special senses Flashcards
what are the five special senses?
- smell
- taste
- hearing
- vision
- balance
what do mechanoreceptors respond to?
stretch, bend or deformation
what special senses are mechanoreceptors responsible for?
hearing and balance
what special sense are photoreceptors responsible for?
vision
what special senses are chemoreceptors responsible for?
smell and taste
what are the special sensory receptors?
- mechanoreceptors
- photoreceptors
- chemoreceptors
what do special sensory receptors do with a stimulus?
convert into action potentials that travel to the brain for interpretation
what are the three major areas of the ear?
- external ear
- middle ear
- internal ear
what is the external ear responsible for?
hearing only
what is the middle ear responsible for?
hearing only
what is the internal (inner) ear responsible for?
hearing and balance
what are the major structures of the external ear?
- auricle (pinna)
- external acoustic meatus
- tympanic membrane
what are the major structures of the middle ear?
- auditory ossicles
- pharynotympanic tube
what are the auditory ossicles?
- malleus=hammer
- incus=anvil
- stapes=stirrup
what is the role of the auditory ossicles?
to transmit and amplify the vibratory motion of the tympanic membrane to the oval window
what is the role of the pharyngotympanic tube?
equalises air pressure in the middle ear cavity with external air pressure
where is the internal (inner) ear located?
temporal bone
what are the two divisions of the internal ear?
- bony labyrinth
- membranous labyrinth
what is the bony labyrinth of the inner ear subdivided into?
- vestibule
- semicircular canals
- cochlea
what is the bony labyrinth of the inner ear filled with?
perilymph
what is the membranous labyrinth of the inner ear?
series of interconnecting sacs and ducts within the bony labyrinth filled with endolymph
what does the cochlea contain?
cochlear duct that houses spiral organ (of Corti)
what is the spiral organ of corti composed of?
cochlear hair cells
what causes depolarisation in the spiral organ of Corti?
pressure waves create movement on the basilar membrane, causing hair cells to move against tectorial membrane
where are action potentials generated in hair cells transmitted along?
vestibulocochlear nerve (CN VIII)
where is the oval window located in the ear?
on the wall of the bony labyrinth at the entrance to the cochlea
what is the cochlea filled with?
perilymph
what are the first two stages of the route of the sound wave through the ear?
- sound waves vibrate tympanic membrane
- auditory ossicles vibrate oval window, pressure is amplified?
what is the third stage of the route of the sound wave through the ear?
-pressure waves created by stapes pushing on oval window move through perilymph
what is the last stage of the route of the sound wave through the ear?
pressure waves of the perilymph vibrate the basilar membrane and bend receptor cells that are embedded in overlying tectorial membrane. This generates action potentials in vestibulocochlear nervee
what are the first 5 components/structures of the sound waves pathway through the ear?
- pinna
- external acoustic meatus
- tympanic membrane
- auditory ossicles
- oval window
what are the last 5 components/structures of the sound waves pathway through the ear?
- cochlea
- pressure waves in the perilymph
- spiral organ
- movement of basilar membrane
- vestibulocochlear nerve
what is the oval window?
opening in the bone that partitions middle ear to start of the cochlea. Movement causes pressure waves within perilymph
what is the round window?
thin membrane that separates the end of the cochlea from the middle ear. Absorbs pressure waves and prevents perilymph from leaking into the middle ear
what does the bending of hair cells in the spiral organ (of Corti) cause?
ion channels to open, causing Na+ to rush into hair cells
what happens within the spiral organ of corti when ion channels open and Na+ ions rush into hair cells?
depolarisation leads to release of neurotransmitter which generates action potentials in sensory (auditory) nerves
where do action potentials generated in the spiral organ travel to?
the medulla oblongata then the auditory reflex centre of the midbrain, then to the auditory cortex in temporal lobe where stimulus is interpreted as sound
what is the role of equilibrium?
to provide info about the location of our head, the movement of the head, how rapid and which direction
what are the two types of equilibrium?
static and dynamic
what is static equilibrium?
evaluating the position if the head relative to gravity (up/down) and forward/backwards. Info supplied when head is motionless, or moving in a straight line
what is static equilibrium detected by?
hair cells in the vestibule (saccule and utricle)
what is dynamic equilibrium?
evaluates the position of the head while its rotating, or moving in an angular direction
what is dynamic equilibrium detected by?
hair cells in the semicircular canals
what are the two membranous sacs within the vestibule?
saccule and utricle
what is the saccule continuous with?
cochlear
what is the utricle continuous with?
semicircular canals
what are accessory structures of the eye?
- eyebrows
- eyelids
- conjunctiva
what do eyebrows do?
- protect eye from perspiration
- shade
what do eyelids do?
- glands secrete oily lubricant to prevent sticking
- eyelashes are richly innervated
what does conjunctiva do?
provides lubricating fluid to prevent eye drying out
what is the pupil?
round central opening that allows light to enter
what does the iris contain?
muscles that can constrict and dilate to change diameter of pupil, controlled by sympathetic and parasympathetic divisions
what shape is the lens of the eye?
biconvex
what does the lens change shape to do?
focus light on the retina
what is the lens of the eye held in place by?
suspensory ligaments called ciliary muscles
if the ciliary muscle contracts does the suspensory ligaments loosen or tighten?
loosen
if the ciliary muscle relaxes does the suspensory ligaments loosen or tighten?
tighten
if the ciliary muscle contracts what happens to the lens?
becomes round and thickened
if the ciliary muscle relaxes what happens to the lens?
flattens
what are the two segments that the lens and ciliary muscles divide?
anterior and posterior segments
what does the anterior segment of the eye contain?
aqueous humour
what does the posterior segment of the eye contain?
vitreous humour
what does the aqueous humour do?
supplies nutrients and oxygen to the lens and cornea and removes waste
what does the vitreous humour do?
supports posterior surface of the eye and hold the retina in place
what are the three layers of the eyeball?
- fibrous layer (outer layer)
- vascular layer (3 regions)
- retina (inner layer)
what does the fibrous layer of the eyeball contain?
-sclera and cornea
what does the vascular layer of the eyeball contain?
- choroid
- ciliary body
- iris
what does the retina layer of the eyeball contain?
- photoreceptors
- fovea centralis
- optic disc
where are photoreceptors located?
retina
what are rods photoreceptors for?
dim light and peripheral vision
what are cones photoreceptors for?
bright light, colour and visual acuity
what is refraction?
bending of light rays as it passes through different mediums (eg. humours, cornea, lens)
what is accomodation?
increasing or decreasing the refractory power of the lens (amount of bending)
what are the four changes of medium involved in the pathway of light to the retina?
- cornea
- aqueous humour
- lens
- vitreous humour
for close vision do ciliary muscles contract or relax?
contract
for distant vision do ciliary muscles contract or relax?
relax
for close vision do suspensory ligaments loosen or tighten?
loosen
for distant vision do suspensory ligaments loosen or tighten?
tighten
for close vision does the lens shape bulge/round or flatten/thinner?
bulges/round
for distant vision does the lens shape bulge/round or flatten/thinner?
thinner/flatten
for close vision does the refraction of light increase or decrease?
increases
for distant vision does the refraction of light increase or decrease?
decreases
for close vision is the autonomic division parasympathetic or sympathetic?
parasympathetic
for distant vision is the autonomic division parasympathetic or sympathetic?
sympathetic
in addition to accomodation what else must occur to focus on an object?
- convergence of the eyeballs
- constriction of the pupil
what is convergence of the eyeballs during close vision?
turning both eyeballs medially eg. looking at tip of nose
how is constriction of the pupil used for close vision?
iris sphincter muscle constricts to decrease the diameter of the pupil. This prevents the most divergent light rays from entering the eye and causing blurred vision
what is near point vision?
closest point at which we can focus
what is the normal ageing process where the lens loses the ability to accomodate called?
presbyopia
why is light that focuses on the optic disc unable to be seen?
is the blind spot and lacks photoreceptors
what is the visual pathway to the brain?
- retina
- optic nerve (II)
- optic chiasma
- optic tract
- thalamus
- optic radiations
- primary visual cortex in occipital lobe
what is binocular vision?
human eyes are located anteriorly so the field of vision from both eyes overlap
what is depth perception?
the ability to determine distance of an object from the eye
