Week 44- Balance and Hearing Flashcards
1
Q
What is sound?
A
Air molecules compressed with forward movement and becoming less dense when the object moves back
2
Q
What is Hertz?
A
Cycles per second:
Distance between successive regions of compressed air molecules (peaks in the wave)
3
Q
What frequencies of sound can be heard in humans?
A
20-20000Hz
4
Q
What determines the loudness/softness of a sound?
A
Pressure wave –> more pressure means loud (higher amplitude)
5
Q
What is the entire role of the hearing apparatus?
A
Converts sound –> vibrations –> neural signals
6
Q
What structure of the ear collects sound pressure waves?
A
The pinna of the ear –> directed along auditory canal to the tympanic membrane
7
Q
What is the role of the tympanic membrane?
A
Vibrates in response to the sound pressure wave
Separates the outer ear from the middle ear
8
Q
What is both the outer and middle ear filled with?
A
Air filled
9
Q
What is the role of the ossicles?
A
They are small bones that transfer the vibrations of the tympanic membrane to the oval window (and amplify them)
10
Q
Where is the oval window located?
A
Base of the cochlea of the inner ear –> vibrations are converted to neural signals here
11
Q
What is the general path for sound detection?
A
Waves of air pressure –> moves tympanic membrane back and forth
Tympanic membrane –> vibrates ossicles
Ossicles amplify the force greatly –> transfer the oval window
Movement in the oval window moves fluid in the cochlea
Fluid movement in cochlea converted to neural signals
Neural signals go to the brainstem then onwards to the auditory cortex
12
Q
What is the ossicle which contacts the oval window?
A
Stapes
13
Q
What does the cochlea wrap around?
A
Central pyramid –> containing nerve cell bodies of the spiral ganglion
14
Q
How many spiral ganglion cells is there in humans?
A
35,000-50,000
15
Q
What does a cross section of a cochlea look like?
A
3 chambers separated by tissue membranes
16
Q
Where do the sensory detector cells sit within the cochlear?
A
Basilar membrane
17
Q
What area of the cochlea is on the other side of the oval window?
A
Scala vestibuli
18
Q
What area is the basilar membrane located?
A
Scala media –> adjacent to the scala vestibuli chamber
19
Q
What is the structure of the membrane between the scala vestibuli and the scala media like?
A
Very flexible –> so when pressure waves propagate through the scala vestibuli both of the membranes vibrate
20
Q
What is the structure of the cochlea at its base (near the oval window)?
A
Narrow and stiff
21
Q
What is the structure of the cochlea at its apex (away from the oval window)?
A
Wide and floppy
22
Q
What is resonance?
A
A property of a system to oscillate at a greater amplitude at some frequencies than at others –> known as resonant frequencies
23
Q
What happens at a systems resonant frequency?
A
The system absorbs vibrational energy –> even small forces can produce large amplitude oscillations
24
Q
How are different frequencies of sound detected by the basilar membrane?
A
Resonant frequencies on the basilar membrane vary along the length of the cochlea from base to apex
25
Where are high frequency sounds detected?
The base of the cochlea --> the start
26
Where are low frequency sounds detected?
The apex of the cochlea --> the end
27
What basilar membrane structure is needed for high frequency sound?
Narrow and stiff
28
What basilar membrane structure is needed for low frequency sound?
Wide and floppy
29
What is on the basilar membrane that actually detects the fluid wave?
The organ of Corti
30
What does the organ of Corti detect?
The location of maximal deformation for a frequency -->converting it to a neural signal at that point
31
What are the two hair cells within the organ of Corti?
Inner hair cells
| Outer hair cells
32
What is the role of the outer hair cells in the organ of Corti?
They act as amplifiers
33
What is the role of the inner hair cells in the organ of Corti?
The terminals of the spiral ganglion cells are mostly located on the base of the inner hair cells
34
How does the hair cells of the organ of Corti detect pressure waves?
Cilia on the apical membrane of the hair cells is deflected in response to sound/pressure waves
35
What membranes deflect the cilia within the organ of Corti?
Relative movement between the tectorial membrane and the reticular lamina
36
How is the cilia movement converted into a neural signal?
Cilia movement drives the hair cell to depolarise or hyperpolarise --> depending on direction of cilia movement
Depolarisation --> neurotransmitters released --> terminals on the spiral ganglion depolarise --> axons on the spiral ganglion enter the brain --> give info on pitch and loudness
37
How are loud sounds converted and conveyed as loud in the brain?
Loud sounds --> pressure waves of greater amplitude
Basilar membrane vibrates with greater amplitude
Larger area of maximal deformity --> more hair cells depolarise
Terminals on the spiral ganglion depolarise and fire action potentials at greater rate
38
How does a cochlear implant function?
1. External sound processor captures sound and converts to digital format
2. Signals sent through the coil to the internal implant
3. Internal implant converts signals to electrical impulses --> bypassing damaged hair cells within the cochlea
4. Hearing nerve delivers the signal to the brain --> allowing sound to be heard
39
What is the path from the cochlear to the auditory cortex?
```
Spiral ganglion
CN8 --> vestibulocochlear
Brainstem --> Ventral cochlear nucleus then superior olive
Midbrain --> inferior colliculus
Thalamus
Auditory cortex
```
40
What side of the cochlear nucleus cells do the spiral ganglion cells synapse at?
Ipsilateral
41
What is tonotopy in the brain?
There are auditory pathways that are activated by the same frequencies --> they end at the auditory cortex in certain positions --> giving a "frequency map" on the brain or "tonotopy"
42
What sides does the cochlea nucleus receive information?
From both ipsilateral and contralateral superior olive region
43
Do signals from the two ears arrive at the same time?
No there is a delay
44
What is the signal delay between the two ears known as?
Interaural delay
45
What is sensorineural hearing loss?
Hearing loss due to issues with the inner ear or the vestibulocochlear nerve (CN8)
46
What is conductive hearing loss?
Hearing loss due to a problem transferring sound waves --> in the outer ear, tympanic membrane, ossicles (middle ear)
47
What are the functions of the cerebellum?
Maintaining equilibrium
Coordination of motor acts
Role in learning motor patterns
May have sensory and cognitive function
48
Where does the cerebellum receive information?
Regions of the cerebral cortex that plan and initiate skilled movements
Proprioceptors
Vestibular systems
49
From cerebellar inputs what does the cerebellum calculate?
"Motor error" from these inputs
50
What does the cerebellum then do after receiving input?
Corrects the motor output of the motor cortex via its thalamic connections
--> these correction occur in real time and also over longer periods as in motor learning
51
What is the 3 lobes of the cerebellum?
Flocculonodular
Anterior
Posterior
52
How many hemispheres does the cerebellum have?
2
53
What is the cortical layers of the cerebellum?
Molecular
Purkinje cell
Granule cell
54
What are the components of balance?
Sensory detection -->of body position and movement
Integration --> sensorimotor information within the CNS
Execution --> MSK response
55
What are the sensory inputs for balance?
Vestibular --> gravitational, linear and angular acceleration of the head
Vision --> measures orientation of the head in relation to surrounding objects
Proprioception --> relative position of body parts to supportive surfaces and each other
56
What is the vestibular system involved in?
Balance
Equilibrium
Posture
57
What are the two crucial components of the vestibular labyrinth?
Otolith organs
| Semicircular canals
58
What is the role of the otolith organs?
```
Detect gravity (including head tilt)
Linear acceleration
```
59
What is the role of the semicircular canals?
Detect angular accelerations (head rotations)
60
What are the two otolith organs?
Utricle
| Saccule
61
How does the semicircular canals function?
Hair cells are stimulated by rotations that occur in the same plane as the canal
--> inertia of the endolymph causes pressure on the capula and a bending of the cilia
62
How many semicircular canals are in the vestibular system?
There is 3 on each side --> to assess all possible head rotation angles
63
Within the semicircular canals what kind of force do they become activated and what considerations have to be made about this?
They activate during angular ACCELERATION
| --> if rotation is at a constant speed they become silent
64
What is the function of the vestibulo-ocular reflex? (VOR)
Fixate gaze on a visual target during head movement
65
What is the mechanism behind the vestibulo-ocular reflex? (VOR)
Senses rotation of the head
| Compensatory movement if both eyes in the opposite direction
66
What is the pathway of the vestibulo-ocular reflex? (VOR)
Connection from semicircular canals --> to vestibular nucleus --> to cranial nerve nuclei --> excite the extraocular muscles
67
What receptors allow for proprioception?
Golgi tendon organs
| Tendon receptors in the joints
68
Where are extrafusal and intrafusal receptors located?
Skeletal muscles
69
What do extrafusal fibres do?
Responsible for contraction
70
What do intrafusal receptors do?
Stretch receptors (important in proprioception
71
What motoneurons innervate extrafusal vs intrafusal?
Extra --> alpha-motoneurons
| Intra --> Gamma-motoneurons
72
What are interesting about the muscle spindle proprioceptors?
They are adjustable --> "the gamma loop" keeps the spindle "online" --> changes the set point of the myotatic feedback loop
73
Where does the vestibulocerebellum (Flocculonodular) lobe in the cerebellum receive input from?
Vestibular nuclei (position and movement of the head)
74
What is the function of the vestibulocerebellum (flocculonodular) lobe?
Maintenance of balance, coordination of head and eye movement
75
What may happen in the vestibulocerebellum (flocculonodular) lobe damage?
Inability to stand upright
| Spontaneous nystagmus
76
What are the inputs for the spinocerebellum?
```
Spinal cord
Visual system
Auditory system
Vestibular system
Motor cortex
```
77
What is the function of the spinocerebellum?
Regulation of posture and movements under continuous sensory control
78
What would happen if the spinocerebellum was damaged?
Abnormal gait
Dysmetria
Action tremor
79
What are the inputs for the pontocerebellum?
Motor and somatosensory centres --> via pontine nuclei
80
What is the function of the pontocerebellum?
Initiation and execution of preprogramed rapid movements with fine coordination
81
What would be some symptoms of a damaged pontocerebellum?
Impairments in highly skilled movements
82
What is the general locations of the vestibulocerebellum, spinocerebellum and pontocerebellum?
Vesti --> peripheral lumps
Spino --> central
Ponto --> lateral
83
What is Medicare in Australia?
Medicare is the broad coverage of many medical based services and subsidised pharmaceuticals to eligible people
84
What is the PBS?
Federal government system that subsidises the cost to some medications --> people with Medicare are able to access PBS listed drug subsidies
85
What is dizziness?
An altered sense of spatial orientation --> where you feel like your balance is off
86
What is vertigo?
A type of dizziness --> normally characterised by feelings of you or your environment spinning
87
What are the differences between central vs peripheral vertigo?
Central --> cerebellum or brain stem pathology
| Peripheral --> inner ear or the vestibular nerve
88
What can trigger vertigo?
Benign paroxysmal positional vertigo (BPPV)
89
What is the vestibule-ocular reflex?
Reflex acting to stabilise gaze during head movement --> eyes move due to activation of the vestibular system
90
What can be seen in vestibule-ocular reflex dysfunction?
Nystagmus --> in a variety of planes depending on affected area
91
What is nystagmus?
Vision condition where the eyes make repetitive uncontrolled movements
92
Clinical signs of cerebellar ataxia?
```
Dizzy
Fatigue
Headaches
Trouble walking/gait
Tremor
```
93
Clinical signs of peripheral sensory ataxia?
Spinal cord/peripheral nerves
Difficulty touching finger to nose (with eyes closed
Inability tosense vibrations
Trouble walking in dim light
94
Clinical signs of central sensory ataxia?
Blurred vision
Nausea and vomiting
Vertigo/dizziness
Trouble walking in straight line
95
What are the symptoms of cerebellar disease?
```
impaired coordination in the torso or arms and legs
frequent stumbling
an unsteady gait
uncontrolled or repetitive eye movements
trouble eating and performing other fine motor tasks
slurred speech
vocal changes
headaches
dizziness
```
96
What is the goal of the Romberg test?
To investigate the cause of loss of motor coordination --> testing neurological function of balance
97
How is the Romberg's test done?
The essential features of the test are as follows:
the subject stands with feet together, eyes open and hands by the sides.
the subject closes the eyes while the examiner observes for a full minute.
98
How is Romberg's test interpreted?
Falls with eyes closed --> positive
Swaying is not positive as it shows proprioceptive correction
Pretty much aims to show that there is vestibular or proprioception dysfunction
99
What is the difference between conductive and sensorineural hearing loss?
Conductive --> outer and middle ear
| Sensorineural --> inner ear (cochlear + nerves)
100
What are some common causes of conductive hearing loss?
```
Infections
Allergies
Impacted wax
Foreign objects in ear
Otosclerosis
Malformation of outer/ear canal or middle ear structures
```
101
What are some common causes of sensorineural hearing loss?
```
Loud noise exposure
Aging
Head trauma
Viral disease
Heredity
Malformation of inner ear
Autoimmune of inner ear
Otosclerosis
```
102
What causes noise induced hearing loss?
physical damage in organ of Corti
decreased blood flow causing the hypoxia of the inner ear
oxidative stress of reactive oxygen species (ROS)
neural degeneration in synaptic terminals of cochlear nerve fibres and spiral ganglion cells.
103
What is the purpose of the Rinne test?
To see if conductive or sensorineural hearing loss
104
What is the purpose of the weber test?
To determine if the affect is the same on both or just one side
105
How does the Rinne test work?
Tuning fork on bone --> then when patient cant hear it anymore --> move to air outside ear canal --> if they can hear it --> normal result --> AC > BC
If they cant hear it BC > AC
AC > BC = sensorineural impairment
BC > AC = conductive loss
106
How does the Weber test work?
Tuning fork in middle of head
If determined sensorineural loss --> will be louder on non affected ear
If determined conductive loss --> will be louder in AFFECTED ear --> as ear with issue has already blocked out ambient noise in room so the bone conduction will be louder
107
Complications of neurological from chronic alcohol abuse?
```
Memory loss.
Frequent blackouts.
Loss of coordination.
Dehydration.
Seizures.
Death.
```
