Download Hearing and Other Senses Lecture Notes

HEARING (Audition)
Physics of sound…
● Frequency (pitch): number of cycles completed by a wave in a given amount of time,
usually a second
● wavelength: the distance from the peak of one wave to the peak of the next.
● long wavelengths = low frequency/pitch
● short wavelengths = high frequency/pitch
● Amplitude/Intensity (Loudness): physical strength in a wave, usually determined by the
height of the wave (from peak to valley)
● decibel: measuring unit for sound strength/energy
Auditory process
●
outer ear (pinna) → auditory canal → tympanic membrane (eardrum) → ossicles
(bones) of the middle ear → oval window → cochlea → basilar membrane (hair cells)
→ auditory nerve → auditory cortex
Perceiving Pitch
● 2 theories
● Frequency theory: the basilar membrane vibrates at the same rate as incoming sound
waves, triggering neural impulses at the same rate
● explains low-pitched sounds
● Place theory: different frequencies cause vibrations at different locations (hair cells)
along the basilar membrane, triggering the neurons at that place
● explains high-pitched sounds
Hearing Loss
● As we age, we lose the ability to detect the higher frequency/pitch sounds
● Why?
●
Conduction deafness: inability to hear resulting from damage to the structures of the
middle ear
●
Sensorineural deafness (nerve deafness): inability to hear resulting from damage to the
cochlea, hair cells or auditory nerve
● Cochlear implant? Good or bad?
Other Senses
Skin and Body Senses (Somatic Senses)
● Include your sense of touch, temperature, pressure, pain and kinesthesia
● Pain
Your body’s way of telling you something is wrong...ultimately it is useful because, in the long run, it
protects you from harm
● How do we experience pain?
● Gate-control theory: pain is a product of both physiological and psychological factors that
cause spinal gates to open and relay patterns of intense stimulation to the brain (sensory
cortex/frontal lobe/limbic system), which then we perceive as pain
→ Substance P = neurotransmitter involved in the transmission of pain messages
● Psychological factors can influence the perception of pain
●
→ Anxiety, fear and a sense of helplessness can increase pain
→ Laughter, distraction and a sense of control can decrease pain
But remember…pain is NOT merely the result of stimulation…
● Phantom limb pain: people who are missing a limb (due to physical defect or amputation)
feel painful sensations that seem to come from the missing part
●
Neurological studies show that the “phantom pain” does not originate from damaged
nerves in the sensory pathways…but from the brain itself
Taste (gustation)
● Saliva dissolves substances
taste buds (grouped together on papillae)
thalamus frontal/temporal/parietal lobes
● 4 main tastes –
gustatory cell
● 2 other “tastes” identified…
Umami: enhances other tastes & is produced by certain proteins and monosodium
glutamate
●
Astringent: taste produced by tannins, like tea
Taste sensitivity diminishes with age
●
●
Smell (olfaction)
● Olfactory receptors
olfactory nerves olfactory bulb temporal lobe (recognition) or limbic
system (emotion)
● Humans can detect approximately 10,000 odors & olfaction has a large connection with
memory
● Many animals use as a sense of communication via pheromones
Sensory interaction: principle that one sense may influence another, like when smell and taste of food
combine to make “flavor”