Chap 6 - Other Senses Flashcards
sound and the ear
- audition depends on ability to detect sound waves
- waves are periodic compressions or air, water, other media
amplitude
refers to the intensity of the sound wave
Loudness
refers to the perception of the sound wave
- Amplitude is one factor
Frequency
refers to the number of compressions per second and is measured in hertz (Hz)
-Related to the pitch (high to low)
Hearing and age…
Children hear higher frequencies than adults; the ability to recognize high frequencies diminishes with age and exposure to loud noises
Anatomists distinguish between:
- The outer ear
- The middle ear
- The inner ear
outer ear
- pinna, structure of flesh and cartilage attached to each side of the head
outer ear responsible for
- Altering the reflection of sound waves into the middle ear from the outer ear
- Helps to locate the source of a sound
middle ear
- tympanic membrane, which vibrates at the same rate when struck by sound waves
(aka the ear drum) - Connects to three tiny bones (malleus, incus, & stapes) that transform waves into stronger waves to the oval window
inner ear
oval window membrane
-Transmits waves through the viscous fluid of the inner ear
contains a snail shaped structure called the cochlea
- Contains three fluid-filled tunnels (scala vestibuli, scala media, & the scala tympani)
hair cells
are auditory receptors that lie between the basilar membrane and the tectorial membrane in the cochlea
- When displaced by vibrations in the fluid of the cochlea, they excite the cells of the auditory nerve
pitch perception theories:
- place theory
- frequency theory
Place theory
each area along the basilar membrane has hair cells sensitive to only one specific frequency of sound wave
Frequency theory
the basilar membrane vibrates in synchrony with the sound and causes auditory nerve axons to produce action potentials at the same frequency
The current pitch theory combines modified versions of both the place theory and frequency theory:
- Low frequency sounds best explained by the frequency theory
- High frequency sounds best explained by place theory
Volley principle
auditory nerve as a whole produces volleys of impulses (for sounds up to about 4,000 per second)
- No individual axon solely approaches that frequency
- Requires auditory cells to precisely time their responses
Hearing of higher frequencies not well understood
Amusia
the impaired detection of frequency changes (tone deafness)
People vary in their sensitivity to pitch
Associated with thicker than average auditory cortex in the right hemisphere but fewer connections from auditory cortex to frontal cortex
Absolute pitch (“perfect pitch”) is the ability to hear a note and identify it
- Genetic predisposition may contribute to it
- Main determinant is early and extensive musical training
- More common among people who speak tonal languages
The primary auditory cortex (area A1) is the destination for most information from the auditory system
Located in the superior temporal cortex
Each hemisphere receives most of its information from the opposite ear
Organization of the auditory cortex parallels that of the visual cortex
Superior temporal cortex contains area MT
- Allows detection of the motion of sound
Area A1 is important for auditory imagery
Requires experience to develop properly
- Axons leading from the auditory cortex develop less in people deaf since birth
The cortex is necessary for the advanced processing of hearing
Damage to A1 does not necessarily cause deafness unless damage extends to the subcortical areas
The auditory cortex provides a tonotopic map in which cells in the primary auditory cortex are more responsive to preferred tones
Some cells respond better to complex sounds than pure tones
Areas around the primary auditory cortex exist in which cells respond more to changes in sound than to prolonged sounds
Cells outside A1 respond to auditory “objects” (animal cries, machinery noise, music, etc.)
- Because initial response is slow, most likely responsible for interpreting the meaning of sounds
Two categories of hearing impairment include:
- Conductive/middle ear deafness
- Nerve or inner-ear deafness
Conductive/middle ear deafness
- Occurs if bones of the middle ear fail to transmit sound waves properly to the cochlea
- Caused by disease, infections, or tumerous bone growth
- Can be corrected by surgery or hearing aids that amplify the stimulus
- Normal cochlea and normal auditory nerve allows people to hear their own voice clearly
Nerve or inner-ear deafness
- Results from damage to the cochlea, the hair cells, or the auditory nerve
- Can vary in degree
- Can be confined to one part of the cochlea
(People can hear only certain frequencies) - Can be inherited or caused by prenatal problems or early childhood disorders
Tinnitus
is a frequent or constant ringing in the ears
- Experienced by many people with nerve deafness
Sometimes occurs after damage to the cochlea
- Axons representing other part of the body innervate parts of the brain previously responsive to sound
- Similar to the mechanisms of phantom limb
Sound localization depends upon comparing the responses of the two ears
Three cues:
- Sound shadow
- Time of arrival
- Phase difference
Humans localize low frequency sound by phase difference and high frequency sound by loudness differences
Sound localization - 3 mechanisms
- High-frequency sounds (2000 to 3000Hz) create a “sound shadow”
- Difference in time of arrival at the two ears most useful for localizing sounds with sudden onset
- Phase difference between the ears provides cues to sound localization with frequencies up to 1500 Hz
- Readjusting sound localization is slow process
The mechanical senses include:
- The vestibular sensation
- Touch
- Pain
- Other body sensations
The mechanical senses respond to pressure, bending, or other distortions of a receptor
Vestibular Sensation
sense refers to the system that detects the position and the movement of the head
- Directs compensatory movements of the eye and helps to maintain balance
- The vestibular organ is in the ear and is adjacent to the cochlea