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how sensations occur

stimulation of receptors leads to impulses in afferent neuron - pathway leads to cerebral cortex for interpretation


change in environment that initiates response in a receptor

sense receptor

specialized nerve ending or cell which detects a specific change in the environment

simple receptor

specialized ending of nerve cells found throughout the body

complex sense receptor

localized in head and made of distinct receptor cells

where conscious sensation is produced

cerebral cortex


sensations persist after simulus has been removed



sensations are referred to point of stimulation

once a sensation forms, the brain interprets the impulse to have come from the receptors being stimulated -- the brain then projects the sensation back to its source
ex. eye sees object, nose smells food


sensations disappear even though stimulus is still present

information about internal environment

interoreceptors (visceral receptors)

taste, fatigue, hunger, thirst, nausea

interoreceptors (visceral receptors)

information about position + movement


information about external environment


hearing, sight, touch, temperature


sensations that
adapt slightly or not at all

visual receptors (tonic receptors)

general or cutaneous senses


general or cutaneous senses:
simple or complex receptors?


excessive stimulation of sense organ


special senses


special senses:
simple or complex receptors?


location of receptors for
sense of smell

superior nasal epithelium

cranial nerve that carries info
for sense of smell

I cranial nerve (olfactory)

location of receptors for
sense of taste

taste buds embedded in epithelium of tongue

cranial nerves that carry info
for sense of taste

VII cranial nerve (facial)
IX cranial nerve (glossopharangeal)

four basic tastes

salty, sour, bitter, sweet

part of tongue sensitive to each taste

sour = lateral tongue
salty = lateral / tip of tongue
sweet = tip of tongue
bitter = posterior tongue

(this classic map is currently being questioned)

three basic layers of the eye

fibrous tunic (sclera + cornea)
vascular tunic (choroids, ciliary body, + iris)
sensory tunic (retina)


opening in center of iris


thin muscular diaphragm responsible for eye color


clear portion of outermost tunic
allows for light passage


white of eye


changes shape to aid in focusing

fibrous tunic

outermost layer of eye

vascular tunic

middle layer of eye
contains many blood vessels

sensory tunic

innermost layer of eye
layer that contains photoreceptors

fovea centralis

most sensitive portion of innermost layer

"dip" at posterior retina in diagram

optic disc

area where optic nerve exits eye

ciliary body

contains smooth muscle
produces aqueous humor

function of
suspensory ligaments

(attach to lens)

function of iris

regulates amount of light entering eye

function of cones

color vision

function of ciliary body

focus and produces aqueous humor
(contains ciliary muscle to pull suspensory ligament)

function of tears

protection + keep eyes moist

function of
extrinsic eye muscles

move eyeball

function of rods

vision with low light
(gray vision)

function of optic nerve

carries impulses from eye to brain

function of
nasolacrimal duct

allows tears to enter nasal cavity

function of lens

focus light onto retina

function of choroid

vascular - nourishes eye

function of pupil

hole - allows light into eye

function of lacrimal gland

produces tears

function of sclera

provides shape of eyeball
anchor for eye muscles

function of cornea

clear - allows light to enter

regulation of size of pupil

smooth muscle in iris regulates size of opening (pupil)

controlled by autonomic nervous system
--> sympathetic dilates
--> parasympathetic constricts

intrinsic eye muscles

ciliary body

anterior chamber

space in front of lens
space between iris + cornea

posterior chamber

space between lens + iris

aqueous humor

fills spaces (anterior chamber + posterior chamber)

where aqueous humor is produced

ciliary body

function of aqueous humor

supplies nutrients + oxygen to lens and cornea

where aqueous humor drains

scleral venous sinus
(canal of Schlemm)

posterior segment

space behind lens

vitreous humor

gel-like substance present at birth

fills posterior cavity (space behind lens)

function of vitreous humor

transmits light
holds lens + retina in psition
maintains eye pressure


bony cavity in skull that surrounds eyeball


eyelids - skin-covered structures that can be drawn over the eye


mucous membrane lines eyelids + covers cornea

function of conjuctiva

prevents eye from drying out


bending of light

where refraction occurs


definition of

adjustability of lens to focus light onto retina

how accommodation occurs

contraction + relaxation of ciliary muscles alters tension on suspensory ligaments to change shape of lens

definition of
optic chiasm

part of brain where optic nerves cross

what occurs at optic chiasma

crossing over of optic nerves allows medial fibers to cross from one optic tract to the other

where nerve impulses from retina are
interpreted visually

occipital lobe of cerebral cortex


inability to focus lens with aging


decreased transparency of lens


increased intraocular pressure due to blocked drainage of aqueous humor


caused by elongation of eyeball


distortion of visual image caused by irregularity of cornea


inflammation of mucous membrane lining eyelid and covering cornea


caused by short eyeball

detached retina

pulled away from choroid

sense receptors contained in ears

hearing + equilibrium

location of cochlea

inner ear

location of semicircular canals

inner ear

location of vestibule

inner ear

location of
opening to auditory tube

middle ear

location of ossicles

middle ear

location of auricle

outer ear

location of
external auditory meatus

outer ear

function of auditory tube

equalizes pressure on both sides of tympanic membrane (eardrum)

function of auricle

gathers sound waves

function of ossicles

vibrate against oval window

function of stapedius +
tensor tympani muscles

protect against loud sounds -
limit vibrations of ossicles

function of cochlea

sense of hearing

function of organ of Corti

receptor for hearing

function of oval window

vibrates when stimulated by ossicles to cause vibrations in perilymph of cochlea

function of
tympanic membrane

vibrates with sound waves to set up vibration in ossicles

function of round window

at end of cochlea
dampens vibrations to prevent reverberation into cochlea

function of
external meatus

carries sound waves to tympanic membrane

function of vestibule

sense of equilibrium (utricle + saccule monitor position of head when head is not moving)

static equilibrium

function of
semicircular canals

sense of equilibrium (monitor position of head when head is moving)

rotational equilibrium

glands in
external auditory meatus

ceruminous glands

what ceruminous glands produce

ear wax to trap dust + repel insects

separates outer and middle ear

tympanic membrane

names of the ossicles


connected by the
auditory tube

middle ear cavity + pharynx

nerve that transmits info
concerning balance + hearing

VIII cranial nerve (vestibulocochlear)

where nerve impulses from the
organ of Corti are interpreted

temporal lobe of cerebral cortex

otitis media

middle-ear infection

danger of otitis media

can block sound waves (hearing loss)
may spread to mastoid sinus (meningitis)


fluid that fills membranous labyrinth


fluid that fills osseous labyrinth

structures that make up
the labyrinth

vestibule + semicircular canals

receptors in cochlea

hearing receptors

receptors in vestibule +
semicircular canals

vestibular receptors (balance)

how sound is changed
into a nerve impulse

hair cells in organ of Corti bend to create nerve impulse

how info concerning
balance + position is transmitted

mechanoreceptors in semicircular canals + vestibule are hair-like projections that bend to create an impulse


"mismatch of sensory input"


involuntary movements of the eye that may be associated with chronic inner ear disorder (Meniere's disease)

motion sickness

disorder of equilibrium where particular motion leads to nausea + vomiting

nerve deafness

due to damage to hair cells of organ of Corti or auditory pathway to brain

conduction deafness

sound vibrations not conducted to inner ear
can be due to blocked external acoustic meatus, ruptured eardrum, or osteosclerosis (overgrowth of bone in middle ear)

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