Physiology

Question 1

What range of frequencies does the human ear perceive?

Answer 1

20Hz - 20,000Hz

Question 2

What is the Tympanic membrane:Oval window ratio and why is it this?

Answer 2

18: 1

- Impedance matching air to liquid

Question 3

What does the Tympanic membrane:Oval window ratio result in?

Answer 3

Pressure gain of ~22x

Question 4

What is the resting state of the cartilagenous part of the eustachian tube?

Answer 4

Closed

Question 5

What opens the cartilagenous part of the eustachian tube?

Answer 5

Tensor veli palatini

Levator palatine muscles

Question 6

What results in eustachian tube dysfunction?

Answer 6

Negative middle ear pressure

Question 7

What are the functions of the oval and round windows?

Answer 7

Permit pressure wave transmission in a closed canal

Vibrate basilar membrane

Question 8

What is the structure of the cochlea?

Answer 8

Scala media (endolymph) suspended between:

 - Scala tympani (perilymph)
 - Scala vestibuli (perilymph)

Question 9

What direction does perilymph flow through the cochlea?

Answer 9

From Scala tympani to Scala vestibuli

Question 10

What are the electrolyte compositions of the perilymph and endolymph?

Answer 10

Perilymph:
     - Sodium -> 150
     - Potassium -> 5
Endolymph:
     - Sodium -> 5
     - Potassium -> 150

Question 11

What is the function of stereocilia?

Answer 11

Convert mechanical ‘bending’ force to an electrical impulse

Question 12

How are stereocilia arranged and how are they connected?

Answer 12

Arranged in height order

Tip links connect them

Question 13

When do depolarisation and hyperpolarisation occur in terms of the sterocilia?

Answer 13

Depolarisation:
- When deflected towards longest
Hyperpolarisation:
- When deflected away from longest

Question 14

What are the central hearing pathways? (auditory cortex)

Answer 14

Superior temporal gyrus

Brodmann areas 41/42

Question 15

Where are the sterocilia contained in the otolith organs?

Answer 15

Macules

Question 16

Where do the stereocilia in the otolith organs project?

Answer 16

Into a gelatinous matrix with otoconia (calcium carbonate crystal)

Question 17

What do the stereocilia in the otolith organs do?

Answer 17

Lend weight
Due to gravity the brain perceives movement when:
- Tilting head
- Moving in an elevator
-> Both are linear movements

Question 18

How do we know when movement stops?

Answer 18

When stereocilia stop firing APs

Question 19

What sits in the ampullae of the semicircular canals?

Answer 19

Cupulae

Question 20

What deflects the structures within the semicircular canals?

Answer 20

Movement of perilymph -> Deflection of stereocilia

Question 21

What reflex do the semicircular canals assist with?

Answer 21

Vestibulo-ocular reflex:

 - Eyes move left when head turns right
 - Vice versa

Question 22

What do most poisons taste like?

Answer 22

Bitter

Question 23

What do off foods taste like?

Answer 23

Sour

Question 24

What is the lifespan of a taste receptor cell?

Answer 24

10 days

Question 25

Where are taste receptor cells replaced from?

Answer 25

Basal cells within taste bud

Question 26

What are the most numerous type of papillae on the tongue and do they contain taste buds?

Answer 26

Filiform | No

Question 27

What are the other three types of papillae (less common ones) and which ones contain taste buds?

Answer 27

Fungiform Vallate Foliate All of them

Question 28

Where are taste buds mainly present?

Answer 28

Tongue Palate Epiglottis Pharynx

Question 29

When a tastant binds to a receptor, what nerves carry the signals to the cortical gustatory areas?

Answer 29

CN VII (chorda tympani) if anterior 2/3 tongue CN IX if posterior 1/3 of tongue CN X if elsewhere (epiglottis and pharynx)

Question 30

What stimulates the following tastes: - Salty - Sour - Sweet - Bitter - Umami (meaty/savoury)

Answer 30

``` Salty: - Salts (Particularly NaCl) Sour: - Acids with free H+ Sweet: - Configuration of glucose Bitter: - Alkaloids - Poisons - Toxic plant derivatives Umami: - Amino acids (esp. Glutamate) ```

Question 31

What is ageusia and what can cause it?

Answer 31

Loss of taste: - Nerve damage - Local inflammation (Glossitis/Radiation/Tobacco) - Endocrine disorders

Question 32

What is hypogeusia and what can cause it?

Answer 32

Reduced taste: - Chemotherapy - Medications

Question 33

What is dysgeusia and what can cause it?

Answer 33

Taste distortion: - Glossitis - Gum infection - Tooth decay - Reflux - URTI - Medications - Neoplasms - Zinc deficiency

Question 34

What are the three cells types in the oflactory mucosa?

Answer 34

Olfactory receptor cells Supporting cells Basal cells

Question 35

What are olfactory receptor cells?

Answer 35

Specialised endings of renewable afferent neurons

Question 36

How are the olfactory receptor neurons composed?

Answer 36

Each has a: - Thick, short dendrite - Expanded end -> Olfactory rod

Question 37

What extends from the expanded end of an olfactory receptor neuron and how many extend from each? what binds to these structures?

Answer 37

Cilia to the mucosa: - 10-12 per neuron - Odorants bind

Question 38

What is the lifespan of olfactory receptors?

Answer 38

2 months

Question 39

What do the basal cells do in the olfactory mucosa?

Answer 39

Act as precursors for new receptors

Question 40

What do the axons of olfactory receptors collectively form?

Answer 40

Afferent fibres of CN 1

Question 41

What route does the olfactory nerve take?

Answer 41

Pierces the cribiform plate of the ethmoid: | -> Enters olfactory bulbs on inferior brain surface

Question 42

How do odorants reach the olfactory receptors during quiet breathing?

Answer 42

By diffusion

Question 43

To be smelled, a substance must be?

Answer 43

Sufficiently volatile Sufficiently water soluble: - To dissolve in mucous covering olfactory mucosa

Question 44

What is anosmia and what can cause it?

Answer 44

Inability to smell: - Viral infection - Allergy - Nasal polyps - Head injury

Question 45

What is hyposmia and what can cause it?

Answer 45

Reduced ability to smell: - Viral infection - Allergy - Nasal polyps - Head injury

Question 46

Hyposmia can be an early sign of what?

Answer 46

Parkinson's Disease

Question 47

What is dysosmia and how can it present?

Answer 47

Altered smell: - Interpreting odours differently - Hallucinations of smell