First class[change | change source] A first-class lever is a lever where the fulcrum is in between the effort and resistance (the load). Seesaws and crowbars are examples of first class levers. Second class[change | change source] A second-class lever is where the resistance is between the effort and the fulcrum.
This system contains the thalamus, hypothalamus, amygdala, and hippocampus. Brain Stem: Underneath the limbic system is the brain stem. This structure is responsible for basic vital life functions such as breathing, heartbeat, and blood pressure. Scientists say that this is the simplest part of human brains because animals' entire brains, such as reptiles (who appear early on the evolutionary scale) resemble our brain stem.
The hypothalamus is a section of the brain responsible for the production of many of the bodyâs essential hormones, chemical substances that help control different cells and organs. The hormones from the hypothalamus govern physiologic functions such as temperature regulation, thirst, hunger, sleep, mood, sex drive, and the release of other hormones within the body. This area of the brain houses the pituitary gland and other glands in the body.