. What is one important idea related to the “substantia nigra” that the writer mentions in paragraphs (3) and (4)?
1) What do drug addiction and Parkinson’s disease have in common? Improper
levels of dopamine. This chemical acts as a messenger between brain cells.
Dopamine is important for many of our daily behaviors. It plays a role in how we
move, for instance, as well as what we eat, how we learn and even whether we
become addicted to drugs.
2) Chemical messengers in the brain are called neurotransmitters. They shuttle
across the spaces between cells. These messengers then bind to docking-station
molecules called receptors. Those receptors relay the signal carried by the
neurotransmitter from one cell to its neighbor.
3) Different neurotransmitters are made in different parts of the brain. Two main
brain areas produce dopamine. One is called the substantia nigra. It’s a tiny strip
of tissue on either side of the base of your brain. It sits in a region known as the
midbrain. Close by is the ventral tegmental area. It, too, makes dopamine.
4) The substantia nigra is very important for movement. The term means “black
substance” in Latin. And sure enough, this area of your brain is actually dark grey
or black! The reason: Cells that produce dopamine also make another chemical
that stains the area a dark color.
5) These two brain areas are very thin and tiny. Together they are smaller than a
postage stamp. But the dopamine they produce relays signals that travel
throughout the brain. Dopamine from the substantia nigra helps us begin
movements and speech.
What is one important idea related to “neurotransmitters” that the writer mentions in paragraphs (1) and (2)?
What does the writer want to show by the example of Parkinson’s disease?
What is the main topic of the passage?
