sound vibration and motion sickness

Question 1

Question 2

impulses are sent from inner ear to brain via

Answer 2

auditory nerve

Question 3

acoustic reflex

Answer 3

The acoustic reflex is a response of the middle ear to sound.

Sound is collected in the outer ear, amplified and transmitted to inner ear. The mechanical energy is converted into electrical energy as it stimulates the auditory nerve. The electrical impulse travels through the auditory tracks of the brainstem which involves the cochlear nucleus and the superior olivary complex.

There is crossing of the nerve tracts at the cochlear nucleus so that sound perceived by one ear will be sent bilaterally to the auditory cortical areas. The acoustic reflex is generated at the level of the superior olivary complex.

When a loud stimulus is presented (70 dBA or above) this complex is stimulated and in turn it sends bilateral electrical impulses via the cranial nerve VII to the stapedius muscles of the middle ears causing a measurable change in the tension of the ear drum.

The acoustic reflex tells us that the brain’s “wiring” is intact and working.

Question 4

auditory nerves go to…..

what happens there?

Answer 4

right and left cochlear nucleus

nerve tracts cross so info is sent bilaterally to the auditory cortical areas/right and left superior olivary complexes

Question 5

a loud sound will cause what after the olivary nucleus?

Answer 5

bilateral impulses sent back to stapedius muscle via facial nerve -> changes tension in ear drum

Question 6

decibel scale

Answer 6

logarithmic, cant be just added

–> for two identical sounds, just add 3 dB

–> for three, add 5 dB

Question 7

dB of hazardous cont/intermittent noise?

discomfort threshold?

hazardous impact/impulse noise?

tissue damage?

death?

Answer 7

85

120

140

170

180+

Question 8

ex: one machine is 90dB

two identical machines?

Answer 8

93 dB

Question 9

STS

standard threshold shift

Answer 9

a change in hearing from baseline when on the audiogram:

sum of the shift at 2000, 3000, and 4000 hz is greater or equal to +30dB

Question 10

how to verify STS?

Answer 10

•Repeat the test twice within the next 30 days; one within 14 hrs of rest from noise

Question 11

audiogram

Answer 11

traces the sensitivity of sound reception

Question 12

three types of audiograms

Answer 12

normal

high freq loss

conductive loss

Question 13

normal audiogram

Answer 13

range between -10 to 25 dB

Question 14

high freq loss audiogram

Answer 14

Losses at 2000 Hz and above are classified as high frequency sensorineural hearing losses. The classic curve is the notched loss. This “notch,” which will be shown on a subsequent slide, most frequently occurs at 4000 Hz

damage to the inner ear and/or the pathway to the brain. It is commonly seen in noise-induced hearing loss, presbycusis (age-related hearing loss) and acoustic trauma

Question 15

conductive hearing loss audiogram

Answer 15

•conductive hearing loss in both ears. Note that the bone conduction (brackets) is better than air conduction.

The gap between bone and air conduction must be greater than 10 dB to be labeled as a a conductive hearing loss.

diseases involving the middle ear such as Eustachian Tube Dysfunction, Otitis Media and Otosclerosis

Question 16

tympanogram

types

Answer 16

measures mobility of the tympanic membrane

• Type A – Normal
• Type Ad – Hypermobile
• Type As – Stiff
• Type B – Immobile
• Type C – Negative Pressure

Question 17

Answer 17

• Type “A” = Normal Middle Ear Status
• Normal Middle Ear Pressure -150 - +100 daPa

Question 18

Answer 18

• Type “Ad” = Hypermobile Middle Ear
• Possible ossicular discontinuity or monomeric TM
• abnormally excessive (or floppy) movement in response to pressure

Question 19

Answer 19

• Type “As” = Stiff Middle Ear system
• Stiff, scarred TM
• “stiffening” pathologies such as otosclerosis or tympanosclerosis.

Question 20

Answer 20

• Type B = Flattened = Immobile Middle Ear
• Fluid behind the TM
• perforated ear drum, cerumen impaction, or a PE tube, although, it is also completely flat when the measuring device is pressed against the ear canal wall.

Question 21

Answer 21

•Type “C” = Eustachian Tube Dysfunction
•Negative pressure behind the TM
•a negative pressure in the middle ear. Most commonly this means eustachian tube dysfunction
•

Question 22

NIHL

Answer 22

noise induced hearing loss

• Sensorineural = affect of the outer hair cells in the inner ear.
• Bilateral and usually symmetric.
• NO profound hearing loss (range is low~40 dB/high ~75 dB).
• NO cumulative effect due to Previous NIHL
• Loss at 3-6k Hz. The greatest at 4k Hz.
• Max loss at 3k, 4k and 6k Hz in about 10-15 years.
• Continuous noise exposure is worse than interrupted.
• Discontinued noise exposure, no significant continued progression.

Question 23

types of vibration

Answer 23

Types of Vibration:

• low-frequency (8 – 15 Hz),
• medium-frequency (16 – 64 Hz),
• high-frequency (more than 64 Hz).
• Dangerous for the development of disease is the vibration with the frequency 16 – 250 Hz.

Question 24

hand- arm vibration medical concerns (chain saw worker etc)

Answer 24

• Circulatory: Raynaud’s phenomenon
• Diagnosis of exclusion
• Sensory & motor disturbances:
• ↓grip strength
• ↓dexterity
• ↓touch & temp sensitivity
• Carpal tunnel, pain & stiffness in upper limb – poorly understood
• Grade using Stockholm Scale

vascular symptoms are usually first but may improve with ceasing; neurologic are usually permanent

Question 25

what causes motion sickness?

Answer 25

Sensory Conflict/Neural Mismatch

Eyes and ears disagree

Anticipation of orientation key

Question 26

pharm for motion sickness

Answer 26

Scopolamine Transdermal Patch

Antihistamines

• Meclizine (Dramamine)
• Diphenhyrdramine (Benadryl)

Promethazine (Phenergan)

• Drowsy
• Add caffeine

Phenergan (50mg IM) + stimulant

Zofran for vomiting (but doesn’t prevent motion sickness)