PAIN! Physiology - The Ascending Pathway, Descending Pain Pathway and the Substantia Gelatinosa

Summary

This video delves into the complex mechanisms of pain perception, focusing on the ascending and descending pathways. The ascending pathway transmits pain signals from the site of injury to the brain, involving first, second, and third order neurons, with key chemicals like substance P and prostaglandins playing crucial roles. Conversely, the descending pathway modulates pain signals, utilizing neurotransmitters such as serotonin and noradrenaline to inhibit pain transmission. The substantia gelatinosa in the dorsal horn serves as a pivotal control point for these interactions, illustrating the intricate balance between pain perception and regulation in the body.

Takeaways

• 😀 The ascending pathway of pain transmits signals from an injury to the brain, where pain perception occurs.
• 😀 The somatosensory cortex is responsible for processing pain signals and correlates specific body areas with corresponding brain regions.
• 😀 The spinal cord contains different tracts, including the spinothalamic tract, which is crucial for the ascending pathway of pain.
• 😀 Prostaglandins are important chemicals released in response to cell damage that trigger pain signals through sensory nerve fibers.
• 😀 The first-order neuron in the dorsal horn of the spinal cord plays a key role in relaying pain signals to the brain.
• 😀 The second-order neuron crosses to the opposite side of the spinal cord and continues ascending to the thalamus, where further processing occurs.
• 😀 Pain perception is contralateral, meaning the brain processes pain from the opposite side of the body from where the injury occurred.
• 😀 Substance P is a critical neurotransmitter released by first-order neurons, facilitating communication between neurons in the pain pathway.
• 😀 The descending pathway modulates pain by inhibiting the ascending signals, primarily through serotonergic and noradrenergic neurons.
• 😀 The substantia gelatinosa in the dorsal horn acts as a 'gate' to control the flow of pain signals to the brain, influenced by descending pathways.

Q & A

What are the main pathways discussed in the video regarding pain perception?

The video discusses two main pathways: the ascending pathway, which transmits pain signals to the brain, and the descending pathway, which regulates and inhibits these pain signals.

What role does the substantia gelatinosa play in pain perception?

The substantia gelatinosa acts as a gate in the dorsal horn of the spinal cord, modulating pain signals by inhibiting the transmission of these signals to higher brain centers.

How does an injury to the right hand affect pain perception in the brain?

An injury to the right hand sends pain signals that travel up to the left side of the brain, specifically the somatosensory cortex, where the sensation of pain is perceived.

What is substance P and what is its significance in the pain pathway?

Substance P is a neurotransmitter released by first-order neurons in the dorsal horn of the spinal cord, playing a crucial role in transmitting pain signals to second-order neurons.

What are the components of the brain stem involved in the pain pathway?

The brain stem is made up of three main components: the midbrain, pons, and medulla, all of which play roles in processing pain signals.

What chemicals do descending pathway neurons release to inhibit pain signals?

Descending pathway neurons release serotonin and noradrenaline, which help inhibit the ascending pain signals at the level of the dorsal horn of the spinal cord.

What happens to first-order neurons when they transmit pain signals?

First-order neurons synapse with second-order neurons in the dorsal horn, where they release neurotransmitters like substance P to propagate the pain signal.

How do endogenous opioids affect pain perception?

Endogenous opioids, such as encephalins, are released in the substantia gelatinosa to inhibit both the release of substance P and the depolarization of postsynaptic neurons, effectively reducing pain perception.

What is the significance of the thalamus in the pain pathway?

The thalamus serves as a relay station where second-order neurons synapse with third-order neurons, which then carry pain signals to specific regions of the somatosensory cortex for perception.

How does the body achieve pain modulation through the descending pathway?

The descending pathway modulates pain by utilizing neurons from the midbrain and medulla that inhibit ascending pain signals, providing a natural way to control pain perception.