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Edit Comment Close Premium member Presentation Transcript The Senses : The Senses SENSE ORGANS : SENSE ORGANS General sense organs Often exist as individual cells or receptor units Widely distributed throughout the body Special sense organs Large and complex organs Localized grouping of specialized receptors SENSES CLASSIFICATION : SENSES CLASSIFICATION Presence or absence of covering capsule Encapsulated Unencapsulated (“free” or “naked”) Type of stimuli required to activate receptors Photoreceptors (light) Chemoreceptors (chemicals) SENSES CLASSIFICATION : SENSES CLASSIFICATION Pain receptors (injury) Thermoreceptors (temperature change) Mechanoreceptors (movement or deforming of capsule) Proprioceptors (position of body parts or changes in muscle length or tension) STIMULUS TO SENSATION : STIMULUS TO SENSATION All sense organs have common functional characteristics All are able to detect a particular stimulus A stimulus is converted into a nerve impulse A nerve impulse is perceived as a sensation in the CNS GENERAL SENSE ORGANS : GENERAL SENSE ORGANS Distribution is widespread Single-cell receptors are common Examples Free nerve endings Pain and crude touch Meissner’s corpuscles Fine touch and vibration Ruffini’s corpuscles Touch and pressure The EYE : The EYE SPECIAL SENSE ORGANS EYE : EYE Layers of eyeball Sclera tough outer coat white” of eye cornea is transparent part of sclera over iris Choroid pigmented vascular layer prevents scattering of light; front part of layer made of ciliary muscle EYE : EYE Iris Colored part of eye Pupil Hole in center of iris Contraction of iris muscle dilates/ constricts pupil EYE : EYE Conjunctiva Mucous membrane covering the front surface of the sclera and lining the eyelid Lens Transparent body behind the pupil Focuses light rays on the retina EYE : EYE Eye fluids Aqueous humor Anterior cavity in front of the lens Vitreous humor Posterior cavity behind the lens EYE : EYE Retina Innermost layer Rods Night vision Cones Day vision and color vision Retinal cell Visual Pathway : Visual Pathway Innermost layer of retina contains rods and cones Impulse travels from the rods and cones through the bipolar and ganglionic layers of retina Visual Pathway : Visual Pathway Nerve impulse leaves the eye through the optic nerve; the point of exit has no receptors and is therefore called the blind spot Visual interpretation occurs in the visual cortex of the cerebrum The EAR : The EAR SPECIAL SENSE ORGANS EAR : EAR Ear functions Hearing Equilibrium and balance Mechanoreceptors Structure External ear Auricle (pinna) EAR : EAR External auditory canal Curving 2.5 cm in length Contains ceruminous glands Ends at the tympanic membrane EAR : EAR Middle ear Houses ear ossicles Malleus Incus Stapes Ends in the oval window The auditory (eustachian) tube connects the middle ear to the throat Inflammation called otitis media Slide 27: middle ear bones , malleus (m), incus (i) and stapes (s) Panel A panel A Panel B head (sh), Manubrium (mm) lateral process are attached to the eardrum Articular facet (af) of the incus forms joint with the head of the malleus, lenticular process (lp) articulates w/ head of stapes EAR : EAR Inner ear Bony labyrinth filled with perilymph Subdivided vestibule semicircular canals cochlea Membranous labyrinth filled with endolymph Cristae ampullaris receptors for balance in the semicircular canals EAR : EAR Organ of Corti Specialized hair cells respond when bent by the movement of surrounding endolymph set in motion by sound waves Slide 32: Vestibular Sense Ear recognizes multiple qualities of our balance and position Slide 33: Vestibular Sense Inner ear recognizes multiple qualities of our balance and position. The three main things that our vestibular senses recognize are: © 2006 STCC Foundation Presswritten by Dawn A. Tamarkin, Ph.D. Slide 34: Our static position This is the position we are in when we are not changing position... so if you are lying down or standing up, that is your current, unchanging position. When you shift positions, it is no longer static. © 2006 STCC Foundation Presswritten by Dawn A. Tamarkin, Ph.D. Slide 35: © 2006 STCC Foundation Presswritten by Dawn A. Tamarkin, Ph.D. Slide 36: Our velocity (and direction) this is the speed of our motion... are we going fast or slow? Along with this we know our direction of movement, so we know if we are going fast in a forward or backward direction. © 2006 STCC Foundation Presswritten by Dawn A. Tamarkin, Ph.D. Slide 37: Our acceleration (and direction) this is a change in speed... so if you are going slowly and you speed up, you have accelerated, while if you decrease the speed you are going you have decelerated. Again, you can tell the direction of your acceleration. © 2006 STCC Foundation Presswritten by Dawn A. Tamarkin, Ph.D. Slide 38: © 2006 STCC Foundation Presswritten by Dawn A. Tamarkin, Ph.D. Slide 39: The left and right horizontal semicircular canals are mirror images. Turn your head to the left The fluid in both canals starts moving to the right But this rightward movement of endolymph will not excite both the left and the right semicircular canal hair cells. Since the left and the right are mirror images of one another only one of them gets depolarized by leftward movement (rightward flow of endolymph). © 2006 STCC Foundation Presswritten by Dawn A. Tamarkin, Ph.D. Slide 40: © 2006 STCC Foundation Presswritten by Dawn A. Tamarkin, Ph.D. Gustation (Taste) : Gustation (Taste) SPECIAL SENSE ORGAN Taste - Gustatory : Taste - Gustatory Chemoreceptors called taste buds Cranial Nerves VII and IX carry gustatory impulses Only four kinds of taste sensations Sweet Sour Bitter Salty Gustatory and olfactory senses work together Slide 44: The Physiology of Taste by Tim Jacob For more info For more info Slide 45: The Physiology of Taste by Tim Jacob For more info Slide 46: Taste - A brief tutorial by Tim Jacob For more info Olfaction – Smell : Olfaction – Smell SPECIAL SENSE ORGANS Icons courtesy of Tim Jacob Smell - Olfactory : Smell - Olfactory Cranial Nerve I carry impulses Receptors for fibers of olfactory Lie in olfactory mucosa of nasal cavity Olfactory receptors are extremely sensitive but easily fatigued Human Pheromones : Human Pheromones By Tim Jacob AimThis site is an attempt to assess the available evidence relating to the vomeronasal organ (VNO), human pheromones and their possible role in human behaviour. 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