Ear 2 Flashcards
What is the tympanic membrane : oval window ratio?
18:1 (impedance matching air to liquid) - leads to pressure gain of x22
What two muscles open the resting state of the eustachian tube?
- Tensor veli palatini
2. Levator palatine
What does dysfunction of the eustachian tube lead to?
Middle ear negative pressure
What are the two openinsg of the chochlea to the middle ear?
Oval and round window
What do the oval and round windows permit?
Transmission of pressure wave in enclosed canal and vibration of teh basilar membrane
Give two features of the inner ear as a receiver and transducer?
Curved spiral lamina
2 half turns around central modiolus
What is scala media in the cochlea?
Endolymph
What is scala tympani and scala vestibuli?
Perilymph
Name the structure in the cochlea of the inner ear which produces nerve impulses in response to sound vibrations?
Organ of corgi (has hair cells)
What do the hair cells in the organ of corgi do?
Transduction - conversion of mechanical bending force into electrical impulse
In relation to hair cell function when does depolarisation occur?
When deflected towards longest
Hyperpolarisation occurs when deflected away
How is the cochlea organised?
Tonotopically
Where is the primary auditory cortex?
Superior temporal gyrus,
brodman areas 41/42
What do the superior canal and posterior canal of the labrynth connect to?
Common orus
What are the vestibular end organs?
Maculae of the utricle and saccule - otolith organs
Ampullae of lateral, posterior and superior semicircular canals
What do the maculae of utricle and saccule (otolith organs) have?
Stereocilia projecting upwards into a gelatinous matrix with otoconia
What direction are the stereocilia orientated?
In all directions so all movements perceived by depolarisation/hyperpolarisation
What are otoconia?
Calcium carbonate crystals
Where does the cupula sit?
In the ampulla of a semiciorcular canal
What is deflection of the cupula caused by?
Movement of perilymph - bending causes stereocilia to deflect
What is the term for when the eyes move without a cognitive, visual or vestibular stimulus?
Spontaneous nystagmus
What is a vestibular schwannoma?
Tumour of VIII nerve sheath (schwann) cells - imbalance due to slowly progressive loss of function
What type of receptors are receptors for taste and smell?
Chemoreceptors which are stimulated by binding to particular chemicals
What is taste perception influenced by?
Information from smell receptors
What are the sense organs of taste?
Taste buds
What do taste buds consist of that are arranged like slices of orange?
Sensory receptor cells and support cells
What is the life span of taste receptor cells?
10 days
What are taste receptor cells replaced from?
Basal cells within the taste buds
Name four places taste buds are present?
Tongue
Palate
Epiglottis
Pharynx
Where do the majority of taste buds sit?
In the papillae in the tongue
What are the four types of papillae?
Filliform - do not contain taste buds
Fungiform
Vallate
Foliate
Where do taste signals conveyed by cranial nerves via the brainstem and thalamus go?
To cortical gustatory areas
What are the five primary tastes?
- Salty
- Sour
- Sweet
- Bitter
- Umani (meat or savory) - triggered by glutamate
What is ageusia?
Loss of taste function