Answer to Question 1
After pain alerts you to a danger, continuing pain messages are unnecessary. The brain puts the brakes on prolonged pain by opioid mechanismssystems that respond to opiate drugs and similar chemicals. Candace Pert and Solomon Snyder (1973) discovered that opiates bind to receptors found mostly in the spinal cord and the periaqueductal gray area of the midbrain
A placebo is a drug or other procedure with no pharmacological effects. In medical research, an experimental group receives a potentially active treatment and the control group receives a placebo. Placebos have little effect on most medical conditions, but they often relieve pain or depression.
Cannabinoidschemica ls related to marijuanaalso block certain kinds of pain. Unlike opiates, cannabinoids act mainly in the periphery of the body rather than the CNS. Researchers found that if they deleted the cannabinoid receptors in the peripheral nervous system of laboratory animals while leaving the receptors intact in the CNS, cannabinoids lost most of their ability to decrease pain.
Another approach uses capsaicin, a chemical in jalapenos and similar peppers that stimulates receptors for heat. Capsaicin rubbed onto a sore shoulder, an arthritic joint, or other painful area produces a temporary burning sensation followed by a longer period of decreased pain. When applied in high doses, or at lower doses for a prolonged period, capsaicin causes an excessive buildup of calcium in heat receptors, and damages the mitochondria in those receptors, rendering the cell nonfunctional for a substantial time
Answer to Question 2
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Different ways that gated channels can be opened.
The Lion Gate of Mycenae (detail)â€â€Âtwo lionesses flank the central column, c. 1300 B
The Primate order displays a diversity of ways of moving around.
Diego Velázquez, Las Meninas (The Maids of Honor)(detail).
Imperial Procession (detail), south frieze, Ara Pacis Augustae, Rome.
Reflex Responses to Pain