Questão de Língua Inglesa

1 The same nerves involved in the fight-or-flight
response can cause permanent damage to the cells
responsible for producing hair color in mice, scientists
4 have found. There is some truth to the longstanding
anecdote that your locks can lose color when you’re
stressed.
7 A team of researchers has found that in mice,
stressful events damage the stem cells that are responsible
for producing pigment in hair. These stem cells, found near
10 the base of each hair follicle, differentiate to form more
specialized cells called melanocytes, which generate the
brown, black, red and yellow hues in hair and skin. Stress
13 makes the stem cells differentiate faster, exhausting their
number and resulting in strands that are more likely to be
transparent — gray.
16 The study also found that the sympathetic nervous
system, which prepares the body to respond to threats,
plays a major role in the graying process. “Normally, the
19 sympathetic nervous system is an emergency system for
fight or flight, and it is supposed to be very beneficial or, at
the very least, its effects are supposed to be transient and
22 reversible,” said Ya-Chieh Hsu.
Stress affects the whole body, so the researchers
had to do some investigation to figure out which
25 physiological system was conveying its effects to hair
follicles. The findings provide the first scientific link
between stress and hair graying. The new study is an
28 important step toward understanding the role of stress on
various tissues.

Internet: (adapted).

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