The Senses: The Sights and Sounds

1. 11 The Senses: The Sights and Sounds

2. Multimedia Asset Directory Slide 19 Opthalmic Mediations and their Delivery Video Slide 29 Eye Anatomy Animation Slide 51 Middle Ear Animation Slide 52 Adolescent Ear Animation Slide 53 Child's Ear Animation Slide 65 Tympanic Membrane Thermometer Measurements Video Slide 74 Heat Therapy Video Slide 75 Cold Therapy Video Slide 88 Cataracts Video Slide 89 Conjunctivitis Video Slide 92 Otitis Media Video Slide 93 Audiologists Video Slide 94 Opthalmologists and Opticians Video

3. Introduction • All of the input from your environment must be taken in by your special senses and interpreted by your brain so you can understand and appreciate the experience. • The senses that gather sensory input are also protective in nature and need to be highly integrated with the nervous system for our survival.

4. Learning Objectives • Distinguish between general and special senses. • Describe the internal and external anatomy and functions of the eye. • Describe the internal and external anatomy and functions of the ear. • Discuss the process involved with the senses of taste, smell, and touch.

5. Learning Objectives • Contrast the types of pain and the pain response. • Explain several common disorders of the eye and ear.

6. Overview • In addition to the senses of vision, hearing, smell, taste, and touch there are also the senses of pain, pressure, temperature, position, balance, and feelings of hunger and thirst that are also important to our survival. • The senses of sight, hearing, balance, taste, and smell are referred to as our special senses.

7. amblyopia (AM blee OH pee ah) aqueous humor (AY kwee us HYOO mer) auricle (AW rih kul) cataract (KAT ah rakt) cerumen (seh ROO men) ceruminous glands (seh ROO men us) choroid (KOH royd) ciliary muscles (SILL ee AIR ee) cochlea (KOCK lee ah) Pronunciation Guide Click on the megaphone icon before each item to hear the pronunciation.

8. conjunctiva (KON junk tih vah) endolymph (EN doe limf) eustachian tubes (yoo STAY she an) external auditory meatus (AW dih tor ee mee AYE tus) glaucoma (glaw KOH mah) gustatory sense (GUSS ta TOH ree) hyperopia (HIGH per OH pee ah) incus (ING kus) Pronunciation Guide Click on the megaphone icon before each item to hear the pronunciation.

9. labyrinth (LAB ih rinth) lacrimal apparatus (LAK rim al app ah RA tus) malleus (MALL ee us) Ménière’s disease (MAIN ee airz) myopia (my OH pee ah) ossicle (AHS ih kull) otitis media (oh TYE tiss MEH dee ah) perilymph (PER ih limf) pinna (PIN ah) Pronunciation Guide Click on the megaphone icon before each item to hear the pronunciation.

10. presbyopia (PREZ bee OH pee ah) sclera (SKLAIR ah) stapes (STAY peez) tactile corpuscles (KOR pus el) tinnitus (tin EYE tus) tympanic membrane (tim PAN ik) vestibule chamber (VES tih byool) vitreous humor (VIT ree us HYOO mer) Pronunciation Guide Click on the megaphone icon before each item to hear the pronunciation.

11. The Different Senses • Our body senses allow us to experience all aspects of our journey, allowing us to see, hear, smell, taste, and feel the world around us. • Our senses allow us to monitor and detect changes in the environment, sending this information to the brain via sensory (afferent) neurons. The brain interprets the information and makes the appropriate motor (efferent), response.

12. Classification of Senses • The senses of sight, sound, equilibrium, taste, and smell are referred to as the special senses. They are in well-defined areas. Other senses scattered throughout our body are referred to as general senses including the sensation of touch, heat, cold, pain, nausea, hunger, thirst, and pressure (or deep touch). • Cutaneous senses use the receptors of the skin, while visceral senses include nausea, hunger, thirst, and the need to urinate and defecate.

13. ESP • One controversial sense is Extrasensory Perception. • This means senses outside the normal sensory perception. • There is still debate over whether this sense exists.

14. Sense of Sight Overview • The eye has many similarities to a camera. The light rays from the image you view pass through the pupil, and then through the lens, where they are focused on the retina (photoreceptors). • The iris allows the right amount of light to enter the eye for proper focusing. • External structures of the eye help to provide protection. • The lacrimal glands secrete tears to help keep the eye clean.

15. External Structures of the Eye • The orbit is a cone-shaped cavity formed by the skull that houses and protects the eyeball. This cavity is padded with fatty tissue that acts as a cushion to prevent injury. • Six short muscles connect the eyeball to the orbit, and allow rotary movement so you can see in all directions.

16. External Structures of the Eye • The eyelids close over the eye to protect it from light, foreign particles, or impact injury. Eyelashes in the eyelid help to prevent large particles from entering the eye. • The eyelids also contain sebaceous glands that secrete oil to keep the eyelids soft and pliant, and make the eyelashes slightly sticky to trap particles.

17. External Structures of the Eye • The conjunctiva is a membrane over the surface of the eyeball that acts as a protective covering for the exposed surface. • The lacrimal apparatus produces and stores tears and contains the lacrimal gland and its corresponding ducts. • The lacrimal gland produces tears, spread by blinking, for cleaning and lubrication. Tears act as an antiseptic.

18. Figure 11-1 Lacrimal structures of the eye.

19. Click here to view a video on the topic of Opthalmic Medications and their Delivery. Back to Directory

20. Internal Structures of the Eye • The globe-shaped eyeball is the organ of vision and is separated into two chambers of fluid that help to protect the eye. • The fluids of the eye are called humors. Aqueous humor is watery and bathes the iris, pupil, and lens and fills the anterior and posterior chambers. Vitreous humor is a clear jelly-like fluid that occupies the entire cavity behind the lens.

21. Layers of the EyeThe Sclera • The eye has three layers. • The sclera is the outermost layer and is a tough fibrous tissue that serves as a protective shield. • The sclera contains the cornea, which is transparent to allow light to pass through and curved to bend the entering light to focus it on the retina.

22. Layers of the EyeThe Choroid • The choroid is the middle layer. It is a highly vascularized and pigmented region that provides nourishment to the eye. • This layer contains the iris and the pupil. The iris is the colored portion of the eye that controls the opening, or pupil, where light passes into the eye. The iris is a sphincter that in low light relaxes, allowing the pupil to dilate so more light can enter.

23. Layers of the EyeThe Choroid • Located behind the pupil is the lens, which is surrounded by ciliary muscles. • These muscles can alter the shape of the lens, making it thinner or thicker to allow the incoming light rays to focus on the retina. • This process is called accommodation, which basically combines changes in the size of the pupil and the lens curvature to make sure the image converges in the same place on the retina and therefore is properly focused.

24. Layers of the EyeThe Retina • The retina is a delicate membrane that continues posteriorly and joins the optic nerve. • The retina contains two types of light sensing receptors called rods and cones. The rods are active in dim light and do not perceive color, while the cones are active in bright light and do perceive color. • These receptors contain photopigments that cause a chemical change when light hits them, causing impulses to be sent to the optic nerve.

25. Layers of the EyeThe Retina • The information is then sent to the brain, where the impulse is interpreted, in the visual cortex of the occipital lobe, and we “see” the object. • In summary, light rays enter the eye and pass through the cornea, aqueous humor, pupil, lens, and vitreous humor and are focused on the retina. Here the photoreceptors in the retina cause an impulse to be sent to the optic nerve (Cranial Nerve II), which carries it to the occipital lobe of the brain for the interpretation we call vision.

26. Figure 11-2 Internal structures of the eye.

27. Table 11-1 Structures and Functions of the Eye.

28. Table 11-1 (continued) Structures and Functions of the Eye.

29. Click here to view an animation on the topic of the Eye. Back to Directory

30. From the Streets:Anisocoria • Anisocoria, or unequal pupils, is a concern in the emergency patient. • Pupillary construction is controlled by the oculomotor nerve (CN III). • In the trauma patient, anisocoria may indicate intracranial injury. • In the medical patient, anisocoria may indicate intracranial bleeding or tumor.

31. From the Streets:Anisocoria • Anisocoria can be a normal finding. • 20% of the population has some degree of anisocoria. • The difference is typically 1mm or less and is not accompanied by other findings.

32. From the Streets:Eye Emergencies • Two types of doctors specialize in these disorders: • Ophthalmalogists • Physicians who specialize in the medical and surgical management of eye disorders. • Optometrists • Doctors of optometry who perform refractive examinations and prescribe glasses and contact lenses.

33. From the Streets:Conjunctival Emergencies • Acute eye pain or a red eye are the most common initial complaints. • Trauma can cause the fragile blood vessels within the conjunctiva to repture, called subconjuctival hemorrhage.

34. From the Streets:Conjunctival Emergencies • Common causes: • Trauma • Sneezing • Coughing • Vomiting • Straining

35. Figure 11-3 Conjunctival abrasion overlying a large subconjunctival hemorrhage.

36. From the Streets:Blunt Eye Trauma • Blunt trauma to the eye can cause swelling of the lids and the periorbital tissues. • Bleeding into the anterior chamber is called a hyphema. • The patient’s head should be elevated to decrease intraocular pressure.

37. From the Streets:Blunt Eye Trauma • Blunt trauma to the eye can result in a blowout fracture in which the walls of the orbit are damaged.

38. Figure 11-4 Trauma to the right eye including complex upper lid laceration.

39. From the Streets:Penetrating Eye Trauma • Any injury that penetrates the globe or ruptures the globe is extremely serious • Common causes: • BB pellets • Lawn mower projectiles • Grinding injuries • Knife wounds • Gunshot wounds • Treatment includes placing a protective shield over the affected eye.

40. Figure 11-5 Enucleation of the right eye following blunt trauma.

41. From the Streets:Chemical Injuries • The severity of a chemical injury is directly related to the chemical agent involved. • Treatment includes irrigating the eye with copious amounts of water for 10 minutes.

42. From the Streets:Ultraviolet Keratitis • Ultraviolet keratitis is sever pain, tearing, light sensitivity, and foreign-body sensation that occurs after exposure to intense heat or bright light.

43. From the Streets:Acute Glaucoma • Failure of the aqueous humor to enter the canal of Schlemm. • The patient complains of cloudy vision, eye ache, frequent nausea and vomiting.

44. The Sense of Hearing • The ear is responsible for hearing and maintaining our equilibrium, or sense of balance. • We hear by receiving vibrations, usually via the air, and translating them into an interpretable sound via the eighth cranial nerve. • The ear can be separated into three divisions: the external ear, the middle ear, and the internal ear, or labyrinth.

45. Figure 11-6 Structures of the ear.

46. The External Ear • The external ear is the outer projection – the part we can see, called the pinna or auricle. • It also includes the canal leading into the middle ear, called the auditory canal or external auditory meatus. • The canal contains ear wax called cerumen, secreted by the ceruminous glands to lubricate and protect the ear.

47. The External Ear • At the end of the canal is the ear drum, or tympanic membrane, where the external ear ends.

48. The Middle Ear • The middle ear, or tympanic cavity, is a space that contains three small bones, or ossicles. • The ossicles are joined so they can amplify the sound waves the tympanic membrane receives from the external ear. • Once amplified, the sound waves are transmitted to the fluid in the inner ear.

49. The Middle Ear • The bones of the ear are named for their shape. • The hammer, or malleus, is attached to the tympanic membrane. • The anvil, or incus, is attached to the hammer. • The stirrup, or stapes, is attached to the incus and connects to a membrane called the oval window that begins the inner ear. • The ossicles can amplify sound up to 22 times the original level.

50. The Middle Ear • The eustachian tubes allow for air pressure on either side of the eardrum to be equalized. • The tubes connect the nasal cavity and pharynx to the middle ear. • This equalizing of pressure allows the eardrum to freely vibrate with incoming sound waves. Sudden pressure changes, like flying in an airplane, can affect this area, which is why our ears “pop.”