Exam 3 (Unit 8, 9, 10, 11, 12) Flashcards
Frequency
-Physical property of sound
- # of compressed or rarefied patches of air
that pass by your ears each second (Hz)
What is a sound?
- Compression of particles in the air
- Crest= compressed air
- valley= rarefied air
Amplitude
- Physcial property of sound
- Different in pressure between compressed and rarefied patches
- Increased amp, increased volume
Complexity
- Physical properties of sound
- In nature, sounds are a mixture of frequencies, amplitudes, and their time courses
Pitch
- Perceptual properties of sound
- Quality of a tone that is described as “high” or “low”
Loudness
- Perceptual properties of sound
- Magnitude of auditory sensation, (decibels or dB)
Timbre
- Perceptual properties of sound
- Differentiates two complex sounds of same fundamental pitch and same loudness
Outer Ear
- Pinna= outer ridges
- Focuses sound to auditory canal
Middle Ear
- Recieves airborne vibrations via large tympanic membrane (drum)
- Moves ossicles (stapes, bone) against small oval window
Ossicles
- 3 tiny bones ands 2 muscles that move them
- Help to decrease amount of energy lost by sound waves going from air (external ear) to fluid (inner ear)
Oval Window
-Stapes presses against the oval window, transduces vibrations from ossicles into waves of fluid
Round Window
-Membrane permits movement of fluid
Inner Ear
- Contains the cochlea
- a spiral bony canal which is filled with fluid (hearing), and the vestibular apparatus, which is similarly comprised
Cochlea
- Within Inner ear
- Acts like a frequency analyzer
- Breaks complex tone into harmonics and responds to each harmonic
- Scalamedia= organ of corti, receptor of sound
- Basal membrane= bottom, tectorial membrane (top), hair cells (middle)
Organ of Corti
- Hair cells in the organ of corti take the fluid movements of the vestibular and tympanic canals of the cochlea and transduce them into receptor potentials
- 1 Inner hair cell row= auditory perception (afferent/sensory)
- 3 outer hair call rows= amplifying and tuning organ of corti (efferent/motor)
- hair cell rows in line with each other
Activation of Hair Cells
- Movement of endolymph in cochlea (wavelike)
- Deforms across the organ of corti
- Basal membrane pushes against techtorial membrane
Transduction in audtion
- Tallest stereocillia bends toward smallest stereocillia–> hyperpolarization of cell
- Tallest bends away from smallest–> depolarized cell
- ***Due to tip links connecting stereocillia- no tension if bend towards, stretching if pulled away (opens K+ channels)
- Depolarization–> release fo Ca+–> hair cell releases glutamate (excites/depolarizes 1st order neuron)
Volley Theory
- Lower frequencies
- Cochlea
- 1st order neuron will respond at rate which sound is moving (frequency)
- Activates hair cell when wave has a volley
Phase Locking
- Volley theory
- a neuron that fires in time with each peak of a sound wave
Place Theory
- Cochlea
- Encoding of sound frequency depends on where sound causes minimal displacement
- Apex tuned for low frequencies
- Base of basilar membrane tuned for high frequencies
- *Organ of corti is more loose as you head towards the apex
Ascending Pathway for hearing
- Spiral ganglion
- Cochlear Nuclei
- Superior Olive
- Inferior colliculus
- Medial Geniculate Nucleus
- Primary Auditory Cortex
Cochlear Nuclei
-Info integrated into left and right audio
Superior Olive
-sound location
Inferior Colliculus
- Auditory spatial map
- Important for reflexive responses to sound
Medial Geniculate Nucleus
- Relay center in hearing
- thalamitic nucleaus
Primary Auditory Cortex
-Conscious awareness of sounds
Semicircular Canals
- Respond to angular acceleration of head (left, right, up, down, ear to sholder/ xyz)
- Cilia in bulb only activated by deformation in one direction
Otolith Organs
- Respond to linear acceleration of head
- Hair cells project into jello substance
- Crystals pull jello and deform cillia
- *crystals deform over time, falling/balance becomes an issue
Pupillary Light Reflex
- Extraocular muscles orient visual field
- Iris dialates pupil in response to light
- Cornea focuses light through pupil
- Ciliary muscles adjust lens shape to focus light on retina (accomodation)
- Retina transduces image; inverted image
Visual Field
- The total amount of space that can be viewed by the retina when the eye is fixed ahead
- Right side of retina= left visual field
- Left side of retina= right visual field
- Upper visual field= bottom of retina
- Lower visual field= top of retina
- Image is inverted
Photoreceptors
- Respond to light (rods and cones)/ electromagnetic energy
- Influence membrane potential of the bipolar cells connected to them
- Outermost part of retina (deepest inside the head, farthest from front of eye)
- Depolarize in dark, hyperpolarize in light (less NTM in light)
Ganglion cells
- Fire action potenetials in response to light
- Impulses propogate along optic nerve to the rest of the brain
- Only source of output in the retina
- Innermost retinal layer= ganglion cell layer
- Types: Mtype and Ptype
Membrane potential at darkness
-Membrane potential in darkness= -30mV
Rod Photoreceptors
- More sensitive to light than cones
- Long, cylinderical outer segment (Lots of disks)
- Scotopic conditions= nighttime lighting, only rods contribute to vision
- Provide poor acuity
- No rods at center of fovea, only periphery
- Unable to distinguish color differences at night
Cone photoreceptors
- Short, tappered outer segment
- Less disks
- Excellent acuity
- Photopic lighting= daytime, cones do work
- Lots of cones at fovea, not as many at periphery
Photopigments
- Rods contain same photopigment (rhodopsin)
- Cones contain 3 diff types (red, blue, green), only responsible for 1 color
- Sensitive to diff wavelengths of light
Phototransduction in Rods and Cones in Dark conditions
-Opsin= GPCR–> Activates 2nd messenger–> opens Na+ channel–> depolarization–> release of glutamate–>depolarization of bipolar cell