Lesson 2 Anatomy II Final Exam Study Guide 1 Olfactory epithelium contains olfactory receptor cells supporting cells and basal stem cells Olfactory receptors are involved in detecting dissolved chemicals as they interact with odorant binding proteins on the cell membrane of the olfactory receptor cell The CNS interprets different smells by the pattern of receptor activity Taste receptors are clustered into taste buds that contain basal cells and gustatory cells The four primary taste sensations are sweet salty sour and bitter The two additional human taste sensations are umami and water Foods of different tastes are detected by the gustatory cells when the dissolved chemicals contact taste hairs and bind to receptor proteins of the gustatory cell Sour and salty receptors have chemically gated ion channels that open when stimulation produces a depolarization of the cell Sweet bitter and umami receptors are activated when a dissolved chemical binds to a membrane receptor protein to activate a G protein by the second messenger system 2 We are more sensitive to bitter and sour foods than to salty and sweet tastes to protect us from eating something harmful that can destroy our cells This is what has helped us survive 3 Three layers of the eye a Outer fibrous layer has the cornea transparent anterior region the sclera white of b the eye and the corneal limbus border between cornea and sclera Intermediate vascular layer uvea has the iris papillary muscles dilate and constrict the ciliary body controls lens position and shape and the choroid delivers oxygen and nutrients to retina c Deep inner layer i Outer layer pigmented part absorbs light that passes through neural part ii preventing rebounding of light Inner layer neural part retina has photoreceptors rods cones bipolar cells horizontal cells amacrine cells and the optic disc blind spot Chambers of the eye Ciliary body and lens divide into a Large posterior cavity vitreous chamber b Smaller anterior cavity aqueous chamber i Anterior chamber extends from cornea to iris ii Posterior chamber between iris ciliary body and lens contains the vitreous body which is a large gelatinous mass that helps stabilize eye shape and supports the retina when there is blockage of normal blood vessels and growth of abnormal blood vessels in the retina blood leaks into this cavity and leads to diabetic retinopathy This occurs in many with diabetes mellitus and acuity decreases as photoreceptors die 4 The iris contains papillary muscles that are controlled by the autonomic nervous system The sympathetic division stimulates the papillary dilator to allow more light to enter the eye The parasympathetic division stimulated the papillary constrictor to allow less light to enter the eye 5 The lens shape and position is controlled by the ciliary body The ciliary body contains ciliary processes and ciliary muscles that attach to suspensory ligaments of the lens When the ciliary muscles contract the lens becomes thicker allowing us to focus on objects close up When ciliary muscles relax the lens becomes thinner allowing us to focus on something far away Thicker lens is like a microscope 6 Rods and cones are photoreceptors that are located at the neural part retina of the inner layer of the eye Rods so not discriminate light colors and are highly sensitive to light so they are used in low light conditions Cones provide color vision and are densely clustered in the fovea at the center of the macula 7 The retinal part of the inner layer of the eye has photoreceptors at the macula bipolar cells that allows rods and cones to synapse with ganglion cells horizontal cells that extend across the outer portion of the retina and amacrine cells that are comparable to the horizontal cells layer and is the location of where bipolar cells synapse with ganglion cells The optic disc is the origin of the optic nerve and it is a circular region just medial to the fovea This blind spot occurs because it is the location of where the optic nerve leaves the eye Scotomas are abnormal blind spots that occur in other areas than the optic disc They may be caused by compression of the optic disc damage to photoreceptors or damage to the visual pathway 8 A cataract is a condition in which the lens has lost its transparency Senile cataracts are a natural consequence of aging Astigmatism is a condition where light passing through the cornea and lens is not refracted properly and the visual image is distorted Presbyopia occurs as older people become farsighted as their lenses lose elasticity Retinitis pigmentosa is the most common inherited visual problem that is caused by mutation in the visual pigment that causes cell death and blindness Nyctalopia is night blindness that results from a deficiency of vitamin A taking a supplement of vitamin A can treat this 9 During photoreception a photon strikes the retinal portion of the photopigment molecule embedded in the membrane of the disc Energy is absorbed and alters the photoreceptor action potential frequency The messages then cross to the bipolar cells and then to the ganglion cells Axons from the ganglion cells converge on optic disc and penetrate the wall of the eye Then the signal proceeds toward the diencephalon on optic nerve II These two optic nerves one for each eye reach the diencephalon at the optic chiasm Half of the fibers travel to the contralateral lateral geniculate nucleus and the other half to the ipsilateral side Optic radiation then occurs as a bundle of projection fibers links the lateral geniculate nucleus with the visual cortex The left half arrives at the right occipital lobe and the right half arrives at the left occipital lobe Some fibers from the lateral geniculate nucleus go to the hypothalamus to regulate other metabolic processes by the circadian rhythm or day night cycle However the pathway of light through the eye is from the ganglion cells to the bipolar cells to the photoreceptors 10 The tympanum and ossicles protect the ear from loud noises The tensor tympani muscle stiffens the tympanic membrane and the stapedius muscle reduces movement of the stapes at the oval window 11 Receptors of the vestibular complex make up the sensations that provide the sense of equilibrium The saccule and the utricle are used to detect linear acceleration and the semicircular canal is used to detect angular acceleration The cochlear duct receptors provide the sense of hearing Hair cells provide information on the direction and
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