Sunlight and Melanin
On page 53-54, Dr. Moalem describes how the natural
response of the pituitary gland to
sunlight is to produce melanin via neuronal signals. This relates with Big Idea 3: Living systems
store, retrieve, transmit, and respond to information essential to life
processes.
Explain why melanin is produced in response to
sunlight. Then, describe the process of
melanin production in response to sunlight using the terms pituitary gland, sunlight, optic nerve, melanocytes, melanin, and
warning signal. Tie this process
back with evolution. How did differences
in the amount of sunlight in different environments create evolutionary
preferences for people with darker skin as well as people with lighter skin? Include the terms survive and reproduce, selective advantage, Vitamin D, and melanin.
-Ken Saito (ksaito4@students.d125.org)
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ReplyDeleteMelanin is an important chemical for skin as it is able to absorb UV light and dissipate it harmless heat so the skin isn't burned. UV radiation comes in 2 forms which are UVA and UVB. UVA is able to penetrate deeper into the skin and leads to the production of melanin by catalyzing the reaction. Melanin, which is produced in melanosomes, comes in 2 forms: eumalenin, which is brown or black, and pheomelanin, which is red and yellow. This spectrum of melanin allows the melanin to absorb all spectra of harmful UV rays. Once this melanin is produced, it is sent to keratinocytes which are barriers cells. When UV hits the keratinocytes, melanin is released to cover the nucleus of cells for protection. Also, melanin acts as a poison for damaged cells and can help prevent cancer. The sun also acts as a catalyst for the production of vitamin D as well as melanin. Vitamin D is an important mineral for bone development in conjunction with calcium. According to the book on page 53, "..when the optic nerve senses light, it signals the pituitary gland to kick-start the melanocytes."In essence, the optic nerve acts as a warning signal against prolonged UV exposure. Because of this, sunglasses can indirectly lead to skin cancer because the optic nerve is not triggered and thus the process of melanin production isn't started.
ReplyDeleteSkin color comes from discrepancies in melanin production. On page 54 it states, "The melanocytes of most Africans, for example, produce many times the amount of melanin that the melanocytes of Northern Europeans produce-and most of it is eumelanin, the brown or black version." The increased UV exposure of Africa selected for more melanocytes because those without many melanocytes would face harmful UV radiation. This selective advantage relates to both unit 1 and Big Idea 1 (The process of evolution drives the diversity and unity of life) and explains why Africans developed darker skin in contrast to Europeans, who receive less light.
http://www.mayoclinic.com/health/vitamin-d/NS_patient-vitamind
http://biology.about.com/od/anatomy/p/pituitary-gland.htm
http://health.howstuffworks.com/skin-care/problems/medical/albinism1.htm
Andrew Arceo - ibanezrg120ftw
Melanin determines the skin color of an individual as the amount and type of the melanin results in a specific type of skin color. Our bodies produce the melanin after this specialized pigment absorbs light. Melanin comes in two different forms-red or yellow pheomalanin or brown and black eumelanin. All types of melanin are produced by melanocytes, however. The trigger for melanin is the response to natural sunlight. The sunlight triggers the pituitary gland, which is connected to the optic nerve that serves as a warning signal for too much sunlight. The pituitary gland produces the hormones that act as boosters for the melanocytes. After this, the melanocytes start the production of melanin. This is why areas of high intensity sunlight-such as Africa- consist of people with darker skin as their cells produce much more melanin.
ReplyDeletehttp://www.sciencebuzz.org/blog/and-dont-wear-sunglasses
http://www.ncbi.nlm.nih.gov/pubmed/23363631
According to Survival of the Sickest, melanin production can be related to the process of evolution. As more melanin is produced for a certain individual, a darker skin color can protect against sunburn in areas with very high ultraviolet light. Over time, populations exposed to this kind of heat have developed the ability to produce more melanin and protect themselves from the harmful effects of the sun. The differences in the amount of sunlight effects dark and light colored people differently. It is said that the melanocytes of most Africans for example produce many times the amount of melanin that Northern Europeans produce. Thus in a hot environment, dark skinned people have an advantage by trapping less UV light but still protecting themselves from sunburn. Both populations however, still are able to convert their cholesterol to Vitamin D, though light skinned people have it easier as their skin absorbs more light. This concept can be related to Big Idea One as it shows how certain individuals of a population have a mutation and are naturally selected to reproduce and pass on their mutation. This in turn results in an overall phenotype change in the population.
Rahul Kosgi (rkosgi4@students.d125.org)