Introduction to Health ScienceIntroduction to Health ScienceSpecial SensesSpecial Senses

Description of the Special Description of the Special SensesSenses• SmellSmell– Smell occurs when specialized cells in the nose Smell occurs when specialized cells in the nose

(chemoreceptors) detect chemicals resulting in (chemoreceptors) detect chemicals resulting in nerve impulses which are sent to the brain for nerve impulses which are sent to the brain for interpretation.interpretation.

NoseNose• In the upper part of the nasal cavity are specialized nerve cells In the upper part of the nasal cavity are specialized nerve cells

called olfactory receptor cells. The olfactory receptor cells called olfactory receptor cells. The olfactory receptor cells contain hair called cilia to which the dissolved chemicals contain hair called cilia to which the dissolved chemicals attach.attach.

• Nerve impulses are transmitted from the olfactory receptors Nerve impulses are transmitted from the olfactory receptors cells to the olfactory bulb, to the olfactory nerve to the brain cells to the olfactory bulb, to the olfactory nerve to the brain where the sense of smell is interpreted.where the sense of smell is interpreted.

• Basic smells include putrid (rotting food), pungent (spicy), Basic smells include putrid (rotting food), pungent (spicy), floral (flowers), ethereal (medicine smell), and mint.floral (flowers), ethereal (medicine smell), and mint.

TasteTaste• Taste occurs when specialized cells on the Taste occurs when specialized cells on the

tongue (chemoreceptors) detect chemicals tongue (chemoreceptors) detect chemicals resulting in nerve impulses which are sent to resulting in nerve impulses which are sent to the brain for interpretation.the brain for interpretation.

Mouth and TongueMouth and Tongue• The sense organs that detect dissolved chemicals for the The sense organs that detect dissolved chemicals for the

sense of taste are the taste buds. Taste buds are located in sense of taste are the taste buds. Taste buds are located in the tongue and throughout the mouth. the tongue and throughout the mouth.

• When the taste buds are stimulated by chemicals, they When the taste buds are stimulated by chemicals, they generate nerve impulses which are sent to the brain for generate nerve impulses which are sent to the brain for interpretation. interpretation.

• There are five basic tastes, although they are not limited to There are five basic tastes, although they are not limited to specific parts of the tongue: sweet (sugars and specific parts of the tongue: sweet (sugars and carbohydrates), sour (acids), salt (salt), bitter (caffeine) and carbohydrates), sour (acids), salt (salt), bitter (caffeine) and umami (protein and amino acids).umami (protein and amino acids).

HearingHearing• Hearing involves the movement of sound Hearing involves the movement of sound

vibrations through the ear until they reach a vibrations through the ear until they reach a specialized region in the inner ear where specialized region in the inner ear where nerve impulses are generated by cells that nerve impulses are generated by cells that detect movement (mechanoreceptors). These detect movement (mechanoreceptors). These nerve impulses travel to the brain where they nerve impulses travel to the brain where they are interpreted as sound. are interpreted as sound.

Outer EarOuter Ear• AuricleAuricle– The visible portion of the ear on the side of the head.The visible portion of the ear on the side of the head.– Composed of cartilage Composed of cartilage – Captures the sound waves from the environment and Captures the sound waves from the environment and

directs them toward the auditory canal.directs them toward the auditory canal.

• Auditory CanalAuditory Canal– Tube lined with hair and wax.Tube lined with hair and wax.– Assists in the passage of sound waves to the middle Assists in the passage of sound waves to the middle

ear.ear.– Provides protection for the ear as particles, debris and Provides protection for the ear as particles, debris and

dust are trapped by the hair and wax.dust are trapped by the hair and wax.

Middle EarMiddle Ear• Tympanic MembraneTympanic Membrane– Known as the eardrum, it is the first structure of the Known as the eardrum, it is the first structure of the

middle ear.middle ear.– It vibrates with the sound waves and passes the It vibrates with the sound waves and passes the

vibrations to the middle ear bones.vibrations to the middle ear bones.• Auditory OssiclesAuditory Ossicles– Three tiny bones in the middle ear that continue the Three tiny bones in the middle ear that continue the

passage of sound vibrations.passage of sound vibrations.– They also amplify the vibrations twenty times.They also amplify the vibrations twenty times.

• Eustachian Tube (auditory tube)Eustachian Tube (auditory tube)– Small tube extending from the middle ear into the Small tube extending from the middle ear into the

throat.throat.– Helps to equalize pressure inside the ear.Helps to equalize pressure inside the ear.

Inner EarInner Ear• CochleaCochlea– Snail shaped structure composed of a series of Snail shaped structure composed of a series of

membrane-lined fluid-filled canals that continue membrane-lined fluid-filled canals that continue to pass along the sound vibrations.to pass along the sound vibrations.

– The sound vibrations eventually reach a The sound vibrations eventually reach a specialized structure of the inner ear called the specialized structure of the inner ear called the Organ of Corti where nerve impulses are Organ of Corti where nerve impulses are generated. The impulses are transmitted to the generated. The impulses are transmitted to the brain where they are interpreted.brain where they are interpreted.

VisionVision• The sense organs that respond to light are the The sense organs that respond to light are the

eyes. eyes. • The light waves travel through the eyes until The light waves travel through the eyes until

they reach the back of the eye called the they reach the back of the eye called the retina where nerve impulses are generated by retina where nerve impulses are generated by specialized cells that are sensitive to light specialized cells that are sensitive to light (photoreceptors). (photoreceptors).

• The impulses travel to the brain where they The impulses travel to the brain where they are interpreted as visual images and provide are interpreted as visual images and provide much information about the external world.much information about the external world.

EyeEye• EyelidEyelid– Structures composed of skin, muscles, and lashesStructures composed of skin, muscles, and lashes– Protect the eye from foreign objects by the blink Protect the eye from foreign objects by the blink

reflex.reflex.– Moves tears along the surface of the eyeball to Moves tears along the surface of the eyeball to

keep the eyeball moist.keep the eyeball moist.

• ConjunctivaConjunctiva– Membrane lining the insides of the eyelids and Membrane lining the insides of the eyelids and

eyeball.eyeball.– Reduces friction during blinkingReduces friction during blinking

EyeEye• ScleraSclera– The white part of the eye.The white part of the eye.– Provides protection and shape to the eye.Provides protection and shape to the eye.

• CorneaCornea– The clear window of the front part of the eye.The clear window of the front part of the eye.– Allows light waves to enter the eye.Allows light waves to enter the eye.– Helps to bend the light waves on to the back of Helps to bend the light waves on to the back of

the eye (retina)the eye (retina)

EyeEye• IrisIris– The colored portion of the eye which contains two The colored portion of the eye which contains two

sets of muscles.sets of muscles.– Regulates the size of the pupil to control the amount Regulates the size of the pupil to control the amount

of light entering the eye.of light entering the eye.• PupilPupil– An opening in the center of the iris.An opening in the center of the iris.– Passage for light.Passage for light.

• LensLens– Transparent disc shaped structure located behind the Transparent disc shaped structure located behind the

iris and pupil.iris and pupil.– Focuses light waves on to the retina.Focuses light waves on to the retina.

EyeEye• RetinaRetina– Most inner layer of the eyeball. Located under the Most inner layer of the eyeball. Located under the

sclera.sclera.– Contains the photoreceptors that when stimulated Contains the photoreceptors that when stimulated

by light generate nerve impulses which are then by light generate nerve impulses which are then sent to the brain for interpretation.sent to the brain for interpretation.

TouchTouch• Touch is the detection of various amounts of Touch is the detection of various amounts of

pressure by the skin. pressure by the skin. • Nerve impulses are generated by cells that are Nerve impulses are generated by cells that are

sensitive to movement (mechanoreceptors) sensitive to movement (mechanoreceptors) and sent to the brain for interpretation.and sent to the brain for interpretation.

SkinSkin• The skin contains several different types of nerve The skin contains several different types of nerve

receptors in the skin which are sensitive to deep receptors in the skin which are sensitive to deep pressure like poking or light touch.pressure like poking or light touch.

• All regions of the skin are sensitive to touch. The All regions of the skin are sensitive to touch. The greatest number of touch receptors are found in the greatest number of touch receptors are found in the fingers, toes, and face.fingers, toes, and face.

• Once the nerve impulses for touch are generated, Once the nerve impulses for touch are generated, they are sent to the brain for interpretation.they are sent to the brain for interpretation.

Disorders of the Special SensesDisorders of the Special Senses• ConjunctivitisConjunctivitis

– Conjunctivitis is the Conjunctivitis is the inflammation of the inflammation of the conjunctiva.conjunctiva.

– Can be caused by viruses, Can be caused by viruses, bacteria, fungi, and bacteria, fungi, and allergies. The most allergies. The most common cause is viral.common cause is viral.

– ””Pinkeye” is the common Pinkeye” is the common term for conjunctivitis.term for conjunctivitis.

Middle Ear Infection (Otitis Media)Middle Ear Infection (Otitis Media)• Causes of otitis media include Causes of otitis media include

anything that causes the anything that causes the Eustachian (auditory) tubes to Eustachian (auditory) tubes to become blocked, inflamed or become blocked, inflamed or irritated.irritated.– Examples include colds, sinus Examples include colds, sinus

infections, allergies, tobacco smoke infections, allergies, tobacco smoke or other irritants, babies who spend or other irritants, babies who spend a lot of time drinking on his or her a lot of time drinking on his or her back.back.

• Most common symptom is Most common symptom is earacheearache

• Treatment includes antibiotics for Treatment includes antibiotics for bactierial infections, use of warm bactierial infections, use of warm cloths and analgesics to relieve cloths and analgesics to relieve pain and possible surgery if ear pain and possible surgery if ear infections recur frequently.infections recur frequently.

DeafnessDeafness

• Deafness is the complete or partial loss of hearing in one or both ears.

• May be caused by a blockage of the sound waves through the middle ear by wax build up, foreign objects, tumors or other matter. – This type of deafness generally improves

once the blockage is removed. • Deafness may also result from damage to

the nerves or to the Organ of Corti. – This type of deafness is usually irreversible

and may progressively get worse.• Treatment may include removal of the

blockage, hearing aids, or cochlear implants.

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MyopiaMyopia

• Nearsightedness; when a Nearsightedness; when a person sees near objects person sees near objects clearly and distant objects clearly and distant objects are blurred. are blurred.

• Occurs when the physical Occurs when the physical length of the eye is greater length of the eye is greater than the optical length. than the optical length.

• Symptoms include blurred Symptoms include blurred vision of distant objects, vision of distant objects, squinting, eyestrain, and squinting, eyestrain, and sometimes headaches.sometimes headaches.

• Treated with concave lenses Treated with concave lenses or LASIK surgeryor LASIK surgery

HyperopiaHyperopia

• Farsightedness; when a person Farsightedness; when a person sees far objects clearly and sees far objects clearly and near objects are blurred.near objects are blurred.

• Occurs when the physical Occurs when the physical length of the eyeball is too length of the eyeball is too small or the focusing power of small or the focusing power of the lens is too weak.the lens is too weak.

• Symptoms include blurred Symptoms include blurred vision of close objects, eye vision of close objects, eye strain, aching eyes, and strain, aching eyes, and headaches while reading.headaches while reading.

• Treated with convex lenses. Treated with convex lenses. Surgical options also available.Surgical options also available.

PresbyopiaPresbyopia• The normal loss of accommodation

power of the eye which occurs as a consequence of aging. It occurs because the lens becomes less flexible and less able to bulge or accommodate for near vision.

• Symptoms are similar to those of farsightedness and include:– blurring of close objects– eye strain – holding objects further from the face to

focus– headaches or fatigue from focusing on

close objects. • Treatments may include the use of

reading glasses or bifocals.