leaves the cell
True
Humans can detect light with a wavelength between ______ and ______nm.
390, 700
Psychophysical experiments with colour discrimination estimate that humans may be able to distinguish between _____ and _____ colours
2.3 million and 7.5 million
The tough fibrous part of the eye:
Sclera
A thin membrane that covers the inner surface of the eyelid and the sclera
Conjunctiva
Inflammation of the conjunctiva is called:
Conjunctivitis
Continuous and modified portion of the sclera, and is the most important part of the light focusing power of the eye
Cornea
True or false: the lens is more powerful than the cornea in terms of focusing power
False
Area of the eye behind the cornea, filled with a clear fluid called the aqueous humor
Anterior chamber
Aqueous humor is secreted by the _________ and is drained by the _________ at the cornea-sclera junction
Ciliary body, canal of schlemm
True or false: aqueous humor only fills the anterior chamber.
False: it also fills the posterior chamber
Has convex surfaces and is elastic, is located immediately behind the anterior chamber
Crystalline lens
Large chamber behind the lens filled with a gelatinous substance called the vitreous humor
Vitreous chamber
Maintains the shape of the eye because it is very stiff and doesn’t flow well
Vitreous humor
Contains several layers of both receptor and processing cells, located at the back of the eye
Retina
Pigmented cell layer just outside the neurosensory retina that nourishes retinal visual cells, and is firmly attached to the underlying choroid and overlying retinal visual cells
Retinal pigment epithelium (RPE)
Provides oxygen and nourishment to the outer layers of the retina, located behind the RPE
Choroid layer
Any light not absorbed by the receptor cells is absorbed by the pigment cells in order to:
Prevent light scatter which would blur the image
What is accommodation?
The process by which the curvature of the lens is increased?
When does accommodation occur?
During near vision
Is the posterior or anterior curvature of the lens most affected by accommodation?
Anterior
Holds the lens in place behind the iris
Suspensatory ligaments/ zonule fibres
The zonule fibres are attached to a sphincter-like muscle called the:
Ciliary muscle
When the ciliary muscle is relaxed, the lens ________, and when the ciliary muscle is contracted the lens _______
Flattens, becomes rounder and thicker
The deflection from a straight path undergone by a light ray in passing obliquely from one medium to another in which the velocity is different
Refraction
The distance from the refractive surface (cornea) to the point where parallel light rays converge is the:
Focal distance
What is the reciprocal of the focal distance?
The diopter
The cornea has a refractive power of _______, which means that parallel light rays striking the corneal surface will be focused ________ behind it.
42-43 diopters, 0.024m
______% of the refraction of the eye occurs at the cornea, and ______% occurs in the lens
70, 30
What is myopia?
Near-sightedness
What is hyperopia?
Far sightedness
What is presbyopia?
Lens becomes stiff due to age, resulting in decreased ability to focus
What is an astigmatism?
The corneal surface is more curved in one plane than another, creating a difference in refraction
What is emmetropia?
Perfect vision
How is myopia corrected?
With a concave lens, which moves the focal point back to the retina
How is hyperopia corrected?
A convex lens, which pulls the focal point up to the retina
What is the primary choice of correction for people with astigmatism?
Eyeglasses
How does a cylindrical lens focus light?
Into a line
How does a spherical lens focus light?
Into a point
_______ is as transparent possible and appears to be built upside down
The retina
The first layer of cells that light strikes in the retina are _________, and the last are _________
Ganglion cells, receptors
In addition to absorbing light not absorbed by photoreceptors, the RPE:
Transports nutrients and ions to the photoreceptors
What is the daily renewal process of photoreceptors?
~10% of their volume (discs) is shed and phagocytoses by the RPE. The discs are replaces from the bottom of the outer segment
- 100-125 million per retina
- vision in shades of grey
- high sensitivity
- low acuity pathways
- lots of convergence
- night vision
- more numerous in retinal periphery
These are characteristics of:
Rods
- 6 million per retina
- colour vision
- low sensitivity
- high acuity
- little convergence
- day vision
- concentrated in fovea
These are characteristics of:
Cones
in the dark, a photoreceptor will release _________, which inhibits the ______ bipolar cells and excites the _______ bipolar cells.
glutamate, ON, OFF
in the light, photons strike the photoreceptors and cause ________ due to activation of opsins which activate all _________, giving energy to stimulate _________ coupled receptors to activate phosphodiesterase which cleaves ________ to _______.
inhibition, trans-retinal, G-protein, cGMP, 5’-GMP
made of retinal and the protein opsin
rhodopsin
the aldehyde form of vitamin A
retinal
an area on the retina which, when stimulated, causes a change in the output of either a particular bipolar cell or ganglion cell
receptive field
the only retinal cell to generate action potentials and the only cell whose output goes to the brain
the ganglion cell
the area of the retinal surface, or corresponding region of the visual field, that upon illumination, enhances or inhibits the activity of a bipolar or ganglion cell
receptive field
true are false: receptor fields have both on and off areas
true
some ganglion cells are luminous detectors but project to subcortical areas and mediate only unconscious reflexes, and example of this is:
pupillary reflexes
true or false: receptive fields are not able to overlap
false
ON channels have their axon terminals in the inner half of the ___________, and the OFF bipolar cells having their terminals in the ___________.
inner plexiform layer, outer half
OFF bipolar cells express what kind of receptors?
AMPA and kainate (ionotropic receptors for glutamate)
ON bipolar cells express what type of receptors?
mGluR6 (a metabotropic receptor)
which bipolar receptor cells hyperpolarize in response to light due to less glutamate arriving from the cone synapse
OFF receptors
which bipolar cells depolarize in response to less glutamate which opens cation channels
ON receptors
where is the temporal hemi-retina located?
the far right side of the right eye-ball and vice versa
where is the nasal hemi-retina located?
the far left side of the right eyeball and vice versa
in thalamus, the first waystation for visual stimulation
lateral geniculate nucleus
what is the frequency range of human hearing?
between 20-20000Hz
how many tones can humans distinguish between?
340 000
what are the three main functions of the external ear?
1) protection
2) pinna funnels sound into the external auditory meatus
3) external auditory meatus gathers sound energy and focusess it on the tympanic membrane
has a bactericidal effect on some strains of bacteria
cerumen
what are the main two features of the external ear that protect the inner membrane from damage
- cerumen
- hairs in the external auditory meatus
by what factor does the external auditory meatus increase sound energy?
30-100 fold
equalizes pressure on both sides of the tympanic membrane allowing it to vibrate frequently
eustachian tube
true or false: the middle ear is air filled
true
what three ossicles connect the tympanic membrane to the inner ear
the malleus (hammer), the incus (anvil), and the stapes (stirrup)
what is the major function of the middle ear?
to match relatively low-impedance airborne sounds to the higher impedance fluid of the inner ear
how much acoustic energy is reflected when sound waves travel from air to water?
99%
in the middle ear, sound energy is boosted 200-fold by these two processes:
1) going from a large diameter tympanic membrane to a smaller diameter oval window
2) lever action of the ossicles
attached to the malleus and the eustacian tube
tensor tympani
attached to the wall of the middle ear and the neck of the stapes near the incus
stapedius
the smallest skeletel muscles in the body
tensor tympani and stapdius
how do the middle ear muscles provide a noise reduction system?
when they contract they dampen the vibration of the ossicles
true or false: the middle ear muscles do not increase contraction when vocalization gets louder
false
what mechanism of the ear allows people to hear others while talking themselves?
contraction of the middle ear muscles
the middle ear muscle contraction ssytem works fairly well with maintained loud sounds, but not sharp intense sounds which make take __________ to fully contract
100-200 msec
the inner ear is composed of the _________
cochlea
- 10mm in diameter
- 2.75 turns
- 35mm long when uncoiled
- appears to be 3 parallel tubes when cut in a cross section
cochlea
the _______ and _______ are one tube joined by a hole at the helicotrema, or essentially one tube wrapped around the scala media
scala vestibule, scala tympani
true or false: the basilar membrane is not a true membrane
true
composed of fibers which are narrow and stiff near the stapes, and are broader and more limber at the apex
basilar membrane
rests on the basilar membrane
organ of corti
in the organ of corti, there are three rows of _________ which have a motor function. there are about ________ per ear
outer hair cells, 10 500
in the organ of corti, there is a single row of ________ which are sensory cells. there are about ________ per ear
inner hair cells, 3500
the thin, gelatinous sheet that rests on the outer hair cells
tectorial membrane
shearing action or stress resulting from applied forces that cause two continguous parts of a body to slide relative to each other in a direction parallel to:
their plane of contact
hair-like bristles of varying length with the shortest in front and the tallest in back, attached to the tectorial membrane
streocilia
when inner hair cells move as little as 0.3nm in the direction of ________ a response may be observed
the tallest sterocilia
has a very high K+ concentration and a very low Na+ concentration
endolymph
due to its high concentration of positive charged ions, the ______ has a high positive potential
endolymph
the potential difference from the endolymph to the hair cells is on the order of 150mV, making it the:
largest electrical potential difference found in the body
what causes the stereocilia to shear against the tectorial membrane?
movement of the basilar membrane and Reissner’s membrane
when the shear tilts the stereocilia _______ channels open. since the endolymph has a high concentration of _______ it enters the cell and depolarizes it, leading to action potentials
K+, K+
the point of maximal displacement is determined by the:
frequency of the sound
high frequencies cause maximal displacement near the _____, and low frequencies cause maximal displacement near the ______
stapes, apex
what is the purpose of the round window?
to absorb any energy that isn’t dissipated and push it into the middle
