Senses & Perception Flashcards
Pathway of light
cornea (3/4 focusing) –> lens (adjusts) –> image on retina –> retinal neurons (initial processing & integration) –> optic nerve –> lgn (thalamus) –> primary visual cortex (occipital)
Binocular Vision Pathway
Visual signals –> optic nerve –> optic chiasm (some crossover) –> both hemispheres receive signals
Fovea
center of retina, light is focused, only red+green cones
Visual Acuity
@ center of gaze, each ganglion gets input from only one or few cones, allowing details.
vs peripheral vision.
Macula
area around fovea, important for driving and reading.
macular degeneration is leading cause of blindness among elderly in developed countries.
Retina layers
first layer (rods, cones) –> middle (interneurons) –> third (ganglion)
Receptive Field (vision cell)
activated when light hits a tiny region in the center, inhibited if around, weak if entire.
Primary Visual cortex
many thin sheets
middle layer cells respond like retinal and lgn cells.
others prefer stimuli shaped like bars/edges at particular orientations (specific for each cell).
External ear
Pinna, External Auditory Canal
Middle Ear
Malleus, Incus, Stapes, Tympanic Membrane
Pathway of Sound Waves
ext. ear –> mid. ear –> oval window –> inner ear –> basilar membrane (separation of tones) –> auditory nerve –> brainstem –> superior temporal gyrus (auditory cortex).
Basilar membrane
covered in hair cells topped w/ stereocilia deflected by tectorial membrane, convert mechanical waves into electric signals.
Left Side
perceives and produces speech, damage can lead to not understanding language.
Taste buds
embedded in papillae, 50-100 specialized sensory cells, detect tastants
Taste Pathway
Taste bud’s sensory cells –> nerve fiber ends –> cranial nerves –> brainstem –> thalamus –> cerebral cortex –> perception.
Smell pathway
Odorants detected by sensory cells of mucus membrane lining roof of nose –> axons pass through perforations in bone –> 2 olfactory bulbs under frontal lobe.
Odorants
Stimulate receptor proteins on cilia of sensory cells, unique pattern of activity.
Touch pathway
Sensory nerves –> spinal cord –> nerves –> thalamus + sensory cortex
Two-point threshold
distance between two points on the skin necessary to distinguish two stimuli.
Nociceptors
respond to stimuli that damage tissue and cause pain.
Persistent Injury
chronic pain, allodynia.
Pain & Itch messages
transmitted by small, myelinated & C fibers (small, unmyelinated).
Small, myelinated fibers
very sensitive, responsible for sharp and fast pain.
Small unmyelinated fibers
slower onset of pain, dull, and more diffuse.
