NEUROFISIOLOGIA DA DOR

Summary

In this video, Pedro explains the physiology of pain, from the moment a painful stimulus is triggered in our organs to the perception of pain in the central nervous system. He discusses two types of pain: fast and slow pain, each transmitted by different nerve fibers (A-delta for fast pain and C fibers for slow pain). The video highlights the role of chemical substances like bradykinin and lactic acid in pain perception, and details the neural pathways involved, including the spinothalamic tract and the connections to the thalamus and brain regions associated with pain. The presentation provides an in-depth look at how the body processes and experiences pain.

Takeaways

• 😀 Pain is triggered when painful stimuli activate specific receptors in the nervous system.
• 😀 There are two types of pain: fast pain (acute) and slow pain (chronic), transmitted by different nerve fibers.
• 😀 Fast pain is transmitted by A-delta fibers and reaches the brain in about 0.1 seconds.
• 😀 Slow pain is transmitted by C fibers and reaches the brain after approximately 1 second.
• 😀 A-delta fibers detect mechanical and thermal pain, while C fibers primarily detect chemical pain.
• 😀 Chemical pain is triggered by substances like bradykinin, potassium ions, and lactic acid, often released during tissue injury.
• 😀 An example of chemical pain is felt when a blood pressure cuff causes temporary ischemia in the arm.
• 😀 Fast pain signals are processed quickly, while slow pain tends to build up gradually and lasts longer.
• 😀 A-delta fibers are found mostly in the skin and superficial tissues, while C fibers are in deeper organs.
• 😀 The pathways for fast and slow pain differ in how they transmit signals through the spinal cord and brain, affecting pain perception.
• 😀 The pain signals for fast pain travel via the neospinothalamic tract, while slow pain signals travel via the paleospinothalamic tract, both reaching areas like the thalamus and the cerebral cortex.

Q & A

What are free nerve endings, and how do they relate to pain perception?

Free nerve endings are sensory nerve receptors located in various organs. They are sensitive to pain stimuli and, when activated, send electrical impulses to the brain, signaling pain perception.

What are the two types of pain and how are they transmitted?

The two types of pain are fast pain and slow pain. Fast pain is transmitted by A-delta fibers, reaching the central nervous system in approximately 0.1 seconds. Slow pain is transmitted by C fibers and reaches the central nervous system in about 1 second.

What differentiates A-delta fibers from C fibers?

A-delta fibers are responsible for fast pain and transmit sharp, quick pain signals. They are associated with mechanical and thermal stimuli. C fibers, on the other hand, transmit slow pain, which is often dull or chronic, and they are primarily involved in detecting chemical stimuli such as those released during tissue injury.

What role do substances like bradykinin and prostaglandins play in pain perception?

Substances like bradykinin, prostaglandins, potassium ions, and others are released during tissue injury. These chemicals activate C fibers by triggering pain receptors, which contribute to the sensation of slow, chronic pain.

How does ischemia contribute to the sensation of pain?

Ischemia occurs when blood flow to an area is reduced, leading to a lack of oxygen and nutrients. This triggers anaerobic metabolism, which produces lactic acid. The accumulation of lactic acid activates C fibers, causing pain, especially after movement or strain in the affected area.

What are the key differences between the pathways for fast and slow pain?

Fast pain follows the neospinothalamic tract, where A-delta fibers transmit signals quickly to the brain. Slow pain, transmitted by C fibers, follows the paleospinothalamic tract, where the pain is processed more gradually, reaching both the brainstem and the limbic system.

What is the function of the neospinothalamic tract?

The neospinothalamic tract is responsible for transmitting fast pain signals from the A-delta fibers through the spinal cord to the brain, specifically to the thalamus and somatosensory cortex, which helps us perceive sharp, quick pain.

What is the role of the paleospinothalamic tract in pain perception?

The paleospinothalamic tract transmits slow pain signals from C fibers, traveling through the spinal cord to the brainstem and the limbic system. It also communicates with the thalamus, where emotional and sensory aspects of pain are processed.

How do emotional responses affect pain perception?

The limbic system plays a crucial role in linking pain perception to emotions. If there is damage to this system, a person may still feel chronic pain, but the emotional response to that pain could be diminished or altered.

Why are A-delta fibers primarily located in the skin while C fibers are found in deeper tissues?

A-delta fibers are concentrated in the skin and other superficial tissues where they detect sharp, quick pain from mechanical or thermal stimuli. C fibers, however, are more common in deeper tissues, where they detect slow, chronic pain and chemical stimuli.