سؤال قراءة ستيب محلول — فهم التفاصيل (تدريب 7286)

(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 the “substantia nigra” that the writer