Midterm 2

• Ossicles - 3-bone lever system that converts large weak oscillations into smaller, more powerful ones
• Pinna - Your external ear, individually distinct; used for localization
• Oval window - membrane at the base of the upper chamber of cochlea; Membrane against which the "Stapes" pushes
• The Auditory Canal is an air channel that leads to the tympanic membrane (aka eardrum)
• Cochlea - Snail-like coiled chamber housing auditory receptor cell
• Timing differences - Involves a race betwen "Onset" cells from the cochlear nucleus via "Inter-Aural Time-Disparity Detectors"
• Phase difference - Concerns which ear is pressured by the condensation, and which by rarefaction of air molecules; best for lower frequencies
• Intensity difference - sound at ear closer to source is more intense than at other due to head shadow; best for higher frequencies
• Basilar membrane - floor of central scala media (cochlea canal); up/down vibration
• Tectorial membrane - ceiling of cochlea canal; left/right vibration
• 1. When cilia bent towards longest cilium, K+ gates open, K+ enters
  2. Influx of K+ decreases polarity from -60 mv
  3. chain reaction allows Ca++ to enter cell —> releases excitatory NT Glutamate
• When cilia bent towards shortest cilium, K+ leaves cell and Ca++ is actively pumped out —> restores polarity
• Place coding - physical structure/displacement of the basilar membrane influences the neurological response to incoming sound; different places along the membrane resonate to different frequencies
• Volley Principle - argues that only if the ganglions are "phase locked" will they produce a volleys of activity at a rate that matches the incoming frequency
• Temporal Coding - entire basilar membrane tends to oscillate at the same rate as the incoming frequency; some hair cells can release more NT than others but fire at same rate
• Inner hair cells - ~3500 per ear, divergent connectivity, 1:Many; codes frequency with little to no loss of info
• Outer hair cells - ~ 12000 per ear, convergent connectivity, Many:1; can’t encode detailed frequency info but can convey amplitude info
• Auditory Pathway

  1. inner & outer hair cells
  2. Spiral ganglions - axons of which form auditory nerve
  3. Cochlear nucleus - monaural site (left receives from left, right from right)
  4. Superior Olive - first biaural site
  5. Inferior colliculus - integrates with visual info from superior colliculus
  6. Medial geniculate nucleus (MGN) - memory
  7. A1 - primary projection area
  8. A2 - secondary auditory cortex
  9. Higher auditory - processes complex patterns, integrates auditory input with other perceptual and cognitive activity
• Isomerization - converting light into a neural signal
• Opsin - long protein chain; visual purple turns pink with light
• Retina - composed of neurons, multi-layered, covering rear inner wall of eyeball
• Fovea - small central area of high concentration of cones only for high detail resolution
• Bipolars - post-synaptic to receptors, show spontaneous firing, graded potentials, released excitatory NT
• Receptive field (RF)- set of receptors whose activity influences the activity of a “target” cell
• Ventral stream (who/what pathway)- for identifying stimuli; specialize in color + detail
• Dorsal stream (where/how pathway)- for visio-spatial mapping; detects motion, locating, navigating, manipulating environment
• Trichromatic color vision - 3 cone types; each with different type of opsin that determine which wavelengths that cone responds to
• Color Opponency - red/green, blue/yellow, black/white opponent system
• Color Constancy - humans recognize colors even under changing light conditions (where actual wavelengths change)
• Most striate muscles come in Antagonistic pairs
• Flexor - muscle that brings the attached bone toward the center of the body
• Sarcomere - The contractile unit within each muscle fiber
• Striate (skeletal) muscle - connected to tendons to bones, voluntary movements; band of parallel fibers
• extensor - muscle that moves bone away from body
• Cardiac (heart) muscle- has endogenous rhythms of activity, modified by neurons
• Smooth (organ) muscle - can sustain contraction, mostly automatically controlled
• Mysosin - thick protein filament with knobby bead-like clusters; has cross-bridges
• Actin - thin protein filament, coiled double-strand braid, anchored to muscle
• Ca++ enters the muscle cell, triggering the cross-bridges to activate, contracting the muscle
• Stretch reflex - proprioceptors called spindles in muscle detect passive stretch of muscle; proprioceptors directly excite motor neurons