Physiology week 7 Flashcards
(88 cards)
1
Q
What is the tympanic membrane connected to
A
Malleus
2
Q
What does the stapes contact with
A
oval window of the cochlea
3
Q
Name the muscle that keeps the tympanic membrane tense for effective vibration transmission
A
Tensor tympani muscle
4
Q
What 2 structures in the ear act as a lever
A
-Malleus and incus act as a lever
5
Q
What is the function of a lever in the ossicular lever systmer
A
- Reduces movement amplitude but increases force
6
Q
What is the external ear composed of
A
pinna and external auditory meatus
7
Q
What is the function of the external ear
A
Directs sound waves into the auditory canal
8
Q
What is the external ear filled with
A
Air
9
Q
What does the middle ear incldue
A
Tympanic membrae and ossicles
-stapes footplate
-Round window
10
Q
What is is the middle ear filled with
A
air
11
Q
What is the inner ear made up of
A
Bony labrinth and membranous labyrinth
12
Q
Name the 3 fluid ducts the cochlea has
A
-Scala vestibuli + scala tympani
-Scala media
13
Q
What does the organ of corti contain
A
- Auditory receptor cells
14
Q
What fluid does the inner ear contain
A
fluid filled
15
Q
What does the scala vestibuli and tympani in the cochlea contain
A
- perilymph, like extracellular fluid
16
Q
What does the scala media contain
A
endolymph, like intracellular fluid
17
Q
In the cochlea what seperates the scala vestibuli from the scala media
A
Reissners membrane
18
Q
What sepertes the scala media from the scala tympani
A
Basilar membrane
19
Q
What else besides auditory cells does the organ of cort contain + function
A
It contains hair cells that detect sound vibrations and nerve impulses
20
Q
Explain how sound is conducted
-Where it enters
A
It enters the Scala vestibuli via the stapes at the oval window
- The faceplate of the stapes moves in and out, pushing fluid forward and backward in the scala vestibuli and the scala media
21
Q
Why does the Reissners membrane not block fluid movement between the scala vestibuli and scala media
A
Bcs it is thin and flexible
22
Q
WHat does the basilar membrane in the cochlea contain
A
Contains 20,000- 30,000 fibers anchored at the modiolus
23
Q
What do the fibers in the basilar membrane act like
A
Reeds of harmonica
24
Q
Where does fiber length increase from
A
Increases from the base (oval window) to the apex (helicotrema)
25
Fiber diamater and stifness decreases towarss what
Apex
26
Where do high frequencies vibrate near
The base (oval window)
27
Where do low frquencies vibrate near + why
The apex (helicotrema), as this is where the fibers are longer and more flexible
28
Explain how a sound wave is initiated
-The stapes pushes inward at the oval window, the round window bulges outward to compensate for fluid movement (due to rigid cochlear walls).
This causes the basilar membrane to bend, starting a traveling wave that moves toward the helicotrema
29
What does a wave move along
Basilar membrane
30
As the sound wave travels, what happens to it
It builds in amplitude unti it reaches the part of the membrane that matches its natural resonant frequency, then dissipates
31
Where do high frequency sounds peak and die
- Peak and die near the base
32
Where do mid frequency sounds peak
Midway along the membrane
33
Where do low frequency sounds travel before peaking
Travel to the apex
34
Where is the sound wave fastest and slowest + why
It is fastest at the base and slows doen toward the apex
Due to the stifness of the basilar fibers , as near the base it is high and lower towards the apex
35
When does membrane vibration occur
It occurs when the membrane resonates with sound
36
How can frequencies be dtsingusihes
- By the location of peak vibration on the basilar membrane
37
Where does the organ of corti lie -
On the surface of the basilar fibers and basilar membrane
38
Explain the nerve pathway of the organ of corti
Neurons from ganglion send axons into the cochlear nerve and then to the brain
39
Name the 2 types of receoptr cells that organ of corti contain + indicate which one is in abundance
-Inner hair cells
-Outer hair cells - a lot of this
40
Explain the structure of the hair cell + bases of the hair cells(sit) + the cilia of hair cells (embedded)
- Mechanoreceptors
-Bases of the hair cells sit on the basilar membrane
+ the cilia of thr hair cells are embedded in the tectorial membrane
41
Explain the first step, cilia bending and shearing force in nerve excitation
- What starts it
- As the organ of corti vibrates, the cilia of the ahir cells bend due to a shearing force as they puch against the tectorial membrane
42
In nerve excitation what does the bending of the cilia in one direction increase + what it causes
- The K+ conductance, causing the hair cell to depolarize
43
In nerve excitation what does the bending of the cilia in the opposite direction decrease + cause
K+ conductancek , leading to hyperpolarization of the hair cell
44
In nerve excitation, what does the depolarization and hyperpolarization of the hair cells generate
-oscillating receptor potential, called the cochlear microphonic potential
45
When the hair cells depolarize, what happens
- Voltage gated calcium channels open, causing ca ions to enter the hair cells and trigger the release of GLUTAMATE an excitatory neurotransmitter
46
What does the glutatmate cause inn nerve excitation
- Causes action potentials in the afferent cochlear nerves
47
What happens to glutamate when the hair cells hyperpolarize
The release of glutamte decreases, which leads to a reduction in action potential firing.
48
What do low frequency sounds activate
- Basilar membrane near the apex of cochlea
49
What do high frequency sounds activate
-Basilar membrane near the base od the cochlea
50
What do intermediate frequency sounds activate
- The membrane at intermediate location
51
What are low frequency sounds detected by
- volley principle
52
What is the volley principle
- A group of nerve fbers in synchrony with the sound frequency
53
What is the function of the cochlear nuclei in the brainstem/ what does it distunguish
It distingusihes the differnet frequencies base on the volley of nerve impulses
54
WHAT is the affect of cochlear damage
It does not fully eliminate the ability to distinguish the low frequencies
55
Name the three things that contribute to the determination of loudness
- Increased Amplitude:
-Spatial summation:
-Outer Hair cells
56
Explain the flow of auditroy signals in steps
1. Sound vibrations stimulate hair cells in organ of corti
2' Auiditry nerve fibers enetr dorsal and ventral cochlear nuclei and synapse
3.Second order neurons cross over to opposite side
4.They ascend in the later lemniscus
5..Then synapse in midbrain
5. Then go to MGN of thalamus
57
Name the types of deafness
-Nerve (sensorineural) eafness
-Conduction deafness
58
What is nerve deafness caused by
- Damage to the cochlea, auditory nerve, CNS auditory pathwayd
59
When is nerve deafness irreversible and permenant
If the cochle or nerve is destroyed
60
What is conduction deafness caused by
- Issues in structures that conduct sound to the cochlea such as :
-Tympanic membrane
-Ossicles
61
What does and audiometer emit
- Emits pure tones of different frequencies through an earphone
62
Name the 2 methods tested in an audiogram
- Air conduction
-Bone conduction
63
Explain the air conduction and bone conduction in relation to hearing loss in nerve deafness
Hearing loss occurs in both air and bonde conduction
64
Which is reduced in conduction deafness :
-Air conduction or bone conduction
Air conductin
65
Where is the olfactory epithelium found
Upper nasal cavity
66
Name the 3 cell types olfactory epitheloum consits of
- Supporting cells
-Basal cells
-Olfactory receptor cells
67
Explain the characteristics of the 3 cell types the olfactory epithelium contains
supporting cells : columnar , have micorvilli
Basal cells , Have stem cells at the base
Olfactory receptor cells- They are primary affernent neurons that detect odor
68
Explain olfactury transduction starting from the Odor molecules
Odor molecules bind to specific G protein–coupled receptors (GPCRs) on the cilia.
Binding activates Golf, a G-protein that stimulates adenylyl cyclase.
Adenylyl cyclase converts ATP → cAMP.
cAMP opens cation channels (for Na⁺, K⁺, Ca²⁺).
Depolarization:
Influx of cations causes membrane depolarization (receptor potential).
Action Potential:
If depolarization reaches threshold → APs travel along axons to the olfactory bulb.
69
Name 3 different olfactory disorders
- Anosmia
-Hyposmia
-Dysosmia
70
What is anosmia
Complete loss of smell
71
What is hyposmia
- Reduced smell sensitivity
72
What is dysosmia
Distorted smell preception
73
What causes the olfactory disorders
- Head trauma , infections, trauma
74
Where are taste receport cells found
- On the tounge, palate, pharynx, larynx
75
Name the 3 cell types taset buds contain
- supporting cells
-Basal cells
-Taste receptor cells
76
Name the 5 tastes
sweet, salty, sour,bitter, umami
77
Name the 3 types of papillae
- circumvallate
-Foliate
-Fungiform
78
Name the tastes that the tip of the tounge detects
- sweet, salty , umami
79
Name the tastes that the sides of the tounge detect
- sour
80
Name the taste that the back of the toung detects
- Bitter
81
What is Ageusia
Loss of taste
82
What is hypogeusia
Reduced tase
83
What is hypergeusia
increased taste
84
What is dysfeusia
Distorted taste
85
For bitter taste what receptor is used + explain the process
- G protein couple receptro is used
Tastant binds GPCR → activates G protein
Triggers IP₃ (inositol triphosphate) production.
IP₃ causes Ca²⁺ release from internal stores.
TRP (transient receptor potential) channels open → membrane depolarization.
86
What receptor is used for sweet taste + umamii explain mechanisms
- Both use a differnet type of GPCRs- PATHWAY SAMe as bitter
- Tastant binds GPCR → activates G protein (gustducin).
Triggers IP₃ (inositol triphosphate) production.
IP₃ causes Ca²⁺ release from internal stores.
TRP (transient receptor potential) channels open → membrane depolarization.
87
What is sour taste mediate by + explain pathway
- mediated by H+ ions
- Pathway:
H+ enters epithelical Na channels (ENaCs) , then causes the cell to depolarise
88
What is salty taste mediated by + pathway
Na ions
- H+ enters through eENaCs, and depolarises membrane
