Chapter 9: Hearing, Vestibular, Taste and Smell Flashcards
Sound
Oscillation of increases and decreases in air pressure.
How is sound typically discussed?
As waves
Amplitude
Distance between the resting position and maximum height of the wave.
What is amplitude measured in?
Decibles (dB)
Frequency
The number of waves passing by a specific point per second.
What is frequency measured in?
Hertz (Hz)
Pure Tone
A single frequency
Most sounds are not…
pure tones
Fourier Analysis
Decomposes sound into its separate sine waves.
What type of force is sound?
Mechanical
What is used to detect sound?
Mechanoreceptors
Middle Ear
Controlled by stapedius and tensor tympani muscles.
How does the middle ear reduce effectiveness of sound?
Stiffening links of bone.
What is the middle ear important for?
Decreasing self-made sounds
Inner Hair Cell
Transduces the physical force into the neural signal.
Basilar Membrane
Has different sensitivities to different frequencies.
What does the stiff base of the basilar membrane respond better to?
High frequencies
What does the floppy apex of the basilar membrane respond better to?
Low frequencies
Inner Hair Cells (IHCs)
Responsible for perception of sound.
What % of the auditory fibers are from IHCs?
90-95%
Outer Hair Cells (OHC)
Help to fine-tune organ of Corti in response to messages from the brain.
Cochlear Amplifier
Amplify movements of basilar membrane in some areas while dampening in others.
Neurons Tuning Curve
Auditory neurons have a precise frequency they are most sensitive to, but also respond to nearby frequencies.
Where do binaural interactions occur?
The brainstem and superiors olivary nucleus
Tonotopic Organization
Organization of the auditory system.
What do the auditory systems try to analyze?
- Pitch
- Source of the sound
Place Theory
Encoded by area of basilar membrane with maximal excitation.
Volley Theory
Frequency encoded by firing frequency.
What type of frequency is the volley theory mainly used for?
Lower frequencies
Binaural Neurons
Serve as “coincidence detectors”
Lateral Superior Olive
Processes latency differences in mammals.
Medial Superior Olive
Processes latency differences but compares ENTIRE activity of MSO on left vs right.
External Ear
Provides spectral filtering and amplifies certain frequencies.
What are the 3 ossicles in the ear?
- Malleus
- Incus
- Stapes
Auditory Cortex
Processes Complex Sounds
The auditory cortex is not involved in…
basic auditory discrimination (can be accomplished at lower levels)
Dorsal Stream
Focuses on localization
Ventral Stream
Analyzes components of sound.
What causes cells to shift their tuning curve?
Experience
What type of neurons have tuning curves?
Auditory cortical neurons
What are the 3 kinds of deafness?
- Conduction
- Sensorineural
- Central
Conduction Deafness
Problem in the outer/middle ear prevents the transmission of vibrations.
Conduction deafness is not a _________ problem.
Nervous system
Sensorineural Deafness
The auditory nerve is unable to become excited and conduct signals.
What can cause sensorineural deafness?
- Genetic mutation
- Toxic drug
- Loud sounds (chronic exposure)
What is damaged to cause sensorineural deafness?
Hair cells
How can sensorineural deafness by treated?
cochlear implants (auditory nerve is still functional)
Central Deafness
Something is wrong in the brain, causing deafness.
What is an example of something that can cause central deafness?
A stroke - damages auditory cortex / MGN projections to the cortex
Is central deafness complete or selective deafness?
Both
Auditory Brainstem Implants (ABIs)
Bypass auditory nerve and directly stimulate the brainstem nuclei
Vestibular Perception
Informs you about forces acting on the body (especially the head)
What are the two major forces in the vestibular system?
Gravity and acceleration
What is the vestibular system important for?
Balance and body/head position awareness
What are the 3 components for awareness in space?
- Vestibular system
- Visual system
- Proprioceptive System
What are the Semicircular Canals important for?
Detecting rotational forces
What are the utricle and saccule important for?
Detecting linear forces (horizontal and vertical)
Each canal is located along a different ___.
Axis
Ampulla
Enlarged region of EACH semicircular canal
Where is the ampulla located?
The junction of canal and utricle
What do the hair cells in the ampulla respond to?
Precise kinds of mechanical rotational force (depends on orientation of hair cells)
Utricle
Saclike structure at the ends of canals
Saccule
Saclike structure below the utricle
What do the utricle and saccule contain?
Otoliths that enhance sensitivity of receptors
Lateral Line System
Array of receptors along the side of the body.
What is the importance of the movements of water stimulate receptors?
Tells animals about current and nearby animals.
What did the auditory system develop from?
Vestibular system
What does the vestibular nucleus send signals to?
- Motor nuclei of eye
- Thalamus
- Cortex
Vestibular Ocular Reflex
Enables you to precisely control the muscles of the eye even as you move your head. (keeps eyes focused on one thing).
What happens after too much spinning of your body occurs?
Conflict between vestibular system and visual system feedback.
Taste and smell is a form of…
chemo detection
Flavors
taste and smell combined
What is taste processed by?
The gustatory system
How many taste receptor cells are on a taste bud?
50-100
What are the 5 tastes?
- salty
- sweet
- sour
- bitter
- umami
Salty
Sodium transported across the cell membrane via channels - leads to depolarization
Sour
Dependent on the acidity of a substance
- Hydrogen ions enter through channels and depolarize
Sweet
Detected by the combination of two members of the T1R family (GPCRs)
Bitter
Often evoked by toxic substances that want to be highly sensitive
What kind of taste is poorly discriminated?
Bitter
Umami
meaty and savory flavor
What are the two receptor types of taste?
- Responds to glutamate (amino acids)
- Responds to most amino acids
What are amino acids highly present in?
meat
How many functional genes do humans have for odor receptors?
350
What does sensitivity reflect?
Evolutionary needs
What is the path of smell?
- Olfactory receptor cells
to - The axons
to - The mitral cell
to - The brain
Mitral Cells
Cells in the olfactory bulb
Where do mitral cells send their axons?
Further into the brain
What does olfactory information have to pass through to reach the cortex?
The thalamus
How does olfactory transduction work?
- Odorant binds to GPCR, leading to G protein activation.
- The G protein activities cyclase, which produces cAMP
- cAMP binds to channels, opening them, leading to depolarization
How many odors can humans discriminate?
5000 odors
Vomeronasal System
Pheromone detection system in the nose of some animals
What are the receptors in the vomeornasal system important for?
Organizing reproductive behavior
Histocompatibility Complexes (MHCs)
Important for detecting degree of relatedness to other animals.
Where is MHC information sent?
To the accessory olfactory bulb, medial amygdala, and to the hypothalamus
What do humans not appear to have?
A functional VNO (both receptor genes are nonfunctional)
What does behavioral evidence suggest humans are sensitive to?
pheromones
Pheromones and ___ ____ may not be so independent.
Olfactory systems
