D.
variable-ratio schedule of reinforcement.
<span>Cells control cell division in order to maintain normal cell function. If something happens to the control of the cell division, the healthy cells will divide uncontrollably. These new cells are cancer cells. </span>
The mutations in three genes are responsible for development of cancers:
1. Mutation in proto-oncogenes. Proto-oncogenes normally signal cells to grow and differentiate. Proto-oncogenes can become oncogenes due to mutations which result in the uncontrollable division of the cells.
2. Mutation in tumor suppressor genes. In normal cells, tumor suppressor genes suppress genes essential for cell cycle and that way they prevent uncontrollable cell division. However, after a mutation in these genes, suppression is lost and the cell may progress to cancer.
3. Mutation in stability genes. In normal cells, they have no role either in cell death or growth, but they control mutation rate. Mutation in stability genes results in situation where all genes, including proto-oncogenes and tumor suppression genes, are more frequently mutated.
Answer: the correct answer is (C) we have very expressive faces.
Explanation:
A cortical homunculus is a distorted representation of the human body based on a "neurological map" of the areas and proportions of the human brain.
Answer is stretch receptors.
Stretch receptors respond to the distention of muscle wall of the bladder and are neurologically linked to the medulla. Stretch receptors in the bladder signal the parasympathetic nervous system to stimulate muscarine receptors, present in the detrusor muscle, to make him contract. This leads to the expulsion of urine.
