Chapter 17 Special Senses

hyperopia

Farsightedness Eyeball is too short Image focused behind the retina

taste thresholds and adaptation

Low to high threshold: bitter > sour > salty & sweet complete adaptation to specific taste can occur in 1-5 minutes; adaptation d/t changes in taste receptors, olfactory receptors, neurons of gustatory pathway in the CNS

external ear contains

auricle (pinna); captures sound external auditory canal; transmit sounds to eardrum tympanic membrane (eardrum) ceruminous glands= secrete cerumen (earwax) for protection

high frequency (high pitched) sounds induce maximal vibrations in what region of the ear low frequency sounds cause maximal vibration of the basilar membrane in what region

base of cochlea because basilar membrane is narrower and stiffer there apex of the cochlea as the basilar membrane is wider and more flexible

2 maculae

in walls of utricle and saccule; have receptors for static equilibrium

photopigments rods contain cones contain photopigments respond to light in a

integral colored protein that undergo structural changes when absorb light rods contain only rhodopsin cones contain 3 different photopigments cyclical process

The olfactory epithelium covers the interior surface of the _____ and extends along the ______

interior surface of the cribriform plate extends along the superior nasal concha

Images focused on the retina are

inverted and right-to-left reversed due to refraction. The brain corrects the image.

vascular tunic

iris: regulars amount of light that enters eye ciliary body; secretes aqueous humor and alters shape of lens for near or far vision choroid; provides blood supply and absorbs scattered light

Basal stem cells (olfactory) function?

undergo mitosis to replace olfactory receptor cells

vision

uses visible light which is part of the electromagnetic spectrum

Myopia

(nearsightedness) Eyeball is too long, so focal point is in front of retina Corrected with a concave lens

Bleaching and Regeneration of Photopigments

1. Isomerization of retinal = trans-retinal 2. trans-retinal separates from OPSIN (BLEACHING) 3. retinal isomerase converts trans- to cis-retinal 4. cis-retinal binds to OPSIN (REGENERATION)

Physiology of Gustation

1. Tastant (chemical stimuli) dissolve in saliva 2. makes contact with plasma membranes of the gustatory microvilli (site of taste transduction) 3. creates receptor potential (depolarization) that stimulates exocytosis of neurotransmitter from the gustatory receptor cells 4. other tastants, bind to receptor on the plasma membrane that are linked to G proteins --> activates second messengers --> depolarization > release of neurotransmitter ex: Na+ ions in salty food enters gustatory receptor cells via Na+ channels and cause depolarization -> release of neurotransmitter ex: H+ ions in sour foods enter gustatory > release of neurotransmitter

physiology of hearing

1. auricle directs sound waves to external auditory canal 2. waves strike tympanic membrane, air waves cause tympanic membrane to vibrate 3. this causes malleus to vibrate along with tympanic membrane > vibration transmitted to incus > stapes 4. stapes vibrates > vibrates oval window 5. causes fluid pressure waves in perilymph of cochlea > as oval window bulges inward, it pushes the perilymph of the scala vestibuli 6. pressure waves transmitted from scala vestibuli to scala tympani and eventually the round window, causing it to budge outward into middle ear 7.As the pressure waves deform the walls of the scala vestibuli and scala tympani, they also push the vestibular membrane back and forth, creating pressure waves in the endolymph inside the cochlear duct. 8. The pressure waves in the endolymph cause the basilar membrane to vibrate, which moves the hair cells of the spiral organ against the tectorial membrane. Bending of the hair cell stereocilia produces receptor potentials that ultimately lead to the generation of nerve impulses in first order neurons in cochlear nerve fibers

Operation of Rod Photoreceptors in darkness

1. cGMP-gated Na+ channels open 2. inflow of Na+ (dark current) 3. depolarization releases inhibitory neurotransmitter glutamate (IPSP) which inhibits bipolar cells from transmitting signals to ganglion cells which provide output from the retina to the brain

Operation of Rod Photoreceptors in light

1. isomerization of retinal activates enzyme that breaks down cGMP 2. cGMP-gated Na+ channels close 3. Inflow of Na+ slows 4. Hyper polarizing receptor potential 5. Glutamate release turned off, which excites bipolar cell

3 types of olfactory epithelium cells

1. olfactory receptor cells 2. supporting cells 3. basal cells

transduction of sound vibrations by the ear's sensory receptors into electrical signals is _________ times ________ than the response to light by the eyes photoreceptors

1000x faster than the response to light by the eyes

sound becomes uncomfortable to a normal ear at

120 dB

Cochlea is divided into

3 channels; cochlear duct scala vestibuli scala tympani

Taste buds contain what? Where are taste buds located?

Contain receptors for taste Papillae of tongue, soft palate, pharynx and epiglottis

fibrous tunic

Cornea: admits and refracts light Sclera: provides shape and protects inner parts

3 types of papillae that contain taste buds?

Vallate papillae; contain high amounts of taste buds 100-300 Fungiform papillae; 5 taste buds each Foliate papillae; located in lateral trenches of tongue - most taste buds degenerate in early childhood

Lens must _____ to properly focus object

accommodate

Olfactory transduction: what happens? chemical reactions involving cyclic AMP (cAMP) cause what? action potential travels where? Impulse travels to where for odor identification?

binding of an odorant molecule to an olfactory receptor protein chemical reaction involving cAMP cause depolarization (Na+ influx) action potential travels to the primary olfactory area impulse travels to the frontal lobe (orbitofrontal area) for odor identification

Otoliths

calcium carbonate crystals

Where is vision sharpest?

central fovea; where an image is projected

the auditory tube (eustachian tube)

channel between the middle ear and the nasopharynx regulate air pressure in middle ear

vitreous humor of eye

contains vitreous humor that helps maintain shape of eyeball and keeps retina attached to choroid

anterior cavity of eye

contains aqueous humor that helps maintain shape of eyeball and supplies oxygen and nutrients to lens and cornea

Iris function in vision

controls size of pupil based on autonomic reflexes pupil constricts as circular muscles of iris contract (parasympathetic) pupil dilates as radial muscles of iris contract (sympathetic)

Light passes through which structures in order?

cornea > anterior chamber > pupil > posterior chamber > lens > vitreous humor > projected onto retina

Antigmatism

defective curvature of the cornea or lens of the eye

Wavelength

distance between 2 consecutive peaks of an electromagnetic wave

Hearing; sound vibrations are transmitted from the eardrum through which structure(s) to the oval window

eardrum through the auditory ossicles = malleus, incus, stapes

Accessory structures of vision

eyelids eyelashes eyebrows lacrimal apparatus (tear producing) extrinsic eye muscles

Papillae that do not contain taste buds

filiform papillae; contain tactile receptors = increase friction to make it easier for tongue to move food

The lacrimal apparatus function? pathway for tears?

function: produce and drains tears pathway: lacrimal glands > lacrimal ducts > lacrimal puncta > lacrimal canaliculi > lacrimal sac > nasolacrimal ducts carry tears into > nasal cavity

vision photopigments contain 2 parts

glycoprotein opsin derivative of vitamin A, retinal

Hearing vs Equilibrium

hearing = response to vibrating air molecules equilibrium = sense of motion, body orientation, balance

Olfaction threshold is high or low

low, only a few molecules need to be present in air ex: methyl mercaptan

The exact center of the retina is the ____________. In its center is the _____________ which is the area of _____________.

macula lutea fovea centralis = area of highest visual acuity

cone photopigments regenerate _______ than the rhodopsin in rods

much more quickly

the two visual fields of each eye are _______ and _______

nasal (medial) temporal (lateral)

How quickly does adaptation (decreasing sensitivity) to odors occur? When does complete insensitivity occur? reduced sensitivity involves adaption of?

olfactory receptors adapt by 50% in the 1st second complete insensitivity occurs in 1 minute after exposure reduced sensitivity involves adaptation in the CNS as well as receptor

vestibular apparatus

organs that maintain equilibrium; saccule, utricle (both otolithic organs), semicircular canals

From the rods and cones of the retina, information flows:

outer synaptic layer > bipolar cells > inner synaptic layer > ganglion cells Axons exit as the optic nerve (II)

vibrations are transmitted from the stapes through the _______ _________ (20x more vigorous than tympanic membrane) to the _________ as fluid pressure waves are transmitted into the ___________ of the ___________. From here, pressure waves travel to the ______ and then to the ______ which bulges into the middle ear

oval window cochlea perilymph of the scala vestibuli scala tympani round window

If all tastants cause release of NT from many gustatory receptor cells, why do foods taste different?

patterns of nerve impulses in groups of first-order taste neurons that synapse with the gustatory receptor cells different taste arise from activation of different groups of taste neurons

rods and cones contain ________ necessary for the ________ that will initiate the events that lead to production of a ________

photopigments absorption of light receptor potential

The retina contains sensors _________ known as ___________

photoreceptors; rods and cones rods = dim light cones = color vision

Supporting cells (columnar epithelium) function?

physical support, nourishment and electrical insulation for olfactory receptor cells

Olfactory glands (Bowman's glands) function?

produce mucus that is used to dissolve odor molecules so that transduction (conversion into electrical impulses) may occur

retina

receives light and converts it into receptor potentials and nerve impulses output to brain via axons of ganglion cells which form the optic nerve

lens

refracts light

Gustation (taste)

sensation that results from action of chemicals on taste buds

Olfaction

sense of smell from chemical stimuli

5 primary tastes

sour, sweet, bitter, salty, umami

Equilibrium: two types

static; maintenance of body relative to force of gravity static equilibrium stimulated by tilting of head and linear acceleration or deceleration dynamic equilibrium: maintenance of position in response to sudden movements > rotational acceleration and deceleration

hair cells have on their surface:

stereocilia of graduated height, 1 kinocilium extending beyond the longest stereocilium

6 extrinsic eye muscles

superior rectus, inferior rectus, lateral rectus, medial rectus superior oblique, inferior oblique

Taste buds contain 3 kinds of epithelial cells

supporting cells, gustatory receptor cells, basal stem cells

sense of tasted direction from receptor to brain

taste buds house receptors > Facial nerve (VII), glossopharyngeal nerve (IX), vagus nerve (X) > gustatory nucleus in the medulla oblongata > thalamus > primary gustatory area of cerebral cortex

Olfaction: receptors in the nasal mucosa send impulses for smell along where?

through cribriform plate synapse with the olfactory bulb impulses travel along the olfactory tract interpretation in the primary olfactory area and the cerebral cortex (temporal lobe)

stereocilium is connected to a mechanically gated ion channel called the ________? as the stereocilium bend in the direction of the taller stereocila, transduction channels open and allow cations in the endolymph, primarily _________ as cation enters, causes what bending of the stereocilia in the opposite direction does what

transduction channel primarily K+ enter the hair cell cytosol depolarizing receptor potential which spreads along plasma membrane and triggers exocytosis of neurotransmitter. As more NT is released, the frequency of nerve impulses in the first order sensory neurons increases closes the transduction channels > hyperpolarization > reduces neurotransmitter release > decrease frequency of nerve impulses

cochlea function semicircular canals function

translates vibrations into neural impulses that the brain can interpret as sound work with cerebellum for balance and equilibrium