SENSORY SYSTEM &NEUROLOGICAL FUNCTIONS

Dr. James M. Alo, BSN ,RN, MAN, MAP, PHD

Sensory & Perception Fxns

¨Sensory System

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SENSORY SYSTEM

¨ Responsible for processing sensory information¤ Senses are physiological capacities of organisms that

provide data for perception.n Physiology is the science of the function of living systems.

This includes how organisms, organ systems, organs, cells,and bio-molecules carry out the chemical or physicalfunctions that exist in a living system.

n Perception (from the Latin perceptio, percipio) is the processof attaining awareness or understanding of the environmentby organizing and interpreting sensory information.Allperception involves signals in the nervous system, which inturn result from physical stimulation of the sense organs.

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¨ VISION involves light striking the retinas of the eyes,smell is mediated by odor molecules and hearinginvolves pressure waves.¤ Perception is not the passive receipt of these signals,

but can be shaped by learning, memory andexpectation.

¤ Perception depends on complex functions of the nervoussystem, but subjectively seems mostly effortless becausethis processing happens outside conscious awareness.

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¨ The senses and their operation, classification, andtheory are overlapping topics studied by a variety offields, most notably neuroscience, cognitivepsychology (or cognitive science), and philosophy ofperception. The nervous system has a specific sensorysystem or organ, dedicated to each sense.

¨ Senses are transducers from the physical world tothe realm of the mind

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¨ Human beings have a multitude of senses.¤ Sight (ophthalmoception),¤ hearing (audioception),¤ taste (gustaoception),¤ smell (olfacoception or olfacception), and¤ touch (tactioception) are the five traditionally recognized

and the only senses proven to to be existent in humans.¨ Some believe in other senses, including temperature

(thermoception), kinesthetic sense (proprioception), pain(nociception), balance (equilibrioception) andacceleration (kinesthesioception)

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Sensory system consists of

¨ Sensory receptors¤ is a sensory nerve ending that responds to a

stimulus in the internal or external environment ofan organism. In response to stimuli the sensoryreceptor initiatesn sensory transduction by creating graded potentials or

action potentials in the same cell or in an adjacent one.

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¨ Transduction is the conversion of a stimulus fromone form to another¤ graded potential, is the transmembrane potential

difference of a sensory receptor

Transmembrane receptor:E=extracellular space;I=intracellular space; P=plasma membrane

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Transduction

Stimulus

Receptor potential(Generator potential)

Action potential

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Action Potentials

Threshold

RestingMembranePotential

-70

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StimulusReceptor potential

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Coding of sensory stimuli

¨ Stimulus strength is coded as the frequency of AP

¨ Higher the stimulus more frequent are the APs

¨ Amplitude of AP is constant

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Stimulus

Receptorpotentials

Actionpotentials

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Sensory coding¨ A receptor must convey the type

of information it is sendingàthe kind of receptor activateddetermined the signalrecognition by the brain

¨ It must convey the intensity of thestimulusà the stronger thesignals, the more frequent willbe the APs

¨ It must send information aboutthe location and receptive field,characteristic of the receptor

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Transduction in different receptors

¨ Different receptors have different ion channels

¨ Their opening causes receptor potential

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NEURAL PATHWAYS and parts of thebrain

¨ Involved in sensory perception.¤neural pathway, neural tract, or neural face,

connects one part of the nervous system withanother and usually consists of bundles ofelongated, myelin-insulated neurons, knowncollectively as white matter. Neural pathways serveto connect relatively distant areas of the brain ornervous system, compared to the localcommunication of grey matter.

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Sensory pathway

¨ Once a receptor is stimulated

¨ impulse travels through a particular pathway

¨ known as sensory pathway or ascending pathway

¨ up to the brain

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Receptor

Sensorymodality

Sensory nerve

Central Connections

AscendingSensory pathway

Sensory areain the brain

Touch stimulus

Sensory pathway

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Receptors

¨ Receptor cells are specific cells that are sensitive todifferent forms of energy from the environment

¨ These cells contain membrane receptors coupled toion channels

¨ They transform the stimulus into electrical signals

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HUMAN SENSORY RECEPTORSClassifications:

¨ Chemosensor – TRANSDUCES a chemical signal intoan action potential

¨ Nociceptor - responds to potentially damagingstimuli by sending nerve signals to the spinal cordand brain

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¨ Mechanoreceptor – RESPONDS to mechanicalpressure or distortion. Transform displacement ormechanical force into action potentials.

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¨ Photoreceptor - specialized type of neuron found inthe retina that is capable of phototransduction.

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¨ Thermoreceptor - is a sensory receptor, or moreaccurately the receptive portion of a sensoryneuron, that codes absolute and relative changes intemperature

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Two ascending pathways

¨ Dorsal column - medial lemniscus pathwayfast pathway

¨ Spinothalamic pathwayslow pathway

These two pathways come together at the level of thalamus

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Dorsal root

Dorsal columns

Dorsal horn

Dorsal root ganglion

Spinothalamictracts

Posterior (dorsal)

Anterior (ventral)

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Dorsal column pathway

Spinothalamic pathway

LateralSpinothalamictract

AnteriorSpinothalamictract

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Dorsal column pathway Spinothalamic pathway

¨ touch: fine degree¨ highly localised touch

sensations¨ vibratory sensations¨ sensations signalling

movement¨ position sense¨ pressure: fine degree

¨ Pain

¨ Thermal sensations¨ Crude touch & pressure¨ crude localising sensations¨ tickle & itch¨ sexual sensations

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Dorsal column nuclei(cuneate & gracile nucleus)

Dorsal column

Medial lemniscus

thalamus

thalamocortical tracts

internal capsule

1storderneuron

2ndorderneuron

3rdorderneuron

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dorsal column - medial lemniscus pathway

¨ after entering the spinal cord¤ lateral branch: participates in spinal cord reflexes¤medial branch: turns upwards

¨ forms the dorsal columns¨ spatial orientation:

¤medial: lower parts of the body¤ lateral: upper part of the body

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dorsal column - medial lemniscus pathway

¨ synapse in the dorsal column nuclei¤nucleus cuneatus & nucleus gracilus

¨ 2nd order neuron cross over to the oppositeside and ascends upwards as mediallemniscus

¨ as this travels along the brain stem fibresfrom head and neck are joined (trigeminal)

¨ ends in the thalamus (ventrobasal complex)¤ventral posterolateral nuclei

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dorsal column - medial lemniscus pathway

¨ spatial orientation in the thalamus¤medial: upper part of the body¤lateral: lower part of the body

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Spinothalamictracts

thalamus

thalamocortical tracts

internal capsule

1storderneuron

2ndorderneuron

3rdorderneuron

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spinothalamic pathway

¨ after entering the spinal cord¤ synapse in the dorsal horn

¨ cross over to the opposite side¨ divide in to two tracts

¤ lateral spinothalamic tract:n pain and temperature

¤ anterior spinothalamic tractn crude touch

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spinothalamic pathway

¨ spatial orientation¤ medial: upper part of the body¤ lateral: lower part of the body

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Dorsal column pathway

Spinothalamic pathway

LateralSpinothalamictract

AnteriorSpinothalamictract

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STIMULUS

¨ Sensory systems code for four aspects of a stimulus;¤ type (modality)n Receptors are sensitive to certain types of stimuli (for

example, different mechanoreceptors respond best todifferent kinds of touch stimuli, like sharp or blunt objects).

¤ Intensityn Receptors send impulses in certain patterns to send

information about the intensity of a stimulus (for example,how loud a sound is)

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¤ Locationn gives the brain information about the location of the stimulus

(for example, stimulating a mechanoreceptor in a finger willsend information to the brain about that finger)

¤ Durationn The duration of the stimulus (how long it lasts) is conveyed by

firing patterns of receptors. These impulses are transmittedto the brain through afferent neurons.

¤ Arrival time of a sound pulse and phase differences ofcontinuous sound are used for localization of soundsources.

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MODALITY

¨ A stimulus modality (sensory modality) is atype of physical phenomenon that can besensed.nExamples are temperature, taste, sound,

and pressure. The type of sensory receptoractivated by a stimulus plays the primaryrole in coding the stimulus modality.

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Structure of human sensory system40

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Typical myellinated vertebratemotorneuron

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I. Anatomy/Physiology

A. Neuron- highly specialized for the processing andtransmission of cellular signals

1. Basic component of the nervous sy.2. Composed of cell body, axon & dendrites

a. Cell body = center of metabolismb. Axon =long fibers > conduct impulses away from the cell

body; usually 1 axon for each cell bodyc. Dendrites = short, unsheathed fibers> receive nerve

impulses> transmit to cell body

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3. Myelin sheath – covering that protects nerve fiber>facilitates> speed of impulse conductor

a. Axon & dendrite – may/may not have myelinsheath

b. Most axons leaving the CNS – heavily myelinatedw/ schwann cells

c. Gaps in myelin sheath – termed Nodes of Ranvier

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4. Primary fxn – transmission of nerve impulsesa. Afferent (sensory) n. – transmit impulses from

peripheral receptors } CNS

b. Efferent (motor) n. – conduct impulses from CNSc. Action potentials travel along axons} end of

nerve fiber }impulse is transmitted acrossjunction bet. nerve cells (synapse) }chemicalinteraction

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5. Neuroglia – glial cellsa. Provide support,b. Nourishment andc. Protection for neurons

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B. PNS } contains cranialnerves, spinal nerves,autonomic nervoussystem(unconsciousreflexes), sympatheticdivision (acceleratesactivity), &parasympatheticdivision(slows bodyprocesses).

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C. CNS contains:1. Cerebrum – divided into: left right hemisphere}

longitudinal fissure

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a. Frontal lobesn Precentral gyrus – contralateral movement; face, arm, leg,

trunkn Broca’s area – dominant hemisphere } respon.> formation of

wordsn Supplementary motor area – contralateral head & eye

turningn Prefrontal area- personality, initiativen Paracentral lobule- contralateral inhibition of bladder &

bowel

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b. Parietal lobes¤ Postcentral gyrus – body sensations; temp, touch,

pressure, pain }from opposite side of the body¤ Dominant parietal lobe- wernickes’ speech area,

auditory & visual aspects> comprehensions areintegrated

n Responsible for skills { handle numbers & calculations

¤ Nondominant parietal lobe- concept of body image &awareness of external envi{ ability to construct shapes

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c. Occipital lobes – visual center; comprehension ofwritten word

d. Temporal lobes¤ Dominant hearing of language; taste, smell¤ Memory¤ Wernicke’s speech area – recognition of language

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2. Basal ganglia – reg & integr skeletal voluntary &autonomic motor activity originating in cerebral cortex

3. Diencephalon – connects the cerebrum & brain stem;contains several small structures, the most important ofw/c are the thalamus & hypothalamusa. Thalamus – relay station for discrimination of sensation

}received from periphery>several nuclei in the thalamus,each w/ specific fxns} such as: integration of sensory stimulinecessary for abstract thinking & reasoning, vision, hearing;relay station for fibers going to limbic system

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¤ Hypothalamus- responsible for maintainingmomeostasis} thru the secretion of hormones & centralcontrol of ANSn Controls vital fxn: water balance, BP, sleep, appetite, tempn Affects some emotional responses ] pleasure/fearn Control center for pituitary fxnn Affects both divisions of the ANS

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c. Limbic system –responsible for controlling variousfunctions in the body. Structures of this systeminclude the hippocampus, hypothalamus, andthalamus¤ Fig.

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4. Brain stem- contains; midbrain, pons & medullaoblangata, extending from the cerebralhemispheres to the foramen magnum @ the base ofthe skulla. Contains nuclei- 5,6,7,8th Cnerves & ascending

sensory & descending motor tractsb. Contains vital center- respiratory, vasomotor &

cardiac fxnc. Reticular formation – relays sensory of info; controls

vasomotor/respiratory activity

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5. Ventricular system & CSF – supports & cushionsCNS¤ Removes metabolic wastes¤ Compensatory mechanisms for ICVolume/pressure¤ Produces 55 cc/d of CSF; 130-150cc amt ave in sy

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6. Cranial meninges¤ Dura mater – dense, fibrous, outermost layer serves as

periosteum for Cnerves¤ Arachnoid matern Delicate, avascular membrane lying under duran Surrounds brain looselyn Subarachnoid space contains; CSF, arteries & veinsn Contains arachnoid granulations that enable CSF } pass from

subarachnoid space>venous system¤ Pia matern Most delicate inner meningeal layern Barrier system

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7. Cerebellum – control of: muscle motion, balance,coordination; trunk mobility & equilibrium¤ Spinal cord – communications link bet CNS & PNSn Ascending pathways ] transmit

n Sensory information

n Descending pathways] relayn Motor instrtuctions

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HUMAN SENSORY SYSTEM

¨ The Human sensory system consists of the followingsub-systems:¤ Visual system consists of the photoreceptor cells, optic nerve, and

V1.¤ Auditory system¤ Somatosensory system consists of the receptors, transmitters

(pathways) leading to S1, and S1 that experiences the sensationslabelled as touch or pressure, temperature (warm or cold), pain(including itch and tickle), and the sensations of muscle movementand joint position including posture, movement, and facialexpression (collectively also called proprioception).

¤ Gustatory system¤ Olfactory system

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I. ANATOMY OF THE EYE

¨ A. three layers¤ Sclera –fibrous outer coat¤ Choroid – middle vascular coat¤ Retina – inner nerve coat

¨ B. Lens¤ Lies behind pupil & iris¤ Held in position by suspensory ligament attached to the

ciliary body¤ Elastic qualities allow accommodation to focus image on

the retina

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¨ C. Iris¤ Colored portion of eye¤ Attached around circumference by ciliary body¤ Opening at center – pupil¤ Controls the amt of light entering eye

¨ D. retina1. Innermost lining2. Contains rods & cons

a. Rods fxns w/ colorless, twilight visionb. Cones fxns w/ perception of color & bright, daylight vision

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c. Optic disk1) Point of entrance of nerve & bld vessels2) Blind spot3) Most prominent structure visible on the fundus (retina

lining of the back of the eye)a) Excessive pallor signals optic atrophy, a partial

or complete destruction of the optic nerveb) Excessive redness- papilledema inflamationc) Papilledema – choked disks: severe form

i. Inflammationii. Passive congestion from ICP

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II. VISUAL FUNCTION

¨ A. Assessment (fig)¤ TestnTonometry –measures IOPnVisual fields – measurement of range of vision

(perimetry)nSnellen test – visual acuitynClient preparation: recumbent/sitting position,

remove contact lenses, not tosquint/cough/hold breath during procedure

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¨ B. S/S of eye problem1. Redness, pain & burning2. Edema3. #lacrimation & exudate4. Headache5. Nausea & vomiting6. Squinting7. Visual disturbances8. Disorders of accommodation

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DISORDERS OF ACCOMMODATION

Types Nsg Considerations

Myopia (nearsightedness) –light rays refract at a point infront of the retina

Corrective lenses

Hyperopia (farsightedness) –light rays refract behind theretina

Corrective lenses

Presbyopia with aging Commonly occurs after age 35

Astigmatism – uneven curvatureof cornea causing blurring ofvision

Corrective lenses

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¨ C. Treatments1. Eye irrigation method

a. Tilt head back toward the side of affected areab. Allow irrigating fluid to flow from the inner to outer

canthusc. Use a small bulb syringe/eye dropper to dispense fluidd. Place a small basin close to head to collect excess

fluid/drainage

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¤ 2. Eyedrop instillationa. Tilt head back toward the side of affected areab. Allow irrigating fluid to flow from the inner to outer

canthusc. Use a small bulb syringe/eye dropper to dispense fluidd. Place a small basin close to head to collect excess

fluid/drainage

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¨ D. Nsg Mgt1. Prevent eye injuries

a. Provide safe toysb. Use of eye protectors when working w/ chemicalsc. Use of eye protectors during sportsd. Protect eyes from ultraviolet rayse. Instruction for first aid

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¤ 2. Emergency Treatmentn A. Burns

Types Nsg Considerations

Chemical – acids, cleanser,insecticides

Eye irrigation w/ copiousamts of H2O for 15-20min

Radiation – sun, lightning,eclipses

Prevention- use ofeyeshields

Thermal – hot metals,liquids, occupationalhazards

Use of goggles to protectthe cornea, patching,analgesics

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¨ B. EyeTrauma

Types Nsg considertions

Nonpenetrating- abrasions Eye patch for24hrs

Nonpenetrating- contusions Cold compresses,analgesics

Penetrating – pointed orsharp objects

Cover w/ patch

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III. Visual Function

¨ A. Assessment

1. Adjustment to vision loss depends upon:a. Age of onsetb. Degree of suddenness

2. Principles of working w/ blind personsa. Facilitate normal lifestyle patterns

a. Adapted household eqptb. Books/newspaper w/ large print for partially sightedc. Information > aids for the blindd. Braile, canes, guide dogse. Facilitate dev patternsf. Enc social devtg. Provide for educ & employment

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¨ 3. Nsg Mgt for the blind pxa. Enhance communication

a. Address px by nameb. Always introduce selfc. State reason for being thered. Inform px when leaving the room

b. Provide sense of safety/securitya. Explain procedures in detailb. Keep furniture arrangement consistent, provide hand railc. Door should never be half opend. Lightweight walking stick if walking alone

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IV. SELECTED DISORDERS OF THE EYE

¨ A. DETACHED RETINA¤ 1. Historyn Flashes of lightn Blurred or sooty visionn Sensation of particles moving in line of visionn Delineated of vision areas blankn Feeling of coating coming u & downn Loss of visionn Confusion/apprehension

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¨ 2. Characteristics¤ Separation of the retina from choroid¤ Causen Trauman Aging processn Diabetesn Tumors

¤ Medical mgtn Sedatives & tranquilizersn Surgery- retina to adhere to choroid

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¨ 3. Nsg Mgt¤ Bedrest¤ Affected eye maybe patch- to decrease movement of

eyes¤ Specific positioning¤ Hairwashing delayed for 1 wk¤ Avoid strenuous activity for 3 mos

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¨ B. CATARACTS¤ 1. HxnObjects appear distorted and blurredn Annoying glaren Pupil changes from black to gray to milky white

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¨ 2. Assessment¤ Partial/total opacity of the normally transparent

crystalline lens¤ Causen Congenitaln Trauman Aging processn Assoc w/ diabetes mellitus, intraocular surgeryn Drugs- steroid therapy

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¤ Surgical Mgt – laser surgeryn Extracapsular extraction – cut thru the anteriorcapsule to express

the opaque lens materialn Intracapsular extraction (method of choice) –entire removal of

lens & capsulen Lens implantation

¤ Nsg Mgtn Observe for post-operative complications

n Hemorrhagen #IOPn Slipped suturen If lens implant, pupil should remain constricted; if aphakic, pupil

remains dilated

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n Avoid straining /no heavy liftingn Bend from the knees only to pick up thingsn Instruct in instillation of eye drops/use of night shieldsn Protect from bright lightn Adjustments needed if aphakicn Diversional activities

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¨ GLAUCOMA¤ 1. Assessmentn Cloudy, blurry visionn Artificial lights appear to have rainbowsn Loss of visionn #decreased peripheral visionn Pain, headachen Nausea, vomitingn Tonometer readings exceed normal IOP (10-21mmhg)

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¨ 2. Characteristics¤ A. Abnormal #IOP leading to visual disability/blindness

– obstruction of outflow of aqueous humor¤ B. Typesn Acute/close(narrow) – angle glaucoma; sudden onsetn Chronic or open (wide) – angle glaucoma; most common

¤ C. Causesn Close-angle glaucoma – assoc w/ ocular d’s, traumanOpen-angle glaucoma – assoc w/ aging, heredity, retinal

vein occlusion

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¤ D. TxnMeds – miotics, carbonic anhydrase inhibitors, oral glycerin

& mannitoln Surgery – laser trabeculoplasty, standard glaucoma surgery

¤ Common nsg diagnosis – sensory/ perceptual/visualalteration

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¨ Nsg Mgt¤ Compliance w/ medical therapy¤ Avoid tight clothing¤ Reduce external stimuli¤ Avoid heavy lifting, straining at stool¤ Avoid use of mydriatics¤ Educate public to 5 danger signs of glaucoma:n Brow archingn Blurry visionn Diminished peripheral visionn Headache or eye pain

I. Anatomy & Physiology of EAR

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¨ A. External Ear¤ Pinna/auricle¤ External acoustic meatus¤ External auditory canal

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¨ B. Middle ear¤ Located in temporal lobe¤ Contains ossiclesnMalleusn Incusn Stapes

¤ Eustachian tube – connects middle ear to the throat &assist in equalizing pressure

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¤ Physiology of soundn Sound waves enter external auditory canal >tympanic

membrane >vibrates, triggering ossicles(m,i,s) } transmittedto oval window to acoustic nerve and brain

¨ C. Inner ear¤ Contains: vestibule, semicircular canals,

cochlea(labyrinth) } movment of the sensory hair signalschanges in position; aids in maintaining stable posture

II. Alterations in Fxn

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¨ A. Assessment¤ S/S } pain, fever, headache, discharge, altered growth

& dev, personality changes (irritability, depression,suspiciousness, w/drawal

¤ Dx } Audiogram – quantitative(degree of loss), Tuningfork – qualitative (type of loss)

¤ Types:n Conductive loss

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¤ Types:n 1. Conductive loss – disorder in auditorycanal, eardrum/ossicles

n Causes: infection, inflammation, foreign body, trauman Complications : meningitis resulting from initial infectionn Nsg Mgt: heat, antibiotics, ear drops/ointments/irrigation, surgery,

hearing aid

n 2. perceptive(sensorineural loss) – due to disorder of organ ofcorti/auditory nerven Causes: congenital-maternal exposure to com’cable d’s, infection,

drug toxicity, trauma, labyrinth dsfxn(Meniere’s d’sn Complications: vertigo, tinnitus, vomitingn Mgt: meds, surgery, combined loss- conductive & sensorineural,

psychogenic loss-functional

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¨ C. Nsg Mgt¤ Ear irrigation¤ Ear drop instillation¤ Px undergoing surgery¤ Discharge teaching – avoid getting water in ear, flying,

drafts, crowds, exercise caution around people w/respiratory infections

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¨ III. Selected disorders¤ A. Acute otitis media – infection of middle ear, cause:

pathogenic organisms(bacteria/virus)¤ B. Mastoiditis –inflammation¤ C. meniere’s syndrome(endolymphatic hydrops) –

dilation of the labyrinth, causes: trauma,intoxication,syphilis, otitis media, otosclerosis

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¨ Medical & Nsg Mgt¤ Salt free/neutral ash diet(furstenberg diet) – restrict

h2o & salt intake¤ Symptomatic treatment: antiemetics, histamines,

vasodilators¤ Px education: need to slow down body motion, self

protection, occupational counseling

SOMATIC SENSATION (TOUCH)

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¨ somatosensory system¤ is a diverse sensory system composed of the

receptors and processing centres to produce thesensory modalities such as touch, temperature,proprioception (body position), and nociception(pain). The sensory receptors cover the skin andepithelia, skeletal muscles, bones and joints, internalorgans, and the cardiovascular system.

CORTICAL homunculus

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Taste/GUSTATION

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¨ Taste (also called smatch)¤is one of the traditional five senses. It

refers to the ability to detect the flavorof substances such as food, certainminerals, poisons

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¨ Taste buds

¨ Taste receptors

Smell/ OLFACTION

¨ Human olfactory system.¨ 1: Olfactory bulb 2:

Mitral cells 3: Bone 4:Nasal epithelium 5:Glomerulus (olfaction)6: Olfactory receptorcells

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All credibility, all good conscience, all evidenceof truth come only from the senses.

Friedrich Nietzsche

THANK YOU.

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