Sensory 2

lots of bipolar/ganglia in front of photoreceptor

evolutionary (photoreceptors require lots of energy and close access to the vascular tunic for blood), filtering (only allows straight beams which clarifies vision)

outer synaptic layer of retina

bipolar cells, accepts visual signal from photoreceptors

inner synaptic layer of retina

retinal ganglion cells, accepts visual signal from bipolar cells

optic disc

where ganglia converge at the back of the eye, is a blind spot

the optic disc merges into ____

optic nerve

brain fills in blind spot by:

1) having two eyes

2) constant microadjustments fill in gap for what is missing

3) hypothesize using context clues of whats around

fovea

spot of maximum visual acuity due to photoreceptors (cones only) not obscured by blood vessels or other cells and having one photoreceptor per ganglion cell (50:1 near edges of retina)

rod photo receptor

single kind of opsin: rhodopsin –peak sensitivity at 498 nm

more sensitive than cones – can be activated by single photons

>100 million per eye

light intensity

cone photoreceptors

three kinds of opsins – peak sensitivities at 420 nm (blue), 534 nm (green), 564 nm (red)

less sensitive than rods – require multiple photons for activation

~6 million per eye

cone shape maximizes area of opsins exposed to photons

light color

color

photons with a given wavelength can strike multiple kinds of opsins, our brains compare the relative activation of each type and combine them

most mammals have ____ vision, but humans have___vision

dichromatic, trichromatic

color blindness

decreased ability to see or distinguish shades of color usually caused by genetic defect in opsin genes of cones

olfaction

smell

special sense of olfaction:

olfactory epithelium

odorant molecules

bind to proteins on olfactory epithelium which causes transduction in olfactory receptor cells

olfactory signals do not ____

pass through the thalamus and go straight to the cerebral cortex

gustation

taste

special sense of gustation

taste buds

receptors for all tastes are distributed equally except for

bitter

gustation submodalities: ion channels

salty (Na+), sour (H+)

gustation submodalities: G protein-coupled receptors

sweet (sugars), bitter (wide range of molecules), umami (amino acids)

warning mechanism of salt

helps regulate Na+ levels

reward mechanism of sweet

rewards for energy rich/sugary foods eaten

warning mechanism of bitter

helps avoid eating dangerous toxic compounds

warning mechanism of sour

helps avoid eating unripe and rotten things

reward mechanism of umami

reward for eating protein, likely ancestral taste

flavor

taste+smell