THE THE SENSESSENSES

CHAPTER 9CHAPTER 9

Receptors and SensationsReceptors and Sensations

Five general types of receptors are recognized:Five general types of receptors are recognized:

11. . ChemoreceptorsChemoreceptors: Are sensitive to changes in : Are sensitive to changes in chemical concentrations. Sense of smell and taste chemical concentrations. Sense of smell and taste fall into this category.fall into this category.

2. 2. NociceptorsNociceptors: These are pain receptors that : These are pain receptors that detect tissue damage.detect tissue damage.

3. 3. ThermoreceptorsThermoreceptors: Sensitive to temperature : Sensitive to temperature changes.changes.

4. 4. MechanoreceptorsMechanoreceptors: Respond to changes in : Respond to changes in pressure or movement.pressure or movement.

5. 5. PhotoreceptorsPhotoreceptors: Respond to light energy.: Respond to light energy.

Sensations are feelings that occur when the Sensations are feelings that occur when the brain receives sensory impulses from the brain receives sensory impulses from the peripheral nervous system.peripheral nervous system.

The impulses are relatively the same; it is The impulses are relatively the same; it is the brain’s interpretation that makes them the brain’s interpretation that makes them seem different and unique.seem different and unique.

SENSATIONS

SOMATIC SENSESSOMATIC SENSES

Somatic senses involve receptors Somatic senses involve receptors associated with the skin, muscles, joints, associated with the skin, muscles, joints, and visceral organs. If they occur at the and visceral organs. If they occur at the body surface, they are called body surface, they are called exteroceptive senses and include touch, exteroceptive senses and include touch, pressure, and temperature. pressure, and temperature.

Sensations associated with changes Sensations associated with changes occurring in visceral organs are called occurring in visceral organs are called visceroceptive senses.visceroceptive senses.

TOUCH AND PRESSURE TOUCH AND PRESSURE SENSESSENSES

Touch results from sensation of Touch results from sensation of tactile receptors just beneath the tactile receptors just beneath the skin. skin.

Pressure sensations result from Pressure sensations result from stimulation of receptors in deeper stimulation of receptors in deeper tissue. Each sensation is triggered tissue. Each sensation is triggered by a degree of displacement of by a degree of displacement of tissues involved. tissues involved.

Types of Touch/Pressure Types of Touch/Pressure SensorsSensors

Three types:Three types: 1. Free ends of Sensory Nerves1. Free ends of Sensory Nerves 2. Meissner’s Corpuscles are receptors 2. Meissner’s Corpuscles are receptors

for light touch. They are also used when for light touch. They are also used when a person wants to judge the texture of a person wants to judge the texture of something. Are found in the dermal something. Are found in the dermal papillae of the skin. Are abundant in papillae of the skin. Are abundant in hairless areas like lips, clitoris, palm.hairless areas like lips, clitoris, palm.

3. Pacinian Corpuscles: Detect deep 3. Pacinian Corpuscles: Detect deep pressure or vibrations. Located in pressure or vibrations. Located in subcutaneous tissues, deep subcutaneous tissues, deep submucosal tissues, and serous submucosal tissues, and serous membranes. Found around joints, membranes. Found around joints, tendons, muscles, mammary glands, tendons, muscles, mammary glands, external genitalia, pancreas, and external genitalia, pancreas, and urinary bladder.urinary bladder.

Temperature SensesTemperature Senses Thermal sensations are perceptions of Thermal sensations are perceptions of

degrees of warmth and coolness (extreme degrees of warmth and coolness (extreme heat or cold are experienced as pain).heat or cold are experienced as pain).

Receptors include two groups of free Receptors include two groups of free nerve endings located in the skin:nerve endings located in the skin:

1. Heat Receptors are sensitive to 1. Heat Receptors are sensitive to temperatures above 77F and become temperatures above 77F and become unresponsive above temperatures of 113F unresponsive above temperatures of 113F – pain receptors kick in and report the– pain receptors kick in and report the

sensation of burning.sensation of burning. 2. Cold receptors respond to 2. Cold receptors respond to

temperatures between 50F and 68F. temperatures between 50F and 68F. If temperatures are below 50F, a If temperatures are below 50F, a freezing sensation is reported by freezing sensation is reported by pain receptors.pain receptors.

Both heat and cold receptors Both heat and cold receptors adapt adapt quickly.quickly.

SENSE OF PAINSENSE OF PAIN

Pain receptors consist of free nerve Pain receptors consist of free nerve endings that are stimulated when tissues endings that are stimulated when tissues are damaged.are damaged.

Protect the body by signaling damage Protect the body by signaling damage and identifying changes that may cause and identifying changes that may cause long-term damage.long-term damage.

Aid medical professionals in diagnosing Aid medical professionals in diagnosing specific diseases or malfunctions of the specific diseases or malfunctions of the body. body.

Pain receptors, called nociceptors, Pain receptors, called nociceptors, are widely distributed throughout the are widely distributed throughout the skin and internal tissues. skin and internal tissues.

Tissue injury releases chemicals Tissue injury releases chemicals called prostaglandins and kinins that called prostaglandins and kinins that stimulate nociceptors. stimulate nociceptors.

Pain persists after initial tissue injury Pain persists after initial tissue injury because these chemicals linger and because these chemicals linger and there is little to no adaption for these there is little to no adaption for these receptors.receptors.

PAIN – ACUTE OR CHRONICPAIN – ACUTE OR CHRONIC ACUTE: Occurs very rapidly and is typically ACUTE: Occurs very rapidly and is typically

not felt in deeper tissues of the body. Is not felt in deeper tissues of the body. Is usually described as sharp or stabbing pain.usually described as sharp or stabbing pain.

Acute pain fibers are thin, myelinated fibers Acute pain fibers are thin, myelinated fibers that carry impulses rapidly and cease when that carry impulses rapidly and cease when the stimulus stops.the stimulus stops.

CHRONIC: Has a slower onset and builds CHRONIC: Has a slower onset and builds slowly in intensity over a period of seconds slowly in intensity over a period of seconds or minutes. Often described as burning, or minutes. Often described as burning, aching, or throbbing. Chronic pain fibers aching, or throbbing. Chronic pain fibers are thin, unmyelinated fibers that conduct are thin, unmyelinated fibers that conduct impulses slowly and continue sending impulses slowly and continue sending impulses long after the stimulus stops.impulses long after the stimulus stops.

VISCERAL PAINVISCERAL PAIN

Visceral pain receptors are the only Visceral pain receptors are the only receptors in the viscera that produce receptors in the viscera that produce sensations. Response of pain receptors is sensations. Response of pain receptors is quite different from those associated with quite different from those associated with surface tissues. surface tissues.

Localized stimulation of the viscera does Localized stimulation of the viscera does not evoke much of a response, but not evoke much of a response, but widespread stimulation may elicit a widespread stimulation may elicit a strong response.strong response.

Stretching of visceral tissues or a Stretching of visceral tissues or a decrease in blood flow elicits the decrease in blood flow elicits the most painful responses.most painful responses.

Visceral pain often seems to come Visceral pain often seems to come from somewhere other than its from somewhere other than its actual origin. This is called referred actual origin. This is called referred pain. It occurs because of common pain. It occurs because of common nerve pathways: the two areas are nerve pathways: the two areas are served by the same segment of the served by the same segment of the spinal. Example, an MI is felt as pain spinal. Example, an MI is felt as pain in the arm.in the arm.

Stretch ReceptorsStretch Receptors

Stretch receptors are proprioceptors that Stretch receptors are proprioceptors that deal with sensations from the deal with sensations from the lengthening and stretching muscles. The lengthening and stretching muscles. The two main types are Golgi tendon organs two main types are Golgi tendon organs and muscle spindles.and muscle spindles.

Golgi Tendon Organ: Golgi Tendon Organ: Found in tendons Found in tendons at the point of attachment to their at the point of attachment to their respective muscles. Are stimulated by respective muscles. Are stimulated by increased tension in the skeletal muscle.increased tension in the skeletal muscle.

Golgi Tendon Organ Golgi Tendon Organ (Cont’d)(Cont’d)

Sensory impulses from these Sensory impulses from these receptors produce an inhibiting reflex receptors produce an inhibiting reflex for muscle contraction. This helps to for muscle contraction. This helps to prevent the muscle from pulling prevent the muscle from pulling away from its insertion point and to away from its insertion point and to maintain posture.maintain posture.

MUSCLE SPINDLESMUSCLE SPINDLES Muscle spindles are located in muscles near Muscle spindles are located in muscles near

the origin of the tendons that serve them. the origin of the tendons that serve them. Each spindle is composed of 3-10 specialized Each spindle is composed of 3-10 specialized muscle fibers called muscle fibers called intrafusal muscle fibers.intrafusal muscle fibers.

The central region of the spindle has few or The central region of the spindle has few or no actin or myosin filaments, but the ends do no actin or myosin filaments, but the ends do contain a few. This central region cannot contain a few. This central region cannot contract. However, there are two types of contract. However, there are two types of afferent (sensory) fibers inside the spindle – afferent (sensory) fibers inside the spindle – they have dendrites that wrap around the they have dendrites that wrap around the central area of the intrafusal fiber. When central area of the intrafusal fiber. When stretched, the spindle stimulates the stretched, the spindle stimulates the dendrites, which send a nerve impulse toward dendrites, which send a nerve impulse toward the spinal cord.the spinal cord.

Muscle spindle fibers respond to the Muscle spindle fibers respond to the rate and degree of length change in rate and degree of length change in a skeletal muscle. The info is a skeletal muscle. The info is transmitted to the cerebrum for transmitted to the cerebrum for perception of limb position and to the perception of limb position and to the cerebellum for coordination of cerebellum for coordination of muscle contraction.muscle contraction.

Structures of the Structures of the EyeEye

ADNEXA – ADNEXA – accessory accessory structuresstructures OrbitOrbit Eye MusclesEye Muscles Eyelids Eyelids EyelashesEyelashes ConjunctivaConjunctiva Lacrimal Lacrimal

ApparatusApparatuswww.ipo.tue.nl/.../seminar-2%20human/ sld015.htm

The Lacrimal ApparatusThe Lacrimal Apparatus – – structures that produce, store, structures that produce, store,

and remove tearsand remove tears Lacrimal Glands: secrete lacrimal fluid Lacrimal Glands: secrete lacrimal fluid

to maintain moisture on the anterior to maintain moisture on the anterior surface of the eyeballsurface of the eyeball

Lacrimal Canaliculi: ducts at the inner Lacrimal Canaliculi: ducts at the inner canthus of each eye – collect tears and canthus of each eye – collect tears and drain them into the lacrimal sacdrain them into the lacrimal sac

Lacrimal sac: an enlargement of the Lacrimal sac: an enlargement of the upper portion of the lacrimal ductupper portion of the lacrimal duct

Lacrimal duct: passageway that drains Lacrimal duct: passageway that drains lacrimal fluid into the noselacrimal fluid into the nose

Pg. 195

Functions of the EyesFunctions of the Eyes – – receive images and transmit to receive images and transmit to

brainbrain Optic: Optic:

pertaining to pertaining to eye or sighteye or sight

Ocular: Ocular: pertaining to pertaining to the eyethe eye Extraocular: Extraocular:

outside the outside the eyeballeyeball

Intraocular: Intraocular: within the within the eyeballeyeball

ORBITORBIT FrontalFrontal SphenoidSphenoid EthmoidEthmoid MaxillaMaxilla ZygomaZygoma LacrimalLacrimal PalatinePalatine

www.lau-verlag.de/anatom/ skeletal-system.htm

Muscles of the EyeMuscles of the Eye Superior/Superior/

Inferior RectusInferior Rectus Superior/Superior/

Inferior Inferior ObliqueOblique

Lateral/Medial Lateral/Medial RectusRectus

Eyelids:Eyelids: protect the protect the eyeball form foreign eyeball form foreign matter, excessive matter, excessive light, and impactlight, and impact

CanthusCanthus: angle where : angle where upper/lower eyelids meetupper/lower eyelids meet Inner CanthusInner Canthus Outer CanthusOuter Canthus

Conjunctiva:Conjunctiva: lines the underside lines the underside

of each eyelid and of each eyelid and provides provides protective protective covering over covering over exposed surface of exposed surface of eyeballeyeball

The Eyeball The Eyeball - - globeglobe

Made up of 3 Made up of 3 layerslayers ScleraSclera ChoroidChoroid RetinaRetina

Interior of eye is Interior of eye is divided into divided into anterior/posterior anterior/posterior segmentssegments

www.optelec.com/ lv_ref.php

The ScleraThe Sclera – – the white of the the white of the eyeeye

Outer layer of eyeOuter layer of eye Maintains shape of Maintains shape of

the eye and protects the eye and protects the delicate inner the delicate inner layers of tissuelayers of tissue Cornea: transparent Cornea: transparent

anterior portion of the anterior portion of the sclerasclera

Provides most of the Provides most of the optical power of the optical power of the eyeeye

The Uveal The Uveal TractTract

The vascular layer of eyeThe vascular layer of eye Choroid:Choroid: opaque (light opaque (light

cannot pass through it) cannot pass through it) middle layer of the eyeball – middle layer of the eyeball – provides blood supply for provides blood supply for entire eyeentire eye

Iris:Iris: colored layer that colored layer that surrounds pupil – it’s surrounds pupil – it’s muscles control amount of muscles control amount of light entering eye – decrease light entering eye – decrease - muscles contract making - muscles contract making opening smaller (visa versa)opening smaller (visa versa)

Pupil:Pupil: black circular opening black circular opening in center of iris – permits in center of iris – permits light to enter eyelight to enter eye

Lens:Lens: focuses images on the focuses images on the retina – located behind iris retina – located behind iris and pupiland pupil

Ciliary Body:Ciliary Body: located located within the choroid, set of within the choroid, set of muscles and ligaments muscles and ligaments that adjust lens to refine that adjust lens to refine the focus of light rays on the focus of light rays on the retinathe retina

Near-by objects = thickerNear-by objects = thicker Distance objects = thinnerDistance objects = thinner

The RetinaThe Retina Nerve layer located Nerve layer located between the posterior between the posterior chamber and the chamber and the choroid layer at the choroid layer at the back of the eyeback of the eye

Contains light Contains light sensitive rods sensitive rods (black/white (black/white receptors) and cones receptors) and cones (color receptors)(color receptors) Receive images and Receive images and

convert them into convert them into nerve impulsesnerve impulses

Optic disk: (blind Optic disk: (blind spot) – contains no spot) – contains no rods/cones – nerve rods/cones – nerve endings of retina endings of retina gather to form gather to form optic optic nerve nerve which which transmits nerve transmits nerve impulses from the impulses from the retina to the brainretina to the brain

RetinaRetina

Macula lutea – In the central region Macula lutea – In the central region of the retina lies a yellowish spot of the retina lies a yellowish spot called the macula lutea. called the macula lutea.

Within the center of this structure Within the center of this structure lies a small depression called the lies a small depression called the central fovea. This region of the central fovea. This region of the retina is the area of the retina is the area of the highest highest visual acuity.visual acuity.

Visual PathwaysVisual Pathways

Optic Chiasma – As the axons of the ganglion Optic Chiasma – As the axons of the ganglion cells of the retina leave the eye, they cells of the retina leave the eye, they converge to form the large optic nerve. converge to form the large optic nerve. These nerves eventually cross at the base of These nerves eventually cross at the base of the brain (just in front of the pituitary gland) the brain (just in front of the pituitary gland) in a formation referred to as the optic in a formation referred to as the optic chiasma.chiasma.

Nerve fibers continue into the posterior Nerve fibers continue into the posterior portion of the thalamus of the brain and portion of the thalamus of the brain and enter nerve tracts that “radiate” to the enter nerve tracts that “radiate” to the

occipital lobe of the brain. Some occipital lobe of the brain. Some fibers continue from the lateral fibers continue from the lateral geniculate nucleus to the brainstem geniculate nucleus to the brainstem where they contribute to where they contribute to simultaneous eye movements and simultaneous eye movements and control of visual reflexes.control of visual reflexes.

The Anterior Segment The Anterior Segment – – front 1/3 of eyefront 1/3 of eye

Divided into anteriorDivided into anteriorand posterior and posterior chamberschambers

Anterior chamberAnterior chamber behind the cornea inbehind the cornea in

front of the irisfront of the iris Posterior chamberPosterior chamber

Between the back of the iris and Between the back of the iris and the front of the lensthe front of the lens

These chambers filled with These chambers filled with aqueous humor (fluid)aqueous humor (fluid) Nourishes intraocular structures Nourishes intraocular structures Constantly filtered and drained which regulates Constantly filtered and drained which regulates

intraocular pressure (IOP = btwn 12 & 21 mm Hg)intraocular pressure (IOP = btwn 12 & 21 mm Hg)

The Posterior The Posterior Segment – Segment – posterior 2/3 of posterior 2/3 of

eyeeye Aids in maintaining theAids in maintaining the

shape of the eyeshape of the eye Contains Contains vitreous vitreous

humorhumor Lined with retina and Lined with retina and

it’s related structuresit’s related structures

Normal Action of the EyeNormal Action of the Eye Accommodation:Accommodation: the eyes make the eyes make

adjustments for seeing at various distancesadjustments for seeing at various distances Includes constriction or dilation of the pupil, Includes constriction or dilation of the pupil,

movement of the eye, and changes in the shape movement of the eye, and changes in the shape of the lensof the lens

Convergence:Convergence: simultaneous inward simultaneous inward movement of both eyes – in an effort to movement of both eyes – in an effort to maintain single binocular vision as an maintain single binocular vision as an object comes nearerobject comes nearer

Visual Acuity:Visual Acuity: the ability to distinguish the ability to distinguish object details and shape at a distanceobject details and shape at a distance Normal vision = 20/20Normal vision = 20/20 Snellen Chart: used to measure visual acuitySnellen Chart: used to measure visual acuity

Summary of SightSummary of Sight

The eye functions somewhat like a The eye functions somewhat like a camera: it receives and focuses light on camera: it receives and focuses light on a photosensitive receiver, the retina. a photosensitive receiver, the retina. Light rays are bent (called refraction) Light rays are bent (called refraction) and brought to focus as they pass and brought to focus as they pass through the cornea and the lens. Once through the cornea and the lens. Once an image is focused on the retina, an image is focused on the retina, stimulated photoreceptors alter the light stimulated photoreceptors alter the light signal into receptor potentials.signal into receptor potentials.

Pathology of the Eyes - Pathology of the Eyes - EYELIDSEYELIDS

Blepharoptosis Blepharoptosis (A)(A)

Ectropion (B)Ectropion (B) Entropion (C)Entropion (C) Hordeolum: (D)Hordeolum: (D)

AB

C D

Functions of the EarsFunctions of the Ears Receive sound Receive sound

impulses and impulses and transmit them to the transmit them to the brainbrain Inner also helps Inner also helps

maintain balancemaintain balance

Auditory:Auditory: pertaining to the pertaining to the sense of hearingsense of hearing

Acoustic:Acoustic: relating relating to sound or hearingto sound or hearing

Structures of the EarStructures of the Ear

The Outer EarThe Outer Ear The Middle EarThe Middle Ear

The Auditory The Auditory OssiclesOssicles

The Eustachian The Eustachian TubesTubes

The Inner EarThe Inner Ear

The Outer The Outer EarEar

Pinna:Pinna: auricle – auricle – External portionExternal portion Catches soundCatches sound

waves and transmitswaves and transmitsthem into the them into the external auditory canalexternal auditory canal(EAC)(EAC)

EAC:EAC: transmits sound waves from pinna to middle transmits sound waves from pinna to middle earear

What is the name for the sticky yellow-brown What is the name for the sticky yellow-brown substance that functions to prevent bacteria and substance that functions to prevent bacteria and dust from entering the middle ear??dust from entering the middle ear??

CERUMEN (earwax)CERUMEN (earwax)

The Middle The Middle EarEar

Tympanic Membrane (eardrum)Tympanic Membrane (eardrum) Transmits sound by vibratingTransmits sound by vibrating Surrounded by hollow air spaces – Surrounded by hollow air spaces – mastoid mastoid

cells cells (which can easily become involved in (which can easily become involved in a middle ear infection)a middle ear infection)

The Auditory The Auditory OssiclesOssicles 3 small bones in the 3 small bones in the

middle earmiddle ear Transmit sound waves Transmit sound waves

from the eardrum to the from the eardrum to the inner ear by vibrationinner ear by vibration

Named for their shapeNamed for their shape

Malleus:Malleus: hammer hammer

Incus:Incus: anvil anvil

Stapes:Stapes: stirrup stirrup

The Inner The Inner Ear-Ear-

labyrinthlabyrinth

Contains sensory receptors for Contains sensory receptors for hearing and balancehearing and balance Cochlea:Cochlea: spiral shaped passage that leads spiral shaped passage that leads

from the oval windowfrom the oval window Cochlear duct:Cochlear duct: filled with fluid that vibrates when filled with fluid that vibrates when

sound waves strike itsound waves strike it Organ of Corti:Organ of Corti: receptor site receptor site

that receives vibrations and that receives vibrations and relays them to the auditory relays them to the auditory nerve fibers that transmit nerve fibers that transmit them to the auditory center them to the auditory center of the cerebral cortex, where of the cerebral cortex, where they are interpreted and heardthey are interpreted and heard

Semicircular canals:Semicircular canals: helps maintain helps maintainequilibriumequilibrium

Normal Action of the Normal Action of the EarsEars

Air conduction:Air conduction: sound waves enter the ear sound waves enter the ear through the pinna, travel down the auditory through the pinna, travel down the auditory canal, and strike the TM between the outer canal, and strike the TM between the outer and middle earand middle ear

Bone conduction:Bone conduction: as the eardrum vibrates, it as the eardrum vibrates, it moves the auditory ossicles and these moves the auditory ossicles and these conduct sound waves through the middle conduct sound waves through the middle earear

Sensorineural conduction:Sensorineural conduction: sound vibrations sound vibrations reach the inner ear via the oval window reach the inner ear via the oval window where the structures of the inner ear where the structures of the inner ear receive the sound waves and relay them to receive the sound waves and relay them to the brainthe brain

Sense of EquilibriumSense of Equilibrium

Sense of equilibrium consists of two Sense of equilibrium consists of two parts:parts:

Static and Dynamic. Static and Dynamic. Static equilibrium helps to maintain the Static equilibrium helps to maintain the

position of the head and body when they position of the head and body when they are still. are still.

Dynamic equilibrium maintains balance Dynamic equilibrium maintains balance when the head and body suddenly move when the head and body suddenly move and rotate.and rotate.

Static EquilibriumStatic Equilibrium Organs are located within the bony Organs are located within the bony

vestibule of the inner ear, inside the vestibule of the inner ear, inside the utricle and saccule (expansions of the utricle and saccule (expansions of the membranous labyrinth). Hair cells lie membranous labyrinth). Hair cells lie inside the utricle and saccule.inside the utricle and saccule.

Gravity causes the gelatin and otoliths Gravity causes the gelatin and otoliths to shift, bending hair cells and to shift, bending hair cells and generating a nervous impulse. generating a nervous impulse. Impulses travel to the brain via the Impulses travel to the brain via the vestibular branch of the vestibular branch of the vestibulocochlear nerve, indicating the vestibulocochlear nerve, indicating the head positionhead position

Dynamic EquilibriumDynamic Equilibrium Three semicircular canals detect motion of the Three semicircular canals detect motion of the

head and aid in balancing the head and body head and aid in balancing the head and body during sudden movement.during sudden movement.

Organs involved are called Organs involved are called cristae ampullaris cristae ampullaris and and are located in the ampulla of each semicircular are located in the ampulla of each semicircular canal of the inner ear.canal of the inner ear.

Rapid turning of the head or body generates Rapid turning of the head or body generates impulses as the cupula and hair cells bend, which impulses as the cupula and hair cells bend, which are interpreted and modified by the brain to are interpreted and modified by the brain to maintain specific positions for the body. maintain specific positions for the body. Mechanoreceptors associated with the joints and Mechanoreceptors associated with the joints and the changes detected by the eyes also help the changes detected by the eyes also help maintain equilibrium maintain equilibrium

Pathology of the EarsPathology of the Ears Outer EarOuter Ear

Otalgia: earacheOtalgia: earache Otitis: inflammation of the earOtitis: inflammation of the ear Otomycosis: swimmer’s earOtomycosis: swimmer’s ear

Middle EarMiddle Ear Eustachitis: inflammation of the eustachian tubeEustachitis: inflammation of the eustachian tube MastoiditisMastoiditis Otosclerosis: ankylosing of the bones of the middle ear Otosclerosis: ankylosing of the bones of the middle ear

= hearing loss= hearing loss Otitis MediaOtitis Media

Inner EarInner Ear Meniere’s syndrome: vertigo, fluctuating hearing loss, Meniere’s syndrome: vertigo, fluctuating hearing loss,

tinnitus (ringing or buzzing in the ears)tinnitus (ringing or buzzing in the ears) Hearing LossHearing Loss

DeafnessDeafness Noise-Induced hearing lossNoise-Induced hearing loss

Diagnostic Procedures of the Diagnostic Procedures of the EarsEars

Audiometry:Audiometry: use of audiometer to use of audiometer to measure hearingmeasure hearing

Speech audiometry:Speech audiometry: measures the measures the threshold of speech reception and threshold of speech reception and speech discriminationspeech discrimination

MonauralMonaural: testing involving one ear: testing involving one ear Binuaral:Binuaral: testing involving both ears testing involving both ears

Treatment Procedures of the Treatment Procedures of the EarsEars

Outer EarOuter Ear Otoplasty: surgical repair of the pinna of Otoplasty: surgical repair of the pinna of

the earthe ear Middle EarMiddle Ear

MastoidectomyMastoidectomy TympanocentesisTympanocentesis Tympanostomy tubesTympanostomy tubes

Inner EarInner Ear FenestrationFenestration LabyrinthectomyLabyrinthectomy LabyrinthotomyLabyrinthotomy

DEAFNESSDEAFNESS

Deafness is defined as any reduction Deafness is defined as any reduction of hearing and is categorized as of hearing and is categorized as follows: conduction-type deafness, follows: conduction-type deafness, sensorineural deafness, central sensorineural deafness, central deafness, mixed-type deafness, deafness, mixed-type deafness, functional deafness, congenital functional deafness, congenital deafness, and neonatal deafness. deafness, and neonatal deafness.

Conduction-Type DeafnessConduction-Type Deafness

Occurs when there is an interference Occurs when there is an interference with the transmission of sounds from with the transmission of sounds from the external or middle ear, the external or middle ear, preventing sound waves from preventing sound waves from entering the inner ear.entering the inner ear.

Sensorineural DeafnessSensorineural Deafness

Also referred to as “nerve deafness” Also referred to as “nerve deafness” and involves the cochlear portion of and involves the cochlear portion of the inner ear of the cochlear division the inner ear of the cochlear division of the vestibulocochlear nerve.of the vestibulocochlear nerve.

Central DeafnessCentral Deafness Involves the acoustic center of the Involves the acoustic center of the

cerebral cortex.cerebral cortex. Mixed-Type DeafnessMixed-Type Deafness

Involves both the conduction system Involves both the conduction system and the nervous system.and the nervous system.

Functional DeafnessFunctional Deafness Sometimes called “selective” deafness.Sometimes called “selective” deafness. Is psychogenic, with no conduction or Is psychogenic, with no conduction or

nerve problem identified.nerve problem identified.

Deafness (continued)Deafness (continued)Congenital DeafnessCongenital Deafness

Present at birth. Cause may be Present at birth. Cause may be hereditary or may be due to the hereditary or may be due to the mother’s exposure to disease or mother’s exposure to disease or toxic drugs during the pregnancy.toxic drugs during the pregnancy.

Neonatal DeafnessNeonatal Deafness Occurs at the time of birth. Is caused Occurs at the time of birth. Is caused

by prematurity, trauma, or Rh by prematurity, trauma, or Rh imcompatability.imcompatability.

SENSE OF TASTESENSE OF TASTE

Special organs of taste are the taste Special organs of taste are the taste buds. They are primarily on the surface buds. They are primarily on the surface of the tongue and are located within tiny, of the tongue and are located within tiny, numerous elevations called numerous elevations called papillae.papillae. Each taste bud consists of cells called Each taste bud consists of cells called gustatory cells gustatory cells that function as receptors.that function as receptors.

Chemicals must be dissolved in saliva Chemicals must be dissolved in saliva that surrounds the taste cells in order to that surrounds the taste cells in order to be tasted. be tasted.

Four Types of Taste BudsFour Types of Taste Buds Each taste bud is stimulated by a specific Each taste bud is stimulated by a specific

type of chemical that produces a certain type of chemical that produces a certain taste sensation: sweet, sour, salty, and taste sensation: sweet, sour, salty, and bitter. (Some recognize two additional bitter. (Some recognize two additional sensations: alkaline and metallic)sensations: alkaline and metallic)

Areas of taste receptors on tongue:Areas of taste receptors on tongue: Sweet – tip of tongueSweet – tip of tongue Sour – lateral edge of tongueSour – lateral edge of tongue Salt – tip and upper portion of tongueSalt – tip and upper portion of tongue Bitter – Back of tongueBitter – Back of tongue

Taste impulses from the anterior two thirds Taste impulses from the anterior two thirds of the tongue are relayed to the brain via the of the tongue are relayed to the brain via the facial (VII) nerve. facial (VII) nerve.

Taste impulses from the posterior one third Taste impulses from the posterior one third of the tongue and back of the mouth are of the tongue and back of the mouth are relayed via the glossopharyngeal (IX) nerve. relayed via the glossopharyngeal (IX) nerve.

Taste impulses from the base of the tongue Taste impulses from the base of the tongue and the pharynx are relayed by the vagus and the pharynx are relayed by the vagus (X) nerve. Impulses from these nerves are (X) nerve. Impulses from these nerves are transmitted to the medulla oblongata, then transmitted to the medulla oblongata, then to the thalamus, and finally to the gustatory to the thalamus, and finally to the gustatory cortex of the parietal lobe.cortex of the parietal lobe.

SENSE OF SMELLSENSE OF SMELL Sense of smell is referred to as olfactory senses. Sense of smell is referred to as olfactory senses.

Humans can distinguish approximately 10,000 Humans can distinguish approximately 10,000 chemicals.chemicals.

Nerve pathways for the sense of smell are Nerve pathways for the sense of smell are directly connected to older, more primitive areas directly connected to older, more primitive areas of the brain (limbic system) that are associated of the brain (limbic system) that are associated with memory and basic primal instincts. For with memory and basic primal instincts. For example, a whiff of perfume can bring up example, a whiff of perfume can bring up memories of an old girlfriend.memories of an old girlfriend.

Smell is an important component for attraction Smell is an important component for attraction and sexuality.and sexuality.

Olfactory senses and taste operate together to Olfactory senses and taste operate together to aid in food selection. Smell accounts for 90% of aid in food selection. Smell accounts for 90% of what we think we taste. what we think we taste.

Mechanics of SmellMechanics of Smell The nasal cavity has a patch of tissue the size of a The nasal cavity has a patch of tissue the size of a

postage stamp with specialized olfactory receptors.postage stamp with specialized olfactory receptors. To be detected, chemicals that enter the nasal To be detected, chemicals that enter the nasal

cavity must be in a cavity must be in a gaseous state and must be gaseous state and must be dissolved in the watery fluid surrounding nasal dissolved in the watery fluid surrounding nasal cilia.cilia.

Once olfactory receptors have been stimulated, Once olfactory receptors have been stimulated, impulses are transmitted along axons of the impulses are transmitted along axons of the receptor cells of the olfactory nerves. receptor cells of the olfactory nerves.

The impulse is then transmitted to the olfactory The impulse is then transmitted to the olfactory tract and then to interpreting centers in the base of tract and then to interpreting centers in the base of the frontal lobes. the frontal lobes.

The impulse then travels along olfactory tracts to The impulse then travels along olfactory tracts to the limbic system, and lastly to the olfactory cortex the limbic system, and lastly to the olfactory cortex within the temporal lobeswithin the temporal lobes

Objectives:Objectives:

Describe the functions and structures of the Describe the functions and structures of the eyes and adnexaeyes and adnexa

Recognize, define, spell, and pronounce Recognize, define, spell, and pronounce terms related to the pathology and diagnostic terms related to the pathology and diagnostic and treatment procedures of eye disordersand treatment procedures of eye disorders

Describe the functions and structures of the Describe the functions and structures of the earsears

Recognize, define, spell, and pronounce Recognize, define, spell, and pronounce terms related to the pathology and diagnostic terms related to the pathology and diagnostic and treatment procedures of ear disordersand treatment procedures of ear disorders