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Anatomy & Physiology > 12: The Ears > Flashcards

12: The Ears Flashcards

1
Q

What is the role of the ears?

A

The ears are the only visible part of a complex structure that can sense hearing and balance

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2
Q

What is sound localisation?

A

Sound localisation is the ability to detect which direction a sound is coming from

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3
Q

How does sound localisation work?

A

Sound localisation works because the ears are located on either side of the head, so we can detect differences in intensity of sound for each ear

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4
Q

What is the process of hearing?

A
  1. Incoming sound waves are sent to the eardrum
  2. This causes the eardrum to vibrate.
  3. These vibrations cause movement in three small bones called ossicles connected to the eardrum on one side and to the inner ear on the other
  4. The movement of the ossicles causes waves in the cochlea
  5. This flow is sensed by tiny nerve cells lining the cochlea’s walls
  6. These nerve cells send electrical impulses through the auditory nerve to the brain
  7. The electrical impulses are decoded and interpreted by the brain, providing meaning and relevance
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5
Q

Where are ossicles located?

A

Ossicles are located connected to the eardrum on one side and to the inner ear on the other

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6
Q

What is the cochlea?

A

The cochlea is a fluid filled organ within the ears

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7
Q

What size is the external acoustic meatus?

A

The external acoustic meatus is 2.5cm long with a 0.7cm diameter

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8
Q

What is the structure of the external acoustic meatus?

A

The external acoustic meatus is somewhat curved. The lateral half is formed by cartilage and the medial half formed by bone

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9
Q

What does the external acoustic meatus contain?

A

The external acoustic meatus contains hairs and glands that produce earwax

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10
Q

What is cerumen?

A

Cerumen is the scientific word for earwax

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11
Q

What is the role of the external ear?

A

The roles of the external ear are to:

  1. Collect sound
  2. Amplify sound
  3. Transfer sound
  4. Localise sound
  5. Protect the inner ear
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12
Q

What is the structure of the middle ear?

A

The middle ear has a tympanic membrane, ossiular chain, Eustachian tube and contains muscles and tendons

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13
Q

What is the role of the ossicles?

A

The ossicles convert sound waves to mechanical vibrations and lead to the inner ear

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14
Q

What are the three bones of the ossicles?

A

The three bones of the ossicles are:

  1. The incus
  2. The stapes
  3. The malleus
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15
Q

What happens to vibrations as they travel from the middle ear to the inner ear?

A

As vibrations are passed from the middle to the inner ear, the energy in the vibration is amplified. This is because the area of the tymphanic membrane is larger than the area of the oval window

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16
Q

Where is the Eustachian tube located?

A

The Eustachian tube connects the middle ear to the nasopharynx

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17
Q

What is the nasopharynx?

A

The nasopharynx is the back of the nose

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18
Q

What is the role of the Eustachian tube?

A

The Eustachian tube equalises air pressure on both sides of the eardrum. This equalisation leads to maximum transfer of sound vibrations through the middle ear

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19
Q

What causes the Eustachian tube to open?

A

The Eustachian tube is opened by swallowing or chewing

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20
Q

What is the role of the middle ear?

A

The role of the middle ear is to transfer sound energy to the inner ear effectively, protect the inner ear and equalise air pressure

21
Q

What is the structure of the cochlea?

A

The cochlea is a spiral shape made of fluid filled tubes. It is made up of bony labyrinth and membranous larynx within which is the organ of corti-sensory receptors for hearing

22
Q

What is the membranous labyrinth?

A

The membranous labyrinth is a cochlear duct which lies within the bony cochlea. It divides into three canals

23
Q

What are the three canals of the membranous labyrinth?

A

The three canals of the membranous labyrinth are:

  1. Upper scale vestibule
  2. Middle scale media
  3. Lower scale tympani
24
Q

What is the role of the organ of corti?

A

The organ of corti is involved in active cochlear mechanics

25
Q

What are the roles of the cochlea?

A

The role of the cochlea is to transform the vibrations of the cochlear liquid and associated structures into a neural signal

26
Q

What is the role of the central auditory system?

A

Electrical impulses that travel up to the auditory nerve are decoded and interpreted by the brain, providing meaning and relevance to the signals

It carries out high level auditory abilities: recognition, interpretation and integration of sound

It also plays a role in some more basic auditory abilities: sound localisation and frequency analysis

27
Q

How do signals from hairs in the ears travel?

A

Signals from the hair cells pass to the special auditory cortex of the fore-brain by a chain of nerves. The hair cells excite the vestibulocochlear nerve

28
Q

Where are the synapses in the auditory system?

A

There is a synapse in the cochlear nuclei of the brain stem, the superior olivary nucleus of the medulla and the inferior colliculus of the thalamus

29
Q

How does the auditory cortex receive input from both ears?

A

When outputs from the cochlear nuclei cross over, the auditory cortex can receive input from both ears. Sound coming from a side position will reach both ears at different times and at different amplitudes

30
Q

How does the auditory system source sounds?

A

The brain uses time, phase and amplitude differences between the input from each ear to compute the sound source. Head or ear movement can refine the location, hence the cortex can derive a 3D representation of the sound source

31
Q

How did Broadman map the brain?

A

In 1909, Broadman looked at the cytoarchitecture of the six layers of the brain, in terms of thickness and cell types. From this he produced a map containing 47 areas

32
Q

What are the three main inputs to the brain that contribute to balance?

A

The three main inputs to the brain that contribute to our sense of balance are the vestibular, visual and somatosensory

33
Q

What are the other factors to balance?

A

There are factors other than brain inputs which contribute to balance. For example:

  • auditory system
  • central nervous system
34
Q

What is the organisation of the balance system?

A

The balance system works as:

  1. Input
  2. Integration
  3. Output
35
Q

What are the “inputs” in the balance system?

A

The inputs in the balance system are:

  1. Vestibular
  2. Vision
  3. Proprioception
36
Q

What are the “integration” in the balance system?

A

The integration in the balance system are:

  1. Brainstem
  2. Cerebellum
37
Q

What are the “output” in the balance system?

A

The outputs in the balance system are:

  1. Motor nerves
  2. Muscle joints
  3. Muscles
38
Q

What are the two distinct sets of structures within the vestibular system?

A

Within the vestibular system are two distinct sets of structures. These are:

  1. Three semicircular canals
  2. Two otolith organs
39
Q

What are the otolith organs of the vestibular system?

A

The two otolith organs of the vestibular system are:

  1. Utricle
  2. Saccule
40
Q

What is the role of the semicircular canals of the vestibular system?

A

In the vestibular system, the semicircular canals have a number of roles:
1. They have ampullas at their ends closest to the utricle. These bulges are where the crista are contained

  1. Signals from all three semicircular canals are used by the brain to determine the direction of motion
  2. The semicircular canals of the two vestibular organs work in pairs. If spinning to the let, the left lateral canal is excited and the right lateral canal is inhibited
41
Q

What are ampullas?

A

Ampulla’s are the bulges within the semicircular canals of the vestibular system

They are at the end of each canal, closest to the utrcle

42
Q

What is the crista?

A

The cista is a sensory apparatus which is contained within the ampulla of the semicircular canals of the vestibular system

43
Q

How do we balance?

A
  1. When our head moves, fluid in the ear annals move
  2. This fluid movement causes a deflection of the capula
  3. This deflection then deflects the cilia of the receptor cell and initiates the nerve impulse
  4. Signals from all three semicircular canals are used by the brain to determine the direction of motion
  5. Movement of the endolymph pushes in the gelatinous cupula and activates the receptor cells
  6. The SSCs of the two vestibular organs work in pairs. When the head turns, fluids in canals can lag behind and push both cupulae to one side
  7. Cilia either move towards or away from the kino cilium, causing the neural activity to increase or decrease
44
Q

Explain what happens in the ears when we turn left:

A

When the head turns to the left, fluids in both lateral canals lag behind, pushing both cupulae to the right

The one on the left is moving its cilia towards the kino cilium, and the one on the right away from the kino cilium

This will cause the neura activity in the left one to increase and the activity in the right one to decrease

45
Q

What structures are involved in the sense of linear movement?

A

Linear movement is sensed by the utricle and the saccule

46
Q

What structures are involved in the sense of angular movement?

A

Angular movement is sensed by the three semicircular canals

47
Q

What happens during linear movement?

A
  1. When stationary, otoliths settle onto the otolithic membrane, causing the stereocilia beneath to bend and send a signal to the brain. If the head moves, the otolithic membrane and otoliths slip
  2. This causes the cilia of different cells to bend
  3. A different signal is passed to the brain
  4. The location and position of these structures give the brain the information it needs to determine a static position
48
Q

Where are stereocilia found?

A

Stereocilia are found in otolithic membrane in the surface regions of receptor cells within the fluid filled sacs, found adjacent to the semicrcular canals

49
Q

Where are otoconia found?

A

Otoconia are tiny crystals found on top of the otolithic membrane of the receptor cels in the sacs adjacent to the semicircular canals

Anatomy & Physiology (13 decks)

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