2. The Sense of Hearing Physical stimulus: sound waves Physical stimulus: sound waves Sound waves are periodic compressions of air, water or other media. Sound waves are periodic compressions of air, water or other media. Sound waves are “transduced” into action potentials sent to the brain. Sound waves are “transduced” into action potentials sent to the brain.

3. Audition Amplitude refers to the height and subsequent intensity of the sound wave. Amplitude refers to the height and subsequent intensity of the sound wave. Loudness refers to the perception of the sound wave. Loudness refers to the perception of the sound wave. Amplitude is one factor. Amplitude is one factor. Frequency refers to the number of compressions per second and is measured in hertz. Frequency refers to the number of compressions per second and is measured in hertz. Related to the pitch (high to low) of a sound. Related to the pitch (high to low) of a sound.

4. Anatomy of the Ear The ear is divided into 3 parts: The ear is divided into 3 parts: Outer ear Outer ear Middle ear Middle ear Inner ear Inner ear The outer ear includes: The outer ear includes: pinna (pl: pinnae) (A): pinna (pl: pinnae) (A): focus sound waves into middle ear focus sound waves into middle ear help locate the source of a sound help locate the source of a sound external auditory canal (B): external auditory canal (B): pathway to middle ear pathway to middle ear The middle ear includes: The middle ear includes: Tympanic membrane (C) (eardrum) Tympanic membrane (C) (eardrum) vibrates when struck by sound waves vibrates when struck by sound waves 3 middle ear bones transmit information to the inner ear: 3 middle ear bones transmit information to the inner ear: malleus (D) malleus (D) incus (E) incus (E) stapes (F) stapes (F)

5. The inner ear includes: The inner ear includes: Oval window (G): a second membrane, like the eardrum Oval window (G): a second membrane, like the eardrum Semicircular canals (H): part of the vestibular system, involved in balance and equilibrium Semicircular canals (H): part of the vestibular system, involved in balance and equilibrium Cochlea (I): a snail shaped structure containing Cochlea (I): a snail shaped structure containing three fluid-filled tunnels three fluid-filled tunnels auditory receptors (hair cells) auditory receptors (hair cells) Organ of Corti (K) Organ of Corti (K) Hair cells and two surrounding membranes in the cochlea Hair cells and two surrounding membranes in the cochlea

6. Audition Auditory nerve (M) Auditory nerve (M) exits the inner ear and carries information about sound to the auditory cortex exits the inner ear and carries information about sound to the auditory cortex

7. Theories of Pitch Perception Frequency theory - the basilar membrane vibrates in synchrony with the sound and causes auditory nerve axons to produce action potentials at the same frequency. Frequency theory - the basilar membrane vibrates in synchrony with the sound and causes auditory nerve axons to produce action potentials at the same frequency. Place theory - each area along the basilar membrane is tuned to a specific frequency of sound wave. Place theory - each area along the basilar membrane is tuned to a specific frequency of sound wave.

8. Audition Primary auditory cortex located in the superior temporal cortex Primary auditory cortex located in the superior temporal cortex Each hemisphere receives most of its information from the opposite ear. Each hemisphere receives most of its information from the opposite ear. The primary auditory cortex provides a tonotopic map The primary auditory cortex provides a tonotopic map cells are responsive to preferred tones cells are responsive to preferred tones Damage can lead to deficits processing auditory info: Damage can lead to deficits processing auditory info: loss of ability to identify a song or voice loss of ability to identify a song or voice It does not result in a loss of hearing It does not result in a loss of hearing

9. Hearing Loss About 99% of hearing impaired people have at least some response to loud noises. About 99% of hearing impaired people have at least some response to loud noises. Two categories of hearing impairment include: Two categories of hearing impairment include: 1. Conductive or middle ear deafness 2. Nerve deafness

10. Sounds that cause hearing loss Heavy city traffic = 90 decibels Heavy city traffic = 90 decibels Car horn = 110 decibels Car horn = 110 decibels Headphones = 120 decibels (common volume) Headphones = 120 decibels (common volume) Jackhammer = 130 decibels Jackhammer = 130 decibels Rock band at close range = 140 decibels Rock band at close range = 140 decibels Rocket launching = 180 decibels Rocket launching = 180 decibels

11. The Mechanical Senses Mechanical senses respond to pressure, bending, or other distortions of a receptor. Mechanical senses respond to pressure, bending, or other distortions of a receptor. Mechanical senses include: Mechanical senses include: Vestibular sensation (balance) Vestibular sensation (balance) Touch Touch Pain Pain Other body sensations Other body sensations

12. The vestibular sense refers to the system that detects the position and the movement of the head. The vestibular 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. Directs compensatory movements of the eye and helps to maintain balance. Vestibular organ: in inner ear, adjacent to cochlea, consists of: Vestibular organ: in inner ear, adjacent to cochlea, consists of: two otolith organs two otolith organs calcium carbonate particles (otoliths) activate hair cells when head tilts calcium carbonate particles (otoliths) activate hair cells when head tilts three semicircular canals three semicircular canals oriented in three different planes oriented in three different planes filled with jellylike substance that activates hair cells when the head moves filled with jellylike substance that activates hair cells when the head moves

13. Part of the brain which helps process information about our vestibular sense Part of the brain which helps process information about our vestibular sense Angular gyrus Angular gyrus integrates balance and movement info with other sensations integrates balance and movement info with other sensations Located at border between parietal and temporal cortex Located at border between parietal and temporal cortex

14. Somatosensory system refers to sensation of the body and its movements and includes: Somatosensory system refers to sensation of the body and its movements and includes: discriminative touch discriminative touch deep pressure deep pressure cold cold warmth warmth pain pain itch itch tickle tickle position and movement of joints position and movement of joints

15. Touch receptors can be: Touch receptors can be: simple bare neurons simple bare neurons elaborated neuron ending elaborated neuron ending bare ending surrounded by non-neural cells that modify its function bare ending surrounded by non-neural cells that modify its function Part of the brain which helps process information about touch: - Somatosensory cortex of parietal lobe - Info from touch receptors in head enters CNS through cranial nerves - Info from receptors below head enters spinal cord and travels through spinal nerves to brain

16. PAIN Pain depends on many axon types, neurotransmitters, and brain areas. Pain depends on many axon types, neurotransmitters, and brain areas. Mild pain triggers the release of glutamate. Mild pain triggers the release of glutamate. Strong pain triggers the release of glutamate and substance P. Strong pain triggers the release of glutamate and substance P. Substance P results in the increased intensity of pain. Substance P results in the increased intensity of pain. Morphine and opiates block pain by blocking these neurotransmitters. Morphine and opiates block pain by blocking these neurotransmitters.

17. The Chemical Senses: Taste Taste refers to the stimulation of taste buds by chemicals. Taste refers to the stimulation of taste buds by chemicals. Our perception of flavor is the combination of both taste and smell. Our perception of flavor is the combination of both taste and smell. Taste and smell axons converge in the endopiriform cortex. Taste and smell axons converge in the endopiriform cortex. Taste receptors: Taste receptors: modified skin cells modified skin cells excitable membranes release neurotransmitters and excite neighboring neurons excitable membranes release neurotransmitters and excite neighboring neurons replaced every 10 to 14 days replaced every 10 to 14 days

18. Papilla(e): structure(s) on surface of tongue that contain up to 10 taste buds Papilla(e): structure(s) on surface of tongue that contain up to 10 taste buds Each taste bud contains approx. 50 receptors Each taste bud contains approx. 50 receptors Most taste buds are located along the outside of the tongue in humans. Most taste buds are located along the outside of the tongue in humans. Western societies have traditionally described sweet, sour, salty and bitter tastes as the “primary” tastes and four types of receptors. Western societies have traditionally described sweet, sour, salty and bitter tastes as the “primary” tastes and four types of receptors. Evidence suggests a fifth type of glutamate receptor. Evidence suggests a fifth type of glutamate receptor.

19. Various areas of the brain are responsible for processing different taste information. Various areas of the brain are responsible for processing different taste information. Somatosensory cortex responds to the touch aspect of taste Somatosensory cortex responds to the touch aspect of taste The insula is the primary taste cortex. The insula is the primary taste cortex.

20. The Chemical Senses: Smell Olfaction: detection and recognition of chemicals that contact membranes inside the nose Olfaction: detection and recognition of chemicals that contact membranes inside the nose Olfactory cells: receptor cells for smell Olfactory cells: receptor cells for smell Olfactory epithelium: Olfactory epithelium: membrane in rear of nasal passage membrane in rear of nasal passage Contains olfactory cells Contains olfactory cells

21. Which part of the brain helps process information about smell? Which part of the brain helps process information about smell? Axons from olfactory receptors carry information to the olfactory bulb in the brain. Axons from olfactory receptors carry information to the olfactory bulb in the brain. The olfactory bulb sends axons to many areas of the cerebral cortex. The olfactory bulb sends axons to many areas of the cerebral cortex. Coding in the brain is determined by which part of the olfactory bulb is excited. Coding in the brain is determined by which part of the olfactory bulb is excited.

22. Vomeronasal organ Vomeronasal organ (VNO): set of Vomeronasal organ (VNO): set of receptors located near the olfactory receptors that are sensitive to pheromones Pheromones: chemicals released by an animal to affect the behavior of others of the same species Pheromones: chemicals released by an animal to affect the behavior of others of the same species The VNO and pheromones are important for most mammals, but less so for humans The VNO and pheromones are important for most mammals, but less so for humans It is tiny in human adults and has no receptors. It is tiny in human adults and has no receptors. Humans unconsciously respond to some pheromones through receptors in the olfactory mucosa. Humans unconsciously respond to some pheromones through receptors in the olfactory mucosa. Example: synchronization of menstrual cycles Example: synchronization of menstrual cycles

23. Integration of the Senses Synesthesia is the experience of one sense in response to stimulation of a different sense. Synesthesia is the experience of one sense in response to stimulation of a different sense. Suggests some axons from one area have branches to other cortical regions. Suggests some axons from one area have branches to other cortical regions.