Auditory & The Vestibular System Flashcards
What are hair cells?
Motion detecting mechanoreceptors
What are hair cells used to detect?
- Movement of surrounding water
- Self movement in water
- Sound waves of different frequencies
- Lateral movement of the head
- Rotational movement of the head
- Direction of gravity
Describe a hair cell in general
- A small nerve cell
- Doesn’t have an axon
- Sits embedded within the tissue with its apical membrane
- Has a bundle of stereocilia sticking out of the tissue
What are the stereocilia bundles sticking out?
Thin processes that are rigid since they have actin cytoskeleton
How does the cell correspond to not having an axon?
- It makes vast glutamatergic sinuses with the dendrites of afferents
- These afferents carry the signal to the brain
How is the glutamate then released?
- Released by depolarisation
- As it happens, these cells have quite a depolarised membrane potential
- Around -40 Mv
How does the hair cell signal?
- Signals the movement of fluid within the Stereocilia compartment
- Does so by the help of tip links
- Tips of each stereocilia is linked to the side of the wall of the next tool
- The base of the stereocilia tip linked have mechanically gated channels
When do the mechanically gated channels open? (PART 1)
- Open when the tip links are put under tension
- Happens if the tip links move the fluids in the taller tip direction then it pulls on the tip link becomes stretched
- Pulls open those channels and causes the cell to depolarise
When do the mechanically gated channels open? (PART 2)
- This then causes the release of more glutamate
- Which then causes the dendrites of the afferents to start generating action potential
What happens if the Tip links go in the other direction?
- The Tip links begin to slack
- This closes the channels that are open at rest
- Causing the cell to become even more negative inside and causing less glutamate to be released
- The afferent then has a pause in its firing
What is the gelatinous structure?
- Transfers force to the stereocilia
- Ensures that movement of fluid in the stereocilia compartment will maximally effect and appropriately affect the sterile cilia
What is the bony labyrinth?
- The primary chamber that has been chiselled out of the bone
- It’s filled with perineum which is an extracellular fluid
- High in sodium, Low in potassium
- Within that, there are inner chambers which separate from the pyramids containing parts by membrane (Membrane labyrinth)
What does the membrane labyrinth form?
- Forms a continuous space running through all these parts of the structure
- Filled with Indolence which is high in Potassium and low in sodium
- Also carries an excess of positive charge creating a potential difference between the endolymph and the rest of the nody
What is the Cochlea?
- The auditory part of the system
- Has like a snake shell in structure
- Has a coil which contains an inner membrane out compartment known as the cochlear duct
What happens in the membranous compartment?
- Movement of fluid within the membrane compartment tilts the stereocilia of the hair cells in the cochlea
- This causes them to depolarise and hyper polarise
Where does the receptors lie in the cochlea?
Receptor cells lie in a long row that stretches all the way from the base to the apex of the spiral
Describe the vestibule apparatus
- Has 3 semicircular canals which sit at right angles to one another
- Has 2 components to it, a balloon like utrickle and a smaller saccule
What is found within the semicircular canals?
- Has Semicircular ducts which connect to the Utricle
- The base of each of the semicircular ducts has an ampullae
How many receptors are there within the vestibular?
Five
Where are these receptors located?
- Utricle
- Saccule
- Ampullae
- Ampullae
- Ampullae
What do the ampullae of the semilunar ducts pick up?
Pick up rotational movements of the head
What is the other vitally important function of the semicircular ducts?
Vitally important in the control of eye movements
