Week 11: Eye and Ear SDL Flashcards
What occupies the anterior chamber of the eye?
clear, watery fluid called aqueous humour
What and where is the conjuctiva?
tissue that lines the inside of eyes and covers the sclera (sclera is the white bit of eye)
What is the function of the conjuctiva?
- provides protection and lubrication of the eye by the production of mucus and tears
- it prevents microbial entrance into the eye and plays a role in immune surveillance
- provides a covering to the sclera
What is the function of the iris?
the iris controls the amount of light that enters the eye by opening and closing the pupil / the iris uses muscles to change the size of the pupil
Which nerve supplies the sphincter pupillae muscle?
CN III
What effect does contraction of the ciliary muscle have on the lens?
when the ciliary muscle is contracted, the lens becomes more spherical and has more focusing power
What is cataracts?
-cataracts is when the lens develops cloudy patches -these usually become bigger overtime, causing blurry, misty vision and eventually blindness
What are the 2 functions of the ciliary body?
- controlling the shape of the lens
- production of aqueous humour
What is glaucoma?
where the optic nerve becomes damaged, usually due to a build up of aqueous humour in the anterior chamber
Give two functions of the choroid layer of the eyeball
- supplies the outer retina with retina
- maintains the temperature and volume of the eye
What 2 layers is the retina made up of?
- an outer pigment cell layer - a single layer cuboidal epithelial cells with melanin filled microvilli extending from their inner surface
- a multi layered neural retina
What are the major cell types in the retina?
- pigment cell layer
- rod cell
- cone cell
- bipolar cell (=first order neurones of visual pathway)
- ganglion cell (=second order neurones of visual pathway)
- interneurones
Give 3 functional differences between rods and cones
- rods are responsible for vision at low light levels, they do not mediate colour vision and have a low spatial acuity
- cones are active at higher light levels, are capable of colour vision and are responsible for high spatial acuity
What is papilloedema?
-an optic disc/ nerve swelling that is caused by increased intracranial pressure
What is the fovea and how is it specialised for visual acuity?
- centre of macula
- the point on the retina at which the image of the object at the centre of the visual axis falls
- contains only cones for specialised visual acuity
Explain the blood supply to the retina
- central retinal artery (CRA)
- the choroidal blood vessels
List the structures through which sound waves enter the external ear, until they reach the auditory receptors
- sound waves arrive at the pinna (auricle)
- once the sound wave have passed the pinna, they move to the auditory canal before hitting the tympanic membrane
- sound waves enter the middle ear
- the vibrations are transmitted via ossicles: malleus, incus and the stapes
- sound waves then pass through the oval window to enter the cochlear in the inner ear
- hair cells in the organ of corti (within the cochlea) are stimulated which stimulates the cochlear branch of the vestibulocochlear nerve
- the cochlear nerve then transmits electrical impulses to the auditory region of the brain in the temporal lobe
What is the function of the tympanic membrane (ear drum)?
- separates the outer ear from the middle ear
- when sound waves reach the tympanic membrane, they cause it to vibrate
- these vibrations are transferred to the ossicles
What is the function of the ossicles?
to transmit sound waves from the air to the cochler
What is the function of the oval window?
receives vibrations from the ossicles which leads to movement of fluid within the cochlear and activation of receptors for hearing
What is the function of the auditory tube (eustachian tube)?
- connects the middle ear to the nasopharynx
- it controls pressure within the middle ear, making it equal with the air pressure outside the body
What fluid is found in the inner ear?
perilymph –> and within this cavity is an epithelial sac filled with endolymph
Which 3 receptors are found in the inner ear?
- maculae
- christae ampullaris
- spiral organ (organ of corti)
What is nystagmus?
when a person suffers with involuntary, uncontrollable eye movements
What is vertigo?
the sensation that you, or the environment around you, is moving or spinning
How does the basilar membrane respond to fluid movement in the inner ear?
- vibrates
- this causes the hairs to be deformed against the overlying tectorial membrane
- this causes depolarisation/hyperpolarisation of the sensory hair cells and generates action potentials in the sensory nerve fibres
Which region of the basilar membrane vibrates maximally in response to sounds of:
- high frequency
- low frequency
- high frequency - basal end of the membrane
2. low frequency - apical end of the membrane
What is conduction deafness?
deficit related to an obstructed, or altered, transmission of sound to the tympanic membrane or through the ossicle chain of the middle ear
What is sensorineural deafness?
hearing loss in which the root cause lies in the inner ear, sensory organ (cochlear and associated structures) or the vestibulocochlear nerve
