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Unit 8: The Senses Amy J. Hilbelink, Ph.D. Tracy Abram, MAIS, BS The Senses Objectives • Classify sense organs as special or general. Discuss their functions. • Discuss how a stimulus is converted into a sensation. • List major senses • Describe eye and ear anatomy • Describe major visual disorders and hearing impairment Classify sense organs as special or general • • • • • Special: Eye Taste buds Ear Nose • General: • Microscopic receptors – Pacinian corpuscles – Meissner’s corpuscles – Muscle spindles Inquiring Minds want to know… • What is the difference between special and general sense organs? All About the “Special” • Special = they have large and complex organs or localized groupings of specialized receptors like taste buds on tongue. • These are the senses that you typically think of; except for perhaps touch! All About the “General” • General = made of microscopic receptors widely distributed throughout the body. – Pacinian corpuscles = pressure and high frequency – Meissner’s corpuscles = fine touch and low frequency – Muscle spindles = propriocetors (muscle length and location) Sense organ functions • • • • • Vision Hearing Smell Taste Balance Eye anatomy • Sclera = white of the eye (cornea) • Choroid = contains a dark pigment to prevent scattering of light rays • Retina = innermost layer of eyeball (rods and comes) • Iris = circular colored part of eye • Conjunctiva = mucous membrane that lines eyelids and covers the sclera • Lacrimal gland = tear duct • Pupil = black center of iris; a hole • Lens = ciliary muscles contract the lens for focusing My Eye Exam 2011 Prof. Abram’s Left Eye Prof. Abram’s Right Eye Prof. Abram OTC Scan Major visual disorders • Refraction disorders – Myopia = nearsightedness • Astigmatism = irregularity in cornea or lens • Conjunctivitis = pink eye • Strabismus = convergent How is a stimulus converted into a sensation? Stimulus detected [sound] Stimulus converted to electrical signal or nerve impulse= [middle ear] Signal transmitted over nervous system “pathway” = [VIII cranial nerve] Sensation perceived in brain = [music] Ear anatomy • External ear – External auditory canal – Tympanic membrane – eardrum Ear anatomy • Middle ear – Ear bones = ossicles • Malleus • Incus • stapes – Auditory or Eustachian tube Ear anatomy • Inner ear – Bony labrinth – Perilymph – Vestibule – Semicircular canals – Cochlea – Crista ampullaris – Organ of Corti Hearing impairment • Blockage of external auditory canal • Otosclerosis = structural irregularities in stapes • Tinnitus = ringing in ears (may be symptom of otosclerosis) • Otitis = ear infection • Meniere’s disease = chronic inner ear disease, resulting in vertigo Which one would be the worst to lose?
