SENSORY SYSTEM &

NEUROLOGICAL FUNCTIONS

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

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Sensory & Perception FxnsSensory System

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SENSORY SYSTEM Responsible for processing sensory information

Senses are physiological capacities of organisms that provide data for perception. 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 physical functions that exist in a living system.

Perception (from the Latin perceptio, percipio) is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information.All perception involves signals in the nervous system, which in turn 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 hearing involves pressure waves. Perception is not the passive receipt of

these signals, but can be shaped by learning, memory and expectation.

Perception depends on complex functions of the nervous system, but subjectively seems mostly effortless because this processing happens outside conscious awareness.

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The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology (or cognitive science), and philosophy of perception. The nervous system has a specific sensory system or organ, dedicated to each sense.

Senses are transducers from the physical world to the 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) and acceleration (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 of an organism. In response to stimuli the sensory receptor initiates 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 from one 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

- 55

+30

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

Action potentials

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Sensory coding A receptor must convey

the type of information it is sending the kind of receptor activated determined the signal recognition by the brain

It must convey the intensity of the stimulus the stronger the signals, the more frequent will be the APs

It must send information about the 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 the brain

Involved in sensory perception. neural pathway, neural tract, or

neural face, connects one part of the nervous system with another and usually consists of bundles of elongated, myelin-insulated neurons, known collectively as white matter. Neural pathways serve to connect relatively distant areas of the brain or nervous system, compared to the local communication 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

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Receptor

Sensory modality

Sensory nerve

Central Connections

Ascending Sensory pathway

Sensory area in the brain

Touch stimulusAFFERENT

Sensory pathway

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Receptors Receptor cells are specific cells that are

sensitive to different forms of energy from the environment

These cells contain membrane receptors coupled to ion channels

They transform the stimulus into electrical signals

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HUMAN SENSORY RECEPTORSClassifications:

Chemosensor – TRANSDUCES a chemical signal into an action potential

Nociceptor - responds to potentially damaging stimuli by sending nerve signals to the spinal cord and brain

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Mechanoreceptor – RESPONDS to mechanical pressure or distortion. Transform displacement or mechanical force into action potentials.

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Photoreceptor - specialized type of neuron found in the retina that is capable of phototransduction.

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Thermoreceptor - is a sensory receptor, or more accurately the receptive portion of a sensory neuron, that codes absolute and relative changes in temperature

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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 rootDorsal columns

Dorsal horn

Dorsal root ganglion

Spinothalamictracts

Posterior (dorsal)

Anterior (ventral)

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Dorsal column pathway

Spinothalamic pathway

Lateral Spinothalamic tract

AnteriorSpinothalamic tract

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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

sensory cortex

internal capsule

1st order neuron

2nd order neuron

3rd order neuron

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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

opposite side and ascends upwards as medial lemniscus

as this travels along the brain stem fibres from 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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Spinothalamic tracts

thalamus

thalamocortical tracts

sensory cortex

internal capsule

1st order neuron

2nd order neuron

3rd order neuron

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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: pain and temperature

anterior spinothalamic tract 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

Lateral Spinothalamic tract

AnteriorSpinothalamic tract

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STIMULUS

Sensory systems code for four aspects of a stimulus; type (modality)

Receptors are sensitive to certain types of stimuli (for example, different mechanoreceptors respond best to different kinds of touch stimuli, like sharp or blunt objects).

Intensity 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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Location gives the brain information about the location

of the stimulus (for example, stimulating a mechanoreceptor in a finger will send information to the brain about that finger)

Duration The duration of the stimulus (how long it lasts)

is conveyed by firing patterns of receptors. These impulses are transmitted to the brain through afferent neurons.

Arrival time of a sound pulse and phase differences of continuous sound are used for localization of sound sources.

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MODALITY A stimulus modality (sensory

modality) is a type of physical phenomenon that can be sensed.

Examples are temperature, taste, sound, and pressure. The type of sensory receptor activated by a stimulus plays the primary role in coding the stimulus modality.

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Structure of human sensory system

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Typical myellinated vertebrate motorneuron

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I. Anatomy/PhysiologyA. Neuron- highly specialized for the processing

and transmission 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 myelin sheath

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

c. Gaps in myelin sheath – termed Nodes of Ranvier

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4. Primary fxn – transmission of nerve impulses

a. Afferent (sensory) n. – transmit impulses from peripheral receptors } CNS

b. Efferent (motor) n. – conduct impulses from CNS

c. Action potentials travel along axons} end of nerve fiber }impulse is transmitted across junction bet. nerve cells (synapse) }chemical interaction

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

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B. PNS } contains cranial nerves, spinal nerves, autonomic nervous system(unconscious reflexes), sympathetic division (accelerates activity), & parasympathetic division(slows body processes).

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

hemisphere} longitudinal fissure

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a. Frontal lobes Precentral gyrus – contralateral movement;

face, arm, leg, trunk Broca’s area – dominant hemisphere }

respon.> formation of words Supplementary motor area – contralateral head

& eye turning Prefrontal area- personality, initiative 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 are integrated

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 of written 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 of w/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 stimuli necessary for abstract thinking & reasoning, vision, hearing; relay station for fibers going to limbic system

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Hypothalamus- responsible for maintaining momeostasis} thru the secretion of hormones & central control of ANS Controls vital fxn: water balance, BP, sleep,

appetite, temp Affects some emotional responses ]

pleasure/fear Control center for pituitary fxn Affects both divisions of the ANS

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c. Limbic system –responsible for controlling various functions in the body. Structures of this system include the hippocampus, hypothalamus, and thalamus Fig.

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4. Brain stem- contains; midbrain, pons & medulla oblangata, extending from the cerebral hemispheres to the foramen magnum @ the base of the skulla. Contains nuclei- 5,6,7,8th Cnerves &

ascending sensory & descending motor tracts

b. Contains vital center- respiratory, vasomotor & cardiac fxn

c. Reticular formation – relays sensory of info; controls vasomotor/respiratory activity

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5. Ventricular system & CSF – supports & cushions CNS 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 mater

Delicate, avascular membrane lying under dura Surrounds brain loosely Subarachnoid space contains; CSF, arteries & veins Contains arachnoid granulations that enable CSF } pass

from subarachnoid space>venous system Pia mater

Most delicate inner meningeal layer Barrier system

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7. Cerebellum – control of: muscle motion, balance, coordination; trunk mobility & equilibrium Spinal cord – communications link bet CNS

& PNS Ascending pathways ] transmit

Sensory information Descending pathways] relay

Motor instrtuctions

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HUMAN SENSORY SYSTEM The Human sensory system consists of the

following sub-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 sensations labelled as touch or pressure, temperature (warm or cold), pain (including itch and tickle), and the sensations of muscle movement and joint position including posture, movement, and facial expression (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 vessels 2) 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 nerve

b) 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)

TestTonometry –measures IOPVisual fields – measurement of range of

vision (perimetry)Snellen test – visual acuity

Client preparation: recumbent/sitting position, remove contact lenses, not to squint/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 ACCOMMODATIONTypes Nsg Considerations

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

Corrective lenses

Hyperopia (farsightedness) – light rays refract behind the retina

Corrective lenses

Presbyopia with aging Commonly occurs after age 35

Astigmatism – uneven curvature of cornea causing blurring of vision

Corrective lenses

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C. Treatments1. Eye irrigation method

a. Tilt head back toward the side of affected area

b. Allow irrigating fluid to flow from the inner to outer canthus

c. Use a small bulb syringe/eye dropper to dispense fluid

d. 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/

chemicals c. Use of eye protectors during sportsd. Protect eyes from ultraviolet rayse. Instruction for first aid

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2. Emergency Treatment A. Burns

Types Nsg Considerations

Chemical – acids, cleanser, insecticides

Eye irrigation w/ copious amts of H2O for 15-20min

Radiation – sun, lightning, eclipses

Prevention- use of eyeshields

Thermal – hot metals, liquids, occupational hazards

Use of goggles to protect the cornea, patching, analgesics

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B. EyeTraumaTypes Nsg

considertionsNonpenetrating- abrasions

Eye patch for 24hrs

Nonpenetrating- contusions

Cold compresses, analgesics

Penetrating – pointed or sharp 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. History

Flashes of light Blurred or sooty vision Sensation of particles moving in line of vision Delineated of vision areas blank Feeling of coating coming u & down Loss of vision Confusion/apprehension

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2. Characteristics Separation of the retina from choroid Cause

Trauma Aging process Diabetes Tumors

Medical mgt Sedatives & tranquilizers 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. Hx

Objects appear distorted and blurred Annoying glare Pupil changes from black to gray to milky white

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2. Assessment Partial/total opacity of the normally

transparent crystalline lens Cause

Congenital Trauma Aging process Assoc w/ diabetes mellitus, intraocular surgery Drugs- steroid therapy

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Surgical Mgt – laser surgery Extracapsular extraction – cut thru the

anteriorcapsule to express the opaque lens material Intracapsular extraction (method of choice) –entire

removal of lens & capsule Lens implantation

Nsg Mgt Observe for post-operative complications

Hemorrhage IOP Slipped suture If lens implant, pupil should remain constricted; if

aphakic, pupil remains dilated

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Avoid straining /no heavy lifting Bend from the knees only to pick up things Instruct in instillation of eye drops/use of night

shields Protect from bright light Adjustments needed if aphakic Diversional activities

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GLAUCOMA 1. Assessment

Cloudy, blurry vision Artificial lights appear to have rainbows Loss of vision decreased peripheral vision Pain, headache Nausea, vomiting 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. Types Acute/close(narrow) – angle glaucoma; sudden

onset Chronic or open (wide) – angle glaucoma; most

common C. Causes

Close-angle glaucoma – assoc w/ ocular d’s, trauma

Open-angle glaucoma – assoc w/ aging, heredity, retinal vein occlusion

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D. Tx Meds – miotics, carbonic anhydrase inhibitors,

oral glycerin & mannitol Surgery – laser trabeculoplasty, standard

glaucoma surgery Common nsg diagnosis – sensory/

perceptual/visual alteration

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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:

Brow arching Blurry vision Diminished peripheral vision Headache or eye pain

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I. Anatomy & Physiology of EAR A. External Ear

Pinna/auricle External acoustic meatus External auditory canal

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B. Middle ear Located in temporal lobe Contains ossicles

Malleus Incus Stapes

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

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Physiology of sound Sound waves enter external auditory canal

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

C. Inner ear Contains: vestibule, semicircular canals,

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

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II. Alterations in Fxn A. Assessment

S/S } pain, fever, headache, discharge, altered growth & dev, personality changes (irritability, depression, suspiciousness, w/drawal

Dx } Audiogram – quantitative(degree of loss), Tuning fork – qualitative (type of loss)

Types: Conductive loss

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Types: 1. Conductive loss – disorder in auditorycanal,

eardrum/ossicles Causes: infection, inflammation, foreign body, trauma Complications : meningitis resulting from initial infection Nsg Mgt: heat, antibiotics, ear drops/ointments/irrigation,

surgery, hearing aid 2. perceptive(sensorineural loss) – due to disorder of

organ of corti/auditory nerve Causes: congenital-maternal exposure to com’cable d’s,

infection, drug toxicity, trauma, labyrinth dsfxn(Meniere’s d’s Complications: vertigo, tinnitus, vomiting 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

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SOMATIC SENSATION (TOUCH)

somatosensory system is a diverse sensory system composed of

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

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CORTICAL homunculus

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Taste/GUSTATION Taste (also called smatch)

is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, poisons

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Taste buds

Taste receptors

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Smell/ OLFACTIONHuman olfactory system.

1: Olfactory bulb 2: Mitral cells 3: Bone 4: Nasal epithelium 5: Glomerulus (olfaction) 6: Olfactory receptor cells

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All credibility, all good conscience, all evidence of truth come only from the

senses. Friedrich Nietzsche

THANK YOU.