Psych210 quiz2&exam

Freberg_3e_PPT_ch07.pdf

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Nonvisual Sensation and Perception

Chapter Seven

• Intensity: amplitude of sound wave – Vary from quiet whisper to rock band – Logarithmic scale of intensity (decibels, dB)

• Frequency: wavelength of a sound wave – Determines pitch – Single frequency = pure tone – Multiple frequencies (timbre vs. noise) – Measured in cycles per second in units of

Hertz (Hz)

Audition: Sound as a Stimulus

The Auditory World Differs Across Species

Sound Results From the Collision of Molecules

Sounds Vary Along the Dimensions of Amplitude, Frequency, and Complexity

Intensity Levels of Common Sounds

• The outer ear – Pinna; auditory canal

• The middle ear – Tympanic membrane (eardrum) – Ossicles (malleus, incus, stapes) – Oval window

• The inner ear – Semicircular canal; cochlea

The Structure and Function of the Auditory System

The Anatomy of the Ear

• Three chambers – Vestibular canal (perilymph) – Tympanic canal (perilymph) – Cochlear duct (endolymph)

• Organ of Corti (inner and outer hair cells)

• Separated by membranes – Reissner’s membrane – Basilar membrane: tectorial membrane – Round window

The Cochlea

Sound Frequencies Are Translated by the Basilar Membrane

The Movement of the Cilia Regulates Neurotransmitter Release by Hair Cells

• Spiral ganglia neurons communicate with cochlear hair cells and the dorsal and ventral cochlear nuclei of the medulla

• Cochlear nuclei synapse directly or indirectly with the inferior colliculus

• The inferior colliculus projects to the medial geniculate nucleus (MGN) of the thalamus

Central Auditory Pathways

• The MGN projects to the primary auditory cortex

• Primary auditory cortex – Columns respond to single frequencies

• Secondary auditory cortex – Activated by complex stimuli – Separate pathways process the “what” and

“where” of sound

The Auditory Cortex

Auditory Pathways from the Cochlea to the Cortex

Tonotopic Organization is Maintained by the Auditory Cortex

• Pitch perception – Tonotopic organization (place theory) – Temporal theory

• Loudness perception – Decibel level describes physical qualities of

sound stimulus – Loudness is the human perception of that

stimulus – Equal loudness contours – Decibel range of auditory neurons

Auditory Perception

Equal Loudness Contours

• Horizontal plane – Comparison of arrival times of sounds at each

ear – Differences in intensities between each ear – Binaural neurons

• Vertical plane – Pinna

Localization of Sound

We Localize Sound by Comparing Arrival Times at Both Ears

• Age-related hearing loss – Poor circulation to the inner ear; exposure to

loud noise • Damage to outer or middle ear

– Conduction loss due to wax build-up, infection, or otosclerosis

– Treated with hearing aids • Damage to inner ear, auditory pathways,

or auditory cortex – Treated with cochlear prosthetics

Hearing Disorders

Cochlear Prosthetics

• The somatosensory system provides information related to: – The position and movement of the body – Touch – Skin temperature – Pain

The Body Senses

• Movement receptors of the inner ear – Otolith organs

• Utricle and saccule • Head position and linear acceleration

– Semicircular canals • Rotation of the head

The Vestibular System

The Vestibular Structures of the Inner Ear

• Central pathways – Axons from vestibular organs travel along

auditory nerve to the cerebellum and vestibular nucleus

– Axons from vestibular nucleus communicate with spinal cord and ventral posterior (VP) nucleus

– VP nucleus projects to primary somatosensory cortex and primary motor cortex

The Vestibular System

• Skin structure – Hairy and glabrous (hairless) skin – Epidermis, dermis, subcutaneous tissue

• Mechanoreceptors – Encapsulated: Meissner’s and Pacinian

corpuscles – Nonencapsulated: Merkel’s disks and Ruffini’s

endings – Free nerve endings – Two-point discrimination test

Touch

Mechanoreceptors in the Skin

Major Features of the Mechanoreceptors

Two-Point Discrimination Thresholds

The Four Classes of Sensory Axons Differ in Size and Speed

• Signals from mechanoreceptors travel from skin along Aβ axons to the dorsal roots of the spinal cord: dermatomes

• From the spinal cord, axons travel along the dorsal column-medial lemniscal pathway to the dorsal column nuclei of the medulla

Touch Pathways

• Axons from the dorsal column nuclei cross the midline to the contralateral ventral (VP) posterior nucleus of the thalamus, then project to the primary somatosensory cortex

• Touch information from the head travels to the VP nucleus via the cranial nerves

Touch Pathways (cont’d.)

Dermatomes Are Areas of Skin Served by the Dorsal Roots of One Spinal Nerve

Touch Pathways

Somatosensory Areas of the Thalamus

The Sensory Homunculus

• Somatosensory cortex rearranges itself in response to changes in the amount of input it receives – Phantom pain – Referred sensations

The Plasticity of Touch

• Damage to the primary somatosensory cortex – Sensation and movement deficits

• Damage to the secondary somatosensory cortex – Neglect syndrome

Somatosensory Disorders

• A purpose for pain – Emotional, cultural, and experiential

components – Relays information about tissue injury

• Receptors for pain – Nociceptors – Mechanical injury, extreme temperature, and

certain chemicals activate nociceptors

Pain

• Ascending pain fibers – Myelinated Aδ (quick, sharp pain) – Unmyelinated C fibers (dull ache) – Glutamate and substance P

• Spinal cord to the substantia gelatinosa to the spinothalamic pathway; synapse in the thalamus – Pain signals from head/neck travel along the

trigeminal nerve, synapse in the spinal trigeminal nucleus; forms trigeminal lemniscus

Ascending Pain Pathways to the Brain

• Spinothalamic and trigeminal lemniscus fibers synapse in VP nucleus or intralaminar nuclei of the thalamus

• Communicate with the anterior cingulate cortex and somatosensory cortex

• Gate theory of pain – Explains the effect of context on pain

perception

Ascending Pain Pathways to the Brain (cont’d.)

Ascending Pain Pathways

• Higher level brain structures project to the periaqueductal gray (PAG) of the midbrain

• PAG projects to the raphe nuclei of the medulla and the spinal cord

Descending Pain Pathways to the Brain

Descending Messages Influence Pain

• Opioid activity • Periaqueductal gray (PAG) associated

with cultural, emotional, and experiential influences on pain sensation

Managing Pain

• Sense of smell • Detection of airborne molecules • Olfactory receptors: bipolar

– Line the olfactory epithelium in the dorsal nasal cavity

– Olfactory neurons form the olfactory nerve – Molecules dissolve in mucus surrounding

olfactory receptors – Depolarization sends action potentials to the

olfactory bulb via the olfactory nerve

The Chemical Senses: Olfaction

• Signals to the olfactory bulb are sorted by glomeruli

• Olfactory bulb axons form olfactory tracts, project to the olfactory cortex – Does not synapse in thalamus first

Olfactory Pathways

• Olfactory cortex connects to the medial dorsal nucleus of the thalamus, which projects to the insula and the orbitofrontal cortex

• Olfactory signals are interpreted as odor identification, motivation, emotion, and memory

Olfactory Pathways (cont’d.)

Olfactory Information Travels from the Epithelium to the Brain

• Sense of taste – Protection from poisonous or spoiled food – Attraction to foods is necessary for survival

• Dissolved chemicals in saliva • Five major taste classes

– Sweet, sour, bitter, salty, umami

The Chemical Senses: Gustation

• Found on tongue and other areas of the mouth

• Papilla contain taste buds • Taste buds have 50-150 receptor cells

– Receptor cells are not neurons, but can form synapses

– Microvilli project into saliva – Transduction mechanisms for chemical stimuli

result in depolarization of taste receptor cells

Gustatory Receptors

The Taste Receptors

• Taste fibers in tongue form parts of cranial nerves VII, IX, and X

• Cranial nerves synapse with gustatory nucleus of the medulla

Gustatory Pathways

• Axons from gustatory nucleus synapse in the ventral posterior medial (VPM) nucleus of the thalamus – Projects to the gustatory cortex in the parietal

lobe for identification of primary taste qualities – Projects to the orbitofrontal cortex in the

frontal lobe for combination with olfaction and vision to produce flavor perceptions

Gustatory Pathways (cont’d.)

Gustatory Pathways to the Brain