Modulation of pain signals is thought to be mediated by the release of Group of answer choices histamine. endorphins. cholecystokinin. glutamine.
The correct answer and explanation is:
Correct Answer: Endorphins
Explanation (300 words):
Pain modulation in the nervous system is a complex process that involves various neurotransmitters and neuromodulators. Among the listed options—histamine, endorphins, cholecystokinin, and glutamine—endorphins are the key substances known to mediate the modulation of pain signals.
Endorphins are endogenous opioid neuropeptides produced by the central nervous system and the pituitary gland. They are part of the body’s natural pain control system and play a crucial role in reducing the perception of pain. When the body experiences stress, trauma, or pain, endorphins are released and bind to opioid receptors in the brain and spinal cord. This binding inhibits the transmission of pain signals by preventing the release of substance P and other pain-promoting neurotransmitters in the spinal cord.
The primary mechanism involves activation of descending inhibitory pathways from the brainstem (particularly from areas like the periaqueductal gray matter) to the spinal cord, which suppresses pain signal transmission from peripheral nociceptors to the brain. This helps produce an analgesic effect, similar to that of opioid drugs like morphine, but without the external administration.
In contrast:
- Histamine is involved in inflammatory responses and can actually enhance pain sensitivity in certain contexts, such as allergic reactions or tissue injury.
- Cholecystokinin (CCK) is a digestive hormone that can modulate pain but is more often associated with reducing the analgesic effects of opioids, making pain worse in some situations.
- Glutamine is a precursor to the neurotransmitter glutamate, which is excitatory and plays a role in transmitting rather than inhibiting pain signals.
Therefore, among the choices, endorphins are the most directly involved in the modulation and inhibition of pain, serving as a key component of the body’s internal pain-relief system.