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Flashcards in Hearing/ Vision Deck (26)
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1
Q

At what frequency ranges do humans normally hear/ speak?

A

Hearing: 20-20,000 Hz Speech: 300-3,000 Hz

2
Q

What dB can cause permanent hearing loss?

A

140 dB

3
Q

Pathway of sound to CN 8?

A

Sound wave goes to PINNA (outer ear) into external auditory canal -Waves hit tympanic memb (ear drum), and middle ear ossicles (Malleus, Incus, and Stapes) vibrate to amplify/focus sound energy, which goes from stapes ot Oval window -In response to this, this moves the fluid in the cochlea. This moving fluid is turned into a neural signal by the ORGAN OF CORTI which is sent thru CN 8 (vestibulococh) hair cells, causes depol and ap which moves down bipolar neurons to form CN 8 -cell bodies of coch nerve are in SPIRAL GANGLION

4
Q

Organ of corti TONOTOPIC organization

A

Hair cells at apex are tall, flexible, numerous and detect lower freq sound

5
Q

What are the two ASCENDING central auditory pathways?

A

MONOAURAL and BINAURAL pathways

6
Q

Monoaural (asc central aud path)

A

LEFT coch nerve in spiral gang goes to L DORSAL coch nuclei at pontomed jxn -DECUSSATES at brainstem via POSTERIOR ACOUSTIC STRIA -goes to RIGHT LATERAL LEMNISCUS (which goes from pons to midbrain) and then RIGHT INFERIOR COLLICULUS (at tectum of midbrain) and then RIGHT MEDIAL GENICULATE NUCLEUS (MGN) part of THALAMUS to realy info via auditory radiations to RIGHT primary auditory cortex (41/42)

7
Q

Binaural (asc central aud path)

A

-LEFT coch nerve in spiral ganglion goes to left VENTRAL coch nuclei -Here, some neurons DECUSSATE at brainstem thru TRAPEZOID BODY, but some stay IPSILATERAL -Both sides: go thru R and L SUPERIOR OLIVARY NUCLEUS (in lower pons near facial nucl) -Like prev path but both: R and L LATERAL LEMNISCUS then R and L INFERIOR COLLICULUS, then R and L MGN, then aud radiations to R/L prim aud cortex

8
Q

What would lesion of dorsal vs ventral cochlear nuclei cause?

A

Dorsal–monoaural unilateral hearing issue, whereas lesion to VEntral would cause bilateral hearing loss

9
Q

What does superior olivary nucleus do?

A

Set of nuclei near facial nucl in pons, where input from two ears is compared and integrated, and LOCALIZES sound in space

10
Q

In sound localization by superior olivary nucl, what aspects are low vs high pitched sounds localized by? (and WHERE in cortex are low vs high freq sounds processed?)

A

LOW pitched sounds are compared by TIMING of inputs HIGH pitched sounds are compared by INTENSITY (L)ow freq sounds are processed in Lateral aud cortex High freq sounds processed in Medial aud cortex

11
Q

What creates otoacoustic emissions?

A

Bilateral faint sounds up to 20dB emitted by EAR ITSELF in olivocochlear projxns of SUP OLIV NUCL (outer hair cells enhance vibr to eardrum), req normal middle/inner ear fxn

12
Q

What is the fxn of the SUPERIOR COLLICULUS?

A

Both in tectum of midbrain SUP COLLIC is inv in head reflex movements in response to sound, INTEGRATES several sensory modalities

13
Q

Testign for otoacoustic emissions can indicate fxn of what?

A

If we detect otoacoustic emissions after sup oliv nucl stim, know middle/inner ear are FXNL (eg in child)

14
Q

Stapes fxn and middle ear reflex?

A

DAMPENS SOUND! If sound too loud: goes from SUP OLIV NUCL to facial nucl to stapes mm to dampen sound -Middle ear reflex uses desc path to dampen amp to prevent dmg to middle ear

15
Q

How do you test for conductive vs sensorineural hearing loss? (with tuning fork)

A

Can use RINNE and WEBER tests -Conductive: abnormalities of ext aud canal or moddle ear, on rinne will show bone conduction greater on side w loss, weber will show tone louder on affected side -Sensorineural: disroders of coch or CN 8, Rinne will show air conduction better than bone (like normal), but tone in weber test will be softer on affected side

16
Q

What is vestibualr system made out of (3 main structures)

A

The semicircular canals (ant/post/lat)

The utricle and saccule (in VESTIBULE)

17
Q

What is the involvement of stereocilia in the vestibular system?

A

Diff heights(***)

Linear accel moves endolymph in semicirc canals which bends stereocilia tos ense motion, causing ap in vest part of CN 8

18
Q

What is benign paroxysmal Positional Vertigo (BPPV)?

A

This occurs when an otalith breaks off and floats in endolymph and gets stuck in semicirc canals causing imbalance (rocks in the ear)

19
Q

What structure is responsible for linear vs rotational acceleration?

A

The urtricle and saccule are resp for LINEAR ACCEL (contains macular portion), and ampullae are resp for ROTATIONAL/angular ACCEL (in cristal ampullaris)

20
Q

Goals/fxn of vestibular apparatus?

A

Fxns include subjective sens of motion and spatial orientation, and maintaining postiion of body in space and posture

-Main goals: keep head and body lined up, keep eyes fixed on target during head movements

21
Q

What does the vestibular nucleus do?

A

This complex integrates info about linear and angular acce, inputs from cerebellum re balance, and sensory input about vision/pressure, leads to output of vestibular REFLEXES

-sends projxns that descend MLF and eventually get to motor ventral horn for muscles

22
Q

VestibuloCEREBELLAR pathway

A

Vest nucl gets input from cerebellumr el to balance and send it back, forming feedback loops to coord mvmnt

-SEnsory info of vest sys carried via aff to SCARPAS GANGLION (vestibular gang with cell bodies of bp neurons), axosn project to vest cohc nerve 8 to vestibular nucl and then to cerebellum (or can bypass vestib nucl and go right to cerebellum)

23
Q

What are the 3 VESTIBULAR REFLEXES? (main info)

A

(unconsciously drive the fxns of vestib apparatus)

1) Vestibulo-Cervical
2) Vestibulo-Spinal
3) Vestibulo-Oculo

REFLEXES

24
Q

Vestibulocervical reflex pathway and fxn?

A

Fxn: POSTURAL AJUSTMENTS of head and neck mm in resp to mvmnt

Crista ampulla in semicirc canals detect angular accel from head movment, generates ap which goes along vest nerves to medial vestibular NUCLEI

-then info sent thru desc path via MLF into medulla, projxxn leave brainstem and enter SC (now called medial vesitublospinal tract), which SYNPASE onto ALPHA MOTOR neurons of ventral horn in vervical region for head and neck mm

25
Q

Vestibulospinal reflex fxn and pathway

A

Maintains equilibrium eg postural stability after input from lower body (responds to both types of accel), goes both thru medial and lateral vestibulospinal tract
-ANGULAR accel info detected by ampullae, project to medial vestib nucl then descend MLF (becomes med vestibulospinal tract in SC)

-LINEAR accel info detected by sensory organs in U/S, proejcts to LATERAL vest nucl, travels in lateral VS tract, synapse onto mm of lower body

(acitivity of moth can be modified by cerebellar outputs)

26
Q

Vestibulo-ocular reflex path and fxn>

A

Maintains visual fixation to stabilize image (adjust eye mvmt to rotational head mvmt– eye moves opp to head mvmt)

If move head to RIGHT, endolymph will move LEFT, angular accel sensed by cristae amp that creates ap, aff syn on med vestib nucl on brainstem and project ot LEFT contralat PPRF then to L abducens nucl (causing L eye to ABduct)