Auditory and Visual Systems Flashcards
Amplitude
Intensity, measured in decibels (dB)
and perceived as loudness
Frequency
Measured in number of cycles per
second, or hertz (Hz), and perceived as pitch
What is the external ear composed of?
1) Pinna
2) Ear canal
Tympanic membrane
Ear drum, seals ear canal
What is the middle ear composed of ?
1) Tympanic membrane
2) Ossicles
3) Oval window
Ossicles
The malleus (hammer), incus (anvil), stapes (stirrup)
What are the ossicles connected to?
The tympanic membrane on one side and the oval window on the other side.
What do the tensor tympani and stapedius do ?
They control volume
Oval window
Connects ossicles to inner ear
& focuses vibrations from sound waves
into the inner ear.
How does sound travel through our ears?
1) Funneled into the ear canal by the pinna and reaches the ear drum
2) Ossicles work to concentrate and amplify the sound
3) Focuses the sound on the oval window which is the entrance to the inner ear
Inner Ear
The cochlea converts vibrational energy into neural activity
Where does sensory transduction occur?
Organ of Corti
The Organ of Corti
Part of the cochlea that converts sound into neural activity
What is the Organ of Corti composed of ?
Tectorial membrane, hair cells, basilar membrane
Basilar membrane
Basal end: Membrane is narrow and stiff
Apex: Membrane is wide and flexible
Tonotopically organized
Neurons or other cells within a neural structure are arranged spatially according to their sensitivity to different sound frequencies
Review steps
- Sounds are vibrations carried
through the air - Sounds pass through the external
ear and vibrate the tympanic
membrane at a similar frequency - Tympanic membrane activates the
lever-action of the ossicles which in
turn vibrate the oval window. - The oval window vibrates causing
pressure changes in the fluid filled
canals of the cochlea. - Pressure changes in fluid will kick-
start sensory transduction
What protrudes from each hair cell?
Stereocilia
Hair Cell depolarization process
- Deflection of stereocilia puts tension
on tip links - Potassium ion channels are
mechanically forced open - Potassium influxes (depolarization)
- Influx of calcium ions
- Glutamate release via exocytosis onto
auditory nerve cell
Auditory signals run from _____ to _______
Cochlea to Cortex
Vestibulocochlear nerve
Contains auditory fibers from the cochlea, contacts the bases of the hair cells
Transduction steps
1) Hair cells from the organ of corti making contact with vestibular cochlear nerve
2) Auditory nerve fibers terminate in the cochlear nuclei located in the medulla
3) The cochlear nuclei send information to the superior olivary nuclei in the pons (where decussation and binaural hearing take place)
4) Information passed to the inferior colliculi (Primary auditory centers)
5) Outputs go to the medial geniculate nuclei of the thalamus
6) Pathways from the MGN of the thalamus terminate in the primary auditory cortex
Why does the superior olive have a medial and lateral component ?
Intensity and latency differences
Duplex theory
Sound localization requires processing of both intensity and latency differences
Sensorineural deafness
Hair cells fail to respond to the movement of the basilar membrane, no action potentials fired.
Conduction deafness
Disorders of the outer or
middle ear prevent sounds
from reaching the cochlea
Central deafness
Damage to auditory brain areas, such as by stroke, tumors, or traumatic brain injury
Wavelength
Distance between two adjacent crests of vibratory activity
High frequency wave
Short distance between peaks
Low frequency wave
Long distance between peaks
The eye needs to convert __________ into ____________ that the brain can interpret
Light energy (photons), electrical signals
Iris
Colored portion of the eye
Sclera
Outermost tissue layer, tough
Cornea
Transparent tissue at the anterior part of the eye
Anterior chamber
Behind the cornea, in front of the lens- contains fluid
Posterior chamber
Behind lens, contains fluid
Aqueous humor
A fluid that light passes through and is nutrient rich
Vitreous humor
A thick, gel-like substance that fills the back of the eye and supports shape
What does vitreous humor contain
Phagocytic cells
Lens
Specialized transparent
tissue (almost like glass) that
refracts the passage of light - which
allows for visual acuity/ sharpened
image
What do the ciliary muscles do?
Changes the shape of the lens and supports viewing far and near objects
Distant objects
Ciliary muscles are relaxed, lens gets flatter
Near objects
Ciliary muscles are contracted, lens gets rounder
Retina
In the back, contains photoreceptors
Fovea
In the back, responsible for high visual acuity due to packed amount of cones
Pigmented epithelium
Melanin-containing thin layer at the back of the eye that prevents light scattering and contains photoreceptor cells, bipolar cells, and ganglion cells.
Rods
Photoreceptors responsible for vision in low light, helps us see in the dark
Cones
Color
Seeing in low light
scotopic system
Seeing in color
photopic system
What cells do not send action potentials?
Photoreceptors, bipolar, & horizontal cells
Graded
cells can release varying amounts of NTs in response to
different levels of local potentials
E.g., More light -> more rhodopsin activation in rods -> less NT release
What does fire action potentials
Ganglion cells
What do ganglion cell axons form
The optic nerve which exits the eye through the optic disk
Optic disk
Does not contain photoreceptors, resulting in a blindspot
Primary visual pathway
Retinal information terminates
in primary visual cortex and striate cortex within the occipital lobe. Most dominant pathway, most of our perceived vision flows through this pathway.
Nasal retina vs temporal retina
Side closest to nose, vs side closest to ears
The optic chiasm
Where visual information crosses
Temporal retina information stays
Ipsilateral
Nasal retina information goes
Contralateral
Optic nerve vs optic tract
One eye, vs both eyes
LGN of the thalamus
major site for termination of optic tract projections
Blindsight
Patients with damage in the primary visual cortex of the brain can tell where
an object is although they claim they cannot see it
Apperceptive Agnosia
inability to copy & intact
object recognition.
Impairment of visual
integration of object features
Associative agnosia
Ability to copy & impaired object
recognition. Impairment of
connection sensory representation to knowledge of object’s meaning
Akinetopsia
“Motion Blindness” - damage to motion
areas (V5) result in “static-y”
movement/stop-motion
