chapter 15: special senses

olfaction

smell

gustation

taste

odorants

dissolve in nasal mucous and bind to chemioreceptors to produce a smell

olfactory epithelium

smell sensory organ, contains olfactory receptor cells, supporting cells, and basal cells

olfactory receptor cells

bipolar neurons modified to detect odors, contain enlarged ends called olfactory bulbs

olfactory hairs

modified cilia with chemoreceptors

what happens when odorants bind to chemoreceptors

adenylate cyclase converts ATP to cAMP opening ion channels

t/f: olfactory nerves travel through the thalamus to the cerebral cortex

false

taste cells

receptors of taste, found in taste buds

taste buds

sensory organ of the mouth/throat, found in papillae

lingual papillae

bumps on your tongue, come in 4 shapes

shapes of papillae

filiform, vallate, foliate, fungiform

filiform papillae

only type of papillae to have no taste buds. most common. help manipulate food. found towards the middle of the tongue.

vallate papillae

form a v on the back of the tongue, only 8-12 in the mouth

foliate papillae

most sensitive taste buds, found on the sides of the tongue

fungiform papillae

scattered randomly along the tongue, appear as red dots

taste pore

apex of taste cell

taste hairs

microvilli extending through the taste pore

tastant

chemical that dissolves in saliva and enters taste pores to create a taste

types of tastes

sour, salty, sweet, bitter, umami

sour taste

occurs when hydrogen ions flood a cell. taste buds found on the inferior lateral parts of the tongue.

salty taste

when sodium diffuses through leak channels. taste buds found on the posterior lateral parts of the tongue.

bitter taste

when tastants bind to g-protein receptors. most sensitive taste. taste buds found on the back of the tongue

sweet taste

when tastants bind to g-protein receptors. taste buds found on the front of the tongue

umami taste

when amino acids bind to g-protein receptors

palpebrae

eyelids

lacrimal glands/ducts/canals/sac

the path tears take. through the gland to the duct, into your eyes, and drained out of the canals into the sac in your nose

fibrous tunic

outside layer of eye. contains cornea and sclera

vascular tunic

middle layer of the eye. contains iris, choroid, and ciliary body

nervous tunic

most deep layer of the eye, contains retina

how do we see (simply)

light hits the lens, which reflects it onto the retina, making it an action potential which travels along the optic nerve to the brain

visible spectrum

the part of the light spectrum we can see

refraction

bending of light when it hits an object denser than the air, causing its speed to slow

convex

thickest in the center, shape of the lens

focal point

where light rays converge

t/f: you see upside down and inverted, but your brain fixes it

true

accomodation

the ciliary muscles pull on the lens to change its shape and shift focus

what happens when you go from looking at something close up to something far away?

ciliary muscles relax, making suspensory ligaments tighten and pull on the lens

pupil constriction related to distance

small pupil means your looking ahead at a distance, big pupils mean you’re looking at something close

emmetropic

perfect vision

hyperopia

farsightedness: light focuses behind the retina instead of on it, causing blurry vision up close

myopia

nearsightedness: light focuses in front of the retina instead of on it, causing blurry vision at distances

presbyopia

age-related decline in vision, causing farsightedness

astigmatism

instead of forming one image due to the refraction, two images are created, resulting in blurred vision

rods

detect light levels

cones

detect color

dark current

photoreceptors continuously release glutamate. stops when light is perceived, which makes bipolar cell depolarize, generating an action potential

why are rods unique

they are depolarized at rest, light causes hyperpolarization

rhodopsin

chemical in membranous discs of rod, contains opsin + retinol

how do rods turn light into an action potential?

retinol changes shape from cis to trans when in contact with light, which makes the alpha proteins break off of the g protein, causing GPT to GTP and cGMP to GMP, which closes sodium leak channels, creating hyperpolarization

colors perceived by cones

red, blue, green

sounds with a bigger amplitude

louder

sounds with more frequency

higher pitched

timbre

how smooth a wave is

how do we hear?

soundwaves strike the tympanic membrane which vibrates causing the ossicles to also vibrate and hit the oval window. the sound travels through the scala vestibuli and produces a wave in its perilymph which distorts the endolymph and activates the hair cells which either depolarize or hyperpolarize depending on the input. while that information goes to the brain, the waves enter the scala tympani and exit through the round window.

scala vestibuli

runs from the oval window to the heliocotrema

scala tympani

runs from the heliocotrema to the round window

perilymph

fluid in scala vestibuli/tympani

endolymph

fluid in the basilar membrane/scala media

hair cells

sterocilia sensory receptors that detect wavelengths in the spiral organ/organ of Corti that convert wavelengths to action potentials

kinocilium

longest sensory hair, direction it points determines if the cell depolarizes or hyperpolarizes

movement towards kinocilium

potassium channels open, cell is depolarized, neurotransmitters are released

movement away from kinocilium

potassium channels close, cell is hyperpolarized

static labyrinth

evaluates the position of the head relative to acceleration, contains the utricle and saccule

dynamic labyrinth

evaluates the position of the head in a 3d plane, contains the semicircular canals

utricular macule

senses horizontal movement

saccular maccule

senses vertical movement

otoliths

tiny crystals embedded un the otolith membrane which weigh the membrane and the macular hairs down, making it more sensitive to movement

cupula

on top of the crista ampularis in the ampula, hair cells that act as a float and are displaced by movement