What is Audition?
Sound: pressure waves generated by vibrating air molecules
What are the 4 major features of sound waves?
Waveform: Amplitude plotted against time
Amplitude: Usually in decibles. Loudness
Frequency: Expressed in Hertz. Pitch
What is molecular condensation?
It is also know as compression and it represents the displacement of molecules closer together
What is rarefaction
The displacement of molecules further apart
What are the 3 perceptual dimensions of sound?
Pitch: Determined by frequency
Loudness: Determined by amplitude and is a function of intensity
Timbre: Determined by the complexity of the sound. For example, the complexity expressed by different musical instruments
How do sound waves get transformed into neural activity?
- External and Middle Ears: The ears collect the sound waves and amplify the pressure to transmit to the inner ear, turning it from air to fluid.
- Inner ear: Once in the inner ear, the signal gets broken into simpler components. The hair cells transduce the frequency, amplitude and phase. Then, the auditory nerve fibers encode the electrical activity.
What is the pinna?
Part of the outer ear. It collects and alters the reflection of sound waves into the middle ear. It also helps locate the source of a sound.
Other parts of the outer ear include the concha and the auditory meatus (ear canal)
What structures are in the middle ear?
What does the tympanic membrane do?
Vibrates at the same rate when struck by sound waves and is connected to teh ossicles
What are the ossicles and what do they do?
The ossicles transform waves into stronger waves
The 1st is the malleus "hammer"
The 2nd is the incus "anvil"
The 3rd is the stapes "stirrup"
What is conductive hearing loss?
Damage to the external inner, or middle ear
What is sensorineural hearing loss?
Damage to the inner ear
What is impendance matching?
Matching of airborne sounds to acoustic waves traveling in fluid of inner ear. This boosts the pressure from the big tempanic membrane through the small oval window. Then the ossicles perform a lever action.
What is the oval window?
A membrane of the inner ear
The stapes presses against it to transmit sound waves into the viscous fluid within the cochlea
What structures are in the inner ear?
Organ of Corti
Scala vestibuli, tympani, & media
What is the cochlea?
It is a snail shaped structure that contains auditory transducing mechanisms. It amplifies sound waves and converts them to neural signals. It also decomposes complex waveforms
What is the Organ of Corti?
It is the receptive organ of the cochlea. It sits on the basilar membrane and contains auditory hair cells. It is the transducer
What are the scala vestibuli, the tympani, & the media?
They are the fluid filled chambers of the cochlea
What is the basilar membrane?
It is a membrane in the cochlea of the inner ear that contains the Organ of Corti
What is the tectorial membrane?
It is located above the basilar membrane and serves as a shelf against which cilia move
What is an auditory hair cell?
It is a receptive cell that lies between the basilar membrane and the tectorial membrane in the cochlea. When hair cells become displaced by vibrations in the fluid of the cochlea, they excite the cells of the auditory nerve.
What is the round window?
An opening of the bone in the cochlea. It vibrates in the opposite phase to the vibrations entering the inner ear. It permits vibrations that are transmitted through the fluid in teh cochlea.
How does the basilar membrane tune frequency?
The physical characteristics of the basilar membrane help to tune the frequency. The wider, more flexible part is at the end, making for a lower sound. The base is more narrow and stiff, making for a higher sound
How does sound travel in the inner ear?
The stapes vibrates against the membrane of the oval window, which makes sound waves to the cochlea
Vibrations cause the basilar membrane to flex
Pressure changes in the fluid underneath the basilar membrane are transmitted to the membrane of the round window
The round window moves in and out - opposite of the oval window. As the stapes pushes in, the round window bulges out
What is cilium
Hair-like appendages of the cell involved in movement or sensory transduction
What is the tip link?
An elastic filament that attaches to the tip of one cilium to the side of an adjacent cilium
What is an insertional plaque
Point of attachment of a tip link to cilium
What are the properties of cochlear hair cells?
There is one row of inner cells and 3 rows of outer hair cells
The inner hair cells are sensory receptors and represent 95% of the fibers of the auditory nerve
The outer hair cells the sites of termination from efferent axons from the superior olive
Nerve deafness or inner-ear deafness is a result of damage to the cochlea, hair cells, or auditory nerve. Only deaf to some frequencies.
What is the auditory pathway?
Organ of Corti stimulates the cochlear nerve, which excite cell bodies in the cochlear nerve ganglion. EPSP's trigger action potentions in the auditory nerve axons. From there, they synapse with neurons in the medulla.
Where are the efferent axons of the cochlear nerve
They are discribed as the olivocochlear bundle and start in the superior olivary complex in the medulla
Where are the afferent axons of the cochlear nerve?
They synapse in the cochlear nucleus of the medulla
What is the cochlear nerve?
A branch of the auditory nerve that transmits auditory information from the cochlea to the brain
What is the olivocochlear bundle?
A bundle of efferent axons traveling from the olivary complex of the medulla to synapse directly on the outer hair cells and on teh dendrites of the inner hair cells
What is the cochlear nucleus?
It resides in the medulla and receives auditory information from the cochlea
What is the superior olivary complex?
It resides in the medulla. It is involved with auditory functions including the localization of a sound source
What is the lateral lemniscus?
A band of fibers running rostrally through the medulla and the pons.
It carries fibers of the auditory system to the inferior colliculus
How is the auditory cortex represented?
Tonotopically. Similar to the topographic representation across other senses, the auditory cortex maps different frequencies of sound.
What and where is the "what" pathway of the auditory system?
It is in the anterior part of the auditory cortex. It i smodulated by emotions.
Where is the "where" pathway of the auditory system?
It is in the posterior portion of the auditory cortex and overlaps with the visual system's "where" pathway in the parietal lobe
What are the four mechanisms of sound?
Sound shadow: created by high-frequency sounds. Thsi makes sound louder to the closer ear
Difference in time of arrival: the ears receive sound at different times. This is the most useful for localizing sounds with sudden onset.
Phase difference: Provides cues to sound location for sounds with frequencies up to 1500 Hz
Analysis of timbre: Determines the height of the sound source
What is the function of the vestibular system?
Balance, maintenance of head in upright position, adjustment of eye movement to compensate for head movements.
Describe the component, vestibular sacs.
Two receptor organs in each inner ear that detect changes in tilt of head. The organs are teh saccule and the utricle. They respond to the force of gravity
Describe the component, semicircular canals
They are three ring-like structures that detect changes in head rotation. They respond to changes in head position and acceleration
What are the three components of labyrinth of the inner ear?
- vestibular sacs
- semicircular canals
Describe the vestibular pathway
- The vestibular ganglion house the cell bodies of afferent axons of the vestibular nerve (most synapse in the medulla, but some travel to the cerebellum)
- The vestibular nuclei send the info to the cerebellum, the spinal cord, the medulla and the pons (nausea and vomiting), and maybe the temporal cortex
What is the vestibulo-ocular reflex?
The vestibular system exerts control on eye movements to compensate for sudden head movements
Name and describe the somatosenses
The somatosenses transduce, encode, and perceive information.
Some of these include the cutaneous sense, which responds to touch; proprioception, which perceives body position; kinesthesia, which perceives the body's own movement; and organic senses, which are sensitive to stimuli around the organs
Describe glabrous skin
Skin that does not contain hair
Found on palms and soles of feet
What is the ruffini corpuscle?
Vibration-sensitive organ located in hairy skin
What is the pacinian corpuscle
It is a specialized, encapsulated nerve ending that detects mechanical stimuli
What is Meissner's corpuscle?
It is touch-sensitive and located in papillae. It transduces low frequency vibrations when things move across skin
What is Merkel's disk?
It is touch sensitive and found at the base of the epidermis
Sensitive to points and edges
What are some cutaneous stimuli?
What are the two types of pain receptors?
Að group-myelinated axon-faster-responds to dangerously intense stimuli
C fiber group-unmyelinated-slower-tissue damage, mechanical, chemical
What are the two types of itch?
histamine & cowhage-induced
What are the two somatosensory pathways and what do they carry?
Dorsal columns/medial lemniscus tract: carries precise information, fine touch
Anterolateral system (spinothalamic tract): carries imprecise information including pain and temperature
What is the nucleus raphe magnus?
It contains serotonin-secreting neurons that project into the dorsal gray matter of the spinal cord. It is involved in the analgesia produced by opiates
What does the periaqueductal gray matter release?
endogenous opioids. Electrical stimulation of the periaqueductal gray matter and rostroventral medulla can cause analgesia
What are the three components of pain?
Immediate emotional consequence
Long-term emotional implications
What is the sensory pathway of pain?
Information goes from the spinal cord to the ventral posterolateral cortex
What is the emotional pathway of pain?
Information goes to the anterior cingulate cortex
What are the six qualities of taste?
How does taste information travel to the brain?
Information from the posterior part of the tongue travels the 9th and 10th cranial nerve to palate and epiglotis.
What is the olfactory epithelium?
Epithelial tissue of the nasal sinus that covers the cribriform plate and contains cilia of olfactory receptors
What is the olfactory bulb?
A protrusion at the end of the olfactory tract. It receives input from the olfactory receptors. Only place, other than the hippocampus that shows neurogenesis in adulthood
What is the Mitral cell?
Neuron located in the olfactory bulb that receives information from olfactory receptors. This cell's axons brings info to the rest of the brain
What is the olfactory glomerulus?
A bundle of mitral cell dendrites and associated terminal buttons of olfactory receptor axons
How does scent travel to the brain?
- Receptors in olfactory epithelium send a process toward the mucosa, which divide into 10-20 cilia that penetrate the mucuus.
- Odorous molecules dissolve in the muscus and stimulate receptor molecules.
- Axons enter through the cribriform plate
- Olfactory bulbs receive a single axon from each receptor cell, forming synapses with Mitral cells, which travel to the rest of the brain through olfactory tracts
Where do the olfactory tracts lead?
The projections onto the amygdala and piriform cortex travel to the hypothalamus
The projection to the entorhinal cortex travels to the hippocampus
How are we able to smell so many different odors with such few receptors?
Because each glomerulus receives information from 2000 receptor cells. Different odorants produce different patterns of activity in the different glomeruli