Chapter 34: The Sensory System Flashcards

Fundamentals of the Sensory System

  • Essential Functions:

    • Allows individuals to experience the world around them.

    • Helps protect the body from harm.

  • Primary Senses:

    • Sight

    • Hearing

    • Taste

    • Smell

    • Touch

Touch and Pain Perception

  • Mechanisms of Touch:

    • Tactile nerves are located within the skin.

    • Spatial Sensitivity: Certain areas of the body are significantly more sensitive than others.

    • Deep Touch Nerves: Sense pressure and prompt individuals to move positions.

  • Pain Perception:

    • Serves as the body's distress signal.

    • Referred (Radiating) Pain:

    • Pain felt in a location distinct from its actual source, where the person does not know exactly where it is coming from.

    • Example: Experiencing left arm pain during a heart attack.

    • Phantom Pain:

    • The sensation of pain in an amputated limb.

Taste and Smell

  • Gustatory Sense (Taste):

    • Tastebuds are located on the tongue.

    • Five Primary Tastes: Sweet, salty, bitter, sour, and umami (savory).

  • Olfactory Sense (Smell):

    • Sense organs of smell are located in the nasal cavity.

  • Effects of Aging on Taste and Smell:

    • The number of chemoreceptors decreases with age.

    • Results in a less intense sense of taste and smell.

    • Leads to a decreased appetite.

    • Places geriatric clients at higher health and nutritional risks.

Structure and Anatomy of the Eye

  • Detection Capabilities:

    • The eyes detect light, color, and shape.

  • Tissue Layers of the Eye:

    • Sclera:

    • Tough outer layer, commonly called the "white of the eye."

    • Cornea: The clear part in front of the eye that allows light to pass through.

    • Choroid:

    • The middle layer containing blood vessels that supply essential nutrients.

    • Ciliary Body: Tiny muscles attached to the lens that change its shape to allow the eye to focus.

    • Iris: The colored part of the eye with a central opening called the pupil; controls the amount of light entering the eye.

    • Retina:

    • The innermost layer containing photoreceptors (rods and cones).

    • Turns light into nerve impulses.

    • Nerve impulses travel through the optic nerve to the brain.

  • Eye Chambers:

    • Anterior Chamber:

    • Located between the cornea and the lens.

    • Filled with aqueous humor.

    • Posterior Chamber:

    • Located between the lens and the retina.

    • Filled with vitreous humor.

    • Gives the eyeball its structural shape.

Visual Function, Defects, and Age-Related Changes

  • Mechanics of Sight:

    • The eye operates like a camera.

    • The retina serves as the "film."

    • The iris and pupil control the amount of light entering.

    • The cornea and lens focus light onto the retina to form a clear image, which the brain then interprets.

  • Refractive Defects:

    • Myopia: Nearsightedness.

    • Hyperopia: Farsightedness.

    • Astigmatism: Blurred vision.

  • Effects of Aging on Sight:

    • Decreased number of photoreceptors in the retina.

    • The lens becomes opaque (cloudy).

    • The iris becomes more rigid, preventing proper adjustment to light.

    • The lens becomes less flexible, preventing focus on close objects (presbyopia).

    • Decreased tear production leads to dryness and eye irritation.

Pathologies and Diseases of the Eye

  • Conjunctivitis ("Pink Eye"):

    • Infection or inflammation of the conjunctiva, causing the sclera to appear red.

    • Chief Complaints: Itching, burning, excessive tearing, and sticky white or yellow discharge.

    • Highly contagious; transferred by rubbing the eye or touching contaminated objects.

    • Treatment: Antibiotic eye drops or ointment.

  • Cataracts:

    • Yellowing and hardening of the lens.

    • Prevents light from entering the eye, causing cloudy vision and eventual blindness.

    • Highly common in geriatric individuals.

    • Treatment: Lens surgery.

  • Glaucoma:

    • Increased pressure in the anterior chamber occurring when aqueous humor is not properly absorbed.

    • Pressure continues to build until the retina is destroyed.

    • High Risk Groups: Individuals over 40 years of age, people with a family history of glaucoma, and individuals with dark irises.

    • Treatment: Early detection, eye drops, and surgery.

  • Macular Degeneration:

    • Protein deposits build up or blood vessels develop on the macula (part of the retina).

    • Damages receptors and central vision.

    • Common cause of blindness in people over 65 years of age.

    • Risk Factors: Smoking, excessive exposure to sunlight, high-cholesterol diet, and inherited tendency.

Visual Impairment Care and Device Maintenance

  • Adaptations to Blindness:

    • Individuals can be legally blind while still retaining partial sight (e.g., seeing light, movement, shapes, or colors without clear identification, while others see total darkness).

    • Individuals born blind typically adapt well and maintain independence.

    • Individuals who become blind later in life typically experience difficulty adjusting.

  • Care of Eyeglasses:

    • Clean with cloths and special solutions made specifically for glasses.

    • Dry with a soft cloth.

    • Do NOT use paper towels or napkins to avoid scratching.

    • Store safely in a case within easy reach.

  • Care of Contact Lenses:

    • Use special cleaning solutions to clean and store lenses.

    • Keep lenses inside a designated case, ensuring correct placement on the "left" and "right" sides.

  • Care of Prosthetic Eyes:

    • Constructed from ceramic or plastic.

    • Shaped as a curved disc (not a ball) that fits underneath the eyelids.

    • If removable, assistance may be needed for cleaning and storage.

    • Must be handled carefully due to high cost; improper handling causes scratches or nicks that can injure or irritate the eyelids.

Anatomy and Physiology of the Ear

  • The Outer Ear:

    • Pinna (Auricle): Collects sound waves and sends them down the canal to the eardrum.

    • External Auditory Canal: Contains small hairs and glands secreting cerumen (earwax) to protect the canal by trapping dirt and particles.

    • Tympanic Membrane (Eardrum): Separates the outer and middle ear; vibrates in response to sound waves.

  • The Middle Ear:

    • An air space containing three small bones called ossicles (malleus, incus, and stapes) that form a bridge between the eardrum and inner ear.

    • Opening of the Eustachian Tube: Connects the middle ear to the pharynx to equalize pressure in the middle ear and prevent tympanic membrane rupture.

  • The Inner Ear:

    • Contains specialized receptors for hearing and balance.

    • Cochlea: Snail-shell-shaped structure filled with fluid; houses hearing receptors.

    • Vestibular Apparatus: Composed of the vestibule and semicircular canals; controls balance.

    • Innervated by the vestibular nerve and cochlear nerve.

  • Mechanism of Hearing:

    • Sound waves captured by the pinna travel down the auditory canal to vibrate the tympanic membrane.

    • Vibrations pass through the auditory ossicles, causing vibrations through the fluid inside the cochlea.

    • Fluid movement stimulates receptors inside the cochlea, sending nerve impulses via the cochlear nerve to the brain for interpretation as sound.

  • Mechanism of Balance and Motion Sickness:

    • Positional changes activate sensor receptors in the vestibular apparatus.

    • Sensors send messages to the brain regarding body position in relation to the ground to maintain balance.

    • Motion Sickness: Occurs when different messages are sent simultaneously from the ears and eyes to the brain, causing confusion that results in nausea, dizziness, and vomiting.

Auditory Pathologies, Age-Related Changes, and Care

  • Effects of Aging on the Ear:

    • Eardrum and ossicles become stiffer.

    • Decreased number of sensory receptors.

    • Presbycusis: Loss of ability to hear high-pitched sounds.

    • Causes trouble distinguishing high-frequency sounds like "th" and "s".

    • Makes conversations difficult to follow, especially with excessive background noise.

  • Cerumen (Earwax) Impaction:

    • Buildup of earwax in the external auditory canal.

    • Manifestations: Decreased hearing, feeling of fullness in the ear, ringing, itching, and pain.

    • Risk Factors: Insertion of objects into the ear (such as hearing aids).

    • Nursing Treatment: Flushing ears and applying special ear drops.

  • Ear Infections:

    • Otitis Media: Middle ear infection causing ear pain, fever, and difficulty hearing. Treated with antibiotics or surgery.

    • Otitis Externa ("Swimmer's Ear"): Infection of the lining of the external auditory canal that is painful to the touch. Treated with antibiotics.

  • Ménière's Disease:

    • Inner ear disorder characterized by periodic episodes of excess fluid buildup.

    • Symptoms: Vertigo (dizziness), tinnitus (ringing in ears), temporary hearing loss, and a feeling of pressure or fullness.

    • Attacks can trigger nausea and vomiting.

    • Immediate Nursing Action: Instruct patient to lie down with eyes fixed on a nonmoving object.

  • Communication Guidelines for Hearing Loss:

    • Face the person directly when speaking.

    • Avoid chewing gum or speaking unusually fast.

    • Use a notepad for written communication.

    • Verify that the person accurately understands the message.

  • Hearing Aid Care Guidelines:

    • Handle with extreme care.

    • Ensure the hearing aid is turned on and the volume is turned up high enough.

    • Troubleshooting if non-functional: Check if batteries need replacing and check if the ear canal is blocked with cerumen.