Audition + Balance (October 8)

Diagram of the ear [Image]?

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Hearing + The Cochlea Diagram 2

Diagram of the three ears [Image]?

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What does the pharyngotympanic tube do?

Connects middle ear to the nasopharynx. Manages pressure between environment and middle ear.

Diagram of the external ear [Image]?

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What do cerumen glands in skin do?

Produce wax to trap foreign bodies. Maintain acidic pH preventing bacterial/fungal overgrowth.

What are the 3 layers of the tympanic membrane?

Skin (externally). Connective tissue (intermediate). Mucosa (internally).

Diagram of tympanic membrane removed [Image]?

Reveals the ossicles in the middle ear interior [Image].

What is the path of vibrations from tympanic membrane?

Mechanical relay of vibrations of tympanic membrane to oval window membrane of the inner ear. Done via the ossicles (three bones)

Diagram of the ossicles [Image]?

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What is infected fluid in middle ear?

Otitis media

Diagram of normal middle ear vs otitis media [Image]?

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Diagram of middle/inner ear [Image]?

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What are the parts of the cochlea/spiral organ?

3 fluid filled channels. (1) Scala media (cochlear duct) - contains tectorial membrane + hair cells (mechanoreceptors) (2) Scala vestibuli - leads to - (3) scala tympani

Where do the vibrations travel from the oval window to?

To round window

Diagram of the path of vibrations after oval window [Image]?

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Diagram of hearing + the cochlea [Image]?

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Diagram of the spinal organ [Image]?

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What are the steps of hearing + the cochlea?

(1) Sound wave through external ear. (2) Hit tympanic membrane. (3) Through suspended ossicles. (4) vibrate oval window. (5) vibrate perilymph. (6) Travel through scala vestibuli. (7) spiral organ. (8) Travel through scala tympani. (9) Dampened via round window.

What happens inside the spiral organ?

Vibrations of oval window sets the fluid inside the cochlea moving. Makes the vestibular membrane vibrate, then basilar membrane. The tectorial membrane shifts, causing hair cells to bend.

Specimen of nerve [Image]?

Vestibulocochlear nerve

Specimen of nerve [Image]?

Olfactory nerve,

What pathway does the vestibulocochlear nerve involve for hearing?

Cochlea (spiral organ) to primary (1o) auditory cortex in temporal lobe.

Diagram of the vestibulocochlear nerve [Image]?

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What are the 2 types of hearing loss?

Conductive hearing loss and sensorineural hearing loss.

What is conductive hearing loss?

Impedance of sound transmission in external and/or middle ear. Low tones typically affected. Causes: tympanic membrane rupture, cerumen impaction, foreign body, infection, damage to ossicles, trauma

What is sensorineural hearing loss?

Disruption at the level of the cochlea, cochlear nerve and/or brainstem. High tones affected first. Causes: stroke, trauma, prolonged noise, drug toxicity, tumors, high endolymph pressure, age.

Do hair cells regenerate?

No.

What are treatments available for hearing loss?

Reconstructive surgery, hearing aids, cochlear implants. Depend on cause of loss.

What does the vestibular apparatus consist of?

Utricle (bag). Saccule (small sac). Semi-circular canals (x3 - superior, posterior, horizontal).

Which organs sense acceleration (equilibrium)?

Otolithic organs + semicircular ducts.

Diagram of vestibular apparatus [Image]?

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What are the otolithic organs and what do they sense?

Utricle and saccule. Sense linear acceleration.

How are the utricle and saccule oriented?

Maculae oriented perpendicularly. Utricle = horizontal. Saccule = vertical.

What do the utricle and saccule consist of?

Supporting cells: secrete otolithic membrane and otolith crystals Hair cells: sensory receptor.

How do the otolithic organs sense linear acceleration?

Otoliths and membrane shift with movement, bending hair cells = linear acceleration.

Diagram of otolithic organs [Image]?

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Diagram of linear acceleration [Image]?

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What do the semicircular ducts sense?

Rotational acceleration

What are the semicircular canals and how are they oriented?

3 semicircular canals @ 90 degrees. Horizontal (lateral), superior (anterior), posterior.

What is the ampulla and what does it consist of?

Dilated region of semicircular ducts. Crista - hair cells (mechanoreceptors), supporting cells. Cupula (gelatinous). Endolymph fluid.

Diagram of semicircular ducts [Image]?

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How do semicircular canals sense rotational acceleration?

Rotation moves endolymph in opposite direction. Cupula displaces + bends hair cells - depolarization/hyperpolarization via mechanoreceptor.

What are the 3 pairs of canals with opposing hair positions?

L + R horizontal. L Superior (ant) + R Posterior. R Superior (ant) + L Posterior.

Diagram of rotational acceleration [Image]?

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Why are there opposing hair positions in each pair of canals?

Turing your head one way pushes fluid in a way that excites one canal and inhibits its counterpart.

What pathway does the vestibulocochlear nerve involve for equilibrium + balance?

Semicircular canals, saccule, and utricle. To: CN VIII nucleus (pons) and then: thalamus, cerebellum (axial/appendicular musculature), CN XI (head position), eye muscle nuclei.

Where are hair cells (mechanoreceptors) + gelatinous layer located?

Spiral organ (hearing). Utricle/Saccule (linear acceleration). Semi-circular canals (rotational acceleration).

Diagram of locations of hair cells (mechanoreceptors) + gelatinous layer [Image]?

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How are sensations of hearing and balance registered?

Via the bending of hair cells embedded within a gelatinous layer that shifts as a result of perilymph or otolith movement.

What are the functions of the nasal cavity?

Warm + humidify inspired air. Trap pathogens + particulate. Smell.

Where is the nasal cavity located?

Anterior to the nasopharynx + opening to the pharyngotympanic tube.

Diagram of the nasal cavity [Image]?

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What must be present for olfaction?

Chemical odorants. Odorants must be present at a minimum threshold (sensitivity) for chemoreceptors.

Where does olfaction occur and where is it processed?

Occurs in olfactory epithelium at superior aspects of nasal cavity. Processed in primary olfactory area - frontal + temporal lobes.

What is olfaction a critical component of?

Limbic system + for taste.

Diagram of olfaction [Image]?

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What are the parts of the olfactory mucosa?

Olfactory receptor cells. Supporting epithelial cells. Olfactory gland. Olfactory bulb.

What do the olfactory receptor cells do?

Axons form CN I. Olfactory cilia = chemoreceptor. Formed by basal (stem) cells.

What do supporting epithelial cells do?

Nourish + insulate receptor cells.

What does the olfactory gland do?

Produces mucus layer.

What does the olfactory bulb do?

Synapse between CN I to form olfactory tract.

Diagram of the olfactory mucosa [Image]?

[Image].

How does olfactory adaption occur?

Peripheral: Receptors decrease their sensitivity rapidly due to negative feedback loops decreasing AP frequency in sensory neurons. Central: Olfactory bulb is suppressed by interneurons + areas in the olfactory cortex (temporal lobe) reduce their processing of a persistent signal over time.

What is the path of olfaction?

Olfactory epithelium. Olfactory nerve. Olfactory bulb. Olfactory tract. Cortical regions.

Where does the olfactory nerve extend to?

Extends through the cribriform plate of the ethmoid bone.

What does olfaction connect to (other nuclei)?

No filtering by thalamus = strong connection to limbic system + memory.

Diagram of olfactory nerve [Image]?

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What does the cribriform plate look like?

Bone that has a bunch of holes.