Flashcards
Sensory Systems
Cards in this deck (27)
- 1Sensory Systems-Photons
-Sound waves
-Chemicals
-Pressure
Physical energy->Stimulus tranduction->Neural activity
-Everything you learn is the result of input from sensory systems (e.g. vision, audition, smell, etc.).
-Peripheral nerves carry info about the environment to the brain where perception occurs. - 2PerceptionPerceptions do not accurately reflect the real world:
-Detection: many forms of energy cannot be detected (e.g. magnetic fields, ultraviolet radiation).
-Translation: Sensory systems must convert one form of energy into electrochemical nerve impulses. - 3Modality(type- e.g. visual)/Quality of the Stimulus-Type of stimulus (e.g. light, color red)
-Nervous system codes this info in two ways: (1) Labeled line code (specialized sensory receptors, e.g. cons) & (2) pattern code (pattern of activity in a variety of receptors, e.g. pattern of activation differs when tasting an apple vs. an apricot)
1. Ad fibers carry fast initial pain sensation. C fibers carry slower, longer-lasting pain.
2. Perceiving color: Three types of cones Red, green, blue. Color perceived depends on a relative activation. - 4Intensity of the Stimulus-Describes how strong a stimulus is.
-Nervous system codes this info in two ways: (1) frequency code (coded by a neuron's firing rate) & (2) population code (coded by the number of active neurons). - 5Duration of the Stimulus-Describes how long a stimulus lasts.
-Encoded by ongoing neural activity. Nervous system responds best to changes in stimuli. A constant stimulus often causes neurons to adapt (i.e. stop firing APs).
-Habituation - the longer a response goes on, the more it lessens. - 6Location of the Stimulus-Describes where a stimulus is.
-Different for each sensory system. - 7Auditory System Detects Sound WavesSound waves are produced by compression & rarefaction of air (vibrations).
- 8Three Components to Sound-Frequency
-Intensity
-Complexity - 9FrequencyHow many cycles/second. Humans hear sounds from 20-20,000 Hz. Experienced as pitch.
- 10IntensityMeasured by wave amplitude (displacement). Loudness.
- 11ComplexityMost sounds are composed of waves of various frequencies, intensities. Timbre, quality.
- 12The EarConverts sound waves into neural activity.
- 13PinnaFunnels sound waves into auditory canal.
- 14Tympanic membranea.k.a. eardrum. Converts air vibrations into mechanical energy.
- 15OssiclesThree small bones (incus, malleus, stapes) that amplify the force of the sound waves.
- 16Oval WindowMembrane that vibrates with the ossicles, creating waves inside the cochlea. Attached to the stapes.
- 17CochleaFluid-filled (endolymph) location of auditory receptors.
- 18The Cochlea-Movement of the oval window creates waves inside the cochlea, which cause the basilar membrane to move. The basilar membrane contains hair cells (receptors for audition).
-Hair cells have stereocilia projecting off the top, which are attached to the overlying tecorial membrane. Movement of the basilar membrane causes the stereocilia to bend. - 19Depolarizing Hair Cells-Stereocilia attached to K+ channels by "springs." Movement of the stereocilia in one direction causes K+ channels to open; when pulled the other way the K+ channels close.
-Open K+ channels: K+ streams into the hair cell, causing depolarization and transmitter release (note: the endolymph has a high K+ concentration). - 20Encoding Pitch-Pitch is encoded by the location of hair cells that respond to the sound. The basilar membrane is thin & tight at the base, & thicker & more flexible towards the apex; therefore, sounds of different frequencies maximally displace the membrane (& thus activate cells) at different sites.
-High pitch/frequency: response at basal end.
-Low pitch/frequency: response at apex.
-Tonotopic organization - not 1:1 - homunculus organization - some frequencies are given more space. - 21Encoding Loudness-Loudness is encoded by creating a bigger wave, which causes a greater displacement of the basilar membrane. This does two things...
1.Causes more hair cells to fire (population code).
2.Creates a greater displacement of the stereocilia, leading to more transmitter release, & thus more frequent AP's (frequency code). - 22Inner Hair CellsAppear to be the primary sensory neurons for audition. There are about 3500 of these, but they are heavily innervated by the auditory nerve (vestibulocochlear, CN VIII).
- 23Outer Hair CellsAre more numerous (about 15,000 neurons), but innervated by only 5% of the auditory nerve. Appear to dampen & amplify sounds by expanding & shrinking.
- 24Central Auditory PathwaysHair cells - vestibulocochlear nerve (VIII) - cochlear nuclei - superior olive nuclei - inferior colliculi - medial geniculate nuclei (thalamus) - auditory cortex (superior temporal gyrus).
-Info shared between left & right sides of the brain before reaching auditory cortex. - 25Tonotopic OrganizationGoing from cochlear base to apex, neurons respond to progressively lower frequencies. This tonotopy (frequency mapping) is preserved throughout the auditory system, from cochlear nuclei to cortex.
- 26Localizing Sounds: Low Frequency SoundsFor low frequency sounds (20-2000 Hz), there is an interaural time delay (difference in when a sound reaches one ear vs. the other ear) if the sound is off to one side or the other (if a sound comes from straight ahead, it reaches both ear simultaneously).
- 27Localizing Sounds: High Frequency SoundsFor high frequency sounds (2000-20,000 Hz), there is an interaural intensity difference between the two ears, because your head blocks the sound; i.e. it casts a "sound shadow."