Anatomy Chapter #17
What are the different structures that would be contacted by a beam of light as it passes through the eye?
Cornea -> pupil and iris -> lens -> vitreous chamber -> retina
What are the different refraction abnormalities of the eye?
Deformations, Myopic, Hyperopic, Cataracts, Blindspots
How does the body sense equilibrium?
Detected by semicircular canals; detect motion in three planes
What happens when in these structures when you spin around and get dizzy?
Fluid is still moving through the semicircular canals
What are the different structures that would be contacted by sound as it passes through the external, middle, and internal ear?
Funneled into auricle/pinna Travels down external auditory canal Causes vibrations in tympanic membrane Vibration transferred to malleus, incus, and stapes ->oval window Sound enters cochlea from oval window
What is the role of the auditory tube in hearing?
It equalizes air pressure; the tympanic membrane can only vibrate correctly when outside air pressure = inner ear pressure
Describe the physiology of vision.
Light is absorbed by photopigments (proteins in the plasma membrane of the outer segment of rods and cones aka photoreceptors) The stimulation of photopigments results in activation of bipolar cells which then activate ganglion that travel to the optic nerve
Describe the structure of the olfactory receptors and other cells involved in olfaction.
Olfactory epithelium, Olfactory receptor cells, Olfactory cilia, Odorants, Supporting cells, Basal cells, Olfactory glands,
Describe the physiology of olfaction.
Olfactory transduction (a generator potential, depolarization, develops and triggers one or more nerve impulses) An odorant binds to a olfactory receptor protein in an olfactory cilium, stimulating a membrane protein called a G protein The G protein activates the enzyme adenylate cyclase to procude cAMP that then opens a Na+ ion channel that allows Na+ to enter the cytosol, which causes a depolarizing generator potential to form in the membrane of the olfactory receptor cell If the depolarization reaches threshold, an action potential is generated along the axon of the olfactory receptor cell
Describe the functions of the accessory structures of the eye.
Palbebra, Eyelash, Lacrimal, Conjunctiva, Lacrimal apparatus
What are the specific structures used to determine equilibrium?
Semicircular canals contain stereocilia embedded within otolithic membrane topped with otoliths Gravity causes the otoliths and otolithic membrane to sway, detected as movement or head position
Where, specifically, in the cochlea is sound perceived?
Sound is perceived at the center of the cochlea at the helicotrema Sound hits a fluid, goes to the center of cochlea and then works its way back out
How does the body localize sound?
Sound localization is based on the amount of time differences it takes for a sound to be heard in one vs the other ear
Regional areas in the tounge were you taste different Tates
Sour: back and sides of tongue Sweet: anterior one-third Bitter: back of tongue Salty: anterior one-third Umami- described as meaty or savory, MSG is known to stimulate umami buds
How does the body sense taste?
Tastants = chemicals that stimulate gustatory receptor cells Tastants are dissolved in saliva, then they can make contact with the plasma membranes of the gustatory microvilli (sites of transduction; where taste is actually sensed; lined with taste receptor proteins) The result of contact with microvilli = receptor potential (depolarization) that stimulates exocytosis of synaptic vesicles from the gustatory receptor cell The liberated neurotransmitter molecules trigger nerve impulses in the sensory neurons that synapse with gustatory receptor cells; different tastes arise from activation of different groups of taste neurons
What are the general tastes that are detected on the tongue and the general area associated with those tastes?
Tastants, Sour, sweet, bitter, salty, umami
Outline the neural pathway for olfaction.
The olfactory nerves terminate in the olfactory bulbs (paired masses of gray matter) Within the bulbs, the axon terminals of olfactory receptor cells form synapses with the dendrites and cell bodies of olfactory bulb neurons Axons of the olfactory bulb neurons extend posteriorly and form the olfactory tract Some of the axons of the olfactory tract project to the primary olfactory area of the cerebral cortex (where conscious awareness of smell begins) Other axons of the olfactory tract project to the limbic system and hypothalamus (emotional and memory-evoked responses to odors: smelling a food that once made you really sick; odor-evoked memory of a childhood moment) From primary olfactory area, pathways also extend to the orbitofrontal area (odor identification and discrimination)
Describe the structure of the olfactory receptors and other cells involved in olfaction. (Olfactory Epithelium)
There are about 10 to 100 million olfactory receptors contained in the olfactory epithelium
How does gustation relate to olfaction?
They are both chemical senses; odors from food can pass upward from the mouth into the nasal cavity, where they stimulate olfactory receptors; a given concentration of food stimulates olfactory system way more than gustatory system bc olfaction is much more sensitive than taste; taste buds also contain supporting cells, basal cells, microvilli and receptor cells
Describe how sound travels through the cochlea.
Vibration of stapes is transferred into scala vestibule and scala tympani, which contain perilymph Sound vibrates the basilar membrane and transfers the vibration into the spiral organ Spiral organ contains tiny hairs called strereocilia, their vibration is what is detected as sound
How does vision and sound perception change as you age?
Vision: lens hardens, making it harder to see up close Sound: high-frequency sounds become less detectable; cochlea has different areas for detecting different frequencies
Describe the physiology of vision. **Operation of photoreceptors in light**
When light strikes the retina and cis-retinal undergoes isomerization, enzymes that break down cGMP are activated As a result, cGMP-gated Na+ channels are closed, inflow decreases and membrane potential decrease to -70 This sequence of events produces a hyperpolarizing receptor potential that decreases the release of glutamate Thus light excites the bipolar cells that synapse with rods by turning off the release of an inhibitory neurotransmitter The excited bipolar neurons stimulate the ganglion cells to form action potentials in their axons
What is the function and structure of the Retina
actually contains photoreceptors (rods and cones); highly vascularized (why albino eyes are red when light is shined on them)
Describe the structure of the olfactory receptors and other cells involved in olfaction. (Olfactory receptor cells)
bipolar neurons with an exposed knob-shaped dendrite and axon projecting through the cribriform plate that ends in the olfactory bulb
Describe the physiology of vision. **Operation of photoreceptors in darkness**
cGMP ligand-gated Na+ channels open, causing an inflow of Na+ ions (aka dark current) This partially depolarizes the photoreceptor and changes the membrane potential from resting -70 to -30; this causes neurotransmitters (amino acid glutamate) to be released Glutamate triggers IPSPs that hyperpolarize the bipolar cells and prevent them from transmitting signals to the ganglion cells
Describe the functions of the accessory structures of the eye. (Lacrimal)
caruncle: contains sebaceous and sudoriferous glands; function is unknown (doesn't create tears, they are just collected there
What is a odorant?
chemicals that have an odor that bind to and stimulate the olfactory receptors in the olfactory cilia
Describe the structure of the olfactory receptors and other cells involved in olfaction. (Odorants)
chemicals that have an odor that bind to and stimulate the olfactory receptors in the olfactory cilia; these olfactory receptors in the plasma membrane of the olfactory cilia detect inhaled chemicals. Olfactory receptor cells respond to the chemical stimulation of an odorant molecule by producing a generator potential, thus initiating the olfactory response
Describe the structure of the olfactory receptors and other cells involved in olfaction. (Supporting cells)
columnar epithelial cells of the mucous membrane lining the nose; they provide physical support, nourishment, and electrical insulation for they olfactory receptor cells
What is the function and structure of the Vitreous Chamber
contains vitreous body; purpose is to hold retina against choroid
Describe the structure of the olfactory receptors and other cells involved in olfaction. (Olfactory cilia)
extend from the dendrite of olfactory receptor cells, the site of olfactory transduction (conversion of a stimulus into a graded potential in a sensory receptor)
What is hyperopic in the eye
far-sighted (can see well far away); eye is too tall
Describe the functions of the accessory structures of the eye. (Lacrimal apparatus)
forms true tears (lacrimal fluid); lubricates and protects the eye from dust, etc; basic flow: produced in lacrimal gland -> excreted through lacrimal duct -> goes across eye ->superior and inferior lacrimal canal -> lacrimal sac -> nasolacrimal duct -> nasal cavity
What is Filiform papillae
hair-like structures that provide friction for swallowing but no taste buds; cover entire surface of tongue
What is the function and structure of the Pupil
hole that light goes through; size = amount of light you're in; big pupil= less light, small pupil= more light
What is a Tastant
it can activate any taste receptor anywhere on the tongue AND chemicals that stimulate gustatory receptor cells
What is cataracts in the eye
lens becomes cloudy; associated with aging or diabetes, family history, or meds can contribute
What is Myopic in the eye
near-sighted (can see well up close); eye is too long
What is Foliate
present in early childhood, also have taste buds, but degenerate; located in small lateral trenches
What is a Vallate Papillae
primary location of taste buds; 12 large form a v at the back of the tongue. Each papillae houses 100-300 taste buds
What is Fungiform
primary location of taste buds; scattered all over the tongue
Describe the functions of the accessory structures of the eye. (Eyelash)
protection from foreign objects, sweat, and direct rays of the sun; infection creates a sty
What is the function and structure of the Cornea
protective; no true focusing ability, assists in gathering light
What is the function and structure of the Iris
regulates amount of light entering in the pupil; pigmented by melanin
what are blind spots in the eye
retina can become unattached from choroid; not abnormal, everyone has it
Describe the functions of the accessory structures of the eye. (palpebra)
shade during sleep, protection, prevents excessive light from entering eye
Describe the structure of the olfactory receptors and other cells involved in olfaction. (Basal Cells)
stem cells located btw the bases of the supporting cells. They continually undergo cell division to produce new olfactory receptor cells
Describe the functions of the accessory structures of the eye. (Conjunctiva)
thin membrane that covers inner eyelid and sclera; vascular and origin of blood shot eyes; infection causes pink eye (conjunctivitis)
How does the lens perform accommodation?
viewing distant objects, your lens is flattened bc it is being stretched in all directions; the lens becomes more spherical when looking at something up close...this increases its focusing power and causes greater convergence of the light rays
What is a Deformation/astigmatism in the eye
when light strikes the eye, its blurry
Describe the structure of the olfactory receptors and other cells involved in olfaction. (olfactory glands)
within the CT that supports the olfactory epithelium; they produce mucous that is carried to the surface of the epithelium by ducts; help transduction occur
What is the function and structure of the Lens
works with ciliary muscles to properly focus light; ciliary muscles relaxed, lens flattened = focusing on distance; ciliary muscles contracted, lens rounded = focusing on near objects.