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Chapter 15 Senses

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SMELL NO GOOD. TASTE NO GOOD. Hear no evil See no evil..

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Intro Millions of sensory neurons Two categories general/special Most numerous general General receptors sense touch, temp., pain, reflexes, homeostasis responses Special receptors sense vision, hearing, balance, taste, smell, reflexes

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Receptor response Receptors respond to stimuli by converting them to nerve impulses Receptors are the dendrite endings Receptors vary according to their jobs heat, pain, etc Receptor potential determines the response required for the stimulus These impulses travel to spinal cord to be determined as hot, cold, etc (sensation) Adaptation allows for decrease of response when necessary

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Distribution of receptors Special sensory receptors nose, tongue, eye, ear General sensory receptors skin, mucosa, connective tissue, muscle, tendons, joints, viscera (somatic senses) Touch receptors very dense on hand and sparse on back

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Classification of receptors Exteroceptors Visceroceptors Proprioceptors

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Exteroceptors On or near body surface external stimuli Cutaneous receptors Pressure, touch, pain, temp.

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Visceroceptors Interoceptors Internally body organs internal environment Stimulated by pressure, stretching, chemical changes from blood vessels, organs, intestines Hunger, thirst

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Proprioceptors Specialized visceroceptor Less numerous and more specialized Limited to skeletal muscle, joint capsules, and tendons Info about body movement, orientation to space dont have to look to find hand

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Classification by stimulus detected Mechanoreceptors activated by mechanical stimuli (pressure to skin) Chemoreceptors change in concentration of chemicals blood glucose, oxygen, etc. Thermoreceptors temp. changes Nociceptors activated by intense stimuli of any type that results in tissue damage welding light, battery acid, etc. Photoreceptors eye only light receptors

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Classification by structure Free nerve endings Encapsulated nerve endings

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Free birds.. Simplest, most common Most widely distributed Not in the brain Primary receptor for pain Responsible for itch, sting, tickling, touch, movement, heat, cold Acute sharp, intense, localized sensation Chronic persistent pain, dull, aching

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Caged birds Six types Covering over dendrite end Activated by mechanical response Vary in size, shape, and distribution Touch receptors in none hair areas Krauses end bulbs- mucus membrane low frequency vibration, cold receptor Ruffinis corpuscle deep in dermis persistent touch receptor (crude)- allows for grasp for long periods of time and still sense stimuli

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Caged birds cont.. Stretch receptors muscle/tendon determines strength of contraction and duration maintains posture

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WHIFF CHECK..SMELL!

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Olfactory receptors Upper surface of nasal cavity Chemoreceptors Gas molecules/chemicals dissolve in mucus lining Cilia help to mix the mucus as the solvent Air flows around and down the airway not to the top usually That is why you sniff for better clarity Filed in temporal lobe Abnormalities sometimes impede normal processing

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SO, BE THANKFUL THAT YOU CAN STOP AND SMELL THE ROSES!

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Yum! Papillae contain taste buds each has 50- 125 chemoreceptors Determine texture, feel Taste receptors are all over the tongue Old maps are incorrect Taste is stimulated by chemicals dissolved in saliva Four flavors detected fifth metal?

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Taste to the brain.. Gustatory cells in taste buds begin assimilation of taste in seconds Anterior two thirds of the tongue to facial nerve to glossopharyngeal nerve to the vagus nerve to medulla oblongata and the thalamus to the cerebral cortex in parietal lobe

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WHAT DID YOU SAY! External ear auditory meatus 3 cm in, forward, down Modified sweat glands produce wax Mechanoreceptors pick up vibrations in the cilia which are transmitted into the bony structures of the inner ear

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Divisions External Middle Inner

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External ear Flap modified trumpet (auricle/pinna) Tube from the auricle external auditory meatus (ear canal) 3cm in, forward, down meds. Pull up and back Over-production of wax will cause pain/deafness End of meatus is the tempanic membrane - eardrum

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Middle ear Tempanic cavity Three tiny ossicles (bones) Malleus, incus, stapes Hammer, anvil, stirrup Tempanic membrane to malleus to the incus then to the stapes Several openings eustachian tube, oval window, round window, meatus

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Middle cont. Air spaces at posterior surface by temporal bone Great opportunity for infection! Eustachian tube bone, cartilage, fibrous tissue lined with mucus membrane Goes down, forward, and in from the middle ear to nasopharynx This tube allows for pressure equalization between inner ear and outer surface

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Inner ear Labrynth complicated shape Two main parts bony and membranous Bony three parts vestibule (contains utricle and saccule), cochlea (means snail), semicircular canals Membranous utricle, saccule, cochlear duct, membranous semicircular canals Vestibule and semicircular canals maintains balance Cochlea hearing Cochlear nerve (8 th ) extends from the base of the cochlear duct in the cochlea

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Hearing: Sound comes from vibrations from air, fluid, or solid material How is sound created through your larynx? Vibrating vocal cords create sound waves by producing vibrations in air passing over them Volume refers to amplitude (height of the wave) Pitch number of waves occuring during a specific time unit (frequency) Ability to hear depends on volume, pitch, and healthy anatomy and cerebral cortex reception in the auditory area in the temporal lobe after going through relay stations in the thalamus, midbrain, medulla, and pons

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WHAT COULD INTERRUPT THE PROCESS OF HEARING?

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Causes of hearing loss: 2 or 3 out of every 1000 babies are born deaf or with a major hearing deficit Millions of individuals are choosing hearing loss due to sound pollution Where do you go for pollution?

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YOU TUBE VIDEOS: Hearing Cochlear implant

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Balance Vestibule and semicircular canals Static equalibrium created in utricle and saccule ability to sense position of the head relative to gravity also acceleration/deceleration Dynamic equilibrium semicircular canals helps to maintain balance when sudden movements occur with spinning motion, semicircular canals move with the body but not at the same rate and the capula moves in an opposite direction until movement stops

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VERTIGO

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Canalith repositioning procedure:

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Hearing loss Conductive hearing loss transmission Middle ear infections Glue ear collection of fluid in middle Wax accumulation Otosclerosis Ossicle damage head trauma, inf. Perforated tempanic membrane

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Loss cont. Presbycusis loss of hairy cells! Acoustic trauma Viral or bacterial inf Menieres disease Drugs Acoustic neuroma benign MS, stroke, tumor Pregnant woman with rubella CMV in pregnancy

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Testing: Whisper test Tuning fork Pure tone audiometry Otoacoustic emissions cochlea Auditory brainstem response cochlea and nerve impulse to the brain MRI Normal 0-20 dB (range of frequencies) Mild loss - 25-39 dB Moderate loss 40-69 dB Severe loss 70-94 dB Profound 95 dB or greater

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TMT: Sign language Hearing aids Cochlear implant Lip reading Surgical excision of tumorous growth

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I see you!!!!! I see you!!!!!

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Structure Three layers: outside in sclera, choroid, retina Anterior portion cornea (avascular) covers iris transparent, sclera is opaque Middle choroid vascular pigmented Anterior choroid three structures ciliary body, suspensory ligament, iris

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Choroid structures Ciliary body fits between the anterior retina and posterior iris Iris smooth muscle fibers hole in middle pupil Retina innermost coat of the eyeball (no anterior portion)

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Conduction of impulses: Photoreceptor neurons Bipolar neurons Ganglion neurons

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Blind spot No rods and cones present Optic disc (part of sclera) contains perforations through which fibers emerge from the eyeball creating the optic nerve Pg 466

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Cavities Anterior two divisions anterior/posterior chambers Lies in front of the lens Aqueous humor fills both chambers clear, watery formed from capillaries Posterior larger than anterior Occupies all space posterior to the lens Vitreous humor semi solid jello Maintains intraocular pressure to keep eye from collapsing normal 20-25 mmHg If over, glaucoma

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Accessory structures Eyebrow Eyelashes Eyelid conjunctiva blepharoplasty Canthus corner Lacrimal gland/duct

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Rods photopigment rhodopsin light sensitivity Grey tones Cones determines color perception

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How do you see? Light enters the eye from the cornea