HEARING SOUND Sound is vibrations of molecules Amplitude

HEARING

SOUND • Sound is vibrations of molecules • Amplitude, wavelength, and purity affect qualities of loudness, pitch, and timbre

HUMAN HEARING CAPACITIES • Frequency (wavelength): measured in cycles per second, hertz (Hz) • Higher frequency creates higher pitch • Humans hear btwn 20 Hz and 20, 000 Hz

HUMAN HEARING CAPACITIES • • Amplitude affects loudness Measured in decibels (d. B) Perceived sound doubles every 10 d. B Loudness requires an interaction of frequency and amplitude

HUMAN HEARING CAPACITIES • Purest sound has only a single frequency of vibration • Most sounds are mixed

SENSORY PROCESSING IN THE EAR • External ear depends on vibrations of molecules • Consists of the pinna • Pinna collects sound and funnels it down the auditory canal to the eardrum

SENSORY PROCESSING IN THE EAR • Middle ear consists of the hammer, anvil, and stirrup • Hammer, anvil, and stirrup are called ossicles • Ossicles amplify changes in air pressure

SENSORY PROCESSING IN THE EAR • Inner ear consists of the cochlea: fluid filled, coiled tunnel that contains receptors for hearing • Sound enters through the oval window • Ear’s neural tissue lies in the cochlea; it sits on the basilar membrane: runs the length of the cochlea, holds auditory receptors • Auditory receptors are called hair cells • Waves in fluids in the inner ear stimulate the hair cells, which convert the motion into neural impulses • Impulses travel to the thalamus, then to the auditory cortex

AUDITORY PERCEPTION: PLACE THEORY • Holds that perception of pitch corresponds to the vibration of different portions, or places, along the basilar membrane • Frequency is detected by specific regions of the basilar membrane

AUDITORY PERCEPTION: FREQUENCY THEORY • Holds that perception of pitch corresponds to the rate, or frequency, at which the entire basilar membrane vibrates • Ex: 3000 Hz would cause the membrane to vibrate 3000 times per second

RECONCILING PLACE AND FREQUENCY THEORIES • Both are valid but both have flaws • Volley Principle: holds that groups of auditory nerve fibers fire neural impulses in rapid succession, creating volleys of impulses • Improves frequency theory

PERCEIVING SOURCES OF SOUND • Auditory localization: locating the source of a sound • 2 cues: intensity and timing of arrival at each ear

OUR CHEMICAL SENSES: TASTE AND SMELL

TASTE: THE GUSTATORY SYSTEM • Physical stimuli for taste are based on chemical substances that are soluble • Taste buds are clusters of taste cells • Taste buds absorb chemical dissolved in saliva, which trigger neural impulses

PRIMARY TASTES • • Sweet, sour, bitter, and salty Some preferences are innate, some are learned Sensitivity to certain tastes depend on density of taste buds Women more likely to be supertasters than men

SMELL: THE OLFACTORY SYSTEM • Olfactory cilia are tiny hairlike structures located in the upper portion of the nasal passages • These receptors have axons that synapse directly with cells in the olfactory bulb at the base of the brain • Only sense not routed through the thalamus

SMELL • Humans can distinguish about 10, 000 different odors • Identifying odors can be difficult • Females tend to be more accurate with identifying odor

SENSE OF TOUCH

FEELING PRESSURE • Skin has receptive fields where CNS cells are most sensitive • Nerves route through the spinal cord to the brainstem • Then project through the thalamus and onto the somatosensory cortex in the parietal lobe • Some cells in the somatosensory cortex respond to specific features of touch

FEELING HOT AND COLD • Skin has warm and cold receptor nerves • When warmth is applied the warm receptors fire rapidly and cold receptors cease and vice versa for when cold is applied

FEELING PAIN • Pain travels to the brain through 2 pathways • Fast pathway registers localized pain---sharp pain---depend on myelinated neurons called A-delta fibers • Slow pathway conveys longer-lasting, aching, or burning pain--depends on unmyelinated neurons called C fibers

PAIN PERCEPTION • Very subjective • Pain can be blocked • Gate-control theory: holds that incoming pain sensations must pass through a “gate” in the spinal cord that can be closed, thus blocking ascending pain signals • Studies suggest that the release of endorphins creates the analgesic effect • Discovery of a descending neural pathway that originates from the periaqueductal gray (PAG) in the midbrain; endorphins initiate activity in the PAG

OTHER SENSES

KINESTHETIC SYSTEM • Monitors the positions of the various parts of the body • Some receptors are in the joints---indicate bending • Others reside in the muscles---register tautness, or extension

VESTIBULAR SYSTEM • Responds to gravity and keeps you informed of your body’s location in space • Provides sense of balance (equilibrium) • Located in the inner ear • Semicircular canals make up largest part