<span>A negative feedback loop works by adjusting an output, such as heart rate, in response to a change in input, such as blood pressure. A basic loop consists of a receptor, a control center and an effector. If you are at rest and your blood pressure increases, pressure receptors in your carotid arteries detect this change in input and send nerve impulses to the medulla of your brain, or control center. This signals the brain to reduce nerve impulses that stimulate your heart muscle, an effector, to contract. Your heart contracts more slowly and your output, or heart rate decreases, causing your blood pressure to decrease to within target levels.</span>
Endosymbiotic theory is a theory of evolution that eukaryotes came from prokaryotes. Mitochondria and chloroplasts both have the double membranes. Each of them also contain genetic material that are replicated with a separate cell cycle. Both organelles have their own ribosomes.
