sistema sensorial

SISTEMA SENSORIAL

RECEPTORES SENSORIAISOs receptores sensoriais so encontrados dentro do sistema nervoso somtico,responsveispelas distintas experincias sensoriais recebidas e interpretadas pelo nosso corpo. A funo mais bsica dos receptores sensoriais fornecer ao sistema nervoso central (SNC) informaes sobre as condies internas das estruturas orgnicas e do meio externo.

RECEPTORES SENSORIAISApenas um receptor no possui acapacidadede identificar sozinho todos os estmulos diferentes que o corpo recebe a cada segundo. Somos supridos com diferentes receptores sensoriais, cada um com sua particularidade, possibilitando a sensao de diferentes estmulos.

RECEPTORES SENSORIAISOs receptores podem ser classificados de acordo com a sua funo:Mecanoceptores;Termoceptores;Fotoceptores;Quimioceptores;Nociceptores.

RECEPTORES SOMTICOS

Tipo morfolgicoTransduoTipo de FibraLocalizaoFunoTerminaes livresMecanoeltrica, Termoeletrica, QuimioeletricaC, AToda a pele, rgos internos, vasos sanguneas, articulaesDor, temperatura (calor), tato grosseiro e propriocepco Corpsculos de MeissnerMecanoeltricaAEpiderme glabraTato, presso-vibratria(textura)Corpsculos de PacciniMecanoeltricaADerme, peristeo, parede das vscerasPresso-vibratria (textura)Corpsculos de RuffiniMecanoeltricaAToda a dermetimos detectores de vibrao mecnica.Discos de MerkelMecanoeltricaAToda a epiderme glabra e pilosaTato, presso-estticaBulbos de KrauseMecanoeltricaABordas da pele com as mucosasTato?? temperatura (frio)?? Folculos pilososMecanoeltricaAPele pilosaTatorgos tendinosos de GolgiMecanoeltricaIbTendes PropriocepcoFusos muscularesMecanoeltricaIa e IIMsculos esquelticosPropriocepco

Os Sistemas Sensoriais do Homem de seus Receptores

SENSIBILIDADE E SENSAOSensibilidade: a propriedade de percepo consciente ou inconsciente das condies externas e internas do corpo.

Sensao: a impresso fsica causada no corpo.Para que uma sensao ocorra, so necessrias quatro condies:Um estmulo ou alterao no ambiente;A converso do estmulo em um impulso nervoso por um receptor ou rgo dos sentidos;A conduo do impulso ao crebro;A interpretao do impulso por uma regio do crebro

SENSIBILIDADE E SENSAOSo os rgos dos sentidos que colocam o organismo em relao com o meio ambiente. Por isso os cinco sentidos possuem receptores e transmissores:Receptor externo: rgo que capta a sensao. Transmissor: rgo que leva a sensao ao crebro (nervo).Receptor interno: regio do crebro que interpreta a sensao.

SENSIBILIDADE CUTNEA OU TATOAs sensaes cutneas incluem as sensaes tteis (tato e presso), as sensaes trmicas (frio e calor) e de dor.

Receptor externo: peleTransmissor: nervos espinhais e cranianosReceptor interno: lobo parietal do crebro

RECEPTORES TTEISCorpsculo de Vater-Pacini: encontrados nas polpas dos dedos, percebem impresses de presso.Corpsculo de Meissner: situam-se na polpa digital e percebem a impresso de tato (toque).Corpsculo de Merkel: reconhecem a parte do corpo tocada.Corpsculo de Ruffini: palmas das mos e sola dos ps, percebem sensibilidade e calor.Corpsculo de Krause: percebe o frioReceptores de dor: so terminaes nervosas livres em todo corpo.

CORPSCULOS TTEIS

Transduo sensorial

Os impulsos nervosos so conduzidos ao longo das fibras aferentes dos neurnios aferentes de primeira ordem at o SNC, seja atravs dos nervos espinhais ou cranianos, conforme a origem no corpo.

Transduo sensorial

Como pesquisar sobre a sensibilidade dos mecanorreceptores da pele? Com um estimulador mecnico sendo aplicado na pele possvel medir as freqncias dos PA desencadeados nas fibras aferentes correspondentes ao campo de inervao.

Transduo sensorial

Na palma da mo observa-se que os campos receptivos dos corpsculos de Pacini so amplos e os de Meissner, bem pequenos.

Transduo sensorial

Aplicando-se estmulos que aumentam progressivamente de intensidade, depois se tornam constantes e, em seguida, so removidos, observa-se que os receptores de Pacini e de Meissner respondem apenas quando o estimulo est sendo aplicado e removido e durante a sustentao do estimulo, param de responder.

Transduo sensorial

Isto significa que a principal propriedade destes receptores a de detectar a presena/ausncia de estmulos ignorando os que se tornam constantes (receptores de adaptao rpida). Essa propriedade os qualifica como detectores precisos da freqncia com que um estimulo mecnico aplicado na pele.

Transduo sensorial

J os de Merkel respondem melhor taxa de variao com que o estimulo est sendo aplicado. Quando a intensidade do estimulo pra de variar, a freqncia dos PA diminui, ou seja, adaptam-se aos estmulos constantes porm mais lentamente.

Transduo sensorial

Os de Ruffini, respondem tanto aplicao como manuteno do estimulo, quase sem nenhuma alterao na freqncia dos PA. Estes receptores de adaptao mais lenta tm como propriedade, a deteco da durao e intensidade dos estmulos mecnicos sobre a pele.

Transduo sensorial

A faixa de freqncia que melhor estimula os corpsculos de Pacini est entre 200 a 300Hz; os de Meissner, em trono de 50Hz. Quando a freqncia cai menos de 50 Hz, as terminaes de Ruffini e Meissner evocam sensaes de adejo.

Transduo sensorial

A sensibilidade que nos permite qualificar precisamente as impresses mecnicas em relao ao local de estimulao mediada pelo tato fino (ou epicrtico). J a sensibilidade que cujos estmulos resultam numa sensao de tato grosseiro (ou protoptico). Voc j reparou como os cegos lem em Braille? Ou como voc mesmo examina um objeto com as mos?

Transduo sensorial

A figura ao lado compara os receptores de dor e de calor em funo do aumento de energia trmica. O eletrodo est registrando a atividade nervosa do nervo mediano que contem ambas as fibras nervosas. Repare que a medida que h aumento de intensidade da energia trmica (ondas quadradas em vermelho) os receptores de calor aumentam a freqncia dos PA, at chegar aos 45oC. A partir da, os receptores trmicos no decodificam mais os aumentos de intensidade, ao contrario dos receptores de dor, que ao contrrio comeam a disparar significativamente, anunciando, uma queimadura iminente (ou em curso).

SENSIBILIDADE OLFATRIA OU OLFATO

As fossas nasais possuem uma mucosa chamada Pituitria, que apresenta duas regies:Zona olfativa: com numerosas clulas olfativas, apresenta colorao amarela e superior, recebendo terminaes do nervo olfatrio.Zona respiratria: muito vascularizada, colorao rsea, apresenta vibrissas e muco nasal.

Receptor externo: mucosa pituitria das fossas nasaisTransmissor: nervo olfatrioReceptor interno: hipocampo (base do lobo temporal do crebro).

MUCOSA PITUITRIA

FISIOLOGIA DO OLFATO Para que possamos perceber os odores das substncias, necessrio que as mesmas desprendam partculas gasosas para impressionar as clulas nervosas da pituitria. Produzida a impresso sensitiva, a mesma levada pelo nervo olfatrio at o hipocampo, de onde retorna como sensao odorfera.

FISIOLOGIA OLFATRIA

SENSIBILIDADE GUSTATRIA OU GUSTAO

Receptor externo: papilas gustativas da lnguaTransmissor: nervo glossofarngeoReceptor interno: hipocampo (base do lobo temporal)

PAPILAS GUSTATIVASPapilas Caliciformes: 9 a 11, dispostas na regio posterior da lngua formando o V lingual.Papilas Uniformes: 150 a 200, espalhadas por toda lngua na frente do V lingual.Papilas Filiformes: muito numerosas, em forma de tubo, esto paralelas ao V lingual.Papilas Foliceas: aparecem nos bordos da lngua,sendo quase imperceptveis.Papilas Hemisfricas: pequenas e abundantes, esto por toda mucosa da lngua.

PAPILAS GUSTATIVAS

FISIOLOGIA DA GUSTAO Para percebermos o sabor da substncia necessria que a mesma seja solvel. As substncias que possuem sabor so chamadas spidas e as que no possuem, inspidas. As diversas sensaes gustativas resultam da associao de 4 sabores fundamentais: sabor doce (ponta da lngua), sabor salgado (meio da lngua), sabor amargo( base da lngua) e sabor cido ou azedo ( bordos laterais da lngua).

SENSIBILIDADE AUDITIVA OU AUDIO

Receptor externo: orelhaTransmissor: nervo vestibulococlearReceptor interno: lobo temporal do crebro.

VIAS AUDITIVASA cclea transforma o som em sinais eltricos;

Axnios conduzem estes sinais para ncleos cocleares;

A via ascendente projeta-se para o tlamo;

os sinais chegam ento ao lobo temporal.

ORELHAA orelha divide-se em trs partes:Orelha externa: pavilho auditivo, meato acstico, membrana do tmpano.Orelha mdia: ossculos martelo, bigorna e estriboOrelha interna: labirinto sseo e membranoso

ORELHA

BIGORNA, ESTRIBO E MARTELO

AUDIOAs ondas sonoras colhidas no pavilho auditivo, so encaminhadas para o conduto auditivo, fazendo vibrar o tmpano, que conectado aos ossos martelo, bigorna e estribo que enviam a vibrao ao labirinto e atravs do nervo vestibulococlear a vibrao sonora chega ao lobo temporal e transformada em som.

SENSIBILIDADE VISUAL OU VISO

Receptor externo: globo ocularTransmissor: nervo pticoReceptor interno: lobo occipital do crebro

FISIOLOGIA DA VISO Os raios luminosos atravessam a crnea, humor aquoso, cristalino e humor vtreo chegando a retina formando a imagem invertida, que atravs do nervo ptico levada ao lobo occipital, onde a imagem corrigida.

DORExperincia sensorial e emocional desagradvel, associada a uma leso tecidular real ou potencial, ou que vivida como tal

International Association for the Study of Pain (IASP), 1994

O processo da dor Um estmulo nocivo ou um estmulo nociceptivo causa a ativao das fibras da dor. A resposta dor comea com o estmulo dos nociceptores, terminaes nervosas especializadas que respondem aos estmulos dolorosos. O estresse ou a leso mecnica dos tecidos excita os nociceptores mecanossenssveis.

Estmulo nociceptivoDor fisiolgicaLesoinflamatriaLesonervosaFibromialgiaSIICefaliasIASP (1994)Dor : Experincia sensitiva e emocional desagradvel associada ou descrita em termos de leso tecidual

Dor causada por leso tecidular (musculo-esqueltica, cutnea ou visceral) Raja et al. in Wall PD, Melzack R (Eds). Textbook of Pain. 4th Ed. 1999.;11-57DOR NOCICEPTIVA

DOR NOCICEPTIVA Dor causada pela ativao das terminaes livres dos nervos perifricos Leso tissularAtivao das terminaes livres dos nervos perifricosConduo e processamento sinaptico do impulsoDor IASP (1994)

DOR NOCICEPTIVAExperincia sensorial, traduzindo-se numa resposta de neurnios sensoriais perifricos especficos (nociceptores) a estmulos nxicos (nocivos)Habitualmente, a regio dolorosa situa-se no local da leso

DOR NOCICEPTIVAPode ser crnica, mas geralmente transitria, desaparecendo aps cura dos tecidos lesadosResponde aos analgsicos convencionais

Frequentemente descrita como latejante, moinha ou rigidez

NOCICEPTORESOs nociceptores so receptores silenciosos e no captam, respondem ou sentem estmulos normais. Somente quando estimulados por uma ameaa em potencial ao organismo humano, eles desencadeiam o reflexo da dor.

NOCICEPTORES

Apercepo da dorse inicia na periferia, atravs da ativao de nociceptores (receptor sensorial da dor). Esses esto presentes por todo o organismo e so classificados em trs subtipos:Receptores mecnicos de alto-limiar: detectam presso;Receptores mecanotermais de baixo-limiar: detectam presso e calor;Receptores polimodais: detectam presso, calor e fatores qumicos.

NOCICEPTORES

Os receptores mecnicos de alto-limiar e os receptores mecanotermais de baixo-limiar so inervados pelasfibras nervosas mielinizadas A e A, enquanto os receptores polimodais so inervados pela fibra nervosa no-mielinizada C.

NOCICEPTORES

As substncias qumicas que ativam os receptores so vrias, dentre elas esto os mediadores inflamatrios como:prostaglandinas, leucotrienos, bradicininas,serotonina, substncia P ehistamina.

NocicepoOs nociceptores so receptores silenciosos e no captam, respondem ou sentem estmulos normais. Somente quando estimulados por uma ameaa em potencial ao organismo humano, eles desencadeiam o reflexo da dor.Alm de ativar os nociceptores, o estmulo doloroso conduzido para amedula espinhalatravs das fibras A, Ae C. Esses so considerados os primeiros moduladores da via da conduo de dor, pois fazem sinapses comneurnios secundrios da medula espinhal, que por suavez, fazem sinapse com um terceiro neurnio nocrebro que completa a conduo nociceptiva. Devido mielinapresentenas fibras A e A, acabam por transmitirem impulsos nervosos 10 vezes mais rpidos que as fibras C.

Activao de nociceptores locaisNervoperifricoMedula espinhalLeso tecidularInformao ascendenteDOR NOCICEPTIVAPercepo da dorModulao descendente

DOR NOCICEPTIVAOs nociceptores possuem dois diferentes tipos deaxnios. O primeiro so as fibras axoniais A. Elas somielinizadase podem permitir um potencial de ao capaz de viajar na velocidade de aproximadamente 20 metros por segundo em direo ao SNC. O outro tipo, as fibras axoniais "C", um condutor mais lento.

DOR NOCICEPTIVAComo resultado disso, a dor origina-se em duas fases: A primeira fase mediada pelas fibras de rpida conduo (fibras axoniais A)

A segunda fase deve-se s fibras de conduo lenta (fibras axoniais C).

DOR NOCICEPTIVAA dor associada s fibras de rpida conduo (fibras axoniais A) podem ser correlacionadas com uma dor inicial extremamente aguda e cruciante, ou seja, "uma pontada fortssima".A segunda fase apresenta uma dor mais prolongada e menos intensa como resultado de um dano tecidual.

DOR NOCICEPTIVANa medula espinhal existem basicamente duas vias ascendentes para a conduo da dor at o crebro:Via neoespinotalmica: conduz a dor somtica, bem-localizada, atravs de poucas sinapses;Via palioespinotalmica: conduz a dor visceral, de localizao precria, atravs de sinapses.

DOR NOCICEPTIVAQuando ha deteco da dor pelo crebro, so conduzidasinformaespor uma via descendente, na medula espinhal, relacionada com a fibra C, que por sua vez, se comunica com interneurnios. Quando esses ltimos so estimulados, liberam opiides endgenos (como encefalinas, endorfinas e dinorfinas) que se combinam com receptores de opiides, diminuindo deste modo, a liberao da substncia P.

LIMIAR DA DOROlimiar da dorvaria de indivduo para indivduo e, tambm, entre os animais.

Ele definido como o momento em que certo estmulo passa a ser reconhecido como doloroso.

Jo limiar de tolerncia definido como o ponto em que o estmulo doloroso alcana tal intensidade que no pode mais ser suportado pelo indivduo.

A resistncia dor a diferena entre os dois limiares e demonstra a amplitude de uma estimulao dolorosa qual o indivduo possa considerar como aceitvel.

MANEJO DA DORO manejo da dor consiste na inibio da percepo, da sensibilizao central (modulao das etapas medulares), da transmisso (inibio da conduo do impulso) e da transduo (inibio da sensibilizao perifrica dos nociceptores). Seu controle feito com a administrao deanalgsicos.

DOR NEUROPTICADor iniciada ou causada por disfuno ou leso primria do sistema nervoso central ou perifrico (incluindo o sistema nervoso autnomo)

International Association for the Study of Pain. IASP Pain Terminology

DOR NEUROPTICAFrequentemente descrita como descarga, choque elctrico ou queimadura Muitas vezes associada a formigueiro ou dormncia

DOR NEUROPTICAA regio dolorosa no se situa, necessariamente, no local da leso; a dor ocorre no territrio nervoso da estrutura afectada (nervo, raiz, medula espinal, crebro) Quase sempre uma situao crnica (por exemplo nevralgia ps-herptica ou dor ps-AVC) Fraca resposta aos analgsicos convencionais

Exemplo de dor neuroptica:leso do nervo cubital aps fractura sseaNervo Cubital

Informao ascendenteModulao descendenteLeso nervosaPercepo da dorImpulsos gerados no nervo cubitalMedula espinhal

DOR NEUROPTICAExemplosNeuropatia diabtica perifrica (NDP)Leso nervosa ps-cirurgiaNevralgia ps-herptica (NPH)Radiculopatia lombarDor ps-AVCDescritores frequentesDescargaChoque elctricoQueimaduraFormigueiroDormncia

AVCsLeses vrtebro-medularesEsclerose mltiplaNeoplasiasDOR NEUROPTICA CAUSAS CENTRAIS

Traumticas: cirurgia, encarceramento do nervo, amputaoMetablicas: Diabetes Mellitus, urmiaInfecciosas: Herpes Zoster, VIHTxicas: quimioterapia, alcoolismoVasculares: Lupus Eritematoso, Poliarterite NodosaNutricionais: niacina (cido nicotnico), tiamina (vit. B1), piridoxina (vit. B6)Neoplasias: metstase, infiltraoDOR NEUROPTICA CAUSAS PERIFRICAS

Dor neuroptica sintomas positivos

Dor espontneaSensao dolorosa sem estmulo evidenteAlodniaResposta dolorosa a um estmulo habitualmente no doloroso (toque, movimento, frio, calor)HiperalgesiaResposta aumentada a um estmulo habitualmente doloroso (frio, calor, picada)DisestesiaSensao desagradvel, espontnea ou evocada (por exemplo sensao de descarga)ParestesiaSensao anormal no desagradvel, espontnea ou evocada (por exemplo sensao de formigueiro, zumbido, vibrao)

Dor neuroptica sintomas negativos

HipoestesiaDiminuio da sensibilidade a estmulos, excluindo os sentidos especiais (por exemplo: toque, dor)AnestesiaPerda total de sensibilidadeAnalgesiaAusncia de dor em resposta a estmulos habitualmente dolorososHipoalgesiaDiminuio da dor em resposta a estmulos habitualmente dolorosos

Dor neuroptica Dor Nociceptiva

Dor MistaDor neuroptica Dor Nociceptiva

DOR MISTA OU COMBINADAA coexistncia dos dois tipos de dor tem sido referida como estado de dor mista ou combinada e pode surgir em mltiplas situaes, tais como sndrome do canal crpico, dor lombar associada a radiculopatia e dor neoplsicaO seu tratamento efectivo requer uma abordagem teraputica abrangente, para aliviar as componentes nociceptiva e neuroptica da dor

Exemplo de dor mista: hrnia discal com radiculopatia

...dor quando o doente diz que di !

**This slide illustrates three broad categories of Pain: neuroptica (pathologic), nociceptiva (physiologic), and mixed Pain states that encompass both nociceptiva and neuroptica components, with examples of common causes of each type of Pain.

The key talking points on this slide are as follows:neuropathic pain has been defined by the International Association for the Study of Pain as initiated or caused by a primary lesion or dysfunction in the nervous system.1 Depending on where the lesion or dysfunction occurs within the nervous system, neuropathic pain can be peripheral or central in origin. Causas of neuropathic pain perifrica include nevralgia ps-herptica (PHN) and neuropatia diabtica perifrica (DPN). Due to the prevalence and characteristics of PHN and DPN, these states may be considered representative of neuropathic pain perifrica.Nociceptive Pain is an appropriate physiologic response that occurs when specific peripheral sensory neurons (nociceptors) respond to noxious stimuli. Nociceptive Pain has a protective role because it elicits reflex and behavioral responses that keep tissue damage to a minimum.Acute Pain, such as that seen with tissue inflamao and chronic Pain, such that accompanying osteoarthritis, are examples of nociceptiva Pain.Although there are no specific descriptors for each type of Pain, neuropathic pain is frequently described as queimadura or formigueiro in quality, while nociceptiva Pain is often described as aching or throbbing.There are cases in which an individual experiences Pain sensations that are a blend of Pain having a nociceptiva and a neuroptica origin. For example, in carpal tunnel syndrome, it is common experience to have nociceptiva Pain, felt around the wrist, and neuropathic pain, felt in the distribution territory of the median nerve (fingers).

ReferencesInternational Association for the Study of Pain. IASP Pain Terminology.Raja et al. in Wall PD, Melzack R (Eds). Textbook of Pain. 4th Ed. Edinburgh, UK: Harcourt Publishers Limited. 1999.;11-57

Additional key words: descriptorLa IASP propose une autre classification de la douleur base sur les mcanismes capable de la dclencher la douleur.La douleur nociceptive due aune lsion tissulaire, c'est parce qu'existent des lments spcifiques du systme nerveux qui ont charge de dtecter, transmettre, analyser, intgrer et mmoriser les informations gnres par un tel dgt. **Note to speaker: this slide contains an animated build. The first bullet appears automatically, then click on the slide to bring up the remaining 4 bullets sequentially.

The painful region is typically localized at the site of injury in nociceptive pain. This contrasts with neuropathic pain where the painful region may not necessarily be the same as the site of injury and occurs in the neurological territory of the affected structure (nerve, root, spinal cord, brain). This is outlined on slide 15.

Nociceptive pain usually responds well to conventional analgesics such as acetaminophen (paracetamol), non-steroidal anti-inflammatory drugs (NSAIDs), cyclo-oxygenase (COX)-2 inhibitors or opioids.*Note to speaker: this slide contains an animated build. The first bullet appears automatically, then click on the slide to bring up the remaining 4 bullets sequentially.

The painful region is typically localized at the site of injury in nociceptive pain. This contrasts with neuropathic pain where the painful region may not necessarily be the same as the site of injury and occurs in the neurological territory of the affected structure (nerve, root, spinal cord, brain). This is outlined on slide 15.

Nociceptive pain usually responds well to conventional analgesics such as acetaminophen (paracetamol), non-steroidal anti-inflammatory drugs (NSAIDs), cyclo-oxygenase (COX)-2 inhibitors or opioids.*Note to speaker: this slide contains an animated build to represent the involvement of the nervous system in chronic nociceptive pain (osteoarthritis of the knee). Clicking on this slide will cause subsequent components of this build to appear automatically.

In osteoarthritis, chronic pain is caused by activation of local nociceptors by inflammation in the affected joint.These activated nociceptors send impulses along the peripheral (afferent) nerves to the dorsal roots where they enter the spinal cord to reach the dorsal horn.Signals ascend from the sensory nerves via various pathways to the brain where they give rise to the experience of pain. Pathways include the brain stem, thalamus, limbic system and other cortical areas, which are all responsible for processing sensation, emotion, stress, and memory.The brain, in turn, sends signals via descending tracts into the dorsal horn to modulate the incoming (afferent) signals from the painful knee joint, and to evoke a reflex or behavioral response to osteoarthritis pain (e.g. rubbing the painful area and restricting movement), or to inhibit the afferent signal entirely.

The goal of osteoarthritis pain treatment is to relieve inflammatory pain with conventional analgesics (acetaminophen [paracetamol], NSAIDS, COX-2 inhibitors or opioids), while maintaining joint function and mobility.*This slide illustrates three broad categories of Pain: neuroptica (pathologic), nociceptiva (physiologic), and mixed Pain states that encompass both nociceptiva and neuroptica components, with examples of common causes of each type of Pain.

The key talking points on this slide are as follows:neuropathic pain has been defined by the International Association for the Study of Pain as initiated or caused by a primary lesion or dysfunction in the nervous system.1 Depending on where the lesion or dysfunction occurs within the nervous system, neuropathic pain can be peripheral or central in origin. Causas of neuropathic pain perifrica include nevralgia ps-herptica (PHN) and neuropatia diabtica perifrica (DPN). Due to the prevalence and characteristics of PHN and DPN, these states may be considered representative of neuropathic pain perifrica.Nociceptive Pain is an appropriate physiologic response that occurs when specific peripheral sensory neurons (nociceptors) respond to noxious stimuli. Nociceptive Pain has a protective role because it elicits reflex and behavioral responses that keep tissue damage to a minimum.Acute Pain, such as that seen with tissue inflamao and chronic Pain, such that accompanying osteoarthritis, are examples of nociceptiva Pain.Although there are no specific descriptors for each type of Pain, neuropathic pain is frequently described as queimadura or formigueiro in quality, while nociceptiva Pain is often described as aching or throbbing.There are cases in which an individual experiences Pain sensations that are a blend of Pain having a nociceptiva and a neuroptica origin. For example, in carpal tunnel syndrome, it is common experience to have nociceptiva Pain, felt around the wrist, and neuropathic pain, felt in the distribution territory of the median nerve (fingers).

ReferencesInternational Association for the Study of Pain. IASP Pain Terminology.Raja et al. in Wall PD, Melzack R (Eds). Textbook of Pain. 4th Ed. Edinburgh, UK: Harcourt Publishers Limited. 1999.;11-57

Additional key words: descriptor*Note to speaker: this slide contains an animated build. The first bullet appears automatically, then click on the slide to bring up the remaining 4 bullets sequentially.

The painful region may not necessarily be the same as the site of injury. Pain occurs in the neurological territory of the affected structure (nerve, root, spinal cord, brain).In peripheral neuropathic pain, it is in the territory of the affected nerve or nerve root.In central neuropathic pain, it is related to the site of the lesion in the spinal cord or brain.

Neuropathic pain responds poorly to conventional analgesics. There is some evidence to show that opioids may have efficacy in the management of neuropathic pain.*Note to speaker: this slide contains an animated build. The first bullet appears automatically, then click on the slide to bring up the remaining 4 bullets sequentially.


Neuropathic pain responds poorly to conventional analgesics. There is some evidence to show that opioids may have efficacy in the management of neuropathic pain.*This slide shows ulnar nerve damage, caused by direct trauma or compression following an elbow fracture, which can result in neuropathic pain.

The nerve damage involves destruction of the myelin sheath of the nerve or part of the nerve (axon).Direct nerve trauma is a key cause of neuropathic pain. The pain exists after tissue healing and no longer represents an alert to injury, but indicates dysfunction within the nervous system. *Note to speaker: this slide contains an animated build to represent the involvement of the nervous system in neuropathic pain (ulnar nerve lesion following bone fracture). Clicking on this slide will cause subsequent components of this build to appear automatically. In ulnar nerve damage, neuropathic pain is caused by direct trauma or compression of the nerve following elbow fracture.Damaged nerve fibers generate abnormal impulses that are transmitted along the sensory (afferent) nerves to the dorsal roots where they enter the spinal cord to reach the dorsal horn.Abnormal impulses over-stimulate the second-order neurons ascending to the cortex through various pathways (brain stem, thalamus, limbic system, and other cortical areas) where pain awareness develops.In neuropathic pain, a lesion or dysfunction of the nervous system may cause an excess of function (positive symptoms) or a deficit of function (negative symptoms):Positive symptoms spontaneous pain, allodynia (pain due to a stimulus that does not normally provoke pain), dysesthesia, paresthesia, and hyperalgesiaNegative symptoms weakness or loss of sensation (e.g. wrist and hand flexion following ulnar nerve damage).

*This slide gives an overview of neuropathic pain, with examples of common causes.

Neuropathic pain has been defined by the IASP as a pain that is initiated or caused by a primary lesion or dysfunction in the peripheral or central nervous system.1Causes of peripheral neuropathic pain include postsurgical and posttraumatic nerve injury, diabetic peripheral neuropathy (DPN), postherpetic neuralgia (PHN) and radiculopathies.Poststroke pain, multiple sclerosis, and spinal cord injuries are all examples of central neuropathic pain.Neuropathic pain is frequently described as a shooting, electric shock-like, or burning pain commonly associated with tingling and/or numbness.


1. International Association for the Study of Pain (IASP) pain terminology. www.iasp-pain.org/terms-p.html (last accessed: 14/12/05)

*neuropathic pain is initiated or caused by a primary lesion or dysfunction in the peripheral or central nervous system. Patients with neuropathic pain have chronic Pain, which is typically considered to be Pain that persists beyond the normal time of healing or for more than 3-6 months.This slide lists some of the most commonly encountered peripheral and central causes of neuropathic pain. The key points on this slide are as follows:Any type of peripheral nerve or root injury may lead to neuropathic pain: traumas, entrapments (like carpal tunnel syndrome), postsurgical iatrogenic nerve lesions, amputations, radiculopathies, etc.Metabolic disturbances may also causa neuropathies associated with neuropathic pain, most notably diabetes mellitus but also uremia and hypothyroidism.Infections such as HIV may also result in peripheral nerve damage.Toxins implicated in peripheral nerve injury include chemotherapeutic agents, lead, organophosphorates and alcohol. Glue sniffing has also been associated with neuropathic pain from peripheral neuropathy.Vascular disorders (polyarteritis nodosa, lupus erythematosus), nutritional deficiencies (niacin, thiamine, pyridoxine), and direct effects of cancer due to metastases and infiltration may also causa peripheral neuropathies leading to neuropathic pain. Central neuropathic pain may be present in about 8% of stroke patients, and in about 28% of patients with multiple sclerosis. Spinal cord lesions and tumors are also known, common causes of central neuropathic pain.ReferencesWall PD, Melzack R (Eds). Textbook of Pain. 4th Ed. Edinburgh, UK: Harcourt Publishers Limited. 1999Galer BS, Dworkin RH (Eds). A clnica guide to neuropathic pain. Minneaplois, MN: McGraw-Hill Healthcare Information. 2000Woolf CJ, Mannion RJ. Lancet. 1999;353:1959-1964..

*neuropathic pain is initiated or caused by a primary lesion or dysfunction in the peripheral or central nervous system. Patients with neuropathic pain have chronic Pain, which is typically considered to be Pain that persists beyond the normal time of healing or for more than 3-6 months.This slide lists some of the most commonly encountered peripheral and central causes of neuropathic pain. The key points on this slide are as follows:Any type of peripheral nerve or root injury may lead to neuropathic pain: traumas, entrapments (like carpal tunnel syndrome), postsurgical iatrogenic nerve lesions, amputations, radiculopathies, etc.Metabolic disturbances may also causa neuropathies associated with neuropathic pain, most notably diabetes mellitus but also uremia and hypothyroidism.Infections such as HIV may also result in peripheral nerve damage.Toxins implicated in peripheral nerve injury include chemotherapeutic agents, lead, organophosphorates and alcohol. Glue sniffing has also been associated with neuropathic pain from peripheral neuropathy.Vascular disorders (polyarteritis nodosa, lupus erythematosus), nutritional deficiencies (niacin, thiamine, pyridoxine), and direct effects of cancer due to metastases and infiltration may also causa peripheral neuropathies leading to neuropathic pain. Central neuropathic pain may be present in about 8% of stroke patients, and in about 28% of patients with multiple sclerosis. Spinal cord lesions and tumors are also known, common causes of central neuropathic pain.ReferencesWall PD, Melzack R (Eds). Textbook of Pain. 4th Ed. Edinburgh, UK: Harcourt Publishers Limited. 1999Galer BS, Dworkin RH (Eds). A clnica guide to neuropathic pain. Minneaplois, MN: McGraw-Hill Healthcare Information. 2000Woolf CJ, Mannion RJ. Lancet. 1999;353:1959-1964..

*This slide (and the following one) can be placed immediately after slide 39, which summarizes the positive and negative sensory symptoms of neuropathic pain.

*This slide (and the previous one) can be placed immediately after slide 39, which summarizes the positive and negative sensory symptoms of neuropathic pain.

*The co-existence of pain types has been referred to as mixed or combined pain.Examples of these conditions include low back pain with associated lumbar radiculopathy, cancer pain and carpal tunnel syndrome.

*The co-existence of pain types has been referred to as mixed or combined pain.Examples of these conditions include low back pain with associated lumbar radiculopathy, cancer pain and carpal tunnel syndrome.

*Note to speaker: this slide contains an animated build. The first bullet appears automatically, then click on the slide to bring up the remaining 3 bullets sequentially.*Note to speaker: this slide contains an animated build to represent co-presenting pain (herniated disc causing low back pain and lumbar radiculopathy). Clicking on this slide causes subsequent components of the build to appear automatically.

Nociceptive pain component: Localized, low back pain at the site of the herniated disc is mediated by the release of inflammatory mediators from degrading cartilage cells, activating peripheral nociceptors and sending impulses along the sensory (afferent) nerves to the dorsal horn and then to the brain.

Neuropathic pain component: Pain impulses are mediated by nerve damage following compression of the dorsal root and abnormal impulses enter the spinal cord to reach the dorsal horn.These abnormal impulses can over-stimulate the secondary nerves ascending to the cortex through various pathways relaying in the brain stem, thalamus and limbic system where pain awareness develops.Such nerve damage (a lesion or dysfunction at any point of the ascending or descending pathways) can cause:Positive symptoms spontaneous pain and tingling, radiating down to the lower legs.Negative symptoms weakness or loss of sensation and numbness, radiating down to the lower legs. Broader analgesic treatment options may be required for the management of co-exisitng pain conditions to encompass both nociceptive and neuropathic elements.

sistema sensorial

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