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 * __PAIN, TEMPERATURE REGULATION, SLEEP, AND SENSORY FUNCTION__

Pain** is a unique sensory experience that is essential to our survival. Pain provides protection by signaling the presence of disease or injury.
 * Fever** is a common manifestation of dysfunction and is often the first symptom observed in an infectious or inflammatory condition. If the body's temperature regulatory mechanism is out of balance, the result may be death.
 * Sleep** is a normal, cyclic process that restores the body's energy and maintains normal functioning. Sleep deprivation causes a wide range of clinical manifestations.


 * __PAIN__**

Pain has various definitions and it is whatever the patient says it is. There are two theories of pain: (1) Specificity theory and (2) Gate control theory. The perception of pain is called **nociception**. The gate control theory explains the experience of pain by emphasizing the modulation of afferent input coming into the dorsal horn of the spinal cord and the dynamic role of the brain in pain processes.

On the post-central gyrus of the parietal lobe there is a topographically organized representation of the body that mirrors the concentration of peripheral sensory receptors known as the **sensory homunculus**. This area of the brain is thought to be involved in the discriminative and cognitive aspects of pain; that is, what we think about the pain.
 * Nociceptors** are bare sensory nerve endings. Primary nocicetive afferents have the remarkable ability to detect a wide range of stimuli. The synaptic connections betwen cells of primary and secondary order neurons located in the substantia gelatinosa and other Rexed lamina function as a "pain gate." This "gate" in the spinal cord regulates the transmission of pain impulses that proceed cephaladly for further processing and interpretation in the brain. The principal target for nociceptive afferents is the thalamus (which is the major relay station of sensory information in general).

The limbic and reticular tracts are involved in alerting the body to danger, initiating arousal of the organism, and emotionally processing the perceived afferent signals not just as stimuli, but as pain.

Many neurotransmitters mediate the transmission of pain in the periphery, the spinal cord, and the brain. Neurotransmitters can be classified as inflammatory, pain excitatory, pain inhibitory, and as modulators of pain. Neurotransmitters are excitatory or inhibitory.
 * Direct excitation - threshold depolarization initiated by the application of heat, radiation, toxic chemical, or tissue trauma.
 * Indirect excitation - occurs via the release of inflammatory mediators after the tissue is injured.


 * __CLINICAL DESCRIPTION OF PAIN__

Pain threshold** is the point at which a stimulus is perceived as pain. **Pain tolerance** is the duration of time or the intensity of pain that an individual will endure before initiating overt pain responses.


 * __PAIN CLASSIFICATIONS:__**


 * Nociceptive pain** is pain with a cause resulting from normal tissue injury; either somatic or visceral.
 * Non-nociceptive** pain is defined as neuropathic pain; subdivided into peripheral and central categories.
 * Acute pain** is a protective mechanism that alerts the individual to a condition or experience that is immediately harmful to the body.
 * Somatic pain** arises from connective tissue, muscle or bone, and skin and is either sharp and well localized or dull, aching, and poorly localized.
 * Visceral pain** refers to pain in internal organs and the abdomen; transmitted by sympathetic afferents and is poorly localized.
 * Referred pain** is pain that is present in an area removed or distant from its point of origin.
 * Chronic pain** is usually defined as lasting at least 3 months.
 * Myofascial pain syndrome (MPS)** are common causes of chronic pain; involves injury to the muscle and fascia.
 * Chronic post-operative pain** occurs in a small percentage of individuals after surgeries such as thoracotomy, radial neck dissection or surgical amputation.
 * Cancer pain** is often chronic.
 * Neuropathic pain** is the result of trauma or disease of nerves and leads to abnormal processing of sensory information by the peripheral and central nervous system.
 * Deafferentation pain** results from tumor infiltration of nerve tissue; trauma or chemical injury to the nerve; or damage from radiation, chemo or surgical sectioning of the nerve.
 * Sympathetically maintained pain (SMP)** is another type of neuropathic pain that occurs after peripheral nerve injury and is characterized as continuous and severe with a burning quality.
 * Central pain** is neuropathic and is caused by a lesion or dysfunction in the CNS.
 * Phantom limb pain** is pain that an individual feels in an amputated limb after the stump has completely healed.


 * __PEDIATRICS AND PERCEPTION OF PAIN__**

Children and infants have the anatomic and functional ability to perceive pain. Painful expressions can be eyebrows drawn together (frown), forehead bulge between brows, eyes tightly closed, cheeks raised, nose broadened and bulging and mouth open (crying). Physiologic responses include an increased HR, BP & RR. Older children, between ages 5 and 18 have a lower threshold to pain.


 * __AGING AND PERCEPTION OF PAIN__**

Pain perception in the elderly can either increase or decrease. It really is specific to that individual


 * __TEMPERATURE REGULATION__**

Body temperature is maintained in a range around 37*C (98.6*F) and rarely exceeds 41*C. The normal range is considered to be 36.2*C to 27.7*C (97.2* to 99.9*F). Temperature regulation is achieved through precise balancing of heat production, heat conservation, and heat loss. It is mediated hormonally by the hypothalamus. Heat production begins with TSH-RH and heat conservation involves stimulating the sympathetic nervous system.


 * //Mechanisms of heat production://**
 * Chemical rxns of metabolism
 * Skeletal muscle contraction
 * Chemical thermogenesis


 * //Mechanisms of heat loss://**
 * Radiation
 * Conduction
 * Convection
 * Vasodilation
 * Decreased muscle tone
 * Evaporation
 * Increased respiration
 * Voluntary measures
 * Adaptation to warmer climates

//**Mechanisms of heat conservation:**//
 * Involuntary vasoconstriction
 * Voluntary mechanisms


 * __PEDIATRICS AND CHANGES IN TEMPERATURE REGULATION:__**

Infants produce sufficient body heat but they are unable to conserve heat produced. This is caused by the infant's small body size and greater ratio of body surface to body weight, which gives the infant more surface area for heat loss. They also have a very thin layer of sub q fat.


 * __AGING AND CHANGES IN TEMPERATURE REGULATION__**:

Elderly persons have poor responses to environmental temperature extremes as a result of slowed blood circulation, structural and functional changes in the skin, and an overall decrease in heat-producing activities.


 * __FEVER__**

Fever is complex integrated cascade of behavioral, neurologic, and endocrine responses to an immune challenge initiated by endogenous pyrogens. It is both a normal adaptive response and a sign of disease. By simply raising the body's temperature it kills many microorganisms and has adverse effects on the growth and replication of others.

//**Disorders of temperature regulation:**//
 * Hyperthermia - can produce nerve damage, coagulation of cell proteins, and death. At 109.4* death results.
 * Heat cramps - severe, spasmodic cramps in the abdomen and extremities that followed prolonged sweating and sodium loss.
 * Heat exhaustion - result of prolonged high core or environmental temperatures.
 * Heat stroke - potentially lethal result of a breakdown in control of an overstressed thermoregulatory center. The brain cannot tolerate temps >104.9*.
 * Malignant hyperthermia - potentially lethal complication of a rare inherited muscle disorder. Precipitated by the administration of volatile anesthetics and neuromuscular blocking agents.
 * Hypothermia - core body temp <35*C; caused by prolonged exposure to cold.
 * Accidental hypothermia - result of sudden immersion in cold water or prolonged exposure to cold environments.
 * Therapeutic hypothermia - used to slow metabolism and thus preserve ischemic tissue during surgery or limb reimplantation.
 * Trauma has varying effects on temp regulation, depending on the systems involved. The types of traumatic injury that usuall affect temperature regulation are: CNS trauma, accidental injury, hemorrhagic shock, major surgery and thermal burns.

__**SLEEP**__

Sleep is an active, multiphase process. The hypothalamus is the major sleep center and the hypocreatins are neuropeptides secreted by the hypothalamus that promote wakefulness and REM sleep. Prostaglandin D2, L-tryptophan and growth factors promote sleep.

Normal sleep has two phases:
 * 1) Non-Rapid Eye Movement Sleep (Non-REM) - accounts for 75-80% of sleep time.
 * 2) Rapid Eye Movement (REM) - accounts for 20-25% of sleep time.


 * //PEDIATRICS AND SLEEP PATTERNS//**: The sleep patterns of the newborn and young child vary from those of the adult in total sleep time, cycle length, and percentage of tme spent in each sleep cycle.
 * //AGING AND SLEEP PATTERNS//**: The sleep pattern of the older adult differs from that of the younger adult or child. Total sleep time is decreased, and the older individual takes longer to fall asleep.

//**SLEEP DISORDERS:**// These are classified by their signs and symptoms rather than by their cause. There are four classifications:
 * 1) Disorders of initiating sleep (insomnia)
 * 2) Sleep disordered breathing (upper airway resistance syndrome, obstructive sleep apnea & obesity hypoventilation syndrome)
 * 3) Disorders of the sleep/wake schedule (jet-lag syndrome)
 * 4) Dysfunctions of sleep, sleep stages, or partial arousals (parasomnias, somnambulism, night terrors & enuresis)

The most common causes of **//secondary sleep disorders//** are depression, alterations in thyroid hormone secretion, pain, and sleep apnea syndromes. Some //**diseases are provoked by certain aspects of sleep**//. Signs and symptoms of the disease appear during, or are enhanced by, sleep. Diseases that are affected by sleep include coronary artery disease, bronchial asthma, chronic obstructive pulmonary disease, diabetes, and duodenal ulcers.


 * __SPECIAL SENSES__**

//**Vision**// - the external structures that protect the eye are the eyelids, conjunctivae, and lacrimal apparatus. Infection and inflammation are the most common conditions affecting the supporting structures of the eyes.
 * **Blepharitis** is inflammation of the eyelids
 * **Hordeolum** (stye) infection of the sebaceous glands of the eyelids
 * **Chalazion** is an infection of the oil-secreting gland
 * **Conjunctivitis** is an inflammation of the conjunctiva (there are several types of conjunctivitis: bacterial, viral, allergic, chronic and trachoma)
 * **Keratitis** is an infection of the cornea


 * //Eye//** - the wall of the eye is formed of three layers:
 * sclera - thick, white, outermost layer; becomes transparent at the cornea.
 * choroid - deeply pigmented middle layer that prevents light from scattering inside the eye. Contains the iris and pupil.
 * retina - innermost layer of the eye, contains rods and cones, optic disc and fovea centralis.

//**Aging and Vision:**// changes in the structure start early on in life. Some examples are: cornea becomes thicker and less curved with a formation of a gray ring at the edge of cornea; decrease in size and volume of the anterior chamber caused by thickening of lens, etc.


 * __VISUAL DYSFUNCTION:__**

//**Alterations in ocular movements**// occur as a result of oculomotor, trohlear, or abducens cranial nerve dysfunction. The three types of eye movement disorders are:
 * 1) **Strabismus** - deviation of one eye from the other when the person is looking at an object.
 * 2) **Nystagmus** - involuntary unilateral or bilateral rhythmic movement of the eyes.
 * 3) **Paralysis** of individual extraocular muscles may cause a variety of abnormalities, including limited abduction, abnormal closure of the eyelid, ptosis, and diplopia.


 * //Alterations in visual acuity//** is more common in advancing age. Specific causes are:
 * 1) **Amblyopia** - reduction or dimness of vision for unknown reason.
 * 2) **Scotoma** - circumscribed defect of the central field of vision.
 * 3) **Cataract** - a cloudy or opaque area in the ocular lens.
 * 4) **Papilledema** - edema and inflammation of the optic nerve at its point of entrance into the eyeball.
 * 5) **Dark adaptation** - low illumination causes impaired visual acuity, particularly in the elderly.
 * 6) **Glaucoma** - intraocular pressures above the normal pressures of 12 to 20 mmHg.
 * 7) **Retinal detachment**.
 * 8) **Age-related macular degeneration** (AMD) - loss of central vision, is the major cause of vision loss in individuals over age 60 years.


 * //Alterations in accommodation//** are caused by pressure, inflammation, and/or disease of the oculomotor nerve. Symptoms may include diplopia, blurred vision and headache. Loss of accommodation in older adults is termed **presbyopia**.


 * //Alterations in refraction//** are the most common visual problem. The three types are:
 * 1) **Myopia** (nearsightedness)
 * 2) **Hyperopia** (farsightedness)
 * 3) **Astigmatism** - unequal curvature of the cornea


 * //Alterations in color vision//** increase with age because of the progressive yellowing of the lens. Color blindness is an inherited trait. Various neurologic disorders may cause visual dysfunction.


 * __HEARING__**

Ear infections are either:
 * //Aging and hearing//** are common and incremental. Loss of hearing for sounds in the high-frequency range (presbycusis) is most common and interferes with understanding speech, particularly high frequency consonant sounds.
 * 1) **Otitis Externa** - most common infection of the outer ear
 * 2) **Otitis Media** - most common infection of infants and children


 * //Auditory dysfunction//** - major categories of auditory dysfunction are:
 * 1) Conductive hearing loss occurs when a change in the outer or middle ear impairs sound from being conducted from the outer to the inner ear.
 * 2) Sensorineural hearing loss is caused by impairment of the organ of Corti or its central connections.
 * 3) Mixed hearing loss is caused by a combination of conductive and sensorineural losses.
 * 4) Functional hearing loss occurs for no organic reason.


 * __OLFACTION AND TASTE__**


 * Olfaction** (smell) is a function of cranial nerve I and part of cranial nerve V. **Taste** is a function of multiple nerves in the tongue, soft palate, uvula, pharynx, and upper esophagus, including cranial nerves VII and IX. Olfaction dysfunction and taste dysfunction may occur separately or jointly. The strong relationship between smell and taste creates the sensation of flavor. If either sensation is impaired, the percetion of flavor is altered.


 * //Aging and Olfaction and Taste//**

Smell declines with age; the most significant impairments develop after 80 years of age. Taste declination is more gradual; the best-known change with aging is the decline in the number of fungiform papillae on the tongue.
 * Hyposmia** is the impaired sense of smell.
 * Anosmia** is the complete loss of smell.
 * Olfactory hallucinations** arise from hyperactivity in cortical neurons and involve smelling odors that are not really present.
 * Parosmia** is an abnormal or perverted sense of smell, may occur with severe depression.
 * Hypogeusia** is decrease in taste sensation.
 * Ageusia** is the absence of taste.
 * Parageusia** is a perversion of taste in which substances possess an unpleasant flavor.


 * __SOMATOSENSORY FUNCTION__**


 * Touch** is not a uniform sensory experience. The sensation of touch involves the fusion of several qualities, including modality, intensity, location, and duration of the sensory stimulus.


 * Proprioception** is perception and awarenes of the position of the body and its parts depend on impulses from the inner ear and from receptors in joints and ligaments. Vestibular nystagmus is the constant, involuntary movement of the eyeball caused by ear disturbances. Vertigo is the sensation of spinning that occurs with inflammation of the semicircular canals in the ear. Meniere disease is a vestibular disorder that can cause proprioceptive dysfunction.

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