Sense Organs Flashcards
Which parts of the ear make up the outer ear
Pinna and auditory canal
What is the function of the pinna
Directs sound waves to the auditory canal
What is the function of the auditory canal
Transmits sound from pinna to the tympanic membrane
What are the parts of the middle ear
Tympanic membrane
Ear ossicles
Oval window
Round window
Eustachian tube
What is the tympanic membrane and what is its function
Tympanic membrane: a thin membrane that covers the opening between the auditory canal and the middle ear
Function:convert sound waves to vibrations that are transmitted to ear ossicles
What do the ear ossicles consist of and what are their function
Consists of anvil, hammer and stirrup
Function: transmit vibration in middle ear to oval window
Magnify the vibration (to accommodate for the fluid in the inner ear because sound in fluid becomes muffled/less clear)
What is the oval window and what is its function
Oval window: a thin membrane connecting middle ear to inner ear
Function: transmits vibration to inner ear
What is the Eustachian tube and what is its function
Eustachian tube: tube connecting the middle ear to the throat
Function: allows pressure in the middle ear to be equal to the atmospheric pressure so that pressure is the same on both sides of the tympanic membrane
What is the structure of the inner ear
Consists of bony labyrinth and membranous labyrinth
Bony labyrinth is system of canals and cavities in the skull
Bony labyrinth filled with perilymph
Membranous labyrinth is a system of membranous tubes and sacs found floating in the perilymph
Membranous labyrinth has the same shape as the bony labyrinth
Membranous labyrinth filled with endolymph
Bony labyrinth and membranous labyrinth filled divided in two sections: 1. Vestibular apparatus - for balance
2. Cochlea - for hearing
What is the vestibular apparatus comprised of and what is each part responsible for
Three semi-circular canals - direction and speed
Utriculus - have maculae which detect gravity
Sacculus - have maculae which detect gravity
What is the role of the utriculus and sacculus
Utriculus and sacculus contain maculae
Each macula has sensory cells with fine hairs embedded in a layer of jelly
Small crystals of calcium carbonate on the jelly called otoliths
Depending on position of head the weight of the otoliths will pull on different hairs
Interpreted by brain to tell us if we’re upright or not
What is the structure of the semi-circular canals
Three semi-circular canals positions at right angles to each other
Ampulla at base of each semi-circular canal
Ampullae contain sensory crista
What the function of the semi-circular canals
Responsible for detecting movement in head (direction and speed)
Endolymph fluid fills semi-circular canals and stimulates sensory crista as head moves
Fluid will flow in one of the semi-circular canals more than the others depending on the direction of movement of the head
This information is fed to the cerebellum help maintain balance
What is the cochlea
A Long, coiled, structure which is divided along its length into three compartments
What is the structure of the cochlea
3 compartments
Upper compartment: has perilymph and connects to oval window
Middle compartment: has endolymph and organ of corti
Lower compartment: has perilymph and connected to round window
Organ of corti has many sensory hairs which connected to the auditory nerve
How does the cochlea work
Vibration is transmitted from the stapes to the oval window then into the endolymph
Vibrations tug at the hair cells of the organ of corti
Sensory hair cells send impulse to the auditory nerve to the cerebrum (temporal lobe) which interprets the sound
Vibrations continue through perilymph of the lower chamber to the round window where they are lost to the air of the middle ear
What’s the function of the round window
Releases inner ear pressure and basilar membrane vibration
What is the difference between conductive deafness and neural deafness
When one of the mechanisms conducting the sound waves/vibrations fails e.g: tympanic membrane damaged
Neural deafness: problems of the inner ear (organ of corti) or the auditory nerve or temporal lobe of brain
What are the possible causes of deafness
Accumulation of wax against tympanic membrane
Long term exposure to loud noise
Hereditary
Infections e.g: meningitis
What are possible treatments of deafness
Hearing aids
Cochlear transplants
How does a hearing aid work
Amplifies sound
Patient must have some hearing
What is a cochlear transplant
An electronic device that is implanted surgically to enable hearing in people with serious or profound deafness, where the inner ear is damaged
How do cochlear transplants work
Device has 2 parts:
External part has a microphone, speech processor and transmitter which allow for sound in the environment to be detected, converted to an electrical signal and sent to the internal part of the cochlear transplant
Internal part: receives the transmitted electrical signal, converts it to an electrical impulse which stimulates the auditory nerve to conduct them to the brain
How do middle ear infections happen so easily
Middle ear has Eustachian tube which is connected to throat
Throat infections can easily connect to the middle ear
How does a middle ear infection happen
Eustachian tube blocks and pressure builds up in the middle ear = causes tympanic membrane to to bulge = pain in middle ear
How can middle ear infection be treated
Anti-biotics
What is the difference between a sense organ and a receptor
SO: comprised of many tissues and one of them is receptors
R: the actual issue/cells responsible for receiving stimulus
How are our eyes positioned and structured (from outside pov)
Eyes positioned in skull sockets to protect from injury
6 eye muscles hold eye in place and help with side to side and up and down movement
Eyelids and eyelashes help protect eye from foreign objects
Tear gland secretes antiseptic tears to protect conjunctiva from infection and dehydration
What is the name of the strong, white inelastic layer in the eye and what is its function
Sclera
Protects eye
Helps eye keep its shape
Place of attachment for muscles
Cornea forms in front of it
What is the name of the transparent layer of the eye and what is its function
Cornea
Allow light to enter the eye
Helps bend/refract light rays to focus the image
What is the choroid
The layer that has pigment which prevents internal reflection of light
What is the ciliary body and what is its function
Part of the eye comprised of ciliary muscles and suspensory ligaments
Changes the shape of the lens to focus the image
What is the name of the pigmented, muscular layer with a hole in the middle and what is its function
Iris - controls the amount of light entering the eye (hole in the middle = pupil)
what is the lens and what is its function
Lens - a rubbery, elastic, transparent Biconcave structure
It can change shape to focus the image on the retina
How does the retina work
Has photoreceptors: rods and cones
Rods = sensitive to low light, only allow black and white vision
Cones = sensitive to bright light, allow for colour
Cones located in the yellow spot (fovea) the part of the retina that is the centre of our focus
What is the function of the optic nerve
Transmits impulses from eye to cerebrum (occipital lobe)
Where is the blind spot
Where the optic nerve leaves the retina; no photoreceptors here
What is the vitreous humour and What is its function
Clear jelly-like substance
Maintains the shape of the eye
Hold retina against the choroid
How does sensation of light occur
Light is refracted as it passes cornea, lens and vitreous humour
The refraction forms an image which is centred at the fovea (yellow spot) of the retina
The image is small and inverted
Many photoreceptors record small parts of the images and send the information to the optic nerve
Optic nerve transmits the information and the brain pieces the information together to form a picture
What is accommodation
The process whereby the eye adapts to focus on objects closer than 6m
How does the eye work when focused on images further than 6m away
The circular ciliary muscles are relaxed
Natural elasticity of eyeball pull ciliary body away from lens on all sides
Sensory ligaments pulled taught
This flattens the lens and its becomes less convex (less confer = less bending of light)
Less refraction occurs
Image is focused on retina
How does the eye work when it focuses on an image closer than 6m away
The circular ciliary muscles contract
Ciliary body moves in towards the lens (because the diameter of the circle created by the ciliary muscle decreases)
Tension on the suspensory ligaments is released
The lens has a more convex shape (more convex = bends light more)
More refraction of light occurs
Image is focused on retina
What is binocular vision
Our two eyes overlap so objects in front of us are observed by both eyes simultaneously
This helps to judge distance more accurately
Field of binoculars vision = 140 degrees
What is pupillary reflex
Reflex action that controls the amount of light that enters the eye by changing the size of the pupil via the circular muscles and radial muscles in the iris
How does the pupillary reflex action work in bright light
Radial muscles relax
Circular muscles contract
Pupil constricts
Less light enters the eye
How does the pupillary reflex work in dim light
Radial muscles contract
Circular muscles relax
Pupil dilates
More light enters the eye
Why is the iris pigmented
So that light only enters through the pupil
What is myopia, what causes it, and how can it be fixed
When distant object are out of focus
Caused by elongated eyeball or abnormal curvature of the cornea
Fixed with concave lenses or laser surgery
What is hypermetropia, what causes it and how can it be fixed
Close up objects are out of focus
Caused by shortened eyeball or an abnormally flat cornea
In some older people it can be becuase the eyeball has lost elasticity and does not return to its round shape when tension in the suspensory ligaments is released
Fixed with convex lenses or laser surgery
What is astigmatism and how can it be fixed
Visual defect caused by an irregularly shaped cornea or lens, causes blurred images at all distances
Fixed with prescription lenses or surgery
What are cataracts and how can they be fixed
Cataract = clouding of the lens that happens gradually leading to gradual loss of vision
Fixed with surgery where lens is replaced with synthetic lens
