Unit 4: Sensation & Perception Module 14: Hearing

Hearing (Audition) Audition: the sense or act of hearing. Sound waves result from mechanical vibration of molecules from a sound source (e.g. voice or instrument).

Hearing (Audition) Amplitude: The height of the sound wave the determines the loudness. The bigger the amplitude, the louder the sound.

Hearing (Audition) Frequency: the number of complete wavelengths that pass a point in a given amount of time.

Hearing (Audition) = = = = Pitch: the highness or lowness of a sound. Shorter Wavelength Higher Frequency Higher Pitch = = Longer Wavelength Lower Frequency Lower Pitch = =

Hearing (Audition) We are most sensitive to frequencies that correspond to the range of human voices.

Prolonged exposure above 85 decibels produces hearing loss. Hearing (Audition) Decibels – measuring unit for sound energy. Prolonged exposure above 85 decibels produces hearing loss.

Stirrup Semicircular Canals Anvil Hammer Auditory Nerves Cochlea Auditory Canal Ear Drum (Goes to throat)

The Ear Outer Ear: visible part of the ear; channels the sound waves through the auditory canal to the eardrum. Middle Ear: the chamber between the eardrum and cochlea. Inner Ear: innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs.

Middle Ear Hammer, anvil, and stirrup: a piston in the middle ear made up of containing three tiny bones that concentrate the vibrations of the eardrum on the cochlea’s oval window (membrane). Eardrum: a tight membrane that vibrates with the waves.

The Inner Ear Cochlea: a coiled, bony fluid-filled tube in the inner ear through which sound waves trigger nerve impulses. (Looks like a snail!) The vibrations on the cochlea’s oval window cause vibrations that move the fluid in the tube.

The Inner Ear Basilar membrane: lined with hair cells that are bent by the vibrations from sounds and triggers impulses in the adjacent nerve fibers that converge to form the auditory nerve. The neural messages travel via the thalamus to the temporal lobe’s auditory cortex – and we hear!

The Ear Semicircular canals: three fluid- filled bony channels in the inner ear. They provide information about orientation to the brain to help maintain balance. Auditory nerve: axons of neurons in the cochlea converge transmitting sound messages through the medulla, pons, and thalamus to the auditory cortex of the temporal lobe.

The Ear Loud sounds damage the hair cells which accounts for most hearing loss. We detect sound by the number of hair cells activated.

The Ear

Determining Pitch How can you discriminate small differences in sound frequency or pitch? Place theory: we hear different pitches because different sound waves trigger activity at different places along the cochlea’s basilar membrane. Works best with high pitched sounds.

Determining Pitch Waves that peak near the close end of the cochlea are perceived as high-pitched. Waves that peak near the far end are interpreted as low-pitched.

Determining Pitch Frequency theory: we sense pitch by the basilar membrane vibrating at the same rate as the sound. The pitch matches how fast the sound is traveling. Frequency theory explains how you hear low-pitched tones. Place theory explains how we sense high pitches and frequency theory explains how we sense low pitches.

Locating Sounds Sound localization: the process by which you determine the location of a sound. With ears on both sides of our head, you can locate a sound source. The side closest to the source of the sound hears it louder.

Locating Sounds Using parallel processing, your brain processes both intensity and timing differences to determine where the sound is. It is hardest to locate a sound directly in front, behind, above, or below you because the sound hits both ears at the same time.

Hearing Loss Conduction hearing loss: loss of hearing that results when the eardrum is punctured or any of the tiny bones in middle ear lose their ability to vibrate. A hearing aid may restore hearing. Nerve (sensorineural) deafness: loss of hearing that results from damage to the cochlea, hair cells, or auditory neurons. Cochlear implants may restore some hearing.

Unit 4: Sensation & Perception Module 15: Other Important Senses

Touch

TOUCH (SOMATOSENSATION) Somatosensation: the skin sensations, or the sense of touch. Made up of four skin senses: Pressure Warmth Cold Pain Touch is also linked to your brain! Rubber hand illusion

TOUCH (SOMATOSENSATION) These parts can combine to create different touch sensations. For example, burning is pain, warmth, and cold. Itching is gentle stimulation of pain receptors.

Touch – Pain Pain is your body telling you something is wrong. Pain is important because it alert you to injury and often prevents further damage. Those born without the ability to feel pain usually die by early adulthood. Hyperalgesia – increased sensitivity to pain.

Touch – Pain Pain follows a slower and less defined pathway, and requires a psychological and physical explanation. Gate-Control Theory: pain is experienced only if the pain messages can pass through a “gate” in the spinal cord on their way to the brain.

Touch – Pain Massage, electrical stimulation, acupuncture, ice, and the natural release of endorphins can close the gate.

Touch – Pain The gate is opened by small nerve fibers that carry pain signals, and is kept open by things like anxiety, depression, and focusing on the pain. The gate is closed by neural activity of larger nerve fibers, which conduct most other sensory signals, or by information coming from the brain.

Touch – Pain Pain is also in the brain! When we are distracted from the pain, it is lessened. Ex. Athletes often can play through the pain until after the game is over. People also feel more pain if others around them feel pain. “I can feel your pain!” – LITERALLY

Taste

Taste Gustation: the chemical sense of taste with receptor cells in taste buds in fungiform papillae (tissue) on the tongue, on the roof of the mouth, in the throat. There are three kinds of tasters: nontasters, tasters, and supertasters. Molecules must dissolved in saliva or a liquid to be sensed.

Taste Five basic taste sensations are: Sweet Sour Salty Bitter Umami (Meaty Taste) Taste is a chemical sense. Taste buds catch food chemicals.

Taste Flavor is the interaction of sensations of taste and odor with contributions by temperature and texture. Babies show a preference for sweet and salty foods, both necessary for survival; and disgust for bitter and sour, which are characteristic of poisonous and spoiled food.

Taste Taste receptors reproduce every week or two. If you burn your tongue, you might lose taste buds, but they grow back. As you get older, you lose taste buds and taste sensitivity. Smoking and alcohol also kill buds. Sensory Interaction – one sense may influence another. Ex. We need to smell food to taste it.

Smell

Smell Olfaction: the chemical sense of smell with receptors in a mucous membrane on the roof of the nasal cavity. Molecules must reach the membrane and dissolve to be sensed. Only sense that does not go through the thalamus.

Smell Odors evoke memories and feelings. We can recognize odors from past experiences and recall those experiences. Pheromones – chemicals released by animals that triggers a social response by another animal. Role of pheromones in humans are not clear.

Our Senses See Hear Smell Taste Touch

BODY SENSES Kinesthesis: body sense that provides information about the position and movement of individual parts of your body with receptors in muscles, tendons, and joints. e.g. close your eyes and touch your nose.

BODY SENSES Vestibular sense: body sense of equilibrium with hair like receptors in semicircular canals and vestibular sac in the inner ear. If we spin around, we get dizzy because the fluids in your semicircular canals and your kinesthetic receptors have not returned to normal.