Anatomy Ch. 9 the Senses Notes

Anatomy and Physiology Chapter 9 The Senses AHSGE: Standard V: Objective 1: Bullet 6, 7 Standard VII: Objective 2: Bullet 2, 3 Standard VIII: Objective 2: Bullet 2 ACOS: # 34, 37 I. Introduction A. Summary 1. Senses are classified into two major groups: a. Special – senses of smell, taste, sight, hearing, and balance b. General – touch (light ), pressure, pain, temperature, vibration, itch, and proprioception (position of the body and its various parts) B. Pain 1. Pain is a sensation characterized by a group of unpleasant perceptual and emotional experiences. 2. There are two types of pain sensation: a. sharp, well localized, pricking, or cutting pain b. diffuse, burning, or aching pain II. Smell A. Summary 1. The sensations of smell and taste are closely related and both are initiated by the interaction of chemicals with sensory receptors. 2. The sense of vision is initiated by the interaction of light with sensory receptors. 3. Hearing occurs in response to sound waves, and balance occurs in response to gravity or motion. III. Olfaction A. Summary 1. The sense of smell called olfaction, occurs in response to airborne molecules called odors that enter the nasal cavity. 2. Olfactory neurons are bipolar neurons within the olfactory epithelium of the nasal cavity. IV. Taste A. Summary 1. The sensory structures that detect taste stimuli are the taste buds. Taste buds are oval structures located on the surface of certain papillae, which are large enlargements on the surface of the tongue.

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2. Taste buds are also distributed throughout other areas of the mouth and pharynx, such as the palate, root of the tongue, and epiglottis. 3. Each taste bud consists of two types of cells. a. Specialized epithelial cells form the exterior supporting capsule of the taste bud, and the interior of each bud consists of about 40 taste cells. 4. Each taste cell consists of hairlike processes called taste hairs. These extend into a tiny opening in the epithelium of the taste bud called a taste pore. 5. Taste sensations can be divided into four basic types: sour, salty, bitter, and sweet. 6. Many taste sensations can be influenced by the olfactory sensations. Ex. Compare the taste of some food before and after pinching your nose. It is easy to detect that the sense of taste is reduced while the nose is pinched. 7. Why does food not taste as good when a person has a cold? A cold my influence a stuffy nose, which decreases air flow and increases the thickness of mucus covering the olfactory epithelium and thus interfere with taste. 8. Taste buds at the tip of the tongue – sweet and salty Back of the tongue – bitter Side of the tongue – sour taste V. Vision A. Summary 1. The visual system includes the eyes and the accessory structures, afferent neurons that project to the cerebral cortex where visual impulses are interpreted. 2. Accessory structures – protect, lubricate, and move the eye. They include the eyebrows, eyelids, conjuctiva, lacrimal apparatus, and extrinsic eye muscles. B. Eyebrows 1. Protect the eyes by preventing perspiration, which can irritate the eyes, from running down the forehead and into them. They also help shad the eyes from direct sunlight. C. Eyelids ( Palpebrae ) 1. Protect the eyes from foreign objects. They suddenly will close rapidly to protect the eye. 2. Blinking which normally occurs about 20 times per minute, also helps to keep the eyes lubricated by spreading tears over the surface of the eye. 3. A sphincter type muscle called the orbicularis oculi – opens and closes the eyelid 4. Eyelids are under voluntary control, the conscious movement of them is not fast enough to prevent injury to the eye. 5. Eyes are controlled by an automatic reflex action that assists in protecting the eye. D. Conjunctiva

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1. The conjunctiva is a thin, transparent mucous membrane that covers the inner surface of the eyelids and the anterior surface of the eye. 2. Conjunctivitis – is an inflammation or some irritation of the conjunctiva (pink eye) E. Lacrimal apparatus 1. This consists of a lacrimal gland situated in the superior lateral corner of the orbit and a nasolacrimal duct in the inferior medial corner of the orbit. 2. The lacrimal gland produces tears, which pass over the anterior surface of the eye. 3. Tears serve to lubricate the eye and cleanse it. 4. Tears also contain an enzyme that helps combat eye infection. F. Extrinsic Eye Muscles 1. Movement of each eye is accomplished by six skeletal muscles called extrinsic eye muscles. Four rectus muscles and two oblique muscles. VI. Anatomy of the Eye A. Summary 1. The eyeball is a hollow, fluid filled sphere. About 1 inch in diameter. It is slightly longer that it is wide. 2. There are 3 layers or tunics that make up the eye. B. Fibrous Tunic 1. The sclera – is the outer layer, it is a white, tough, fibrous membrane, which helps to maintain the spherical shape. 2. The cornea – is the transparent and colorless part of the eye through which light waves pass. It is often called the window of the eye. Cornea is very sensitive. It bends and refracts the light entering. C. Vascular Tunic 1. This layer contains most of the blood vessels. 2. The choroid – a thin structure consisting of a vascular network and large numbers of melanin pigment. Therefore it appears black. The black absorbs light so that it is not reflected inside the eye. This would interfere with vision. 3. The ciliary body contains smooth muscles for shape. 4. Attached to the ciliary body is the iris or colored part of the eye. 5. The hole in the center of the iris is called the pupil. The iris regulates the diameter of the pupil. D. Nervous Tunic

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1. The retina or nervous tunic is the innermost tunic. 2. Contains the cells responsible for converting light into impulses that are transmitted to the CNS. These cells are called rods and cones. 3. Rods – very sensitive to light and can function in dim light. Do not provide colored vision. 4. Cones – require much light and provide us with colored vision. There are 3 types of cones: blue, green, or red. VII. Disorders of the eye A. Defects of the Eye 1. In a human eye the quality of the image is affected by the shape of the cornea, the lens, and eyeball. 2. Any slight irregularity of the cornea, lens, or eyeball may result in abnormalities that require correction. 3. Astigmatism – the cause is the cornea with an imperfect curvature. As a result light fails to come to a single point on the retina and blurred vision results. 4. Myopia – Nearsightedness – Light focuses in front of the retina instead of on the retina. This happens because the cornea is too long. Result – Person can read a book close up but cannot see things far off. Cure – Concave lens 5. Hyperopia – Farsightedness – Light focuses behind the retina. This happens because the cornea is too short. Result – Cannot read a book but can see things far off. Cure – Convex lens. VIII. Hearing and Balance A. The Ear and its Function 1. External Ear a. The auricle – is the fleshy part of the external ear on the outside of the head. b. The auricle opens into the external auditory meatus - a passageway that leads to the eardrum. c. The auricle directs sound waves toward the external auditory meatus. d. The meatus is lined with hairs and ceruminous glands that produce ceruminous – earwax e. eardrum – often called tympanic membrane – a thin membrane that separates the external ear from the middle ear. Sound waves reaching the eardrum cause it to vibrate. 2. Middle Ear a. The middle ear contains three auditory ossicles (ear bones) – - malleus – hamer - incus – anvil - stapes – stirrup

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b. eustachian tube – enables air pressure to be equalized between the outside air and the middle ear cavity. Ex. Changing altitude causes pain. A person can swallow, yawn, chew, or hold nose and mouth shut while gently trying to force air out of the lungs might open the auditory tube. 3. The Inner ear a. Consists of tunnels called the bony labyrinth (maze) – filled with fluid called perilymph b. the inner ear has three parts – semicircular canals, the vestibule, and the cochlea. c. cochlea is involved in hearing d. semicircular canals and cochlea are involved with balance 4. Steps involved in Hearing a. sound waves are collected by the auricle and conducted through the external auditory meatus to the tympanic membrane, causing it to vibrate. b. the vibrating tympanic membrane causes the malleus, incus, and stapes to vibrate. c. vibration of the stapes produces vibration in the perilymph of the scala vestibuli. d. this vibration causes vibration in the cochlea e. vibration is detected by hair cells which induce action potential in the cochlear neurons. f. these action potential are conducted to the CNS g. these are perceived as sound by the cerebral cortex. IX. Assign a disorder for each student to teach to the class: 1. Astigmatism 2. Myopia 3. Hyperopia 4. Color Blindness 5. Cataracts 6. Glaucoma 7. Snellen Eye Chart 8. Stye 9. Presbyopia 10. Strabismus 11. Cataract 12. Night Blindness 13. Diabetes Mellitus 14. Retinal Detachment 15. Conjunctivitis 16. RK Radial Karotoma 17. Otitis Media 18. Motion Sickness Include the following 1. History – include who named or who first discovered

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2. Symptoms 3. System or systems affected by the disease 4. prognosis – what is the prediction for the patient? 5. Treatment 6. What research is being done. 7. Cause – Genetic 8. Other interesting facts – support groups

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Activities for Chapter 9 1. The Taste Test 2. Smelling is Tasting 3. Right Eye – Left Eye 4. Now you See it 5. Your Blind Spot 6. It’s All in your head 7. Look Here 8. Listen Here

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