Senses PDF - McGraw Hill Education

SENSES ROMEL M. DURANTE, RN, MAN ( C ) Clinical Instructor Copyright © McGraw-Hill Education. Permission required for reproduction or display. 1  Learning Outcomes 1. Define senses, sensation, and perception. 2. Distinguish between general senses...

SENSES ROMEL M. DURANTE, RN, MAN ( C ) Clinical Instructor Copyright © McGraw-Hill Education. Permission required for reproduction or display. 1  Learning Outcomes 1. Define senses, sensation, and perception. 2. Distinguish between general senses and special senses. 3. List and describe the types of sensory receptors. 4. Define and describe pain and referred pain. 5. List the structures of the eye and their functions. 6. Describe the anatomy of the ear and state the function of each. 7. Describe changes that occur in the senses with aging. 2 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Senses Sense: ability to perceive stimuli Sensation: is the process initiated by stimulating sensory receptors Perception conscious awareness of stimuli received by sensory neurons Sensory receptors: sensory nerve endings that respond to stimuli by developing action potentials 3 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Senses General senses: - receptors over large part of body - somatic provide info. about body and env’t - visceral provide info. about internal organs, pain, pressure - touch, pressure, pain, temp., and itch Special senses: smell, taste, sight, hearing, and balance Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Receptors Mechanoreceptors: - detect movement - Ex. touch, pressure, vibration Chemoreceptors: - detect chemicals - Ex. Odors Photoreceptors: detect light 5 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Thermoreceptors: detect temp. changes Nociceptors: detect pain 6 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Touch Receptors Merkel’s disk: detect light touch and pressure Hair follicle receptors: detect light touch Meissner corpuscle: - deep in epidermis - localizing tactile sensations Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Ruffini corpuscle: - deep tactile receptors - detects continuous pressure in skin Pacinian corpuscle: - deepest receptors - associated with tendons and joints - detect deep pressure, vibration, position (proprioception) Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Pain What is it? unpleasant perceptual and emotional experience 9 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Pain Localized: - sharp, pricking, cutting pain - rapid action potential Diffuse: - burning, aching pain - slower action potentials 10 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Pain Control Local anesthesia: - action potentials suppressed from pain receptors in local areas - chemicals are injected near sensory nerve General anesthesia: - loss of consciousness - chemicals affect reticular formation 11 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Referred Pain What is it? - originates in a region that is not source of pain stimulus - felt when internal organs are damaged or inflamed - sensory neurons from superficial area and neurons of source pain converge onto same ascending neurons of spinal cord Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Olfaction What is it? - sense of smell - occurs in response to odorants - receptors are located in nasal cavity and hard palate - we can detect 10,000 different smells 14 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  How does olfaction work? 1. Nasal cavity contains a thin film of mucous where odors become dissolved. 2. Olfactory neurons are located in mucous. Dendrites of olfactory neurons are enlarged and contain cilia. 3. Dendrites pick up odor, depolarize, and carry odor to axons in olfactory bulb (cranial nerve I). 4. Frontal and temporal lobes process odor. 15 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Taste Taste buds: - sensory structures that detect taste - located on papillae on tongue, hard palate, throat Inside each taste bud are 40 taste cells Each taste cell has taste hairs that extend into taste pores 16 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  How does taste work? 1. Taste buds pick up taste and send it to taste cells. 2. Taste cells send taste to taste hairs. 3. Taste hairs contain receptors that initiate an action potential which is carried to parietal lobe. 4. Brain processes taste. taste sensations are carried by three cranial nerves: facial nerve (VII) , glossopharyngeal nerve (IX) , and vagus nerve (X) 18 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Tastes Sweet Sour Salty Bitter Umami Certain taste buds are more sensitive to certain tastes. Taste is also linked to smell. 19 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Tastes 20 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Vision Accessory Structures Eyebrow: - protects from sweat - shade from sun Eyelid/Eyelashes: - protects from foreign objects - lubricates by blinking 21 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Conjunctiva: thin membrane that covers inner surface of eyelid Lacrimal apparatus: produces tears Extrinsic eye muscles: help move eyeball 22 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Figure 9.8 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Anatomy of Eye Hollow, fluid filled sphere Composed of 3 layers (tunics) Divided into chambers 25 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Fibrous Tunic Outermost layer Sclera: - firm, white outer part - helps maintain eye shape, provides attachment sites, protects internal structures Cornea: - transparent structure that covers iris and pupil - allows light to enter and focuses light Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Vascular Tunic Middle layer Contains blood supply Choroid: - black part (melanin) - delivers O2 and nutrients to retina Ciliary body: helps hold lens in place Suspensory ligaments: help hold lens in place 27 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Lens: - flexible disk - focuses light onto retina Iris: - colored part - surrounds and regulates pupil Pupil: - regulates amount of light entering - lots of light = constricted - little light = dilated 28 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Nervous Tunic Innermost tunic Retina: - covers posterior 5/6 of eye - contains 2 layers Pigmented retina: - outer layer - keeps light from reflecting back in eye Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Sensory retina: - contains photoreceptors (rods and cones) - contains interneurons Rods: - photoreceptor sensitive to light - 20 times more rods than cones - can function in dim light Cones: - photoreceptor provide color vision - 3 types blue, green, red Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Rhodopsin: photosensitive pigment in rod cells Opsin: colorless protein in rhodopsin Retinal: - yellow pigment in rhodopsin - requires vitamin A 32 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Effects of Light on Rhodopsin 1. Light strikes rod cell 2. Retinal changes shape 3. Opsin changes shape 4. Retinal dissociates from opsin 5. Change rhodopsin shape stimulates response in rod cell which results in vision 6. Retinal detaches from opsin 7. ATP required to reattach retinal to opsin and return rhodopsin to original shape Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Figure 9.13 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Retina Structures Continued Rods and cones synapse with bipolar cells of sensory retina Horizontal cells of retina modify output of rods and cones Bipolar and horizontal cells synapse with ganglion cells Ganglion cells axons’ converge to form optic nerve Copyright © McGraw-Hill Education. Permission required for reproduction or display. Nervous Tunic (Retina) Innermost layer 2 parts of retina: sensory and pigmented Keeps light from reflecting back into eye Rods: photoreceptors that detect amount light Cones: - photoreceptors that detect colors - 3 types: red, blue, green 36 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Macula: small spot near center of retina Fovea centralis: - center of macula - where light is focused when looking directly at an object - only cones - ability to discriminate fine images Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Optic disk: - white spot medial to macula - blood vessels enter eye and spread over retina - axons exit as optic nerve - no photoreceptors - called blindspot Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Chambers of Eye Anterior chamber: - located between cornea and lens - filled with aqueous humor (watery) - aqueous humor helps maintain pressure, refracts light, and provide nutrients to inner surface of eye Posterior chamber: - located behind anterior chamber - contains aqueous humor 40 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Vitreous chamber: - located in retina region - filled with vitreous humor: jelly-like substance - vitreous humor helps maintain pressure, holds lens and retina in place, refracts light 41 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Functions of Eye Light Refraction Bending of light Focal point: - point where light rays converge - occurs anterior to retina - object is inverted Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Copyright © McGraw-Hill Education. Permission required for reproduction or display. Near vision Distant vision Ciliary muscles in the ciliary body contract, moving Ciliary muscles in the ciliary body toward lens. ciliary body are relaxed. Tension in suspensory Tension in suspensory ligaments is high. ligaments is low. FP A FP A Lens flattened Lens thickened (a) (b) Copyright © McGraw-Hill Education. Permission required for reproduction or display. Focusing Images on Retina Accommodation: - lens becomes less rounded and image can be focused on retina - enables eye to focus on images closer than 20 feet Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Neuronal Pathway for Vision Optic nerve: leaves eye and exits orbit through optic foramen to enter cranial cavity Optic chiasm: where 2 optic nerves connect Optic tracts: route of ganglion axons Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Eye Defects Myopia: - nearsightedness - image is in front of retina Hyperopia: - farsightedness - image is behind retina Presbyopia: - lens becomes less elastic - reading glasses required 47 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Clinical Focus 9A Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Astigmatism: - irregular curvature of lens - glasses or contacts required to correct Colorblindness: - absence or deficient cones - primarily in males Glaucoma: - increased pressure in eye - can lead to blindness 49 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display. Hearing and Balance Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Hearing and Balance External (Outer) Ear Extends from outside of head to eardrum Auricle: fleshy part on outside External auditory meatus: canal that leads to eardrum Tympanic membrane: - eardrum - thin membrane that separates external and middle ear 52 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Middle Ear Air filled chamber Malleus (hammer): bone attached to tympanic membrane Incus (anvil): bone that connects malleus to stapes Stapes (stirrup): bone located at base of oval window 53 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Oval window: separates middle and inner ear Eustachian or auditory tube: opens into pharynx equalizes air pressure between outside air and middle ear 54 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  55 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Inner Ear Set of fluid filled chambers Bony labyrinth: tunnels filled with fluid 3 regions: cochlea, vestibule, semicircular canals Membranous labyrinth: - inside bony labyrinth - filled with endolymph 56 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Endolymph: clear fluid in membranous labyrinth Perilymph: fluid between membranous and bony labyrinth Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Scala vestibuli: in cochlea; filled with perilymph Scala tympani: in cochlea; filled with perilymph Cochlea duct: in cochlea; filled with endolymph Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Spiral organ: in cochlear duct; contains hair cells Tectorial membrane: in cochlea; vibrates against hair cells Hair cells: attached to sensory neurons that when bent produce an action potential Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Vestibular membrane: wall of membranous labyrinth that lines scala vestibuli Basilar membrane: wall of membranous labyrinth that lines scala tympani Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Balance (Equilibrium) Static equilibrium: - associated with vestibule - evaluates position of head relative to gravity Dynamic equilibrium: - associated with semicircular canals - evaluates changes in direction and rate of head movement Copyright © McGraw-Hill Education. Permission required for reproduction or display. Static Equilibrium Copyright © McGraw-Hill Education. Permission required for reproduction or display. Dynamic Equilibrium Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Vestibule: - inner ear - contains utricle and saccule Maculae: - specialized patches of epithelium in utricle and saccule surround by endolymph - contain hair cells Otoliths: - gelatinous substance that moves in response to gravity - attached to hair cell microvilli which initiate action potentials Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Semicircular canals: - dynamic equil. - sense movement if any direction Ampulla: base of semicircular canal Crista ampullaris: in ampulla Cupula: - gelatinous mass - contains microvilli - float that is displaced by 67 endolymph movement Copyright © McGraw-Hill Education. Permission required for reproduction or display.  68 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  69 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Effects of Aging on the Senses Elderly people are less conscious of something touching or pressing the skin, which increases the risk of skin injuries. The sense of two-point discrimination decreases, and the elderly have a more difficult time identifying objects by touch. Altered balance and coordination Decline in functions of receptors for proprioception Slight loss in the ability to detect odors Decrease in sense of taste “presbyopia” - the lenses of the eyes lose flexibility because the connective tissue of the lenses becomes more rigid. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Effects of Aging on the Senses Gradual decline in visual acuity and color perception “presbycusis” - age-related sensorineural hearing loss Decreased sensitivity to gravity, acceleration, and rotation Copyright © McGraw-Hill Education. Permission required for reproduction or display.