Boron Chapter 15 Sensory Transduction

Aspartame

Artificial sweeteners made from two amino acids: L-aspartyl-L-phenylalanine methyl ester

Umami

The taste of the amino acid glutamate (monosodium glutamate)

Capsaicin

Ingredient in hot peppers that stimulates heat-sensitive pain receptors

Mucoid layer

Wets the surface of the cornea and allow the tears to spread smoothly

Lysozymes

Enzyme in tears, saliva, human milk and mucus that damages the bacterial cell wall and prevents infections

Cornea

Thin, transporting epithelium that covers the external portion of the eye and is devoid of blood vessels

Ciliary epithelium

Secretes aqueous humor

Canals of Schlemm

Drain the aqueous humor

Glaucoma

Excess fluid pressure (aqueous humor) in the anterior chamber of the eye

Lens

Onion-like structure with closely packed columnar cells arranged in concentric shells and encased by a thin, tough, transparent capsule that is composed of epithelial cells, hleps to refract light on the retina

_-crystallins

Proteins that help increase the density of the lens and enhance its focusing power

Accommodation

Changing the shape of the lens shifts the focal point of the eye

Presbyopia

With age, the lens becomes stiffer and less able to accommodate (diminished ability to focus on near objects)

Myopia

Eye is too long, distant objects focus in front of the retina and appear blurred (nearsightedness)

Hyperopia

Eye is too short, near objects focus behind the retina and appears blurry (farsightedness)

Astigmatism

Uneven curvature of the refractive surfaces of the eye produces an inability to foucs a point source of light on the retina

Iris

Adjusts opening of the pupil and helps regulates the total amount of light that enters the eye

Miosis

Constriction of the pupil

Mydriasis

Dilation of the pupil

Retina

Contains light-sensitive photoreceptors that capture photons and convert their light energy into chemical free energy

Rods

Photoreceptors responsible for monochromatic dark-adapted vision

Cones

Photoreceptors responsible for color-sensitive vision in brighter environments

Fovea

Central area of the retina that collects light from the center of our gaze (only cones)

Rhodopsin

G protein coupled receptor for light made up of opsin (protein) and retinal

Retinal

Aldehyde of vitamin A (retinol)

Opsin

GPCR found in the photoreceptor cells of the retina

Transducin

G protein that couples to rhodopsin receptors in the retina

Phosphodiesterase

Hydrolyzes cyclic guanosine monophosphate to 5_-guanosine monophosphate

Bleaching

After isomerization of 11 cis-retinal, all-trans retinal and opsin separate

Monochromacy

Lack of two of the three functional cone pigments leading to color blindness

Stereovilli

Projections on hair cells that cause cation channels to open or to close when they are bent in one direction

Perilymph

Extracellular fluid in caompartments of the inner ear with relatively low [K+], high [Na+]

Endolymph

Extracellular fluid in caompartments of the inner ear with relatively high [K+] and low [Na+]

Semicircular canals

Detect head rotation

Saccule

Otoliths move against a vertically oriented macula and detect movement of the head up and down

Utricle

Otoliths move against a horizontally oriented macula and detect tilting of the head

Macula

Contain hair cells that detect movement or linear acceleration of the head

Otoliths

Crystals of calcium carbonate

Vestibulocochlear nerve

Transmits sound and equilibrium information from the inner ear to the brain

Crista ampullaris

Clusters of sensory epithelium in the semicircular canals

Ampulla

A bulge in the semicircular canal that contains the sensory epithelium

Cupula

Gelatinous dome-shaped structure that cover the hair cells of the crista ampullaris

Pinna

Skin-covered flap of cartilage that funnels sound waves into the external auditory canal

External auditory canal

Cylinder lined with skin that penetrates into the temporal bone and directs sound waves to the tympanic membrane

Tympanic membrane

Membrane that transmits sound waves from the air to the ossicles

Eustachian tube

Connects the middle ear to the nasopharynx

Ossicles

Transfer vibrations of the tympanic membrane to the oval window

Tragus

Smal, pointed extension of the outer ear

Tensor tympani

Muscle that inserts onto the malleus, exerts some control over the stiffness of the ossicle and dampens the transfer of sound waves to the cochlea (oval window)

Stapedius

Muscle that inserts onto the stapes, exerts some control over the stiffness of the ossicle and dampens the transfer of sound waves to the cochlea (oval window)

Cochlea

Spiral of three parallel, fluid-filled tubes that performs the auditory function of the ear

Scala vestibule

Perilymph-filled cavity in the cochlea that conducts sound vibrations to the scala media

Reissner's membrane

Separates the scala vestibuli from the scala media

Scala media

Endolymph-filled cavity in the cochlea between the scala tympani and the scala vestibuli

Organ of Corti

Part of the cochlea that contains the sensory hair cells for hearing

Scala tympani

Perilymph-filled cavity in the cochlea that is separated from the scala media by the basilar membrane

Tectorial membrane

Collagen containing structure in the cochlea that stimulates the sensory hair cell in response to sound waves

Prestin

Motor protein that causes contraction in outer hair cells when they depolarize

Pacini's corpuscle

Mechanoreceptor in skin that is sensitive to pressure and vibrations

Meissner's corpuscles

Mechanoreceptor in skin that is sensitive to light touch and tactile discriminations

Proprioception

Sense of body position and movement including direction and speed

Muscle spindles

Measure the length and rate of stretch of the muscles

Golgi tendon organs

Gauge the force generated by a muscle by measuring the tension in its tendon

Nociception

Specialized sensory endings that transduce painful stimuli