The Senses: The Sights and Sounds

CHAPTER

ESSENTIALS OF A&PFOR EMERGENCY CARE

Copyright ©2011 by Pearson Education, Inc.All rights reserved.

Essentials of A&P for Emergency CareBruce J. Colbert • Jeff Ankney • Karen T. Lee • Bryan E. Bledsoe

The Senses: The Sights and Sounds

11



Multimedia Asset Directory

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



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.



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.



Learning Objectives

• Contrast the types of pain and the pain response.

• Explain several common disorders of the eye and ear.



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.



Pronunciation GuideClick on the megaphone icon before each item to hear the pronunciation.

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)




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)




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)




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)



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.



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.



ESP

• One controversial sense is Extrasensory Perception.

• This means senses outside the normal sensory perception.

• There is still debate over whether this sense exists.



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.



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.




• 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.




• 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.



Figure 11-1 Lacrimal structures of the eye.



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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.



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.



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.



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.



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.



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.



Figure 11-2 Internal structures of the eye.



Table 11-1 Structures and Functions of the Eye.



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



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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.



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.



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.



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.



From the Streets:Conjunctival Emergencies

• Common causes:– Trauma– Sneezing– Coughing– Vomiting– Straining



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



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.



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.



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



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.



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



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.



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.



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.



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.



Figure 11-6 Structures of the ear.



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.



The External Ear

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



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.



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.



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.”



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The Inner Ear

• The oval window transmits sound waves into the inner ear.

• The inner ear is divided into three separate, hollow, bony spaces that form a maze, or labyrinth. As a result, this area can also be called the bony labyrinth.

• The three areas include the cochlea, the vestibule chamber, and the semicircular canals.



Sound Transmission in the Inner Ear

• The cochlea is a bony spiral or snail shell-shaped entrance to the internal ear, and is connected to the oval window membrane.

• The cochlea contains fluid called perilymph which helps transmit the sound through this area.

• The sound is then transmitted to another section of the cochlea which contains another fluid, endolymph.




• The sound is then carried to tiny hairlike receptors that are stimulated and conduct the signal to the brain via the vestibulocochlear nerve (cranial nerve VIII).

• In summary, sound waves enter the external canal and vibrate the eardrum or tympanic membrane in a process called sound conduction.

• The middle ear then amplifies the sound through the respective ossicles. This process is called bone conduction of sound.




• The last ossicle (stapes) vibrates and causes a gentle pumping against the oval window membrane. This causes cochlear fluid to vibrate small hairlike neurons found in an area called the organ of Corti. A nerve impulse is sent to the temporal lobe of the brain, where it is interpreted as sound, a process called sensorineural conduction.




• Low-intensity sound waves, similar to a clock ticking, send vibrations that cause the sensory cells to move in waves that are interpreted by the brain as that “tick tock” sound.



Vestibular Sense in the Inner Ear

• The ear is also responsible for your sense of balance or equilibrium. The semicircular canals process sensory input related to equilibrium. They contain nerve endings or receptors in the form of hair cells. The semicircular canals are three loops within the inner ear that help to maintain balance.




• Like the cochlea, the semicircular canals are filled with endolymph fluid, and each canal contains a sensory receptor. This fluid moves when you change body position. The movement is picked up by the sensory receptor, which triggers a nerve impulse to travel to the brain stem and the cerebellum.




• Here the impulse is interpreted as body position to help maintain muscle coordination and body equilibrium.



Figure 11-7 The structures of the inner ear.



Table 11-2 Structures and Functions of the Ear.



Table 11-2 (continued) Structures and Functions of the Ear.



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Taste

• The sense of taste is referred to as the gustatory sense.

• The tongue is covered by tiny bumps called papillae, each of which contains several taste receptors (taste buds). Taste buds can also be found in other parts of the mouth, including the lips and back of the throat.



Taste

• Taste buds send signals to the brain via three distinct cranial nerves. One nerve detects the anterior two-thirds of the tongue, a second detects the posterior portion of the tongue, and the third detects the throat area.



Taste

• Taste buds detect five tastes: sweet, sour, salty, bitter, and umami. Umami is included with the traditional four because it is the distinct taste of glutamates, which cannot be duplicated by the combination of any of the other four tastes.

• Taste preferences may change with the body’s need, which is why pregnant women may crave a variety of foods throughout their pregnancy.

• The refinement of food taste is primarily dependent on the sense of smell and the number of functioning taste buds.



Figure 11-8 The sense of taste.



Smell

• The sense of smell arises from the receptors located in the olfactory region or the upper part of the nasal cavity.

• We “sniff” to bring the smell into the area where it can be interpreted.

• Taste and smell are closely related, and pleasant food odors stimulate digestive enzymes.

• Smell is also closely linked to memory.



Figure 11-9 The sense of smell.



Touch

• Touch receptors are small rounded bodies, called tactile corpuscles, located in the skin, especially concentrated in the fingertips and the tip of the tongue.

• Temperature sensors are also located in the skin, with separate sensors for heat and cold.

• Adaptation occurs when sensory stimulation is continually applied, changing your perception of temperature.



Clinical Application:Heat and Cold Therapy

• Heat and cold therapy are used for a variety of injuries, relying on our bodies physiological response to temperature change. Heat relaxes muscles and dilates blood vessels, bringing more blood flow to the site of injury. Cold constricts blood vessels and minimizes the amount of bleeding and swelling at the site.



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Pain

• Pain is a very important protective sense. It is our body’s way of making us pay attention to danger.

• Pain is the most widely distributed sense, being found in skin, muscle, joints, and internal organs.

• The pain receptors are merely branchings of nerve fibers called free nerve endings.

• Pain receptors do not adapt and you feel pain as long as the stimulus is there.

• Pain threshold appears to vary among patients.



Types of Pain

• Referred pain – originates in an internal organ and is felt in another region of the skin; an example is liver and gallbladder pain which may be felt in the right shoulder

• Phantom pain – pain felt in an area that no longer exists, for example, pain felt after an amputation



Figure 11-11 Various sites of referred pain.



Figure 11-12 The sense of touch.



From the Streets:Pain

• Analgesics are medications that help to alleviate pain.

• Inadequate analgesia remains a problem in emergency care, especially in children.

• Because pain is subjective, it is often difficult to assess.

• NSAIDs are used to treat mild to moderate pain.

• Opioid analgesics are used to treat moderate to severe pain.



Common Disorders of the Eye

• Conjunctivitis – inflammation of the membrane that covers the eye; can be acute or chronic, caused by pathogens or irritants, and is sometimes called pink eye.

• Cataract – clouding of the lens; incidence may increase with increased exposure to sunlight; untreated, cataracts can lead to blindness. Cataract surgery was one of the earliest surgical procedures, dating back to ancient Greece.




• Glaucoma – increased pressure in the fluid of the eye which interferes with optic nerve function; occurs in 20% of adults over forty, and is cause of 15% of cases of blindness in the U.S.

• Hyperopia – results from the flattening of the globe of the eye or a refraction problem where light rays focus behind the retina; Farsightedness




• Presbyopia – is farsightedness that occurs with age, usually between 40 and 45 years.

• Myopia – objects at a distance appear blurred; also called nearsightedness

• Amblyopia – also called a lazy eye, this occurs in childhood and results in poor vision because one eye does more work than the other



Using the Eyes to Diagnose Other Problems

• The eyes can help diagnose a variety of non-visual diseases.

• A yellow tint to the conjunctiva (jaundice) can indicate liver disease.

• REM (rapid eye movement) is a stage of sleep and can be measured in sleep studies to help diagnose sleep disorders.

• Responsiveness of the pupil to light can diagnose neurological problems (PERLA).



Figure 11-13 Some common eye disorders. (A) Cataract of right eye.



Figure 11-13 (continued) Some common eye disorders. (B) Pinkeye.



Figure 11-13 (continued) Some common eye disorders. (C) A herpes virus infection.



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Common Disorders of the Ear

• Otitis Media – infection of the inner ear• Labyrinthitis – inflammation of the inner

ear, often caused by high fevers, resulting in vertigo

• Ménière’s disease – a chronic infection that affects the labyrinth and leads to progressive hearing loss and vertigo



Common Disorders of the Ear

• Deafness – partial or complete hearing loss caused by many conditions including damage of any ear structure from the tympanic membrane to the auditory nerve

• Tinnitus – ringing in the ear, sometimes caused by taking too much aspirin



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Snapshots from the Journey

• The senses of sight (eyes), sound and equilibrium (ears), taste (tongue), and smell (nose) are called special senses. The body feels other sensations, such as touch, heat, cold, and pain, which are called general senses.

• The eye is very similar to a camera with lens cover (eyelids), opening (pupil), the shutter (iris), the lens (eye lens), and the photoreceptive film (retina).




• Light rays enter the eye and pass through the cornea, aqueous humor, pupil, lens, and vitreous humor and are focused on the retina. The photoreceptors in the retina cause a chemical impulse to be sent to the optic nerve, which carries it to the brain for the interpretation we call vision.

• The ear has three major divisions: the external, middle, and inner ear. The ear is the organ for hearing and maintaining our sense of balance.




• Sound waves enter the external canal and vibrate the tympanic membrane. The middle ear amplifies the sound through the receptive, tiny ossicles.




• The last ossicle, the stapes, vibrates and causes a gentle pumping against the oval window membrane, causing cochlear fluid (perilymph) to move and transmit the sound to endolymph, and then to small hairlike nerves, eventually reaching the hearing centers in the brain where the sound is interpreted.




• The semicircular canals are responsible for maintaining body balance.

• Our sense of taste, or gustatory sense, has traditionally been thought to consist of sweet, sour, salty, and bitter, but a fifth taste, umami, has recently been distinguished as its own category. The sense of taste originates on taste buds on the tongue and is closely associated with the sense of smell.




• The sense of smell arises from the olfactory region of the nose.

• The sense of touch allows perceptions of pain, temperature, pressure, traction, and the sensation of being “tickled.”



Case Study

A 40-year-old male patient presents with complaints of tinnitus and vertigo. He complains that his hearing is getting progressively worse and he is having dizzy spells and nausea.



Case Study Questions

• Describe the patient’s complaints in your own words.

• What possible disease is present? • What part of the ear is affected, and why?



From the Streets

• You respond to a 22 year-old carpenter who complains of left eye pain after using a power sander without eye protection. His left eye hurts more when it moves and the outer most layer is red, moist, & inflamed. His pupil exam reveals PERLA and extra-ocular movements (tracking an object moving six directions in the visual field) are intact.



From the Streets Questions

• What is his most likely diagnosis?• What is the outermost layer of the eye

called?• What does PERLA stand for?• What cranial nerve is assessed during an

eye exam?• What cranial nerves are assessed when

checking extraocular movements?• What is his prognosis?




• What is his most likely diagnosis? Foreign body in the eye (conjuctivitis)

• What is the outermost layer of the eye called? Conjunctiva

• What does PERLA stand for? Pupils equal, reactive to light and accommodation.

• What cranial nerve is assessed during an eye exam? Cranial nerves II (optic)




• What cranial nerves are assessed when checking extraocular movements? Cranial nerves III (oculomotor), IV (trochlear), and VI (abducens)

• What is his prognosis? Most foreign bodies can be removed with irrigation of sterile water



End of ChapterReview Questions

1. The part of the eye that allows varying amounts of light into the retina is the:a. Lensb. Humorc. Irisd. Optic nerve




2. The photopigment structures responsible for the ability to see colors are:a. Conesb. Rodsc. Irisd. Pupil




3. The incus is found in the:a. Inner earb. Middle ear c. External eard. Region of South America




4. What is the correct descending order for the media through which sound travels, with the best medium listed first:a. Liquid, air, solidb. Solid, liquid, airc. Air, liquid, solidd. They are all equal




5. Another word for the sense of taste is:a. Olfactoryb. Vertigo c. Masticationd. Gustatory




6. Damage to the tympanic membrane can cause this kind of deafness:a. Nerveb. Conduction c. Membranousd. All of the above




7. Which part of the body has the highest density of touch receptors?a. Fingersb. Forearm c. Backd. Buttocks




1. The two functions of the auditory system are __________ and _____________.

2. The three ossicles of the ear are__________, __________, and __________.

3. A man with red green color blindness is missing one type of ________, a retinal cell.

4. A woman presents with pain in her upper right abdomen and back. Which organ is inflamed?




5. People who spend a lot of time in the sun are more likely to develop this eye disorder.




1. Differentiate between special and general senses.

2. What are the five basic tastes? How are taste and smell related?

3. Define “adaptation” in relation to temperature sensors.

4. Trace the path of light rays from the world to the brain. Explain how rays are focused.

5. Explain the journey of sound waves from the environment to the brain.

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The Senses: The Sights and Sounds