1 pain, temperature regulation, sleep, and sensory function chapter 15

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Pain, Temperature Regulation, Sleep, and Sensory FunctionChapter 15

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Pain “Pain is an unpleasant sensory and emotional

experience associated with actual or potential tissue damage or described in terms of such damage” —International Association for the Study of Pain

“Pain is whatever the experiencing person says it is, existing whenever he says it does” —McCaffrey

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Pain Theories Specificity theory

Amount of pain is related to the amount of tissue injury

Accounts for many types of injuries but does not explain psychological contributions

Gate control theory Developed to explain the complexities of the pain

phenomenon

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Neuroanatomy of Pain Nociception

Perception of pain Nociceptors

Bare nerve endings in skin, muscle, joints, arteries, and the viscera that respond to chemical, mechanical, and thermal stimuli

Can detect a wide range of stimuli Aδ fibers Unmyelinated C polymodal fibers

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Pathways of Nociception

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Pathways of Nociception

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Pathways of Nociception

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Neuromodulation of Pain Segmental inhibition Diffuse noxious inhibitory controls Integration of:

Peripheral sensory axon terminals Spinal interneurons Top-down control pathways

All converge on the spinal dorsal horns

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Neuromodulation of Pain

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Neuromodulation of Pain Chemicals and neurotransmitters

Pain excitatory Pain inhibitory Modulators of pain Direct excitation

Threshold depolarization from direct stimuli Indirect excitation

Threshold depolarization from inflammatory mediators after tissue injury

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Endorphin Response

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Clinical Description of Pain Pain threshold

Point at which a stimulus is perceived as pain Perceptual dominance

Pain at one location may cause an increase in the threshold in another location

Pain tolerance Duration of time or the intensity of pain that a

person will endure before initiation of pain responses

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Pain Classifications Nociceptive pain

Pain with a cause of normal tissue injury Somatic Visceral

Non-nociceptive pain Neuropathic pain

Peripheral and central

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Acute Pain Protective mechanism

Alerts an individual to a condition or experience that is immediately harmful to the body

Manifestations Fear and anxiety

Tachycardia, hypertension, fever, diaphoresis, dilated pupils, outward pain behaviors, elevated blood sugar levels, decreased gastric acid secretion and intestinal motility, and a general decrease in blood flow

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Acute Pain Acute somatic

Arises from connective tissue, muscle, bone and skin

Aδ fibers—pain is sharp and well localized C fibers—dull, aching, and poorly localized

Acute visceral Pain in the internal organs and abdomen Poorly localized due to the lesser number of

nociceptors

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Acute Pain Referred pain

Pain that is present in an area removed or distant from its point of origin

The area of referred pain is supplied by the same spinal segment as the actual site Myocardial infarction pain

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Referred Pain

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Chronic Pain A situation; state of existence May be sudden or develop insidiously Usually defined as lasting at least 3 months Response patterns vary Produces significant behavior and

psychological changes

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Common Types of Chronic Pain Myofascial pain syndromes

Injury to the muscle and fascia Spasm, tenderness, and stiffness

Chronic postoperative pain Cancer pain

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Neuropathic Pain Result of trauma or disease of nerves Most often chronic Painful diabetic neuropathy Postherpetic neuralgia

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Neuropathic Pain Deafferentation pain Sympathetically maintained pain Complex regional pain syndromes (CRPS) Central pain Phantom limb pain

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Pediatrics and Pain Pathways and chemicals associated with pain

are functional in preterm and newborn infants Nociceptor system is functional by 24 weeks’

gestation Expressions of pain

Facial expression Crying Body language

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Pediatrics and Pain

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Aging and Pain Increase in pain threshold

Peripheral neuropathies Skin thickness changes

Decrease in pain tolerance Alteration in metabolism of drugs and

metabolites

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Temperature Regulation Variable

Location Activity Environment Circadian rhythm Gender

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Temperature Regulation Peripheral thermoreceptors Hypothalamic control Heat production and conservation

Chemical reactions of metabolism Skeletal muscle contraction Chemical thermogenesis Vasoconstriction Voluntary mechanisms

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Heat Loss Radiation Conduction Convection Vasodilation Decreased muscle tone Evaporation Increased respirations Voluntary measures Adaptation to warmer climates

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Temperature Regulation Pediatrics

Produce sufficient body heat but are unable to conserve heat produced Small body size and high body surface to weight ratio Thin subcutaneous layer

Aging Slow blood circulation, vasoconstrictive response, and

metabolic rate Decreased sweating and perception of heat and cold

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Fever Resetting of the hypothalamic thermostat Activate heat production and conservation

measures to a new “set point” Exogenous pyrogens Endogenous pyrogens Endogenous cryogens

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Fever

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Benefits of Fever Kills many organisms Decreases serum levels of iron, zinc, and

copper Deprives bacteria of food Promotes lysosomal breakdown and

autodestruction of cells Increases lymphocytic transformation and

phagocyte motility

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Hyperthermia Not mediated by pyrogens No resetting of the hypothalamic set point 41o C (105.8o F): nerve damage produces

convulsions 43o C (109.4o F): death results Forms

Heat cramps, heat exhaustion, heat stroke

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Heat Cramps Severe spasmodic cramps in the abdomen and

extremities Following prolonged sweating and associated

sodium loss Common in individuals not accustomed to heat or

those performing strenuous work in warm climates Fever, rapid pulse, and increased blood pressure

often accompany the cramps

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Heat Exhaustion Collapse due to prolonged high core or

environmental temperatures Prolonged vasodilation and profuse sweating

Dehydration, depressed plasma volumes, hypotension, decreased cardiac output, tachycardia

Manifestations Dizziness, weakness, nausea, and syncope

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Heatstroke Potentially lethal result of a breakdown in an

overstressed thermoregulatory center Brain cannot tolerate temperatures >40.5o C

(104.9o F) Temperature maintained by blood flow through

the veins in the head and face Cardiovascular and thermoregulatory centers may

cease functioning with higher temperatures

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Heatstroke Manifestations

Cerebral edema, degeneration of the CNS, swollen dendrites, and renal tubular necrosis

Rapid peripheral cooling will cause peripheral vasoconstriction and limit core cooling

Children are more susceptible Produce more metabolic heat when exercising Greater surface area to mass ratio Sweating capacity is less than adults

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Malignant Hyperthermia Complication of inherited muscular disorder Precipitated by the administration of volatile

anesthetics and neuromuscular blocking agents Increased calcium release or decreased calcium

uptake with muscle contraction Causes sustained muscle contractions

Increased oxygen consumption and lactic acid production

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Hypothermia Body temperature less than 35° C Produces:

Vasoconstriction, alterations in the microcirculation, coagulation, and ischemic tissue damage

Ice crystals, which form inside the cells, causing them to rupture and die

Tissue hypothermia slows the rate of chemical reactions; increases blood viscosity and slows blood through the microcirculation; facilitates blood coagulation and stimulates vasoconstriction

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Hypothermia Accidental hypothermia

Commonly the result of sudden immersion in cold water or prolonged exposure to cold

Therapeutic hypothermia Used to slow metabolism and preserve ischemic

tissue during surgery or limb reimplantation May lead to ventricular fibrillation and cardiac

arrest

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Trauma-Induced Temperature Change CNS trauma Accidental injuries Hemorrhagic shock Major surgery Thermal burns

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Sleep Active, multiphase process Hypothalamus is the major sleep center

Hypocreatins (ovexins) Promote wakefulness and rapid eye movement (REM)

sleep

Two phases Rapid eye movement (REM) sleep Non–rapid eye movement (NREM) sleep

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EEG Stages of Wakefulness and Sleep

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NREM Sleep 75% to 80% of sleep time Four stages evaluated by EEG

Stage I Stage II Stage III Stage IV

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REM Sleep 20% to 25% of sleep time Also known as paradoxic sleep Occurs every 90 minutes beginning after 1 to

2 hours of sleep

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Normal Sleep Cycles

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Pediatrics and Sleep Newborns sleep 16 to 17 hours per day 53% of that time is spent in active (REM)

sleep The infant sleep cycle is about 50 to 60

minutes Infants enter REM sleep immediately upon

falling asleep

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Aging and Sleep Total sleep time is decreased Elderly take longer to fall asleep, and awaken

more frequently during the night Amount of time in stage IV sleep decreases Potential causes

Physical ailments, lack of daily routine, circadian rhythm changes, and medications

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Sleep Disorders Four classifications

Disorders initiating sleep Insomnia

Sleep-disordered breathing Upper airway resistance syndrome Obstructive sleep apnea Obesity hypoventilation syndrome

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Sleep Disorders Four classifications (cont’d)

Disorders of sleep/wake cycle Parasomnias Somnambulism Night terrors Enuresis

Dysfunctions of sleep, sleep stages, or partial arousals

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Sleep and Disease Secondary sleep disorders

Alterations in the quality and/or quantity of sleep due to primary diseases

Depression, pain, sleep apnea syndromes, and alterations in thyroid hormone secretion

Sleep-provoked disorders Sleep stage alterations produced in certain disease

states

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Vision Blepharitis

Inflammation of the eyelids Hordeolum (stye)

Infection of the sebaceous glands of the eyelids Chalazion

Infection of the meibomian (oil-secreting) gland Keratitis

Infection of the cornea

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Vision Conjunctivitis

Inflammation of the conjunctiva Acute bacterial conjunctivitis (pinkeye)

Highly contagious Mucopurulent drainage from one or both eyes

Viral conjunctivitis Allergic conjunctivitis Trachoma (chlamydial conjunctivitis)

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The Eye

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Visual Field and Neuronal Pathways

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Vision Changes and Aging Cornea Anterior chamber Lens Ciliary muscles Retina

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Visual Dysfunctions Alterations in ocular movements

Strabismus Diplopia

Nystagmus Pendular nystagmus Jerk nystagmus

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Visual Dysfunctions Alterations in visual acuity

Amblyopia Scotoma Retrobulbar neuritis Cataracts

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Visual Dysfunctions Alterations in visual acuity

Papilledema Dark adaptation Glaucoma Age-related macular degeneration (AMD)

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Visual Dysfunctions Alterations in accommodation

Accommodation is the process whereby the thickness of the lens changes

Oculomotor nerve changes Decreased flexibility of the lens Manifestations:

Diplopia, blurred vision, and headache

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Visual Dysfunctions Alterations in refraction

Myopia (nearsighted) Hyperopia (farsighted) Astigmatism

May coexist with myopia or hyperopia

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Alterations in Refraction

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Visual Dysfunctions Alterations in color vision

Age-related yellowing of the lens Colorblindness

Generally an X-linked recessive trait Commonly red-green colorblindness

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Visual Dysfunctions Neurologic disorders

Hemianopia Injury to the optic chiasm Homonymous hemianopsia

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Neurologic Disorders Causing Visual Dysfunction

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The Ear

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The Ear

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Aging and Hearing Cochlear hair cell degeneration Loss of auditory neurons in spiral ganglia of

organ of Corti Degeneration of basilar conductive membrane

of the cochlea Decreased vascularity of cochlea Loss of cortical auditory neurons

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Ear Infections Otitis externa

Infection of the outer ear Commonly caused by prolonged moisture

exposure (swimmer’s ear) Otitis media

Acute otitis media Otitis media with effusion

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Auditory Dysfunction Conductive hearing loss

Impaired sound conduction Sensorineural hearing loss

Impairment of the organ of Corti or its central connections

Presbycusis (age-related hearing loss) Mixed hearing loss Functional hearing loss

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Olfaction Cranial nerve I and part of V Strong relationship between taste and smell Olfactory stimulants

Camphoraceous Musky Floral Peppermint Ethereal Pungent Putrid

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Taste Cranial nerve VII and part of IX Nerves in the tongue, soft palate, uvula,

pharynx, and upper esophagus Gustatory stimulants

Sour Sweet Salty Bitter

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Age-Related Olfaction and Taste Changes Olfaction

Decline in odor sensitivity Loss of olfactory sensory neurons and cells in the

olfactory bulbs Causes diminished appetite and food selection

Taste Higher concentration of flavors is required Decline in the number of fungiform papillae

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Olfactory Dysfunction Hyposmia Anosmia Olfactory hallucinations Parosmia

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Taste Dysfunction Hypogeusia Ageusia Parageusia

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Somatosensory Function Touch

Sensation involves modality, intensity, location, and duration

Receptors are present in the skin Proprioception

Depends on inner ear, vision, and receptors in joints and ligaments

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Proprioceptive Dysfunction Vestibular nystagmus Vertigo Ménière disease