Block 1- Ear

Question 1

What type of sensation is hearing?

Answer 1

Mechanical sensation

Question 2

What actually is a sound?

Answer 2

-Sound is our perception of air molecules banging off each other
-Sound waves are changes in air pressure caused by vibrating air molecules. The energy of sound waves decrease with the distance from the source

-However no sound is perceived unless someone is there to covert the sound waves into electrical signals

Question 3

What type of waves are sound waves?

Answer 3

Longitudinal

Question 4

What are the two basic features of sound waves?

Answer 4

Frequency (pitch) and amplitude (loudness)

Question 5

Describe what frequency is. what does this look like? What unit are they measure in?

Answer 5

• Air molecules -The rate at which air molecules vibrate is frequency. Slow vibrations generate low frequency sound waves and are perceived as having low pitch. High frequency sound waves are caused by fast vibrations and have a high pitch
• Measured in- Frequency is the number of sound waves per unit time (second), measured in Hz
• Uses the number of peaks

Question 6

Describe what amplitude is. what does this look like? What unit are they measure in?

Answer 6

• This refers to the number of air molecules vibrating in a sound wave. An increased number of vibrating air molecules, increases the amount of energy in a sound wave, which makes them seem louder. So the more air molecules there are, the more sound there is-
• measured in decibels
• This is the size of the wave

Question 7

What is the doppler effect?

Answer 7

— Doppler effect ( eg emergency vehicles, as they come towards you, the sound seems to go up in pitch as sound is catching ups on own sound waves, and as it leaves you the sound comes down in pitch, as it is going further away from its sounds waves

Question 8

Why is sound complex?

Answer 8

-Sounds are rarely very simple, ie we have a mixture of frequencies, mixture of amplitudes - so they aren’t pure tones — the particular mixture of these things, determines the sounds complexity

Question 9

How many parts can we split the ear anatomy into - what are they ?

Answer 9

1. Outer ear
2. Middle ear
3. Inner ear

Question 10

Describe the outer ear

Answer 10

• The pinna collects and amplifies sound waves.
• Sound waves that occur around 3000hz ( human speech) are selectively amplified
• So sound waves travel down the external ear cana- and hit the ear drum

Question 11

What are the 2 components of the inner ear?

Answer 11

-Tympanic membrane (ear drum)
-Ossicles

Question 12

What are the 3 ossicles names and their nicknames
( remember mnemonic)

Answer 12

-These are the smallest bones in the body

• The Malleus (Hammer)
• The Incus ( Anvil)
• The Stapes ( Stirrup)

MIS

Question 13

What is the structure called that connects the ossicles to the cochlear?

Answer 13

Oval window

Question 14

So how does the sound get from outer ear - inner ear?

Answer 14

When these air molecules are vibrating on the tympanic membrane, they then vibrate the ossicles
These ossicles then vibrate onto the cochlear

Question 15

What happens when things go wrong with the middle ear?

Answer 15

Glue ear - (usually happens to children)

This is where the middle ear fills up with fluid, lymphatic fluid, so yo hear as if your head is under water, so the bones are trying to vibrate off each other in water — which could cause a problem for kids in their speech development

Question 16

What are the two structures that make up the inner ear?

Answer 16

-Semi-circular canals
-Cochlear

Question 17

Describe the purpose of the semi-circular canals?

Answer 17

These are really important in our balance and our vestibular system ( Knowing where we are in space)

Question 18

What is the overall purpose of the cochlear?

Answer 18

Inside the cochlea is where you get the conversion of those mechanical vibrations - into those electrical signals, so inside. your cochlea is actually where the transduction happens

Question 19

What does the cochlear look like/ what is it made up of?

Answer 19

• The cochlea itself is quire a boney structure, but inside it is fluid filled ( endolymph)
• The cochlea is all wound up inside ( like a fruit winder)
• Cochlea is protected by the petrous bone ( strongest and densest bone in the body)

Question 20

Describe an uncoiled cochlear

Answer 20

• Cochlea is the place that contains the auditory receptors neurones ( these are found next to the basilar membrane ) -which is what converts the sound into electrical signals
• If you were to unwind the cochlea, you would find endolymph ( fluid ), but you would also find a membrane running all along the cochlea. This is known as the basilar membrane.

Question 21

So how does the cochlear determine what frequency the sound is?

Answer 21

The interesting thing about the basilar membrane, is that it responds selectively, depending on the frequency of the sound. So different parts of the basliar membrane vibrate at different frequencies of sound
- eg - if you have high frequencies, the part of the basilar membrane that responds to that is at the base (narrow and thick) -top bit
- The area of the basilar membrane that responds to Low frequencies - is towards the end of the basilar membrane- so wide/ thin apex

Question 22

As receptor neurons on the basilar membrane respond to different frequencies of sound0 what is this called?

Answer 22

Tonotonic map

Question 23

Describe a cross-section of the cochlear?

Answer 23

• This is a cross-section on the tube of the cochlea
• Contains 3 main chambers seperated by membrane

-So you have your basliar membrane and above this you have your tectorial membrane

-Embedded in your basliar membrane, you have two different types of hair cells.- inner hair cells and outer hair cells

-The outer hair cells are connected to the tectorial membrane (through the little filaments called cilia), but the inner hair cells are not

Question 24

How are sound waves - converted to electrical signals

Answer 24

Inner hair cells-

-The hair cells that are attached to the basilar membrane vibrate if the appropriate frequency is heard

-The vibrations of these hairs result in the physical opening and closing of ion Chanel- this is because the vibrations the hair cell closer to the tectorial membrane

-This goes from cochlear nerve - Brain

Question 25

What do the outer hair cells do?

Answer 25

-What the outer hair cell do, is attune you to certain frequencies ( very basis to Cherrys cocktail party effect)- as the outer hair cells contract and relax on instruction from the brainstem — changing the stiffness of the tectorial membrane -So what allows Cherrys cocktail party effect is that - is the outer hair cells, bringing the tectorial membrane closer, attuning you to the frequency you are trying to hear- so makes you more sensitive to hearing that frequency The fact that the tectorial membrane is closer, makes it more likely that your inner hair cells will be brushing off the tectorial membrane

Question 26

What happens when thing go wrong within the basilar membrane?

Answer 26

Hearing loss can come from damage to these hairs - usually due to repeated exposure to lound sounds

Question 27

So what is a simple overview of this entire process of the mechanical sensation- electrical signal?

Answer 27

-Sound waves comes in through our external ear canal -This bangs off our tympanic membrane -That moves our osiclles against each other, Hammer, anvil , stirrup, -This moves the stapes (strirrup ) against the oval window -This displaces the endolymph inside the cochlea -That then displaces the basliar membrane ( depending on the frequency of the sound wave) - displaces at a particular place, that then causes the inner hair cells to brush against the tectorial membrane -Hence, depolarisation/ activation -This is then transmitted to the cochlear nerve —> brain = sensory transduction pathway

Question 28

What is the process of these electrical signals getting to the brain?

Answer 28

- Receptor neurons (hair cells) in the cochlear send their axons to regions of the brainstem. ( we get mixing of sensory information of the two ears) - These signals are then relayed to the midbrain (inferior conicullus), thalamus (medial geniculate nucleus) and then cerebral cortex ( temporal lobe/auditory cortex)

Question 29

What is the audible spectrum for humans?

Answer 29

20-20,000 Hz

Question 30

How do we detect where a sound is coming from?

Answer 30

This comes from the integration of information between the left and right ear - So things that originate to the left of the body, will reach the left ear first, before it reaches the right ear, so our brain does have to do a certain amount of processing to work out where a single sound is coming from - So works out where sound is coming from based on how long it takes for the sound to get from our right ear to our left - This all happens at the brainstem and the midbrain - But the differences are not interpreted as two different sounds, but are perceived as a single sound, coming from one specific location This all happens at the brainstem and the midbrain

Question 31

How do we determine what a sound is within the brain?

Answer 31

The brain can determine the pitch of the sound based on the location of the hair cell Louder sounds move the hair cells more, leading to bigger graded potentials, which generate more frequent action potentials- so amplitude or loudness is denoted by the frequency of action potienals **Tonotopic map** -So we had the tonotopic map in the basilar membrane - and that is faithfully transmitted up to the level of the brain -Neurons in the primary auditory cortex respond to different frequencies of sound - maps directly onto those neurons that come from the Basiliar membrane -The primary auditory cortex is deep behind the lateral sulcus -We’ve got specialisations along the primary auditory cortex for different frequencies ( a bit like we did with the somatosensory cortex)

Question 32

Where is there a localisation of language?

Answer 32

Left hemisphere

Question 33

What is werncikes area? What is is responsible for? Where is it located?

Answer 33

- One of the main areas for language would be Wernickes - This is important in speech comprehension - contains sound images of words - Located with the temporal lobe If you are listening to speech first processed in primary auditory cortex - then Wernickes area

Question 34

What is Brocas area? What is is responsible for? Where is it located?

Answer 34

-For speech production - Brocas area is really important -This is located within the frontal cortex -This is where you have your motor programs to talk So Brocas area is a **premotor area,** this then transmitted to face and lips area, Larnyx areas that control the contractions and that goes from the primary motor cortex

Question 35

Is there a connection between Broca and Wernickes area?

Answer 35

You'd think you have a tract of nerves that go straight from Wernickes area to Brocas area- but you don't Instead you have a tract of nerve fibres called the **arcuate fasciculus** — which goes behind the lateral sulcus and up to Brocas area and its **bi-directional**

Question 36

What is Brocas aphasia?

Answer 36

Brocas aphasia - The inability to speak fluently despite the presence of normal comprehension and intact vocal mechanisms

Question 37

What is Wernickes aphasia?

Answer 37

Wernickes aphasia - Inability to understand or produce meaningful language even through the production of words is intact

Question 38

How can stuttering develop?

Answer 38

So most people are lateralised to the left hemisphere eg language and speech production -Langauge initially develops in both hemispheres, but in 95% of people by the time they are 5, this shifts to the left hemisphere and the abonded speech areas in the right hemisphere are taken over by other things ( eg music) -A disturbance to this lateralisation may underlie the problems faced by people with stutters eg both hempishres are fighting for dominance with who is going to speak first

Question 39

What does right hemisphere do?

Answer 39

-The right hemisphere does music and emotionality -Makes contribution in the emotional content of language - prosody, that are needed to generate the full richness of everyday speech -Also important in processing music