The Human Ear Flashcards
What are the 2 functions of the ear?
- Mediates the sense of hearing
2. Mediates the sense of balance
What are the 3 sections of the ear?
- Outer ear or ear canal
- Middle ear
- Inner ear
What does the outer ear consist of?
- Flap of cartilage framing a 25mm long canal that terminates at the eardrum
What is the ear canal made up of?
- Obstacle course of hairs
- About 4,000 wax producing cells
What is the purpose of the wax-producing cells in the ear canal?
- Prevent intrusions such as insects or dust from reaching the eardrum
- Protects eardrum from extreme heat and cold
If too much wax is produced what can be done?
- Can be assessed and removed by a doctor with a syringe
As the eardrum vibrates to sound waves arriving by the canal, 3 tiny bones; the hammer, anvil and stirrup…
Amplify and conduct those vibrations to the cochlea
The stirrup connects to the cochlea at a location called the….
Oval window
What happens at the oval window?
The mechanical energy of vibration is converted to electrical energy of nerve impulses which are carried to the brain via the cochlear nerve
the middle ear is vented to the atmosphere via what?
The eustachian tube which connects to the upper throat
Parts of the middle ear?
- Eardrum
- The hammer
- Anvil
- Stirrup
- Oval window
- Cochlea
- Cochlear nerve
- Eustachian tube
What is mounted above the cochlea in the inner ear?
- Semicircular canals
What do the semicircular canals do?
- Detect acceleration in pitch, roll, and yaw
What is the cochlea?
A tiny bone structure that looks a little like a snails shell
What is the cochlea filled with?
- Fluid called Endolymph
- Hair like cells
the hairlike cells in the cochlea respond to pressure waves and generate what?
- Nerve impulses which the brain interprets as sound
What does constant exposure to loud noise do to the hairlike cells?
Damages them
Is the damage to hairlike cells from exposure to loud noise reversible?
No
What are the semi-circular canals filled with?
- Endolymph fluid like the cochlea
- Hairlike cells called Cupula
How do the semicircular canals sense balance?
As the head changes its speed or attitude, the fluid washes over the hairlike cells which respond by sending nerve impulses to the brain to maintain orientation
True or false?
The Cupula respond to the INITIAL change in angular acceleration only
True
What happens to Cupula during a prolonged level turn with constant angular acceleration?
The initial flow of fluid stops and the cupula return to an upright position, no longer communicating information to the brain
What tiny organ senses linear acceleration?
- otolith organ
Where is the Otolith organ located?
At the top of the cochlea
What two components make up the Otolith organ?
- Utricle; lies horizontally
- Saccule; lies vertically
What does the Utricle detect?
Detects horizontal acceleration
What does the Saccule detect?
Detects vertical acceleration
What else assists the brain in a sense of balance?
- Eyes
- Postural cues
Two characteristics of sound…
- Frequency or pitch
- Intensity or loudness
What happens as a pressure wave arrives at the eardrum?
The pressure wave pushes against the eardrum causing it to bend inwards and then spring back to its original position
What is frequency?
- If we count the number of pressure waves (bounces) per second
- Number of vibrations per second is called Hertz
- The range of intelligible speech is 300-5000 Hz
What is intensity?
- Intensity/ loudness is determined by the degree to which the eardrum is bent by each pressure wave
- Also called the amplitude
What is the intensity of sound measured in?
Decibels
Every increase of ten decibels indicates a …… increase in the intensity of sound
Tenfold
Above what decibel does the ear experience discomfort and long-term exposure can cause permanent damage?
80db
Sound intensity above 140db produces…..
Ear pain
At what decibel level is hearing protection recommended?
85db
Early warning signs of hearing loss…..
- It is easier to hear on the telephone than normal face to face conversation
- Missing a lot of conversation in a noisy environment
- Feeling the need to turn the TV up when others are having no problem hearing
- Finding it difficult to hear when the speakers face is turned away
A general rule for when to use hearing protection….
- Should be worn when the noise level is such that you need to shout to be heard at a distance of half a meter
How much will well-fitting earplugs reduce db?
- About 25db
How many decibels will a well-fitting headset reduce noise level?
- About 40db
Effects of high noise levels on body….
- Increase stress
- Reduces concentration
- Aggravates fatigue
- Reduction in efficiency
Noises of 100db in the frequency range below 100hz will cause body to…
Vibrate
Noises of 150db or more will cause….
Sweating between fingers and under the collar
The Otolith organ and semicircular canals respond only to …
CHANGES in motions
