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)
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)
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.
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.
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.
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.
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.