Lecture 10 - The Neurology Of Hearing And Balance

Question 1

What are the three parts of hearing system?

Answer 1

Outer ear, Middle ear and Inner ear

Question 2

What are the structures of outer ear?

Answer 2

Pinna and External Auditory Canal

Question 3

What are the functions of outer ear?

Answer 3

Sound waves are captured by the outer ear and funnelled through the external auditory canal to the tympanic membrane

Question 4

Structures of Middle ear

Answer 4

Tympanic membrane, malleus, incus, stapes

Question 5

What is the function of middle ear?

Answer 5

To convert the vibration in the air into some vibrations in the body so we can collect importante signals and process it

Question 6

Sound waves can cause _______________ to vibrate.

Answer 6

Tympanic membrane

Question 7

What are the functions of the three bones of the middle ear?

Answer 7

Transmit and amplify the vibrations to the oval window of the inner ear

Question 8

What use the lever system principle in the middle ear, and what are the functions?

Answer 8

• Incus and stapes
• To save energy to have a higher efficiency using a lever system
• Amplify the signal and ensure the internal device can save space

Question 9

What is the mechanism in middle ear?

Answer 9

The area in tympanic membrane is much larger than the oval window, so the pressure in the oval window is higher than that of tympanic membrane and that can amplify the pressure.

Question 10

What can the bony structures in middle ear do?

Answer 10

It can selectively stop some parts to prevent the large sound from being sent to inner ear by tightening of tympanic membrane and increasing tendons in middle ear bones

Question 11

What does inner ear convert?

Answer 11

Converts the mechanical signals into electrical signals

Question 12

What is the structure for hearing in inner ear?

Answer 12

Cochlea

Question 13

Why is cochlea needed?

Answer 13

• To save space
• To have a very long structure to capture different sounds with high-frequency sound travelling a shorter distance than low-frequency sound

Question 14

Where in cochlea detect the high-frequency and low-frequency sounds?

Answer 14

• Sensors at the beginning of cochlea can detect high-frequency sound
• Sensors at the apex of cochlear (the end) will detect low-frequency sound

Question 15

Where does liquid travel from and to in cochlea?

Answer 15

Liquid travels form oval window to round window in the cochlea, and that both structures are elastic that provides freedom to the perilymph inside

Question 16

What is present in the cochlea?

Answer 16

Cochlear duct

Question 17

What are the four hair cells in the cochlea?

Answer 17

3 outer hair cells and 1 inner hair cell

Question 18

What are the functions of outer hair cells?

Answer 18

Backward connection from the brain and fine tune the sounds by pulling/ relieving the signals.

Question 19

What are the functions of inner hair cell?

Answer 19

The main sensor for sound and transforming vibration into electrical signals

Question 20

What are the two functions in inner ear?

Answer 20

• Fluid in the inner ear stimulate hair cells (nerve endings)
• Electrical impulses are sent from the hair cells along the auditory nerve to the brain

Question 21

What is the procedure of converting mechanical waves into electrical signals?

Answer 21

1. The mechanoreceptor induces influx of potassium ions (K+).
2. Causing depolarization of cell.
3. Further include influx of Calcium ions (Ca2+).
4. Causing movement of vesicle to the membrane and release the neural transmitters, that will transform to electrical signals.
5. The downstream processes are similar to neural synapse.

Question 22

What can vibrate along the liquid environment in the inner ear?

Answer 22

Cilia

Question 23

What can be detected by the brain if cilia can vibrate?

Answer 23

If cilia can vibrate, the small devices can be opened/ closed that cause change in the signals that can be detected by the brain.

Question 24

What is energy transduction?

Answer 24

To transform some form of energy to another form of energy (and that goes through 5 kinds of energy in hearing)

Question 25

Energy transduction procedure in hearing

Answer 25

1. Auditory signal perceived from the ear 2. Acoustic energy (air wave) 3. Mechanical energy (membrane vibration) 4. Hydraulic energy (fluid wave in perilymph) 5. Mechanical energy (cilia bending) 6. Electrochemical energy (neural activity) 7. Temporal lobe in the brian

Question 26

What are the five things in neural pathway in hearing?

Answer 26

1. Cochlear nucleus 2. Superior Olivary Complex 3. Inferior colliculus 4. Medial geniculate body 5. Primary auditory cortex

Question 27

What are the two types of cochlear nucleus?

Answer 27

Dorsal cochlear nuclei and Ventral cochlear nuclei

Question 28

What does cochlear nucleus receive?

Answer 28

Electrical signal will arrive at cochlear nucleus for collecting different processing information?

Question 29

What does dorsal cochlear nuclei do?

Answer 29

It makes sure the **sound can quickly arrive at the brain** to support/ find a **shortcut** to the brain

Question 30

What does ventral cochlear nuclei do?

Answer 30

IT arrives at superior olivary nucleus to quickly **analyse where** the sound comes from that is detected bad calculated by superior olivary complex

Question 31

What does superior olivary complex do?

Answer 31

- Binaural hearing: sound localisation, and intensity, timing - Stapedius reflex (via CNVII): to send neural back to control and protect your ear structure

Question 32

What does inferior colliculus do?

Answer 32

Startle reflex: immediately move/shake the body that can protect your body

Question 33

Does startle reflex pass through the brain?

Answer 33

Startle reflex does not pass through the brain as the reflex happens very fast

Question 34

Where is medial geniculate nucleus?

Answer 34

In thalamus

Question 35

What does primary auditory cortex receive?

Answer 35

Both sides receive **bilateral (binaural) information**

Question 36

What does the neurology of balance sense?

Answer 36

- sense of head and body **movements**: direction of movement and rotations, accelerations - sense of head and body **postures**

Question 37

How many semicircular canals are there i the peripheral vestibular system?

Answer 37

3 semicircular canals

Question 38

What is the three basic head and neck movements that can be decomposed?

Answer 38

1. Movement along the **sagittal plane** 2. Movement along the **coronal plane** 3. Movement along the **horizontal plane**

Question 39

What are the three sensors to detect the 3 kinds of movements?

Answer 39

The three semicircular canals

Question 40

What are the relationship between the three semicircular canals to each other (in terms of position)?

Answer 40

The three semicircular canals are **perpendicular to** each other.

Question 41

What do the three semicircular canals capture?

Answer 41

They capture the **3D movements** by linking **neural activity with movement directions**.

Question 42

What is the sense of direction based on?

Answer 42

The sense of direction is based on **combinatorial computations of different canals** while the activity strength of different canals are different

Question 43

What are the two different sensors to capture information related to movement?

Answer 43

Crista and Macula

Question 44

What is crista responsible for?

Answer 44

It **senses rotation** and detects the location

Question 45

What is the fluid movement in semicircular canal when you turn your head?

Answer 45

When you turn your head, the **fluid in semicircular movement** will turn to a direction that is **different** from the direction of **head rotation**.

Question 46

When will crista be excitatory?

Answer 46

When crista is pushed to the certain direction of **clockwise***, crista will be excitatory.

Question 47

When will crista be inhibitory?

Answer 47

When fluid rotates **anticlockwise**, crista will be pushed to the certain direction and becomes **inhibtory**.

Question 48

What is on the totuer layer of macula? What is its function?

Answer 48

Otoconia. Whenever we change the direction, the otoconia will move (being pulled back).

Question 49

What is the function of macula?

Answer 49

Macula senses body posture and acceleration.

Question 50

What in macula has the same mechanism as hair cells in the hearing system?

Answer 50

Stereocilia

Question 51

What are the four different nuclei divided to give our body a balanced state in vestibular node?

Answer 51

1. Superior Vestibular Nucleus 2. Lateral Vestibular Nucleus 3. Medial Vestibular Nucleus 4. Inferior Vestibular Nucleus

Question 52

What is the connection of superior vestibular nucleus?

Answer 52

Reciprocal connection with cerebellum

Question 53

What is the function of superior vestibular nucleus?

Answer 53

Coordination of body movement and send information to the cerebellum in terms of motor errors

Question 54

What is the output of lateral vestibular nucleus?

Answer 54

Output to lateral vestibulospinal tract

Question 55

What is the function of lateral vestibular nucleus?

Answer 55

Vestibulospinal reflex and sends information to the body

Question 56

What is the output of medial vestibular nucleus?

Answer 56

Output to medial vestibulospinal tracts

Question 57

What is the function of medial vestibular nucleus?

Answer 57

Vestibulocollic reflex and sends information **adjust information of head and neck**

Question 58

What is the function of output to cranial nerves for controlling eye movements?

Answer 58

Vestibulo-ocular nerves

Question 59

What information does vestibular nucleus with the output to the nucleus?

Answer 59

Sends **balance information** to **oculomotor nucleus**, **trochlear nucleus** and **abducens nucleus** so that you can quickly observe surrounding thing and put body back to the correct position that **controls eye movements**

Question 60

What does vestibulo-ocular reflex do?

Answer 60

It keeps us **staring at one place**?

Question 61

Is vestibulo-ocular reflex lasting for a long time or a short time?

Answer 61

Instantaneous that is not using the brain to control it

Question 62

What is the process of vestibulo-ocular reflex?

Answer 62

The fluid will **activate the left vestibular nuclei** that is connected to CN III and CN VI nucleus that controls the **medial and lateral muscles** repsectively to **pull down the eyes in a clockwise direction**.