Hair Cells in Auditory and Vestibular Systems

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Questions and Answers

What type of receptors are found in hair cells that respond to mechanical force?

Mechanosensitive receptors.

How does the movement of the head affect the hair cells in the vestibular system?

Head movement causes the otoconia to move, which transfers motion to the otolithic membrane, deflecting the hair cells.

What is the function of the otolithic membrane?

The otolithic membrane mediates the deflection of hair cells in response to head movements.

What effect does depolarization have on hair cells?

Depolarization opens voltage-gated Ca2+ channels, leading to neurotransmitter release. Signup and view all the answers

Explain the role of the tip link in hair cell function.

The tip link connects stereocilia and, when activated by bending, causes ion channels to open. Signup and view all the answers

What fluid composition differences exist between endolymph and perilymph?

Endolymph has high K+ and low Na+ concentrations, while perilymph has high Na+ and low K+ concentrations. Signup and view all the answers

In what way do the hair cells in the vestibular system and auditory system differ?

While they share the same underlying mechanisms, the stimuli that activate them differ in each system. Signup and view all the answers

What role does fluid movement play in the auditory system?

Fluid movement causes the basilar membrane to move, bending hair cells against the tectorial membrane. Signup and view all the answers

How do ion concentrations in endolymph and perilymph affect hair cell functioning?

The high K+ concentration in endolymph is crucial for depolarizing hair cells, while the low Na+ and K+ concentrations in perilymph help maintain the electrochemical balance necessary for signal transmission. Signup and view all the answers

What mechanisms underlie hair cell functioning in the auditory system?

Hair cells in the auditory system convert mechanical vibrations from sound waves into electrical signals through hair bundle deflection, leading to neurotransmitter release. Signup and view all the answers

What are the primary differences in function between outer and inner hair cells?

Inner hair cells primarily transduce sound into neural signals, while outer hair cells amplify sound vibrations through their motility. Signup and view all the answers

Describe the role of the inner hair cells in the auditory pathway.

Inner hair cells are responsible for converting sound-induced mechanical movements into electrical signals that are transmitted along the auditory nerve. Signup and view all the answers

What happens to endolymph motion during rapid head movement?

During rapid head movement, the endolymph in the semicircular canals lags behind the movement of the head, causing a delay in fluid motion. Signup and view all the answers

How does the movement of the ear drum affect the cochlea in the auditory system?

The ear drum's vibrations create mechanical waves in the cochlea, which displace the fluid and stimulate the hair cells. Signup and view all the answers

Explain the significance of the high K+ concentration found in endolymph.

High K+ concentration in endolymph is critical for depolarizing hair cells and initiating synaptic transmission by causing the release of neurotransmitters. Signup and view all the answers

Why is the lag of endolymph important for balance detection in the vestibular system?

The lag allows the vestibular system to detect head acceleration and deceleration accurately, contributing to the sense of balance. Signup and view all the answers

Study Notes

Hair Cells

Hair cells are crucial for hearing and balance.
Ion concentrations significantly affect hair cell function.
Mechanisms underlying hair cell function are similar in the auditory and vestibular systems.
Outer and inner hair cells have distinct functions.
The inner and outer hair cells play a vital role in the auditory and vestibular systems.

Big Picture

Outer ear pressure changes initiate mechanical movement.
Middle ear mechanically transmits sound to inner ear.
Inner ear fluid movement influences hair cells.
Hair cells generate neural signals.
Neural signals ascend through the auditory pathway and descend through the auditory pathway.

Hair Cells - Vestibular and Auditory Systems

Vestibular system is responsible for balance.
Movement of the head displaces fluid in semicircular canals.
Auditory system is responsible for hearing.
Ear drum movements cause fluid to move within cochlea.
Both systems rely on hair cells to sense movement and initiate sensory transduction.

Physics of Semicircular Canals

Acceleration relative to the surroundings will initially push your body in the opposite direction.
As acceleration continues the relative motion between the body and its surrounds diminishes, reducing the force acting upon it.
The motion from acceleration will cease as the surrounds stop stimulating the body. This stimulation will lag the stopping acceleration, and the body will move further, in the same direction of the final acceleration.
Semicircular canals are filled with a fluid called endolymph.
Head movement causes the canals to move, but endolymph lags.
Endolymph continues to move briefly after head stops.

Endolymph & Perilymph

Endolymph has high potassium (K+) and low sodium (Na+) concentration.
Perilymph, on the other hand, has high sodium (Na+) and low potassium (K+) concentration.
Hair cell stereocilia are surrounded by endolymph.
Hair cell bodies are surrounded by perilymph.

Hair Cells in Vestibular System

Hair cells are found within the utricle and saccule, structures connected to semicircular canals.
These hair cells contain a mechanosensitive receptor mechanism.

Gated Receptors

Ligand-gated receptors open when a ligand binds to them.
Voltage-gated receptors open in response to depolarization.
Mechanosensitive receptors open when exposed to mechanical forces.
Hair cells in the ear, skin, and muscles have mechanosensitive receptors.

Hair Cells - Otolthic Membrane

A gelatinous sheet called the otolithic membrane is attached to the tops of the hair cells.
Otoconia (ear stones) are situated within and on the otolithic membrane.

Hair Cells Transduction

When the head moves, it causes the canals, otoconia, and otolithic membrane to move.
This movement deflects the hair cells.
Deflection of the tip link opens channels, allowing potassium (K+) to enter the cell.
This depolarization opens voltage-gated calcium (Ca2+) channels.
Ca2+ influx triggers the release of neurotransmitters.
K+ flows out of the cell via different channels.

Hair Cells in Vestibular System - Deflection

Deflecting the hair cells opens channels due to the interaction of the tip link.

Vestibular and Auditory Systems

Hair cells in both systems share similar underlying mechanisms.
Stimuli leading to hair cell response differ between the two systems.

Stimulating Hair Cells in Cochlea

Fluid movement within the cochlea moves the basilar membrane.
Hair cells attached to the basilar membrane bend against the tectorial membrane.
Movement of hair cells results in transduction.

Transduction

Deflecting hair cells opens channels due to the interaction of the tip link.

Flow of K+

Influx of potassium (K+) into hair cells depolarizes the cell.
Depolarization opens voltage-gated calcium (Ca2+) channels, and Ca2+ influx triggers neurotransmitter release.
Potassium (K+) flows out of the cell.

Reticular Lamina

The reticular lamina separates the endolymph from the perilymph.
It's formed by tight junctions between hair cells and supporting cells.

Outer Hair Cells

Outer hair cells respond to basilar membrane movement using similar mechanisms as inner hair cells.
Depolarizing outer hair cells changes their shape (elongation or contraction).
This mechanical energy alters the basilar membrane's responsiveness.

Outer Hair Cells - Active Mechanism

Outer hair cells amplify sound by changing shape in response to voltage changes.
This amplification is referred to as the active mechanism of the cochlea.
The active mechanism also increases frequency selectivity.

Behind the Science

Notable researchers like Joseph Santos-Sacchi have contributed to studies on hair cell mobility.

Additional Information

Hair cell movement can be visualized using videos.

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Description

Explore the essential role of hair cells in both hearing and balance. This quiz covers the mechanisms of hair cell function, their distinct types, and how they contribute to the auditory and vestibular systems. Test your understanding of how sound and head movement affect these vital cells.