chapter 15 - special senses

what do the special senses of the body include

vision, taste, smell, hearing, equilibrium

special sense of gustation; primarily associated with the tongue; involves chemoreceptors

taste (gustation)

5 primary tastes

sweet, salty, sour, bitter, umami (savory), fat/lipids

for a chemical to be perceived as taste, it must

dissolve in saliva, diffuse into taste pore, and contact gustatory hairs

contain gustatory receptor cells that detect chemicals dissolved in saliva

taste buds

4 types of papillae

circumvallate, fungiform, filiform, foliate

largest taste buds/papillae with 8-12 forming ‘V’ at back of tongue, contain a lot of taste buds

circumvallate

tops of these mushroom shaped-structures house most taste buds; scattered across tongue

fungiform

do not contain taste buds, found all over surface of tongue, create a rough surface for friction to help move found around

filiform

on side walls of tongue; lateral aspect of tongue

foliate

what type of cells release neurotransmitters

activated receptor cells

neurotransmitters stimulate sensory neurons in

facial, glossopharyngeal, vagus nerve

taste likes/dislikes have homeostatic value

guide intake of beneficial and potentially harmful substances

important roles of taste involve

increased salivary secretion and gastric juice production, initiate protective responses

special sense of smell

olfaction

in nasal cavity contains bipolar sensory neurons

olfactory epithelium/receptors

triggered by chemicals (odorants) dissolved in nasal fluid/mucus

chemoreceptors

where do odorants bind to

olfactory receptors on cilia

axons pass through the cribriform plate of the…

ethmoid bone to the olfactory bulb in the frontal lobe

loss of sense of smell; may be caused by blunt trauma shearing olfactory axons, antibiotics damaging neurons; effects= diminished taste perception

anosmia

process of transducing sound waves into neural signals

audition or hearing; ear is divided into external, middle, and inner ear

neuron action potentials travel along the

vestibulocochlear nerve

equilibrium transmissions

vestibular branch

hearing transmissions

cochlear branch

auricle (pinna), auditory canal, tympanic membrane

external ear

eustachian tube (pressure equalization) and ossicles (malleus, incus, stapes)

middle ear

cochlea (hearing) and semicircular canals (balance); part of bony labyrinth within temporal bone; organ of corti in cochlea

inner ear

funnels sound waves into the auditory canal

auricle

transmits sound waves to tympanic membrane (ear drum); ceruminous glands (make ear wax - cerumen)

auditory canal

transfers sound wave energy to the ossicles of the ear (3 tiny ear bones of the middle ear)

tympanic membrane

attached to ear drum

malleus

in between malleus and stapes

incus

fits over the oval window

stapes

vibration is transmitted where? what does it have and purpose

oval window; perilymph fluid that will vibrate from transmission

connects middle ear to nasopharynx and equalizes pressure

pharyngotympanic (eustachian) tube

includes the cochlea (hearing), vestibule, and semicircular canals (balance)

inner ear

transmits signals for equilibrium

semicircular canals

spiral, snail shell shaped structure; contains spiral organ; contains hair cells that when stimulated cause AP’s down cochlear branch

cochlea

houses saccule and utricle; saccule connects to cochlea utricle connects to semicircular canals, each contains macula

vestibule

helps depict linear acceleration but not rotation

macula

depicts rotational movements of the head

semicircular canals

encodes balance and spatial orientation using hair cells with stereocilia acting as mechanoreceptors

vestibular system

detect head position and linear acceleration; BOTH CONTAIN MACULA

utricle and saccule

detect rotational head movements

semicircular canals

neural signals travel via vestibular ganglion through the

vestibulocochlear nerve

in utricle and saccule detect linear movements

maculae

sit atop hair cells

otoliths

three canals (1 horizontal, 2 vertical) detect rotational movement in 3 planes

semicircular canals

swelling at base of each canal contain hair cells with stereocilia embedded in the cupula

ampulla

endolymph fluid lags, deflecting cupula and bending stereocilia in opp. direction of movement

rotation

stabilizes vision during head movement by moving the eyes in the opposite direction of head movement; coordinates eye movements with head movements

vestibulo-ocular reflex

transduction of light into neural signals by the eye

vision

protects eye

bony orbit

eyelids, eyelashes, conjunctiva, lacrimal apparatus, and extraocular muscles

accessory structures

white part of eye; provides structure

sclera

transparent and reflects light, overlays iris and pupil

cornea

contains the choroid, ciliary body, and iris which control light entry and lens shape

uvea

convert light to neural impulses

photoreceptors

focus light onto retina

cornea and lens

opening in iris that regulates light entry

pupil

maintain intraocular pressure and eye shape

aqueous humor and vitreous body

central retina with high visual acuity; fovea centralis is point of sharpest vision (high den. of cones)

macula lutea

blind spot where optic nerve exits; no photoreceptors

optic disc

internal fluids of the eye

humors

anterior cavity

aqueous humor

posterior cavity

vitreous humor

transparent mucous membrane that covers the sclera and the underside of the eyelids

conjunctiva

blood supply to eye layers, brown pigment absorbs scattered light

choroid

colored part of eye, contains sphincter pupillae muscle (constricts pupil)

iris

changes shape of lens to help with light entering

ciliary body

contains lacrimal gland and duct

lacrimal apparatus

produces tears

lacrimal gland

collects the tears after they move across the eye

lacrimal duct

keep the eye moist and contain lysozyme that is antibacterial

tears

cornea, humors, and lens work together to get light to bend on

fovea centralis

6 muscles control eye movement

extraocular muscles

type of muscles are names for where they are located and movement they perform

rectus

moves the eye superior

superior rectus

moves the eye inferior

inferior rectus

moves the eye lateral (abducts)

lateral rectus

moves the eye medial (adducts)

medial rectus

innervates superior rectus, inferior rectus,
medial rectus, and inferior oblique

cranial nerve III (oculomotor)

innervates only superior oblique

cranial nerve IV (trochlear)

innervates only lateral rectus

cranial nerve VI (abducens)

highly sensitive to light, enabling vision in dim conditions; do not detect color (photoreceptors)

rods

detect color; require bright light for function (photoreceptors)

cones

light activates __ which cause a membrane potential that modulates

photopigments, neurotransmitter release

neurotransmitter release generates AP’s that end in the

primary visual cortex

moves the eye down and in and down and out

superior oblique

moves the eye up and out

inferior oblique

connects to cochlea

saccule

connects to semicircular canals

utricle