Biomed Medical Interventions 1.3 Ear

Conductive hearing loss

Conductive hearing loss

-Caused by interference with sound waves reaching the cochlea
-Typically involves issues with the outer and middle ear structures, such as the tympanic membrane, ossicles, or auditory canal.
-Mostly temporary, treatable, and less common
-Causes: Illness, infection, objects in ear

Sensorineural hearing loss

-Occurs due to damage to the cochlea, particularly the sensory hair cells, or the auditory nerve, resulting in difficulties in converting sound vibrations into electrical signals for transmission to the brain
-Inner ear
-More common and because it's mainly due to old age

Sue's hearing loss

Sensorineural hearing loss from bacterial meningitis

Oval window

- An opening in the Cochlea where sound can enter
- Allows sound to move from the Stapes to the Cochlea
- Border of the inner and middle ear

Round window

- Moves in and out of the Cochlea as the stapes enters the oval window, allowing for the fluid in the cochlea to move.
- Without this organ, the Cochlea would not move at all, causing hearing loss of 60 dB.
- Inferior to the oval window

Cochlear nerve

-Component on the auditory nerve
-Transmit electrical signals from the cochlea to the brain, where they're interpreted as sound

Vestibular nerve

- Transmits neural signals from the sensory hair cells of the vestibules to the brain.
- The information from the vestibule helps to keep the body balanced.
- Superior to the Cochlear nerve

Waves

The movement sound creates as it moves through air, liquids, or other gases.

Wave compression

A specific type of wave where the energy moves in the same direction as the particles displaced by it. Think of a beach, where the energy from the ocean moves towards the beach and with that energy water is displaced in the direction of the beach. This is also the way that sound moves.

Speech in noise hearing test

- Used to determine how well a patient can determine what someone is saying despite background noise.
- Tests the background noise and the words at various amplitudes to see which work best for the patient.

Audiogram

- Visual rendition of the amplitude of audio a person needs to be able to hear sounds at different frequencies.
- Most common test used for hearing loss.
- Requires a person to wear a headset in a quiet environment, which plays an audio at various frequencies, at each frequency increasing the amplitude until the person can hear.

Healthy/normal hearing

-10 to 20 dB

Mild hearing loss

20 to 40 dB

Moderate hearing loss

40 to 55 dB

Moderately-severe hearing loss

55 to 70 dB

Severe hearing loss

70 to 90 dB

Profound hearing loss

90 to 120 dB

Rinne test

- Used to test for conductive hearing loss.
- Done by holding the singular end of a tuning fork against the mastoid process until the patient cannot hear anything, and then subsequently on the other end in front of the ear until the patient cannot hear.
- The first part of the test measures the body's ability to hear the conduction of sound through the bones of the body (bone conduction), and the second measures the body's ability to hear sound conducted through the air (air conduction).
- The patient should be able to hear sound through air conduction for twice as long as they could bone.

Weber test

- Used to test both conductive and sensorineural hearing loss
- Patient has a vibrating tuning fork placed on the top of their head, and is asked if they can hear the sound equally well in both ears. If it sounds better in one ear, it can indicate sensorineural or conductive hearing loss.

Pinna

-Collects sound waves and acts as a funnel to direct them into the ear canal
-Outer ear

Auditory canal aka ear canal

-Channels sound waves from the pinna to the eardrum for further processing
-Outer ear

Eustachian tubes

-Assists in equalizing air pressure between the middle ear and the air outside of the body
-Middle ear

Malleus

(Hammer): Receives vibrations from the eardrum and transmits them to the incus

Incus

-(Anvil): transmits vibrations from the malleus to the stapes

Stapes

(Stirrup): transmits vibrations from the incus to the inner ear
-Hits oval window

Tympanic membrane (eardrum)

-When sound waves strike the tympanic membrane, it vibrates, which transmits these vibrations to the ossicles, which are then able to amplify and transmit them to the inner ear
-Middle ear

Cochlea

-Spiral-shaped, fluid-filled structure in the inner ear that converts sound waves to nerve impulses
-Contains sensory hair cells
-Attached to the auditory nerve
-Inner ear

Sensory hair cells

-When sound vibrations cause the fluid in the cochlea to move, the sensory hair cells bend, triggering the release of neurotransmitters that stimulate nearby nerve fibers
-The stimulation generates electrical signals that can be transmitted along the auditory nerve (then to the brain)
-Inner ear

Vestibule

-Contains sensory structures (saccule and utricle) that detect changes in head position and movement, which allows it to help with balance and spatial orientation (equilibrium)
-Inner ear

Antibiotic resistance

- Traits that help bacteria live despite medical interventions from antibiotics.
- Caused by misuse of antibiotics or use in situations where they are not necessary or helpful.
- Can make many bacteria much more deadly.

Fluoroquinolone

- Type of antibiotic that enters through the porins and attaches to the DNA gyrase, preventing DNA synthesis from occuring.
- Works for both, but is better for gram
- Examples are ciprofloxacin, delafloxacin, and Gemifloxacin.

Penicillin (Beta-lactam antibody)

- A type of antibiotic that bonds to penicillin bonding proteins (PBPs) and prevents them from building up the cell wall. This causes the cell to be fairly unprotected against foreign threats, like antibiotics.
- Primarily works for gram + because gram - has the additional outer membrane.
- Examples include penicillin, amoxicillin, and ampicillin.

Tetracycline

- A type of antibiotic that binds to ribosomes and blocks the attachment of tRNA molecules to mRNA molecules, preventing the creation of proteins and causing cell lysis.
- Works for both gram - and +
- Examples include Demeclocycline, Doxycycline, and Lymecycline

Sulfa antibiotics (Sulfanomides)

- A type of antibiotic that blocks the creation of folic acid, which is necessary for a cell to grow, develop, and divide.
- Because the cell cannot divide, this process causes cell lysis.
- Examples include Sulfamethazine, Sulfadiazine, and Sulfamethoxazole.

Hearing loss scale

How does sound travel through the air?

Sound travels through the air by when an object vibrates, it pushes and pulls on nearby air molecules, which causes them to compress and expand. This creates regions of high and low pressure. The pressure changes ripple through the air as sound waves, allowing the sound to travel through the air.