Chapter 41: Hearing apparatus

Question 1

What is sound?

Answer 1

• Sound is defined as a wave of vibration of air molecules
o We are hearing the waves, as the brain receives the action potential
o The waves are converted into electrical activities

Question 2

What are sensory cells?

Answer 2

o Cells that transduce (convert) physical or chemical signals into action potentials
o Look like cells, but function like neurons because they exhibit electrical activity (excitatory cells)
o Also called receptor cells or modified neurons

Question 3

Name the seven kinds of receptors

Answer 3

Photoreceptors
Mechanoreceptors
Cehmoreceptors
Thermoreceptors
Nociceptors
Electroreceptors
Magneto-receptors

Question 4

What are photoreceptors?

Answer 4

Cells of the eye
 Receive light information
 Possess pigments to absorb light

Question 5

What are mechanoreceptors?

Answer 5

Cells of our ears

 Need to move the cell to get electrical activity

Question 6

What are chemoreceptors?

Answer 6

Sense chemicals

Question 7

What are thermoreceptors?

Answer 7

Measure temperature.

Found inside and outside the cell.

Question 8

What are nociceptors?

Answer 8

Pain receptors

Question 9

What are Electroreceptors?

Answer 9

Sense the electrical field

Question 10

Magnetoreceptors

Answer 10

Sense the magnetic field

Question 11

How are mechanoreceptors used to interpret sound?

Answer 11

o Mechanoreceptors must move in order to be interpreted into electrical activities
 Brian interprets sound/voice based on how intense the vibration (wave) is
• Amplitude: loudness/volume
• Frequency: pitch

Question 12

What makes up the outer ear?

Answer 12

Pinna/Oracle

Auditory Canal

Question 13

What does the pinna/oracle do?

Answer 13

• Amplifies the signal
• Functions like a funnel
• Directs the sound/vibration to the auditory canal

Question 14

What is the auditory canal?

Answer 14

• Where the sounds/vibration goes

Question 15

What membrane separates the outer and the middle ear?

Answer 15

the tympanic membrane

Question 16

What is the tympanic membrane?

Answer 16

 Moves due to the sound/vibration
• Support by the ossicles
 Separates the outer and the inner ear

Question 17

What makes up the middle ear?

Answer 17

The ossicles

Question 18

What are the three ossicles?

Answer 18

• Malleus: connected to tympanic membrane
• Incus: in between malleus and stapes
• Stapes: connected to the cochlea (inner ear)
o Connected to oval window
o Makes the perilymph move

Question 19

What is the difference between the outer, middle, and the inner ear?

Answer 19

The outer and the middle ear are air filled membranes, while the inner ear is a fluid filled chamber?

Question 20

What is significant about the inner ear?

Answer 20

It is where the vibration of the inner ear gets converted to electrical activity

Question 21

What makes up the inner ear?

Answer 21

• Scala Vestibuli
• Scala Typani
• Cochlear duct (organs of corti: Hair cells, Tectorial membrane, basilar membrane)

Question 22

What fluid is located in the Scala Vesibuli?

Answer 22

Perilymph (High in Na+)

Question 23

What fluid is located in the Scala Tympani?

Answer 23

Perilymph (High in Na+)

Question 24

What fluid is located in the Cochlear duct?

Answer 24

Endolymph (high in K+)

Question 25

What occurs in the organs of corti?

Answer 25

Hearing

Question 26

What are hair cells?

Answer 26

mechanoreceptors
 Have cilia on top
 Form synapses between hair cells and the neuron
 Movement causes electrical activities

Question 27

What is the basilar membrane?

Answer 27

 What the hair cells sit on, facilitate vibrations

 The hearing apparatus

Question 28

How is sound transmitted?

Answer 28

o Vibration of air molecules goes through the pinna, passing through the external auditory canal
o The waves then vibrate the tympanic membrane which causes the three ossicles to move
o The ossicles cause the oval window to vibrate
o This leads to the stimulation of hair cells inside the cochlea

Question 29

Hair cell activity (PROCESS/STEPS)

Answer 29

o Located in the Cochlear duct. Sits on top of the basilar membrane and is covered by the tectorial membrane
o Contains cilia
 Kinocilium: one long cilia
 Stereocilium: many different cilia
• Vibration leads to electrical activity
o Forms synaptical relationships with neurons
 Releases neurotransmitters
o Do not have action potential, instead they have graded potential
 Are happening in receptor cells, so they are called receptor potentials
• Small way of depolarization (change of potential) in hair cells
 Causes calcium gated channels to open, which causes calcium influx in the cell, which causes vesicle movement and vesicle release of neurotransmitters
o Stretch gated ion channel are stimulated when the membrane is moving (being stretched) LOCATED ON THE STEREOCILIA
 Caused by the vibration of the cell
• Cilia bend and the channels open
• Movements towards the kinocilium
 Hair cells depolarized (hyperpolarized at rest):
• The endolymph has the positive charge (K+) which causes depolarization
• Depolarization then signal to the brain
o Movement of the stereocilia towards the kinocilium activates the stretch activated channels
o VGCC are activated and cause an influx of calcium which causes the release of glutamate, which activates afferent neurons
• Movement of the stereocilia away from the kinocilium closes the stetch activated channels

Question 30

What is the neural pathway of hearing?

Answer 30

o The cochlear nerve fiber synapse on neurons in the cochlear nuclei in the medulla oblongata
o The signal is then sent to the medial geniculate nucleus in the thalamus
 Then the information travels to the auditory cortex of the temporal lobe