1.Does ThatMake Sense?Crosswords

2. Exteroceptors are sensory receptors that Types, distribution,receive external stimuli located in hands,feet, face and other sensitive body party.Viceroreceptors are receptors that include and functions ofthose located in visceral organs such asthe heart, liver and kidney. receptorsProprioceptors are sensory nerve receptorssituated in the muscles, tendons, and jointsthat furnish information to the centralnervous system concerning themovements and positions of the limbs,trunk, head, and neck, and, morespecifically for dentistry, the oral cavityand its associated structures. (5)Mechanoreceptors detect changes inpressure, position, or acceleration; includereceptors for touch, stretch, hearing, andequilibrium.Chemoreceptors detect ions or molecules.Smell (olfaction) and taste rely onchemoreceptors.Thermoreceptors detect hot or coldtemperatures.Photoreceptors have pigments in receptorcells that absorb light energy and triggeraction potentials. (6)nociceptor is a sensory receptor that sendssignals that cause the perception of painin response to potentially damagingstimulus. (7) 3. Balance & Hearing HearingBalance The outer ear includes both the fleshy protrusion from the head and theThe human balance system works from the collaboration of threecomponents: the visual (eyes), skeletal systems (the muscles andcanal that leads to the ear drum. The ear canal is where cerumen (i.e. earjoints and their sensors), and the vestibular system (inner ear wax) is generated and stored. The outer ear acts as a funnel for sound,balance organs). Nerve signals from those three componentsdirecting sound towards the ear drum.are accurately sent to and processed by the brain to keep The inner ear is composed of a series of interconnected fluid-filled canalshuman balance. (17)encased in the dense bone of the skull (the temporal bone). Lining portionsThe function of the utricle and the saccule is to detect theposition of the head. Both these two cavities contain a pad ofof these canals are the cells that have tiny hairs at their tops that vibrate withcells, laid with a jelly-like substance, which in turn has smallmovement of the inner ear fluids. Vibration of these hairs induce these cells granules of chalk embedded inside. When the body is straight, appropriately called hair cells -- to begin the chain reaction that leads tothe gravitational force makes these granules press againstnerve impulses carried along the hearing and balance nerves.sensitive hairs in the jelly. The hairs then send nerve signals to thebrain that tell it, upright. When the head leans front, back or The middle ear is an air-filled cavity that bridges the ear drum with thesideways, the chalk granules push against the hairs, and bend membranous window of the inner ear fluids. The middle ear contains thethem in a different direction. This sends off new messages to the three smallest bones in the body the incus, malleus, and stapes that formbrain, which can then, if needed, send out instructions to thethis bridge. These three bones, or ossicles, are interconnected so as tomuscles to immediately adjust the position of the body. Theutricle is also springs into action when the body starts to movefocus the forces of ear drum motion in order to drive the inner ear fluids toforwards or backwards. If a child, for example, begins to run, thevibrate during sound stimulation. The middle ear in abnormal cases canchalk granules get pushed back against the hairs, which makes collect body fluid and bacteria, and this situation is what occurs in the typicalit seem as if the child were falling backwards. As soon as theear infection commonly seen primarily in children.brain receives this information it sends out signals to the muscles;this makes the body lean forwards thus restoring its balance. (18) The external ear acts as a funnel for sounds. Sound travels inside the ear toDynamic equilibrium - The special sense which interpretsthe tympanic membrane (eardrum). The sound waves that come intobalance when one is moving, or at least the head is moving; the contact with the tympanic membrane are converted into vibrations that aresemicircular canals contain the receptors for dynamic sensed by a group of tiny bones, known as the middle ear ossicles. They areequilibrium; within each semicircular canal is a complexcomprised of the malleus (hammer), incus (anvil) and stapes (stirrup). Themechanoreceptor called a crista ampullaris which contains themechanoreceptors (Hair cells) for dynamic equilibrium; when the malleus is the first to conduct the vibration, which then continues through theperilymph in one of the semicircular canals moves, the hair cells incus and ends at the stapes, which is in contact with the oval (vestibular)in the crista ampullaris are stimulated to send nerve impulses to window, which separates the middle ear from the inner ear. The function ofthe brain; this advises the brain of whether or not a person hasthe inner ear starts when conduction of the sound wave reaches the ovaltheir balance during body movements or if their body is inmotion, e.g, riding in a car or turning ones head from side to side. window. The sound wave then travels through the cochlea, which looks like a(19)snails shell. The cochlea is divided into three fluid-filled chambers. Differentchambers are receptive to different frequencies. The signal then goes intothe cochlear duct causing vibration of endolymph (a specialized fluid) wherethe signal is converted into an electrical impulse that is transferred to thecochlear and vestibular nerves. The brainstem sends the signal to themidbrain and then subsequently to the auditory cortex of the temporal lobesof the brain where the electrical impulses are interpreted as the sounds thatwe experience. (20) 4. Golgi tendon organs are receptor organs thatgives the body information about the forcethat a muscle is developing as it contracts.Muscle spindles are stretch receptors in musclecells involved in maintaining muscle tone.Pacinian corpuscles are receptors deep in thedermis that detects pressure on the skinsurface.Structure of receptorsMeissner corpuscle are sensory receptorslocated in the skin close to the surface thatdetects light touch.Merkel disks are expanded dendrite endings.Root hair plexuses are entwined around theroot of each hair is a twirl of dendrites.Free nerve endings are dendrites of sensoryneurons that are specialized receptors in theskin that respond to pain. (9)(11)(8)(12)(10) 5. Olfactory receptors expressed in the cellmembranes of olfactory receptor neurons areresponsible for the detection of odor molecules.Olfactory pathways are a set of nerve fibersconducting impulses from olfactory receptors tothe cerebral cortex.Compare Olfactionin a Human and Smell & Tastewith a canine: dogshave an olfactorysenseapproximately100,000 to1,000,000 timesmore acute than ahumans.Taste buds any of theclusters of bulbousnerve endings on thetongue and in thelining of the mouththat provide the senseof taste.Neural pathways areneural tractsconnecting one partof the nervous systemwith another. 6. The pupil, which is the opening in the colored part of Structures of the Eye the eye (iris). The iris controls the size of the pupil in response to light outside the eye so that the proper Cavities and Humors amount of light is let into the eye. The lens, which is located behind the iris and isThe front of the eye houses the anterior cavity which is normally clear. Light passes through the pupil to thesubdivided by the iris into the anterior and posterior lens. Small muscles attached to the lens can changechambers. The anterior chamber is the bowl-shaped its shape. Tightening or relaxing these muscles causes the lens to change shape, allowing the eyes to focus cavity immediately behind the cornea and in front of the on near or far objects.iris. The posterior chamber of the anterior cavity lies behind Vitreous gel (also called vitreous humor), which is athe iris and in front of the lens. The aqueous humor forms in thick liquid that fills the eye. It helps the eyeball maintain its shape.this chamber and flows forward to the anterior chamber The retina, which is a thin nerve membrane thatthrough the pupil. detects light entering the eye. Nerve cells in the retinaThe posterior cavity is lined entirely by the retina, occupies send signals of what the eye sees along the optic60% of the human eye, and is filled with a clear gel-like nerve to the brain. The optic nerve, which is the nerve at the back of the substance called vitreous humor. Light passing through the eye that carries visual information from the eye to thelens on its way to the retina passes through the vitreous brain. humor. The macula, which is near the center of the retina at the back of the eyeball. The macula provides theThe vitreous humor consists of 99% water, contains no cells, sharp, detailed, central vision a person uses forand helps to maintain the shape of the eye and support its focusing on what is directly in the line of sight. internal components.Eye Muscles The aqueous humor is a clear watery fluid which facilitates2 Types Of Eye Muscles: good vision by helping maintain eye shape, regulating the Accessory Structuresintraocular pressure, providing support for the internalExtrinsic: Skeletal muscles that Eyebrow &structures, supplying nutrients to the lens and cornea, andattach to the outside of the Eyelashes: Cosmeticdisposing of the eyes metabolic waste.eyeball and to the bones ofpurpose and givethe orbit. They move the protection againsteyeball in any desired foreign objects. Eyelids: Consistdirection and are, voluntary mainly of voluntarymuscles. muscle and skin.Intrinsic: smooth, involuntary Lacrimal Apparatus:muscles located within the Secrete tears toeye. Consist of the iris and remove foreignciliary muscles, which control objects from thethe shape of the lens. face of the eyeball.(2) 7. Formation of retinal image: There are four processes thatfocus light so that they form a clear image. Refraction- bending of light rays Accommodation- increase in curvature,constriction of pupils, and convergence of two eyes Constriction- called near reflex of the pupil and Retinal Imageoccurs simultaneously with accommodation of the lens in nearvision Convergence- seeing only one object whenboth eyes are used. Light rays from an object fall oncorresponding points of two retinas. Photopigments are light sensitive compounds. Allphotopigments can be broken down into a glycoproteincalled opsin and vitamin A derivative called retinal. Rods are highly light sensitive. Light causes the opsin toexpand. When opsin and retinal open a process calledbleaching takes place and active sites cause actionpotential to be created in the cell. The objects are seen inshades of grey until the opsin is back to its original shape. Red, green, and blue reflect light rays of a differentwavelength. On a certain cone the photopigment breaksdown and initiates impulse conduction by the cone. Conephotopigments are less sensitive to light and rods so brighterlight is necessary in order for them to break down. (2)(21) 8. Questions:Q: Why dont deer see Hunters who wear Brightorange?A: Deer do not have red-sensitive cone cells in theireyes, so they cant tell red or orange from green andbrown. (4)Q: What is the difference between "nearsighted" and"farsighted"? How are each of these corrected?A: Nearsighted means someone is able to see thingsclose to them but not far from them, and farsightedmeans someone is able to see things far from thembut not close to them. Nearsightedness andfarsightedness can both be corrected by glasses,contacts, or sometimes through LASIX eye surgery.