Balance for artifact


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Balance for artifact

  1. 1. Look inside!WE HAVE SENSE!
  2. 2. Sensory receptors Types, distribution, and functions of receptors (16) ©A sensory receptor is a part of a sensory neuron or cell (and possibly associated cells)that receives information from the world and relates it to your nervous system. Somesensory receptors are activated when they are bent, squished, or disturbed in someway. Others are activated by chemicals. Others by temperature. And others by light.(12) ©Exteroceptors- A sensory receptor that receives external stimuli. (13) ©
  3. 3. Visceroceptors- A sensory receptor located within body organs that responds toinformation concerning the internal environment. (13) ©Proprioceptors- neuromuscular receptors that register stimuli, such as stretch, tonicity,and movement within muscles. (13) Stimulus Detected of ReceptorsMechanoreceptors are activated by mechanical stimuli that in some way deform to change the positionof the receptor, resulting in the generation of a receptor potential. An example is when pressure isapplied to the skin or blood vessels or caused by stretch or pressure in muscle, tendon, or lung tissue.Chemoreceptors are activated by either the amount or the changing concentration of certain chemicals.Our sense of taste and smell depends on them. Specialized ones also sense the concentration ofchemicals like hydrogen ions and blood glucose. Thermoreceptors are activated by changes intemperature. Nocieptors are activated by intense stimuli of any type that results in tissue damage. Thecause may be a toxic chemical, intense light, sound, pressure, or heat. Pain is produced. Photoreceptorsare only found in the eye. They respond to light stimuli if the intensity is great enough. ©8 Structure of ReceptorsFree nerve endings are the simplest, most common, and most widely distributed sensory receptors.They are located on both the surface and deep visceral organs. Brain tissue lacks these and is incapableof sensing painful stimuli. Free nerve endings also mediate pain and other sensations like itching andtickling. Root hair plexuses are delicate, weblike arrangements of free nerve endings that surround hairfollicles and detect hair movement. Merkel discs are flattened or disc shaped variations of free nerveendings. They are responsible for mediating sensations of light or discriminative touch. Messiner’scorpuscle is relatively large and superficially placed ovoid or egg shaped mechanoreceptors. Whendeformed by a mechanical type of stimuli, this type of receptor mediates sensations of discriminativetouch and low frequency vibration. They are most numerous in hairless areas. Pacinian corpuscles arelarge mechanoreceptors which when sectioned show thick laminated connective tissue capsules. Theyare found in the deep dermis of the skin, especially the skin and feet. Muscle spindles consist of adiscrete grouping of about 5 to 10 modified muscle fibers called intrafusal fibers which are surroundedby a delicate capsule. They have striated ends that are capable of contraction but devoid of contractiblefilaments in their central area, instead they are surrounded by clear cytoplasm. Golgi tendon organs areproprioceptors. They are located at the point of junction between muscle tissue and tendon. Each organconsists of dendrites of afferent nerves called type Ib nerve fibers. They act opposite of muscle spindles.©8
  4. 4. Olfactory Receptors: Olfactory receptor neurons are chemoreceptors. Receptorpotentials are generated in olfactory receptor neurons when gas molecules or chemicalsdissolved in the mucus covering the nasal epithelium bind to receptors of the membrane of the olfactory receptors. (pg. 453)
  5. 5. Olfactory Pathways: “If the level of odor-producing chemicals dissolved inthe mucus surrounding the olfactory cilia reaches a threshold level, a receptor potential, andthen, an action potential will be generated and passed to the olfactory nerves in the olfactory bulbs.” (pg. 434- 455)
  6. 6. Human olfactory compared to a canine’s:Olfactory receptors are the first dedicated molecules with which odorants physically interact to arouseon olfactory sensation. Several elements such as size of the olfactory epithelium, the density of theneuronal cells, and the number of olfactory receptors expressed on their surface, as well as size of theolfactory bulb, have to be taken into consideration when comparing either of the sensory capacities ofany mammal. In this case comparing a human and a canine, a canine obtains a longer and larger nasalcavity than a human’s, concluding there to be more functional olfactory receptors in a dog. A dogs ORrepertoire is thirty percent larger than a humans.
  7. 7. Neural pathway of taste: Once taste signals are transmitted to the brain,several efferent neural pathways are activated that are important to digestive function. A very largenumber of molecules elicit taste sensations through a rather small number of taste receptors.Furthermore, it appears that individual taste receptor cells bear receptors for one type of taste.
  8. 8.  A single taste bud contains 50–100 taste cells representing all 5 taste sensations; each taste cell has receptors on its apical surface. These are trans membrane proteins which o Admit the ions that give rise to the sensation of salty o Bind to the molecules that give rise to the sensations of sweet, bitter, and umami. A single taste cell seems to be restricted to expressing only a single type of receptor. Taste receptor cells are connected, through an ATP-releasing synapse, to a sensory neuron leading back to the brain. However, a single sensory neuron can be connected to several taste cells in each of several different taste buds. The sensation of taste — like all sensations — resides in the brain.
  9. 9. Hearing ©18 Mechanism of hearingSound is created by vibrations that may occur in the air,fluid, or solid material. The height, of a sound wavedetermines its volume. The number of sound wavesdetermines the pitch. Sound waves must be of certainamplitude to initiate movement in the tympanicmembrane which would move hair cells along the basilarmembrane. The basilar membrane will vibrate and bulgeupward at different areas along it. Different frequencysound waves cause different parts of the basilarmembrane to vibrate.
  10. 10. Neuronal Pathway of HearingDendrites of neurons whose cell bodies lie in the spiralganglion and whose axons make up the cochlear nerveterminate around the organ of corti, and the tectorialmembrane adheres to their upper surfaces. Themovement of the hair cells stimulates the dendrites andinitiates impulse conduction by the cochlear nerve to thebrainstem. Before reaching the auditory area of thetemporal lobe, impulses pass through relay stations innuclei in the medulla, pons, midbrain and thalamus.
  11. 11. Balance Vestibule and semicircular canals ©15 The sense of balance includes sense organs such as the vestibule andsemicircular canals. The sense organs in the utricle and saccule, which are insidethe vestibule, are involved in static equilibrium- a function needed to sense theposition of the head relative to gravity or to sense acceleration or deceleration inthe body. The sense organs involved with the semicircular canals function indynamic equilibrium- a function needed to maintain balance when there is asudden movement in the head or the body is suddenly moved. ©8 Dynamic Equilibrium, in depth, depends on the functioning of the cristaampullaris, located in the ampulla of each semicircular canal. Each cone-shapedcrista has many hair cells, with their processes in a gelatin cap called the cupula.The cupula does not respond to the pull of gravity, but moves with theendolymph in the semicircular canals. When a person spins, the semicircularcanals move with the body, but inertia keeps the endolymph in them frommoving at the same rate. The cupula moves in a direction opposite to headmovement until the movement stops. Dynamic equilibrium is therefore able todetect changes both in the direction and in the rate at which movement occurs.©8
  12. 12. Vision Structure of the Eye ©17Cavities and Humors:The eyeball has an interior space that is divided into two cavities: anterior andposterior. The anterior cavity has two subdivisions called the anterior andposterior chambers. The entire anterior cavity lies in front of the lens. Theanterior chamber is the space anterior to the iris but posterior to the cornea. Theposterior chamber is the small space posterior to the iris but anterior to the lens.Aqueous humor fills both chambers of the anterior cavity; the substance is clearand watery and leaks out when the eyeball is injured. The posterior cavity is largerthan the anterior because it occupies the area posterior to the lens, suspensoryligaments, and ciliary body. It contains vitreous humor a substance similar to softgelatin. Both humors help maintain intraocular pressure to prevent the eyeballfrom collapsing. Aqeuos humor is formed from blood in the capillaries. The ciliarybody actively secretes the aqueous humor into the posterior cavity. ©8
  13. 13. Muscles:There are two types of eye muscles: extrinsic and intrinsic. Extrinsic eye musclesare skeletal muscles that attach to the outside of the eyeball and to the bones ofthe orbit. They move the eyeball in any direction making them voluntary muscles.Four of them are straight muscles while two are oblique. Their names aresuperior, inferior, medial, and lateral rectus muscles and superior and inferioroblique muscles. Intrinsic eye muscles are smooth, involuntary muscles in the eye.Their names are the iris and ciliary muscles. The iris regulates the size of the pupilwhile the ciliary muscle controls the shape of the lens. ©8Accessory StructuresAccessory structures of the eye include the eyebrows, eyelashes, eyelids, andlacrimal apparatus. The eyebrows and eyelashes give some protection against theentrance of foreign objects into the eye but also help shade the eyes and protectthem from light rays. Eyelids consist mainly of involuntary muscles and skin withthe tarsal plate at the edge of each lid. The lacrimal apparatus consists of thestructures that secrete tears and drain them from the surface of the eyeball. Thelacrimal apparatus contains the lacrimal glands, lacrimal ducts, lacrimal sacs, andnasolacrimal ducts. ©8
  14. 14. Process of SeeingPhotopigments are light-sensitive pigmented compounds that are found in the outer area of both typesof photoreceptors near the pigmented area. They can all be broken down into a glycoprotein calledopsin and a vitamin A derivative called retinal, which acts as the light-absorbing portion.Rods- highly light sensitive that even dim light causes a rapid breakdown of the photopigment into itsopsin and retinal components. They do not mediate color vision, and have a low spatial acuity.Cones- 3 types of cones are present in the retina. Each of the three primary colors reflect light rays of adifferent wavelength. The wavelength will cause its photopigment to break down and initiante impulseconduction. 1. Why don’t deer see hunters when they wear orange? a. Deer have no red-sensitive cone cells in their eyes, so they cant tell red or orange from green and brown. 2. What is the difference between "nearsighted" and "farsighted"? How are each of these corrected? a. Each of these are corrected with lenses of some sort. Nearsightedness means that someone can clearly see objects close to them, but objects farther away appear blurry. Farsightedness means that the person can clearly see distant objects, but not objects close to them.