sensory systems Flashcards
EXTEROCEPTIVE SENSORY SYSTEMS
Visual
Auditory
Somatosensory
Olfactory
Gustatory
SENSORY SYSTEM ESSENTIALS
Should discriminate among different forms of energy
Should respond reliably and rapidly
Should discriminate among different stimulus intensities
Should suppress extraneous information
All sensory systems have:
specialized organ(s)
specialized receptor cells
* Transduce information (energy) from the environment
a specific pathway from receptor to cortex
* includes a relay center (nuclei) in the thalamus
Secondary cortex
Receives input from the primary cortex
Processes higher-order information (specific form, motion)
Primary cortex
Receives input directly from the thalamus
Processes elementary information (basic form)
Association cortex
Receives input from more than one sensory system and interacts with the motor system
Visible light spectrum
Electromagnetic energy between 380 and 760 nanometers
* VIBGYOR
what are the 3 dimensions of color perception?
brightness
hue
saturation
iris
Eye color and contractile tissue
pupil
Hole in the iris that allows light to enter the eye
sclera
the white of the eye
lens
Focuses incoming light onto the retina using ciliary muscles
retina
Back of the eye where signal transduction occurs
includes fovea & optic nerve
cornea
The protective covering over the eye
fovea
Indentation at the center of the retina
*Specialized for high acuity vision
optic nerve
Gap in the retinal tissue where the ganglion cell axons leave the eye
can’t see because of completion
Creates a blind spot
photoreceptors
rods - dim lighting/lines
cones - colors
5 layers of cells before signal leaves the eye
Photoreceptors
Horizontal cells (Lateral communication)
Bipolar cells
Amacrine cells (Lateral communication)
Retinal ganglion cells
scotopic vision
*Mediated by rods
*Peripheral to fovea
*Low Acuity - Poor detail
*High sensitivity
*Functions well in dim light
*Lacks color vision
Photopic vision
*Mediated by cones
*Located in the fovea
*High acuity - Fine detail
*Low sensitivity
*Functions only in bright light
*Responsible for color vision
Rhodopsin
Photopigment receptor molecule
*In Rods
Primary visual cortex
Located in the posterior medial occipital Lobe
Receives input from LGN (Thalamus)
Responsible for elemental Processing (basic form, some depth)
Retina-geniculate-striate pathway
Retinal ganglion cells exit eye through blind spot
-> Optic nerve to optic chiasm
-> To optic tract to Lateral geniculate nucleus of the
thalamus
-> Serves as a relay station to primary visual cortex (striate/occipatal cortex) via optic radiations
“What” stream
Primary cortex to inferotemporal cortex
*Ventral pathway
*Responsible for identifying objects
Secondary visual cortex
Receives input from primary & other secondary cortex
Responsible for higher-order processing (form, motion)
“Where” stream
Primary cortex to prestriate cortex
*Dorsal pathway
*Responsible for determining special location and guide movement toward
Association cortex
Parietal Lobe (posterior parietal cortex)
Integrates information across senses & with motor system
Damage at the Retina Level
Myopia (Nearsightedness)
*Difficulty seeing distant objects
*Object focuses in front of the retina
*Can be corrected
Macular Degeneration
* abnormal growth of capillaries leads to retinal detachment or death of the photoreceptors
*blurred central vision
Color deficiency
*Cannot see all colors
*Normal acuity
Damage to secondary or association cortex
Optic ataxia
*Difficulty using vision to reach for and grasp objects
Prosopagnosia (face blindness)
*Inability to recognize faces
Akinetopsia (motion blindness)
*inability to see movement; especially in a smooth pattern
reflectance
The perception of color depends on the wavelength of light that the object reflects
Trichromatic hypothesis
Perception of any color can be created by the ratio of activity in three kinds of receptors
Each has different color sensitivity
* Blue-sensitive cone (short)
* Green-sensitive cone (medium)
* Red-sensitive cone (long)
Opponent process hypothesis
Colors are perceived as paired opposites in three classes of cells
* Red vs Green
* Blue vs Yellow
* Black vs White (brightness)
Cells of the visual system are excited by one color and inhibited by the complementary color
*Hyperpolarization of cell produces one color and depolarization the other
