6: Physiology - Sensory transduction: auditory and vestibular system Flashcards
Which cells, found in the inner ear, convert sound energy (moving them) into action potentials?
Hair cells (stereocilia)
Hair cells are connected to ___ ___ neurons.
special sensory
What excites stereocilia?
Movement by sound energy
Which channels are found at the tips of stereocilia?
What enters when they are open?
Tip links
K+ (which ENTERS unusually and depolarises the membrane)
When stereocilia are excited by movement and the opening of tip link channels, the sensory neurons connected to them are EXCITED.
Which neurotransmitter is released to cause an excitatory action potential?
Glutamate
Hair cells are found throughout the labyrinth of the inner ear, which is responsible for hearing and balance.
The function of hair cells changes based on their ___ in the labyrinth.
position
What properties of a sound wave match to
a) pitch
b) volume?
a) Frequency
b) Amplitude
Why do vibrations received by the tympanic membrane need to be amplified before they pass into the cochlea?
It takes more energy to vibrate fluid compared to air
Which bones are mostly responsible for amplifying the vibrations received by the tympanic membrane?
Ossicles
Which chamber in the Organ of Corti contains the hair cells?
Scala media
Which membrane do hair cells sit on in the Organ of Corti?
Basilar membrane
What properties of the basilar membrane allow to discriminate between sounds of different pitches?
Oval window end (the base) is wide and flexible
Apex is narrow and stiff
So different energy levels i.e pitches of sound are required to move the hair cells depending on what end you’re at
Which membranes are found
a) superior to
b) inferior to
hair cells in the Organ of Corti?
a) Tectorial / Reissner’s membrane
b) Basilar membrane
The basilar membrane changes the ___ of hair cells by bending in response to sound energy.
The tectorial membrane actively ___ hair cells by vibrating.
basilar membrane changes hair cell position
tectorial membrane moves hair cells by vibrating
The potassium concentration of the fluid surrounding hair cells (?endolymph) is (high / low).
high K+ concentration
In which direction does potassium move when the tip links of hair cells are open?
Why?
Inwards
K+ concentration in endolymph is high
Which fluid is found in the scala media?
Endolymph
Which fluid is found in the scala vestibuli and scala tympani?
Perilymph
What happens to the potassium which enters hair cells through tip links?
After action potential K+ is recycled back into scala media to keep conc. gradient the same
How are hair cells arranged in the Organ of Corti?
Outer layer
Inner layer
Which layer of hair cells is concerned primarily with sensory input?
Inner layer
Which nerve carries the sensory neurons from the inner hair cells?
Cochlear part of CN VIII
Each inner hair cell is supplied by (a single / many) sensory neuron(s).
each inner hair cell has its own sensory neuron
What is the primary function of outer hair cells?
Movement of the tectorial membrane to enhance vibration
How many outer hair cells are connected to each somatic efferent fibre?
Many
Where do sensory neurons synapse between the inner hair cells and CN VIII?
Spiral ganglion
superior olivary ganglion somatic efferents outer hair cells
sensory coding of pitch depends on firing rate of hair cells AND where they are on the basilar strip
On which side of the brain are auditory signals processed?
Both
processing is bilateral
Briefly describe how auditory stimuli reach the primary auditory cortex from the inner ear.
CN VIII fibres > Spiral ganglion > Cochlear nucleus > Superior olivary nucleus > Inferior colliculus > Medial geniculate nucleus > Primary auditory cortex
sorry
Briefly describe how visual stimuli reach the visual cortex from the eyes.
CN II fibres > Lateral geniculate nucleus > Superior colliculus > Visual cortex
What information does the sensory pathway use to localise the position of sound?
1. When it is heard
2. Volume
both different for each ear
What sense is the vestibular system broadly concerned with?
Balance
Which parts of the vestibular system detect
a) head rotation
b) linear acceleration (e.g side to side, front to back, head tilt on one plane)?
a) Semicircular canals
b) Otolith organs (saccule and urticle)
How are hair cells involved in the vestibular system?
Different movements cause movements in fluid and otolith which move the hair cells
What movements are detected by the semicircular canals?
Rotation
Which fluid is found in the semicircular canals?
Perilymph
In the semicircular canals, (perilymph / endolymph) exerts force on hair cells during ___ movement.
perilymph
rotational movement
Which type of sensory signal is generated by the hair cells on the
a) ipsilateral side
b) contralateral side
of a head movement?
a) Excitatory
b) Inhibitory
b acts as a confirmation to the brain that the movement is occurring
Which cranial nerve receives the sensory impuses from the vestibular organs?
Vestibular part of CN VIII
Which part of the vestibular system detects acceleration on one plane and gravity?
Otolith organs
What are the two otolith organs?
Saccule
Urticle
Which otolith organ is responsible for detecting linear movement
a) vertically
b) horizontally?
a) Saccule
b) Utricle
u for up and then the opposite of that kill me
Which substance exerts on a force on the hair cells in the otolith organs during linear movements?
Otolith
calcium carbonate crystals
Which reflex keeps the eyes focused during head movement?
Vestibulo-ocular reflex
