Dr. Blackwell caused rats to stop breathing when he lesioned their MEDULLA. When doctor Blackwell induced a lesion in the rats' medulla, he discovered that the rats stopped breathing. He explained this observation by saying that the medulla has functional role to play in the breathing process of rats.
A signal molecule must bind to its receptor to initiate a response. Receptors are proteins that bind to their signal molecule either externally (cell-surface receptors) or internally (nuclear receptors) within the cytoplasm or nucleus. ... Once a ligand binds to its receptor, a series of reactions are initiated.
High tides and low tides are caused by the moon. The moon's gravitational pull generates something called the tidal force. The tidal force causes Earth—and its water—to bulge out on the side closest to the moon and the side farthest from the moon. These bulges of water are high tides.
