Name: pain signaling and inflammation
Uploaded: 2025-10-23T11:49:14.000Z
Duration: 1 min 44 s
Channel: JoVE

- A nocicepção, geralmente chamada de dor é o processo através do qual um estímulo nocivo é transmitido através dos sistemas periféricos respiratório e sistema nervoso central para avisar sobre possíveis danos ou ferimentos. 
Quando um sinal prejudicial é detectado, nociceptores, terminações nervosas livres, são ativadas. 
Os mastócitos próximos liberam substâncias, tipo histaminas, enquanto os macrófagos secretam citocinas, pequenas proteínas que são fatores críticos na sinalização da resposta imune. 
Simultaneamente, os axions dos nociceptores transmitem o sinal para o chifre dorsal da medula espinal, principalmente através de duas fibras de dor diferentes. 
As primeiras a serem ativadas são as fibras A-delta finamente mielinizadas, que conduzem a dor imediata, aguda e bem localizada a uma velocidade muito rápida para permitir que o corpo possa controlar o estímulo nocivo. 
O outro tipo de axions são as fibras C, que conduzem o impulso lentamente por não serem mielinizadas e transmitem dor ardente prolongada. 
Da medula espinhal, os sinais de dor atravessam e viajam até o tronco cerebral, seguidos pelo tálamo e córtex somatossensorial onde os sinais de dor são interpretados para determinar a localização da lesão. 
Regiões adicionais do cérebro processam a dor, estas são as estruturas corticolimbicas, elas incluem a amígdala e o córtex pré-frontal que se relacionam com memórias emocionais e cognição. 
Em última análise, as múltiplas interações dentro do cérebro contribuem para a percepção subjetiva que os indivíduos experimentam.

"Avanços na compreensão da nocicepção e da dor neuropática." Jornal de Neurologia 265, nº 2 (2018): 231–38. [<a href="https://doi.org/10.1007/s00415-017-8641-6" target="__blank">Fonte</a>]

Pinho-Ribeiro, Felipe A., Waldiceu A. Verri e Isaac M. Chiu. "Interações neurológicas-imunes sensoriais do nociceptor na dor e na inflamação." Tendências em Imunologia 38, nº 1 (janeiro de 2017): 5–19. [<a href="https://doi.org/10.1016/j.it.2016.10.001" target="__blank">Fonte</a>]

nocicepção

Nociception

A nocicepção—a capacidade de sentir dor—é essencial para a sobrevivência e o bem-estar geral de um organismo. Estímulos nocivos como dor perfurante de um objeto afiado, calor de uma chama aberta ou contacto com produtos químicos corrosivos são detectados primeiro por receptores sensoriais, chamados nociceptores, localizados em terminações nervosas. Nociceptores expressam canais iónicos que convertem estímulos nocivos em sinais elétricos. Quando esses sinais atingem o cérebro através de neurónios sensoriais, eles são percebidos como dor. Assim, a dor ajuda o organismo a evitar estímulos nocivos.
 
 O sistema imunitário desempenha um papel essencial na patologia da dor. Ao encontrar estímulos nocivos, células imunes como mastócitos e macrófagos presentes no local da lesão libertam substâncias químicas inflamatórias como citocinas, quimiocinas, histaminas e prostaglandinas. Estes químicos atraem outras células imunes, como monócitos e células T para o local da lesão. Eles também estimulam nociceptores, resultando em hiperalgesia—uma resposta mais intensa a um estímulo anteriormente doloroso, ou alodínia—uma resposta dolorosa a um estímulo normalmente inócuo, como o toque leve. Essa sensibilização da dor ajuda a proteger o local ferido durante a cura.
 
 Em alguns casos, a dor ultrapassa o seu papel como um sistema de alerta agudo se a sensibilização não se resolver ao longo do tempo. Dor crónica—dor persistente ou recorrente que dura mais de três meses—acompanha frequentemente condições inflamatórias, como artrite reumatóide. Anti-inflamatórios não esteróides (NSAIDs) como aspirina e ibuprofeno reduzem a dor inibindo a síntese das moléculas inflamatórias prostaglandinas. No entanto, os NSAIDs e opióides atualmente usados para combater a dor têm efeitos colaterais severos e o potencial de viciar. Portanto, compreender os mecanismos subjacentes à patologia da dor pode ajudar a desenvolver fármacos mais eficazes para suprimir a percepção da dor com efeitos colaterais negativos menos graves.

Nocicepção

A nocicepção - a capacidade de sentir dor - é essencial para a sobrevivência e o bem-estar geral de um organismo. Estímulos nocivos, como piercing ...

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pain signaling and inflammation

Pain signaling begins when the body detects a harmful stimulus. Sharp objects, open flames, and corrosive chemicals can trigger this response. Sensory receptors called nociceptors, which sit on nerve endings, detect these noxious stimuli and use ion channels to turn them into electrical signals.

Those electrical signals travel through sensory neurons to the brain, where they are experienced as pain. This warning system helps an organism avoid damage and stay safe. Pain is therefore an important part of survival and overall well-being.

The immune system also shapes pain after an injury. Mast cells and macrophages at the injury site release inflammatory chemicals such as cytokines, chemokines, histamines, and prostaglandins. These signals attract more immune cells, including monocytes and T cells, and they also stimulate nociceptors.

This immune response can increase pain sensitivity. Hyperalgesia is a stronger response to a stimulus that was already painful. Allodynia is pain caused by something that is usually not painful, such as light touch. These changes help protect the injured area during healing.

Pain can become a problem when sensitization does not fade. Chronic pain is persistent or recurring pain that lasts longer than three months. It often occurs with inflammatory diseases such as rheumatoid arthritis. NSAIDs, including aspirin and ibuprofen, reduce pain by blocking the production of prostaglandins. However, NSAIDs and opioids can cause serious side effects and may lead to addiction, so researchers continue to study pain mechanisms to find safer drugs.

Pain Signaling and Inflammation

what is the skeletal system?

Human Skeleton: Bones, Cells, and Disease

The human skeleton is a living framework made of 206 bones in adults. Bones connect with cartilage, tendons, and ligaments. This system gives the body support, protects organs, and helps with movement and locomotion. The skeleton has two main parts: the axial skeleton and the appendicular skeleton. The axial skeleton has 80 bones and includes the skull, the vertebral column, and the rib cage. The cranium, or upper skull, has eight bones that enclose the brain, while the lower part of the skull...

bone structure

Inside a Long Bone

Inside a long bone, osseous tissue is organized into two main types: cortical bone and cancellous bone. A femur is a clear example of this structure. The bone also includes outer coverings and inner spaces that support growth, repair, and blood cell production. Cortical bone, also called compact bone, forms the dense outer layer along the diaphysis, or shaft. It is covered by the periosteum, a membrane with connective tissue, capillaries, and nerves. Beneath the cortical layer is the medullary...

joints

Types of Joints in the Human Body

Joints are the places where adjacent bones connect. They are also called articulations or articular surfaces. Joints help the body move and stay stable. Joints can be classified by structure or by function. Structural classification depends on the material that forms the joint and whether there is a space between the bones. By structure, joints are fibrous, cartilaginous, or synovial. Fibrous joints are connected by fibrous tissue and have no cavity between the bones. Because of this, they do...

bone remodeling

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Bone turnover is a continuous process in which old bone is broken down and new bone is built. Osteoclasts carry out bone resorption, and osteoblasts carry out bone formation. In adults, this balanced cycle helps maintain bone mass and calcium homeostasis. Mechanical stress can also stimulate turnover as part of normal maintenance and repair. Parathyroid hormone, or PTH, helps control blood calcium levels by increasing bone resorption when calcium is low. It is released from the parathyroid...

skeletal muscle anatomy

Muscle Fibers, Tendons, and Contraction

Skeletal muscle moves the body by pulling on bones through tendons. Tendons are the connective tissue that attaches skeletal muscle to bones. When skeletal muscles contract, they create voluntary movement. Skeletal muscle is wrapped in layers of connective tissue. The outer layer is the epimysium, which helps protect the muscle. Beneath it, the perimysium surrounds and groups fasciculi, which are bundles of skeletal muscle cells called myocytes. These cells are also called skeletal muscle...

classification of skeletal muscle fibers

Skeletal Muscle Fiber Speed and Energy

Skeletal muscle fibers can be grouped by how fast they contract and how they make ATP, the energy cells use for movement. These differences also shape their physical features. Most human muscles contain all three fiber types, but in different amounts. Slow oxidative fibers, also called slow-twitch fibers, appear red because they have many capillaries and high levels of myoglobin, an oxygen-storing protein. They also contain more mitochondria, which make ATP through oxidative phosphorylation,...

muscle contraction

Nerve Signals That Trigger Muscle Contraction

Nerve signals trigger muscle contraction in both skeletal and smooth muscle, but the two muscle types use different control systems. In skeletal muscle, the signal begins at the motor end plate, which is the synapse between a motor neuron and a muscle fiber. In smooth muscle, contraction is controlled by the autonomic nervous system and happens without conscious control. In skeletal muscle, motor nerve terminals release acetylcholine. This neurotransmitter binds to receptors on the sarcolemma,...

cross-bridge cycle

Calcium Control in Muscle Contraction

Calcium control in muscle contraction depends on ATP, motor neurons, and the sliding action of actin and myosin. As a muscle contracts, the thin and thick filaments overlap more, and the sarcomere, which is the contractile unit of the muscle, becomes shorter. This process uses energy from ATP and happens in a repeating cycle at the molecular level. Myosin drives the movement of actin through a cross-bridge cycle. When ATP attached to the myosin head is hydrolyzed to ADP, myosin shifts into a...

motor units

How Motor Units Control Muscle Movement

Motor units control skeletal muscle movement. A motor unit includes one efferent motor neuron, which carries signals away from the central nervous system, and all of the muscle fibers it innervates. A single motor neuron can connect with multiple muscle fibers, but each muscle fiber is innervated by only one motor neuron. Lower motor neurons are the efferent neurons that control skeletal muscle, the most abundant type of muscle in the body. Their cell bodies are found in the spinal cord or...

the spinal cord

Spinal Cord Structure and Dermatomes

The spinal cord is the main nerve pathway of the central nervous system. It carries sensory signals from the body to the brain and motor signals from the brain to the body. It begins at the foramen magnum, the opening at the base of the skull, and extends to the level of the first or second lumbar vertebra. In cross-section, the spinal cord is cylindrical and contains both gray matter and white matter. The central canal lies in the middle and is a remnant of the lumen of the primitive neural...

nociception

Pain signaling begins when the body detects a harmful stimulus. Sharp objects, open flames, and corrosive chemicals can trigger this response. Sensory receptors called nociceptors, which sit on nerve endings, detect these noxious stimuli and use ion channels to turn them into electrical signals. Those electrical signals travel through sensory neurons to the brain, where they are experienced as pain. This warning system helps an organism avoid damage and stay safe. Pain is therefore an...

key terms and concepts

Learn how nociceptors detect harmful stimuli, how inflammation boosts pain sensitivity, and why chronic pain can persist after injury.

Pain Signaling and Inflammation | JoVE K12

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Pain Signaling and Inflammation

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