Smell, Taste, TOUCH & Hearing Chapter 7 Smell, Taste, TOUCH & Hearing

Sensation and Perception SENSATION: the psychological experience associated with sound, light, or other simple stimulus and the initial information-processing steps by which sense organs and neural pathways take in stimulus information from the environment PERCEPTION: the recognition, organization, and meaningful interpretation of sensory stimuli

Breakdown of the Sensory Systems PHYSICAL STIMULUS: that in the environment that activates the sense organs PHYSIOLOGICAL RESPONSE: pattern of electrical or chemical activity that occurs as a result of the stimulus SENSORY EXPERIENCE: subjective sensation and perception experienced by the person Physical stimulus Physiological response Sensory experience

Each Sensory System Has Distinct Receptors and Neural Pathways SENSORY RECEPTORS: specialized structures (cells or tips of neurons) that respond to physical stimuli SENSORY AREAS: areas of the brain’s cerebral cortex that receive and analyze input from the body’s senses

Sensory Transduction Concepts TRANSDUCTION: process by which a receptor cell produces an electrical change in response to the energy of a physical stimulus RECEPTOR POTENTIAL: the actual electrical charge that occurs in the receptor cell in response to the physical stimulus SENSORY CODING: process by which information about the quality and quantity of a stimulus is preserved in the pattern of action potentials SENSORY ADAPTATION: temporary decrease in sensitivity to sensory stimulation that occurs when a sensory system is stimulated for a period of time, and vice versa

Transduction and Coding for the Sense of Smell Physical stimulus: ODORANTS Sensory Receptors: olfactory receptor cells Location: mucous membrane of the olfactory epithelium

Differences Among People in Olfactory Sensitivity Women are more sensitive to smells than men Sensitivity decreases with age (decline begins at 30) Genetic and environmental influences: ANDROSTENONE & differentiation learning

Discriminating Among Individuals by Smell Smell plays a role in mother-infant bonding Involved in mate selection (major histocompatibility complex) PHEROMONES: a chemical that is released by an animal and that acts on other members of the species to promote some specific behavioral or physiological response Vomeronasal Organ

Anatomy and Physiology of Taste Sensory receptors: taste receptor cells Location: Tongue (Taste buds), roof of the mouth, entrance of the throat

Five Primary Tastes SALTY SOUR BITTER SWEET UMAMI Best stimulus: NaCl Best stimulus: H+ ions BITTER Best stimulus: quinine SWEET Best stimulus: glucose/fructose UMAMI Best stimulus: Monosodium Glutamate

An Evolutionary Account of Taste Quality What is edible (safe) and what is not (poisonous)? Sour taste due to bacterial decay; bitter taste due to toxic compounds Women and children are most sensitive to bitter

Neural Pathways for Pain Physical stimuli: pressure vibration (to judge an object’s roughness) temperature pain (events that cause tissue damage)

Touch Sensory Receptors C fibers: thin, unmyelinated, slow-conducting (dull, radiating, longer-lasting pain) A-delta fibers: thicker, myelinated, faster conducting (sharp, initial pain) Limbic system – the amygdala, hippocampus, thalamus, hypothalamus, basal ganglia, and cingulate cortex, insulate cortex. Emotion and memory centers.

Touch Sensory Receptors Damage to cingulate cortex, insulate cortex = asymbolia Stress-induced analgesia Belief-induced analgesia Extreme, painful rituals Placebo effect Meditation

Sound as a Physical Stimulus AMPLITUDE  LOUDNESS (Decibels) FREQUENCY  PITCH (Hertz) High Amplitude Low Amplitude Low Frequency High Frequency

How the Ear Works

The Inner Ear Tectorial membrane

Deafness and Hearing Aids Sensorineural deafness results from damage to the hair cells or auditory neurons A COCHLEAR IMPLANT may be used to transmit electrical impulses directly to the cochlea by means of an implant Conduction deafness occurs when the ossicles (hammer, anvil, stirrup) fail to move and transmit vibrations to the inner ear

Von Bekesy (1961) High frequencies produce a wave that travels a short distance Low frequencies produce a wave that travels a longer distance Which part of the cochlea is being worn out the most?