What does the pain control system inhibit in central sensory pathways?
Pain transmission and perception.
Through which impulses does the pain control system act?
Ascending and descending impulses.
How do pain responses vary among individuals?
Pain responses differ between individuals.
When may injuries be ignored despite pain?
During stressful conditions like accidents or battles.
What effect does irritating skin over a diseased viscus have?
It can relieve pain.
What does the gate theory state about dorsal horn cells?
They act as a gate controlling pain transmission.
Which region's cells in the dorsal horn are especially involved in the gate theory?
The substantia gelatinosa region cells.
What effect does substance P released from C pain fibers have on the dorsal-horn gate?
It opens the dorsal-horn gate.
What happens when substance P release is prevented in pain fibers?
It produces presynaptic inhibition and decreases or blocks pain sensation.
Name one way presynaptic inhibition of pain transmission can be produced.
By opioid peptides.
What system can produce presynaptic inhibition of pain transmission?
The supraspinal central descending analgesic system.
What type of impulses can produce presynaptic inhibition of pain transmission?
Spinal peripheral impulses.
What are opioid peptides?
Morphine-like endogenous ligands acting on morphine receptors in the CNS.
How does morphine act as an analgesic?
By combining with receptors in the central nervous system.
Which three opioid peptide types are important?
Enkephalins, β-endorphins, and dynorphin.
Where are enkephalins released in the CNS?
In areas including the periaqueductal gray and spinal substantia gelatinosa.
What effect do enkephalins produce?
Analgesic effects.
From where are β-endorphins released as neurotransmitters?
The hypothalamus and limbic system.
What role do β-endorphins play during stress?
They produce stress analgesia when secreted with pituitary ACTH.
What is dynorphin's relation to addiction?
It is released from brain stem neurons and is related to addiction.
Which three components block pain signals in supraspinal descending analgesia?
Periaqueductal gray area, raphe magnus nucleus, and pain-inhibitory interneurons.
What does β-endorphin stimulate in the descending analgesic pathway?
The periaqueductal gray area.
Where does the periaqueductal gray area lie anatomically?
In the midbrain and upper pons around the aqueduct of Sylvius.
Where is the raphe magnus nucleus located?
In the upper medulla.
Where are pain-inhibitory interneurons located?
In the dorsal horn of the spinal cord.
What links ascending and descending pain pathways in the spinal cord?
Collaterals from the lateral spinothalamic pain pathway.
How does stimulation of large Aβ sensory fibers inhibit pain C fibers?
It activates inhibitory interneurons releasing GABA or enkephalin causing presynaptic inhibition.
What are examples of spinal peripheral gate inhibition methods?
Rubbing, mustard plaster counter-irritation, and acupuncture.
What does medical treatment of pain include besides analgesics?
Treatment of the cause like antacids, antispasmodics, or vasodilators.
Which analgesics are used in medical pain treatment?
NSAIDs and opiates.
What targets can electric stimulation use for analgesia?
The analgesia system or large sensory Aβ fibers.
What surgical procedure cuts the spinothalamic tract for severe pain?
Anterolateral cordotomy.
Which surgery relieves emotional reaction to intractable cancer pain?
Prefrontal lobectomy.
Test your knowledge with 14 questions on Pain Control Systems.
1. Which treatment plan best reflects the two broad medical approaches to managing pain?
2. Which intervention pairing correctly matches each procedure with its principal target in uncontrollable severe pain?
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