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Special Senses

Special Senses. Chapter 12. Introduction. Special senses Sensory receptors located in head Nose – smell Tongue – taste Eyes – vision Ears – hearing and equilibrium Touch is a generalized sense. How do senses work?. Receptors collect information Stimulate neurons

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Special Senses

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  1. Special Senses Chapter 12

  2. Introduction • Special senses • Sensory receptors located in head • Nose – smell • Tongue – taste • Eyes – vision • Ears – hearing and equilibrium • Touch is a generalized sense

  3. How do senses work? • Receptors collect information • Stimulate neurons • Information is sent to the brain • The cerebral cortex integrates the information with that from other senses • Forms a perception (a person’s particular view of the stimulus)

  4. Receptor Structure • Receptors are structured in two basic ways: • Nerve endings • Cells which are associated with nerve endings • When these are stimulated, they produce graded potentials. If they hit threshold, nerve fires.

  5. The Ear

  6. Ear The Ear and the Senses of Hearing and Equilibrium: Structures External Ear • Auricle (pinna) • Collects sound waves • External auditory canal • Guides sound wave to tympanic membrane

  7. Ear The Ear and the Senses of Hearing and Equilibrium: Structures (cont.) • Tympanic membrane • Concave shaped membrane • Separates external canal and middle ear • Vibrates when sound hits it • Ear ossicles • Malleus, Incus, Stapes • Ossicles vibrate in response to vibration of tympanic membrane • Tympanic Cavity • Surroundsossicles • Eustachian tube • Connects middle ear to throat • Equalizes pressure on eardrum • Oval window • Separates middle ear from inner ear The Middle Ear

  8. Middle Ear Diagram

  9. Ear The Ear and the Senses of Hearing and Equilibrium: Structures (cont.) Inner Ear Labyrinth of communicating chambers • Semicircular canals (3): detect balance of the body • Vestibule: central part of labyrinth; equilibrium • Cochlea: coiled canal ofdense bone tissue of the skull; shaped like a snail; • Filled with two fluids (endolymph and perilymph). • The Organ of Corti is the sensory receptor inside the cochlea which holds the hair cells, the nerve receptors for hearing.

  10. Ear Wax • Cerumen; naturally produced by your body • Produced in sebaceous and modified apocrine glands of the ear • Coats the ear canal to moisturize it, fight off infection, keep dust, dirt, and other debris from getting inside ear • 20 to 50 percent fat

  11. The Ear and the Senses of Hearing and Equilibrium: Hearing Process • Sound waves collected through external ear canal • Waves cause tympanic membrane to vibrate • Ossicles amplify vibrations • The mechanical energy from movement of the middle ear bones pushes in a membrane (the oval window) in the cochlea. • This force moves the cochlea's fluids that, in turn, stimulate tiny hair cells. • Movement of hairs lining cochlea are converted into nerve impulses • Impulses are transmitted by auditory nerve to the brain for interpretation

  12. The Ear and the Senses of Hearing and Equilibrium: Hearing Process (cont.) • Bone conduction • Alternative pathway • Bypasses external and middle ear directly to inner • Useful in determining cause of hearing problem

  13. Equilibrium Position of Body/Movement • Above the cochlea are two interconnecting chambers filled with endolymph, the sacculus and utriculus. • On their inner surface are patches of hair cells to which are attached thousands of tiny spheres of calcium carbonate (CaCO3). • Gravity pulls these downward. As the head is oriented in different directions, these ear stones (otoliths) shift their position. Impulses initiated in the hair cells are sent back to the brain. • Motion of the body is detected in the semicircular canals • Whenever the head is moved, the fluid within the canals lags; this stimulates the hair cells to send impulses back to the brain. • When the hair cells send messages that are incongruent with what the eyes are seeing and our body is feeling, as may occur in a boat or aircraft during rough weather, motion sickness can result. • Some people also suffer severe dizziness because otoliths have become dislodged from their utriculus (following a blow to the head) and settled in a semicircular canal.

  14. How to Recognize Hearing Problems in Children • Guidelines • Infants to 4 months • Startled by loud noises • Recognize mother’s voice • 4 to 8 months • Regularly follow sounds • Babble at people • 8 to 12 months • Respond to the sound their name • Respond to “no”

  15. The Aging Ear • External ear larger / earlobe longer • Cerumen dryer and prone to impaction • Ear canal narrower • Eardrum shrinks and appears dull and gray • Ossicles do not move as freely • Semicircular canals less sensitive to changes in position – affects balance

  16. Hearing Loss Symptom of a disease, not a normal part of aging Conductive hearing loss Sensorineural hearing loss • Interruption in transmission to inner ear • Causes • Obstruction of ear canal • Infection of middle ear • Reduced movement of stirrup • Sound waves not perceived by brain as sound • Causes • Hereditary • Repeated exposure to loud noises / viral infections • Side effect of medication

  17. Hearing and Diagnostic Tests • Hearing tests • Tuning forks – differentiate between types of loss • Audiometer – measures hearing acuity • Diagnostic testing • Tympanometry • Measures the ability of the eardrums to move • Detects diseases and abnormalities of the middle ear

  18. “Cauliflower Ear” • Cauliflower ear is medically known as an auricular hematoma.  • The external ear is made of cartilage and it is the shape of the cartilage that gives the ear its distinctive shell-like shape.  The cartilage is lined by perichondrium, a tight layer of connective tissue. • Auricular hematoma occurs when the ear cartilage is injured • Trauma results in fluid or blood collecting between the perichondrium and the cartilage.  This blood or fluid can become permanent and scarred, resulting in the appearance of cauliflower ear.

  19. Olfaction – Sense of Smell • Olfactory epithelium in roof of nasal cavity • Pseudostratified columnar epithelium • Has millions of bipolar neurons = olfactory receptor cells • Only neurons undergoing replacement throughout adult life • Olfactory cilia bind odor molecules • Mucus captures & dissolves odor molecules • Each receptor cell has an axon – the cells are bundled into “filaments” of olfactory nerve • Penetrate plate of ethmoid bone & enter olfactory bulb

  20. Olfaction!

  21. Olfaction • Olfactory receptors • Chemoreceptors – respond to changes in chemical concentrations • Chemicals must be dissolved in mucus

  22. Day 2 - Taste Chapter 12 – Special Senses

  23. Olfaction Smell sensation Activation of smell receptors  information sent to olfactory nerves that send the information along olfactory bulbs and tracts to different areas of the cerebrum; cerebrum interprets the information as a particular type of smell

  24. Nose and Sense of Smell (cont.) • Sensory Adaptation • Chemical(s) can stimulate receptors for limited amounts of time • Chemoreceptorsfatigue and stop responding to chemical • Result = no longer smell odor

  25. The Tongue… • The tongue is a muscular organ in the mouth. • Covered with moist, pink tissue called mucosa. • Tiny bumps called papillaegive the tongue its rough texture. • Thousands of taste buds (receptor cells) cover the surfaces of the papillae. Taste buds are collections of nerve-like cells that connect to nerves running into the brain. • The tongue is anchored to the mouth by webs of tough tissue and mucosa. • The tether holding down the front of the tongue is called the frenum. • In the back of the mouth, the tongue is anchored into the hyoid bone. • The tongue is vital for chewing and swallowing food, as well as for speech.

  26. Tongue Tongue and Sense of Taste • Taste buds: detect chemicals dissolved in saliva from food in the mouth and throat (chemoreceptors) • Taste buds send their sensory information through neurons to the gustatory center of the brain. • The average person has around 10,000 taste buds in their mouth and throat, although the number of taste buds peaks in early childhood and declines throughout our lives. • Location • Papillae of the tongue • Roof of mouth • Walls of throat } fewer than on tongue

  27. Papillae Types • Foliate papillae: these are ridges and grooves towards the posterior part of the tongue found at the lateral borders. • Fungiform papillae: small, on entire surface of tongue • Vallate papillae: inverted “V” near back of tongue • Filiform papillae: these are thin, long papillae "V“shaped cones that don't contain taste buds but are the most numerous. These papillae are mechanical and not involved in gustation

  28. Taste Buds

  29. Tongue Maps…

  30. Umami 5th basic taste Glutamic acid Spicy foods Activate pain receptors Interpreted by brain as “spicy” Tongue Tongue and Sense of Taste (cont.) • Taste sensation • 4 primary • Sweet • Sour • Salty • Bitter

  31. Tongue and Sense of Taste (cont.) Taste sensation Activation of taste cells Cranial nerves Gustatory cortex of cerebruminterprets information

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