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The Senses Nestor T. Hilvano, M.D., M.P.H. (Images Copyright Discover Biology, 5 th ed., Singh-Cundy and Cain, Textbook, 2012.)

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Presentation on theme: "The Senses Nestor T. Hilvano, M.D., M.P.H. (Images Copyright Discover Biology, 5 th ed., Singh-Cundy and Cain, Textbook, 2012.)"— Presentation transcript:

1 The Senses Nestor T. Hilvano, M.D., M.P.H. (Images Copyright Discover Biology, 5 th ed., Singh-Cundy and Cain, Textbook, 2012.)

2 Learning Objectives 1.State the functions of sensory pathways. 2.Define sensory receptors and describe the 5 general categories of sensory receptors. 3.Describe the human eye and its function. 4.Compare the rods and cones of retina. 5.Explain myopia, hyperopia, presbyopia and astigmatism. 6.List the structure of ear in the order in which they participate in hearing. 7.Explain how body position and movement are sense in the ear. 8.Discuss how odor and taste receptors function.

3 Sensations All stimuli represent forms of energy Sensation involves converting energy into a change in the membrane potential of sensory receptors The brain interprets sensations, giving the perception of stimuli General senses (Somatic)- skin, muscles, joint, and viscera (internal organs) Special senses- sight (vision), smell (olfaction), taste (gustation), hearing (audition), and vestibular (balance/equilibrium)

4 Fig. 50-2 Slight bend: weak stimulus Stretch receptor Membrane potential (mV) Axon Dendrites Strong receptor potential Weak receptor potential Muscle –50 –70 Membrane potential (mV) –50 –70 Action potentials Membrane potential (mV) Large bend: strong stimulus Reception Transduction 0 –70 0 1 2 3 4 5 6 7 Membrane potential (mV) Time (sec) 1 2 3 4 5 6 7 Time (sec) Transmission Perception Brain Brain perceives large bend. Brain perceives slight bend. 1 2 3 4 1 2 34 0 0 Functions of Sensory Pathways: sensory reception, transduction, transmission, and integration (brain perception)

5 Sensory Receptors : Transduce Stimuli into Action Potential Classification of Receptors: Pain (nociceptors) receptors – inflame/damage tissues Thermoreceptors – change in temp., hot or cold Mechanoreceptors – change in pressure or fluid movement; touch, pressure, stretching of muscles, motion, sound Chemoreceptors – change in odor and taste Electromagnetic receptors – electricity, magnetism, and light (photoreceptors ) Receptors for General senses: a)Pain - free nerve endings b)Temperature –Ruffini (hot); Kraus End Bulb (cold) c)Crude (light) touch - Meissner’s corpuscle d)Proprioception (deep touch and pressure) -pacinian corpuscle Receptors for Special senses: a)Vision – rods and cones b)Audition – organ of corti c)Vestibular – maculae, cristae d)Olfaction- olfactory cell e)Gustation- taste bud


7 Eyeball - Vision Fibrous (outermost) layer = sclera and cornea Vascular (middle) layer = choroid, ciliary body, and iris *pupil – central opening * Light passes through a transparent lens that focuses images on the retina Nervous (innermost) layer = retina, photoreceptor layer (rods and cones) Rods - sensitive to low level of light; night vision Cones - detect colors of light; day vision _____ - center of sharpest vision (cones only) _____ - Blind spot (w/ nerve & b.v.) a. optic disc b. fovea centralis Aqueous humor filled the chamber in front of the lens Vitreous humor filled the chamber behind the lens



10 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

11 Visual Problems Passage of light: Light cornea aqueous humor pupil lens vitreous humor retina Nearsightedness (myopia)- Can’t see far distance; eyeball is longer; focus distant objects in front of retina; corrective lenses that are thinner in the middle Farsightedness (hyperopia)- Can’t see near distance; eyeball is short; focal point is behind the retina; corrective lenses that are thicker in the middle *presbyopia – hyperopia in old age, inelasticity of lens Astigmatism – blurred vision caused by misshapen lens or cornea; corrective asymetrical lens

12 Clinical Correlation ___ = clouding of lens –aging, diabetes, smoking, and UV light ___ = death of retinal cells due to elevated pressure within the eye ___ = pink eye, results from damage or irritation of conjunctival surface. a. glaucoma b. conjunctivitis c. cataract

13 Ear: Hearing Mechanoreceptor (change in pressure due to sound waves) Outer ear = pinna and auditory canal * tympanic membrane Middle ear = contain ossicles (malleus, incus, stapes) * oval window Inner ear = cochlea (contains organ of corti) Auditory nerve Sound volume (loudness) ranging from 0 to 120 db. (long exposure to 90 db can cause hearing loss) Pitch (frequency) from 20 – 20,00 Hz. Sound at pinna auditory canal tympanic membrane middle ear oval window cochlea (organ of corti) send impulses to the brain (auditory cortex)

14 Figure 29.4B Skull bones Semicircular canals (function in balance) Auditory nerve, to the brain Cochlea Eustachian tube (connects to the pharynx) Eardrum Stirrup Anvil Hammer Oval window (behind the stirrup)

15 Ear: Vestibular Sense: (Body Position and Balance) Inner ear – houses organs of balance a) Semicircular canals = crista ampullaris, receptor for changes in head’s rate of rotation b) Utricle and saccule – maculae, receptor for head position relative to the force of gravity and linear motion

16 Fig. 50-11 Vestibular nerve Semicircular canals Saccule Utricle Body movement Hairs Cupula Flow of fluid Axons Hair cells Vestibule

17 Taste Receptors Chemoreceptors in taste buds 4 types a) sweet b) sour c) salty d) bitter A fifth taste perception called umami (elicited by glutamate) Taste perception varies with individuals and may be related to genetic traits


19 Smell Receptors Chemoreceptors in nose (olfactory mucosa) – olfactory (bipolar) cells Integration of signals in the brain results in an odor perception Smell is tied with limbic system, evoking emotions and memories.


21 Homework 1.Define terms: rods, cones, presbyopia, myopia, hyperopia, astigmatism, cornea, lens, tympanic membrane, semicircular canals, utricle and saccule, cataract, glaucoma, conjunctivitis, optic disc, fovea centralis, macula, cristae ampullaris. 2.Give the sensory receptors of the following: __ pain a. bipolar (olfactory) cells __ pressure and deep touchb. organ of corti __ tastec. free nerve endings __ olfaction d. pacinian corpuscle __ hearing e. taste bud 3.Classify the receptors of the items listed below: __ change in pressure or fluid movement a. chemoreceptor __ change in light perception b. thermoreceptor __ change in smell of CO2c. photoreceptor __ change in climate’s temperature d. mechanoreceptor

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