That would be A. Carbon dioxide.
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Answer:
At a level in the spinal cord
Explanation:
The gate theory was elaborated in 1965 by P.D. Wall and r. Melzack, to explain the influence of tactile skin stimulation on pain relief. It essentially admits that there exists in the medullar posterior horns (located behind the central canal of the spinal cord) a gate-acting neural mechanism that can control the passage of nerve impulses transmitted from the peripheral fibers to the CNS through the medulla.
The gate regulates the influx of nociceptive impulses even before a perception of pain is created. The variation in the passage of action potentials (nociceptive) that the gate produces is determined by the activity of the thick (A-alpha and A-beta) and thin (A-delta and C) fibers, as well as cognitive influences.
Answer:
Horizontal gene transfer
Explanation:
Horizontal gene transfer or lateral gene transfer is when an organisms of different species can acquire a gene from a different one. This process is well understood in bacteria and is responsible for the appearence of antibiotic resistant bacteria. Bacteria can take DNA fragments through a process known as transformation, but this is less common in eukaryotes. Gene transfer agents like viruses could carry the gene from one specimen to the other. Another way could be Horizontal transposon transfer but the exact mechanisms behind it are still under research.
