Ch. 6 Flashcards
Chapter 6 of The Mind's Machine
How does energy transmitted through air become the speech, music, and other sounds we hear?
Our auditory system detects changes in the vibration of air molecules that are caused by sound sources. The outer ear directs sound into the inner parts of the ear, where the mechanical force of sound is transduced into neural activity: the action potentials that inform the brain
Decibels (dB)
A measure of sound intensity, perceived as loudness
Hertz (Hz)
Cycles per second, as of an auditory stimulus. Hertz is a measure of frequency
Transduced
to convert one form of energy to another
Pure Tone
A tone with a single frequency of vibration
Amplitude
Also called intensity. The force that sound exerts per unit area, which we experience as loudness
Frequency
The number of cycles per second in a sound wave, measured in hertz
Fundamental Frequency
The predominant frequency of an auditory tone
Harmonics
A multiple of a particular frequency called the fundamental
Timbre
The characteristic sound quality of a musical instrument, as determined by the relative intensities of its various harmonics
Pinnae
the external part of the ear that funnels sound waves into the second part of the external ear
Ear Canal
Also called auditory canal. The tube leading from the pinna to the tympanic membrane
Inner Ear
The cochlea and vestibular apparatus
Middle Ear
The cavity between the tympanic membrane and the cochlea. Contains the tympanic membrane, ossicles, and a specialized patch of membrane called the oval window.
Tympanic Membrane
Also called eardrum. The partition between the external ear and the middle ear
Ossicles
Three small bones (incus, malleus, and stapes) that transmit vibration across the middle ear, from the tympanic membrane to the oval window
Oval Window
The opening from the middle ear to the inner ear
How do sound waves interact with middle ear?
Sound waves in the air strike the tympaic membrane and cause it to vibrate with the same frequency as the sound; as a result, the ossicles start moving too. The Occiscles concentrate and amplify the vibration, focusing the pressures collected from the relatively large tympanic membrane onto the small oval window
What is the purpose of the tensor tympani and the stapedius?
These are two tiny muscles that contract with the arrival of a loud sound, which stiffens the chain of ossicles and reduces the effectiveness of sounds
Cochlea
A snall-shaped structure in the inner ear canal that contains the primary receptor cells for hearing
what are the three parallel canals in the cochlea?
- the scala vestibuli (or the vestibular canal)
- the scala media (middle canal)
- the scala tympani (tympanic canal)
Scala Vestibuli
Also called vestibular canal. One of three principal canals running along the length of the cochlea.
Scala Media
Also called middle canal. The central of the three spiraling canals inside the cochlea, situated between the vestibular canal and the tympanic canal.
Scala Tympani
Also called tympanic canal. One of three principal canals running along the length of the cochlea. Contains the receptor system (organ of Corti)
Organ of Corti
A structure in the inner ear that converts vibration (from sound) into neural activity. Contains three main sturcutes:
1. the auditory sensory cells, called hair cells
2. an elaborate framework of supporting cells
3. the auditory nerve terminals that transmit neural signals to and from the brain
Hair Cells
One of the receptor cells for hearing in the cochlea, named for the stereocilia that protrude from the top of the cell and transduce vibrational energy in the cochlea into neural activity. Also bridges between the basilar membrane and the overlying tectorial membrane.
Basilar Membrane
A membrane in the cochlea that contains the principal structures involved in auditory transduction. The basilar membrane ripples in response to waves created in the fluid of the scala vestibuli. This rippling is then created into neural activity
Tectorial Membrane
A gelatinous membrane located atop the organ of Corti
Stereocilia
Minuscule hair that protrudes from a hair cell in the auditory or vestibular system
What does a bend of the stereocilia produce?
a large and rapid depolarization of the hair cells
Inner Hair Cells (IHCs)
One of the two types of receptor cells for hearing in the cochlea. Compared with outer hair cells, IHCs are positioned closer to the central axis of the coiled cochlea
Outer Hair Cells (OHCs)
One of the two types of receptors cells for hearing in the cochlea. Compared with inner hair cells, OHCs are positioned farther from the central axis of the coiled cochlea
Vestibulocochlear Nerve
Cranial Nerve VIII, which runs from the cochlea to the brainstem auditory nuclei
What are the four kinds of neural connections with hair cells?
- IHC afferents
- IHC efferents
- OHC afferents
- OHC efferents
What is the job of IHC afferent pathway?
Conveys to the brain the action potentials that provide the perception of sounds
What is the job of IHC efferent pathway?
Leads from the brain to the IHCs. They allow the brain to control the responsiveness of IHCs
What is the job of OHC afferent pathway?
Conveys information to the brain about the mechanical state of the basilar membrane, but not the perception of sounds themselves
What is the job of IHC efferent pathway?
Enables it to activate a remarkable property of OHCs: the ability to change their length almost instantaneously. This results in both sharpened tuning and pronounced amplification
Cochlear Nuclei
Brainstem nuclei that receive input from auditory hair cells and send output to the superior olivary nuclei
Superior Olivary Nuclei
Brainstem nuclei that receive input from both right and left cochlear nuclei and provide that first binaural analysis of auditory information
Inferior Collicluli
Paired gray matter structures of the dorsal midbrain that process auditory information
Medial Geniculate Nuclei
Either of two nuclei- left and right- in the thalamus that receive input from the inferior colliculi and send output to the auditory cortex
Tonotopic Organization
The organization of auditory neurons according to an orderly map of stimulus frequency, from low to high
Primary Auditory Cortex (A1)
the cortical region, located on the superior surface of the temporal lobe, that processes complex sounds transmitted from lower auditory pathways
What is the auditory pathway from ear to brain?
cochlea-> cochlear nucleus-> superior olivary nucleus-> inferior colliculus-> medial geniculate nucleus-> auditory cortex
Place Coding Theory
Theory that the pitch of a sound is determined by the location of activated hair cells along the length of the basilar membrane
Temporal Coding Theory
Theory that the pitch of a sound is determined by the rate of firing of auditory neurons
Infrasound
very-low-frequency sound, generally below the 20 Hz threshold for human hearing
Ultrasound
Very-high-frequency sound, generally beyond 20,000 Hz, which is the upper bound for a young adult human
What are the two kinds of binaural cues that signal the location of a sound source?
interaural intensity differences (IIDs) and Interaural temporal differences (ITDs)
Interaural Intensity Differences (IIDs)
A perceived difference in loudness between the two ears, which the nervous system can use to localize a sound source
Interaural Temporal Differences (ITDs)
A difference between the two ears in the time of arrival of a sound, which the nervous system can use to localize a sound source
Spectral Filtering
The process by which the hills and valleys of the external ear alter the amplitude of some, but not all, frequencies in a sound
What sounds does the auditory cortex process?
complex soundscape of everyday life, not simple tones
Amusia
A disorder characterized by the inability to discern tunes accurately or to sing. Associated with subtly abnormal connectivity between primary auditory cortex and regions of the right frontal lobe known to participate in pitch discrimination
Hearing Loss
Decreased sensitivity to sound, in varying degrees
Deafness
Hearing loss so profound that speech perception is lost
What are the three main kinds of problems that prevent hearing?
problems with sound waves reaching the cochlea, trouble converting those sound waves into action potentials, or dysfunction of the brain regions that process sound information
Conduction Deafness
A hearing impairment in which the ears fail to convert sound vibrations in air into waves of fluid in the cochlea. It is associated with defects of the external ear or middle ear.
Sensorineural Deafness
A hearing impairment most often caused by the permanent damage or destruction of hair cells or by interruption of the vestibulocochlear nerve that carries auditory information to the brain
Tinnitus
A sensation of noises or ringing in the ears not caused by external sound. Caused by long-term exposure to loud sounds.
Central Deafness
A hearing impairment in which the auditory areas of the brain fail to process and interpret action potentials from sound stimuli in meaningful ways, usually as a consequence of damage in auditory brain areas
Word Deafness
A form of central deafness that is characterized by the specific inability to hear words although other sounds can be detected
Cortical Deafness
A form of central deafness, caused by damage to both sides of the auditory cortex, that is characterized by difficulty in recognizing all complex sounds, whether verbal or nonverbal
Cochlear Implants
An implantable device that detects sounds and selectively stimulates nerves in different regions of the cochlea
Vestibular System
The sensory system that detects balance. It consists of several small inner-ear structures that adjoin the cochlea. Action potentials are produced by hair cells.
Semicircular Canals
Any one of the three fluid-filled tubes in the inner ear that are part of the vestibular system. Each of the tubes, which are at right angles to each other, detects angular acceleration in a particular direction. The three canals are oriented in the three different planes in which the head can rotate.
Ampulla
An enlarged region of each semicircular canal that contains the receptor cells (hair cells) of the vestibular system
How does the semicircular canal relate to the brain knowing how the head has moved?
Movement of the head in one axis sets up a flow of the fluid in the semicircular canal that lies in the same plane, bending the stereocilia in that particular ampulla and signaling the brain that the head has moved
The utricle and saccule each contain what?
an otolithic membrane: a gelatinous sheet studded with tiny crystals
What function does the otolithic membrane have?
helps the stereocilia of nearby hair cells to track straight line acceleration and deceleration
Vestibular information is crucial for what?
planning body movements, maintaining balance agains gravity, and smoothly directing sensory organs like the eyes and ears toward specific locations, even when our bodies themselves are in motion
Vestibular Nuclei
Brainstem nuclei that receive information from the vestibular organs through cranial nerve VIII (the vestibulocochlear nerve)
Motion Sickness
The experience of nausea brought on by unnatural passive movement, as may occur in a car or boat
Flavors
The sense of taste combined with the sense of smell
What are the five basic tastes?
salty, sour, sweet, bitter, and umami
Tastes
Any of the five basic sensations detected by the tongue- sweet, salty, sour, bitter, and umami
Taste Buds
A cluster of 50-150 cells that detects tastes. Taste buds are found in papillae
Papillae
A small bump that projects from the surface of the tongue. Papillae contain most of the taste receptor cells
What are the three kinds of papillae?
circumvallate, foliate, and fungiform papillae
Microvilli
Fine fibers that extend from the taste receptor cells into a tiny pore
Besides taste, what are some other sensory capabilities of the tongue?
it is also sensitive to pain, touch, and temperature
T1R
A family of taste receptor proteins that, when particular members bind together, form taste receptors for sweet flavors and umami flavors
Umami
One of the five basic tastes- the meaty, savory flavor
T2R
A family of bitter taste receptors
Are taste receptor proteins found only on the tongue?
No, they are expressed in numerous tissues of the body
Gustatory System
The sensory system that detects taste
Where do taste projections extend to?
They extend from the tongue to several brainstem nuclei, then to the thalamus, and ultimately to gustatory regions of the somatosensory cortex
How does the brain encode taste perception?
The brain monitors which specific axons are active in order to determine which tastes are present (labeled line system)
Olfaction
The sensory system that detects smell; the act of smelling
Anosmia
The inability to sense odor
Olfactory Epithelium
A sheet of olfactory receptors and other cells that lines the dorsal portion of the nasal cavities and adjacent regions
Olfactory Receptor Neurons
A type of neuron, found in the olfactory epithelium, that senses airborne odorants via specialized receptor proteins
In the olfactory epithelium, what three types of cells are found?
supporting cells, basal cells, and olfactory receptor neurons
Odorants
substances that we can smell from the air that we inhale or sniff
Cilia
A long, slender apical dendrite that divides into branches on each olfactory receptor cell
What are the olfactory receptor proteins?
a variety of G protein-coupled receptors (GPCRs)
How do odorants interact with receptors?
Odorants dissolve into the mucosal layer and interact with receptors studding the dendritic cilia of the olfactory neurons
How is the production of receptor proteins different in the olfactory neurons compared to neurons in the brain?
There is more diversity of olfactory receptor protein subtypes- up to a dozen subtypes of receptors for neurotransmitter in the brain, hundreds or thousands of subtypes within the family of odorant receptors
How do olfactory neurons regenerate?
An adjacent basal cell will differentiate into a neuron and begin extending a dendrite and an axon.
Where does each olfactory neuron extend to?
Each olfactory neuron extends a fine, unmyelinated axon into the nearby olfactory bulb of the brain, where it terminates on one specific glomerulus.
Olfactory Bulb
An anterior projection of the brain that terminates in the upper nasal passages and, through small openings in the skull, provides receptors for the sense of smell
Glomerulus
A spherical clump of neurons, one of thousands of glomeruli that exist in the olfactory bulb. Each glomerulus receives inputs exclusively from olfactory neurons that are expressing the same type of olfactory receptor protein. It then actively tunes and sharpens the neural activity associated with corresponding odarants
What is the “olfactotopic” map?
The organization of glomeruli in the olfactory bulb according to an orderly, topographic map of smells, with neighboring glomeruli receiving inputs from receptors that are closely related. There is also segregation of the four receptor protein subfamilies in the olfactory epithelium
What makes olfactory information different from other sensory modalities?
It synapses directly in the cortex rather than having to pass through the thalamus
After smell has reached the glomeruli, how does it get transported to the brain?
Olfactory information is conveyed to the brain via the axons of mitral cells, which extend from the glomeruli in the olfactory bulb to various regions of the forebrain
Brain regions that receive olfactory inputs include:
the hypothalamus, the amygdala, and the prepyriform cortex
Pheromones
A chemical signal that is released outside the body of an animal and affects other members of the same species
Vomeronasal Organ (VNO)
A collection of specialized receptor cells, near to but separate from the olfactory epithelium, that detect pheromones and send electrical signals to the accessory olfactory bulb in the brain (not present in humans)
Vomeronasal System
A secondary chemical detection system that is specialized for detecting pheromones. Its receptors are found in the vomeronasal organ (VNO), near the olfactory epithelium
From the VNO, how is information about pheromones transported?
Information is transmitted to the accessory olfactory bulb (adjacent to the main olfactory bulb), which projects to the medial amygdala and hypothalamus (structures that play crucial roles in governing emotional and sextural behaviors and in regulating hormone secretion)
Trace Amine-Associated Receptors (TAARs)
Any one of a family of probable pheromone receptors produced by neurons in the main olfactory epithelium (receptors in the main olfactory epithelium in mice)
