Special senses - ears Flashcards by Mary Tilling

What are the middle and inner ear housed in?

Temporal bone

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What is the outer ear flap bit called?

Auricle/pinna

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Ear canal name?

External auditory meatus

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What nerve moves the auricle?

Facial nerve

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What is the main notch in the ear called and what is it between?

Intertragic notch - between the tragus and antitragus

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What is the margin of the auricle called?

Helix

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What is it called when there is an ear infection and wat is used to treat it?

Erythema - red

Lateral wall resection

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What is the external acoustic meatus lined with?

Skin containing sebaceous and ceruminous glands

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What is the external acoustic meatus between?

Base of auricle and ear drum/tympanic membrane

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What is the air filled space in the middle ear called?

Tympanic cavity

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What is the middle ear in?

Petrous part of the temporal bone - more dense bone

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What is the bulge behind the ear called?

Tympanic bulla - involved in improving sound

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What is the tympanic membrane made up of?

Double layer of epithelium with connective tissue between

Medial epithelium - cuboidal

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What is the tympanic membrnae innervated by?

The auriculotemporal branch of mandibular branch of trigeminal nerve
auricular branch of vagus nerve

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How does the middle ear communicate with the nasopharynx? Why?

Via auditory tube

Equalises pressure

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What are the windows between the middle and inner ear called?

Fenestra

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What are the names of the two fenestra? Which are dorsal and ventral?

Vestibular/oval window - more dorsal

Cochlear/round window - more ventral

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What are the names of the ossicles?

Malleus
Incus
Stapes

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What attaches to the oval window?

Stapes

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WHat is the function of ossicles?

Mediate the transmission of sound into the inner ear

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What is the relationship of the middle ear with the facial nerve?

Enters the internal acoustic meatus with the vestibulocochlear nerve
Crosses the temporal bone
Exits at the stylomastoid foramen

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What branch of the facial nerve is associated with the middle ear?

Chorda tympani branch

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What does the chorda tympani branch do?

Lies on the upper part of the tympanic membrane

Supplies taste to the rostral 2/3 of the tongue

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What are the two parts of the inner ear?

Membranous labyrinth

Bony labyrinth

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What is in the membranous labyrinth?

Endolymph

What make up the bony labyrinth?

Semicircular canals Cochlear Vestibule - containing utricle and saccule

What does the cochlea do?

Converts sound to an electrical signal

What are the 3 sections of the cochlea?

Scala vestibuli Scala tympani Scala media

What do the scala tympani and scala vestibuli contain?

Perilymph

What does the scala media contain?

Endolymph

What does the scala vestibuli do?

Take the sound waves from the stapes/oval window to the helicotrema (apex)

What does the scala tympani do?

Take sound waves from the helicotrema to the round window

What separates scala media from scala vestibuli?

Vestibular membrane

What separates scala media from scala tympani?

Basilar membrane

What other membrane does the scala media contain?

Tectorial membrane

What is the main thing that is in the scala media?

Organ of Corti

What specialised receptors detect rotational movement?

Ampullary crests

What specialised receptors detect position of head and linear movements?

Maculae - otolith organs

What are the semicircular canals filled with?

Endolymph

What contains the hair cells in the semicircular canals?

Ampulla

What do the stereocilia of the hair cells in the semicircular canals project into?

Cupola

What does the utricle detect?

Horizontal movements

What does the saccule detect?

Vertical movements

What do the stereocilia project into in the maculae?

Otolith membrane

What is in the otolish membrane and why?

Calcium carbonate crystals to increase the mass so it lags behind in acceleration

What are the two parts of the maculae

Utricle and saccule

What are the outer and middle ear refered to as compared to the inner ear?

Outer and middle - conductive | Inner - sensory

What is impedance matching?

Fluid has greater inertia so takes more energy to move it | Therefore eardrum has a bigger SA than the oval window and ossicles have a lever action

What is the makeup of perilymph?

Low potassion conc | Potential of 0mV

What is the makeup of endolymph?

High potassium conc | High potential of 18mV

Where is the organ of corti located?

On the basilar membrane in the scala media

What do the stereocilia of the hair cells in the cochlea project into?

The tectorial membrane

What are the two type sof hair cells in the cochlea?

Inner hair cells and outer hair cells

What shape are inner hair cells?

Flask shaped

What type of innervation are inner hair cells?

Afferent

What shape are outer hair cells?

Columnar

What type of innervation are outer hair cells?

Efferent

How many rows of hairs are on outer and inner hair cells?

1 on inner | 3 on outer

What are inner hair cells responsible for?

Sound encoding - turning sounds into electrical signals

What are outer hair cells responsible for?

Sound amplification and tuning

What does movement of the stereocilia cause?

Tension on the tip links which opens transducer channels causing depolarisation

What is the phase locking mechanism?

Where the electrical activity is linked to the peak of the wave of the initial stimulus doesnt happen at higher freqs than 4kHz

What allows hearing of higher frequencies?

Tonotopy

What is tonotopy?

The spacial arrangement of frequency information provided by the basilar membrane

What are the structural differences in the basilar membrane?

Narrow and stiff at base - high freqs | Wide and floppy at apex - low freqs

How are these different regions of the basilar membrane detected in the brain?

Isofrequency bands in the auditory cortex

How is loudness encoded?

Different afferent nerves High spontaneous rate fibers - low sounds medium " Low " - only activated at highest frequency, dont get saturated

What does depolarisation of the outer hair cells cause?

Activation of prestin which causes cells to shorted and amplify the movement of het basilar membrane

What is the primary central pathway?

Spiral ganglion - ventral cochlear nucleus - superior olive - inferior colliculus - medial geniculate nucleus -auditory cortex

How is sound localised?

Low freqs - time difference to each ear | High freqs - interaural intensity difference

What reflex detects deafness?

Preyer's reflex - startle

How are vestibular cells activated?

Directionally sensitive Towards tallest kinocilia - depolarisation, excitation Towards shortest - hyperpolarisation, less excitation

What is the place in the utricle and saccule where the stereocilia are oriented in opposite directions?

Striola

What does orthogonal mean?

Oriented at 90 degrees to each other