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Pain, Temperature
Regulation, Sleep, and
Sensory Function
Chapter 15
1
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
2
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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
3
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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
4
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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
8
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Neuromodulation of Pain
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Neuromodulation of Pain

Chemicals and neurotransmitters



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Pain excitatory
Pain inhibitory
Modulators of pain
Direct excitation


Threshold depolarization from direct stimuli
Indirect excitation

Threshold depolarization from inflammatory
mediators after tissue injury
10
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Endorphin Response
11
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Clinical Description of Pain

Pain threshold


Perceptual dominance


Point at which a stimulus is perceived as pain
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
12
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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
13
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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
14
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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
15
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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
16
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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
18
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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
19
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Neuropathic Pain




Result of trauma or disease of nerves
Most often chronic
Painful diabetic neuropathy
Postherpetic neuralgia
20
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Neuropathic Pain





Deafferentation pain
Sympathetically maintained pain
Complex regional pain syndromes (CRPS)
Central pain
Phantom limb pain
21
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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
22
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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
25
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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
26
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Heat Loss









Radiation
Conduction
Convection
Vasodilation
Decreased muscle tone
Evaporation
Increased respirations
Voluntary measures
Adaptation to warmer climates
27
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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
28
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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
33
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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
34
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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
35
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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
37
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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
38
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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
39
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Trauma-Induced Temperature
Change


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
CNS trauma
Accidental injuries
Hemorrhagic shock
Major surgery
Thermal burns
40
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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
41
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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

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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
44
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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
46
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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
47
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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
48
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Sleep Disorders

Four classifications (cont’d)

Disorders of sleep/wake cycle

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
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Parasomnias
Somnambulism
Night terrors
Enuresis
Dysfunctions of sleep, sleep stages, or partial
arousals
49
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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
50
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Vision

Blepharitis


Hordeolum (stye)


Infection of the sebaceous glands of the eyelids
Chalazion


Inflammation of the eyelids
Infection of the meibomian (oil-secreting) gland
Keratitis

Infection of the cornea
51
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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)
52
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The Eye
53
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Visual Field and Neuronal
Pathways
54
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Vision Changes and Aging





Cornea
Anterior chamber
Lens
Ciliary muscles
Retina
55
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Visual Dysfunctions

Alterations in ocular movements

Strabismus


Diplopia
Nystagmus


Pendular nystagmus
Jerk nystagmus
56
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Visual Dysfunctions

Alterations in visual acuity




Amblyopia
Scotoma
Retrobulbar neuritis
Cataracts
57
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Visual Dysfunctions

Alterations in visual acuity




Papilledema
Dark adaptation
Glaucoma
Age-related macular degeneration (AMD)
58
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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
59
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Visual Dysfunctions

Alterations in refraction



Myopia (nearsighted)
Hyperopia (farsighted)
Astigmatism

May coexist with myopia or hyperopia
60
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Alterations in Refraction
61
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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
62
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Visual Dysfunctions

Neurologic disorders



Hemianopia
Injury to the optic chiasm
Homonymous hemianopsia
63
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Neurologic Disorders Causing
Visual Dysfunction
64
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The Ear
65
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The Ear
66
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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
67
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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
68
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Auditory Dysfunction

Conductive hearing loss


Sensorineural hearing loss




Impaired sound conduction
Impairment of the organ of Corti or its central
connections
Presbycusis (age-related hearing loss)
Mixed hearing loss
Functional hearing loss
69
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Olfaction



Cranial nerve I and part of V
Strong relationship between taste and smell
Olfactory stimulants


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

Camphoraceous
Musky
Floral
Peppermint
Ethereal
Pungent
Putrid
70
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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
71
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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
72
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Olfactory Dysfunction



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Hyposmia
Anosmia
Olfactory hallucinations
Parosmia
73
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Taste Dysfunction



Hypogeusia
Ageusia
Parageusia
74
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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
75
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Proprioceptive Dysfunction



Vestibular nystagmus
Vertigo
Ménière disease
76
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