Answer to Question 1
In ancient times, stress usually involved physical danger, and the response to it was violent physical exertion. In the modern world, stress is seldom physical, but the body reacts the same way. Modern stresses may be a pop quiz or financial trouble. Under these stresses, you are not supposed to fight or run, as ancient ancestor did. But still, the heart races, and hormones flood the bloodstream with glucose and fat. A common enemy today is not a saber-toothed tiger but a disease of modern civilization: heart disease. In modern times, stresses that strain the heart often lead to heart attacks, especially when a body accustomed to chronic underexertion experiences sudden high blood pressure.
Answer to Question 2
The hormonal and nervous systems work together to enable a person to respond to physical danger, known as the fight-or-flight reaction, or the stress response. This stress response is present with only minor variations in all animals, showing how universally important it is to survival. When danger is detected, nerves release neurotransmitters, and glands supply the compounds epinephrine and norepinephrine. Every organ of the body responds, and metabolism speeds up. The pupils of the eyes widen so that you can see better; the muscles tense up so that you can jump, run, or struggle with maximum strength; breathing quickens and deepens to provide more oxygen. The heart races to rush the oxygen to the muscles, and the blood pressure rises so that the fuel the muscles need for energy can be delivered efficiently. The liver pours forth glucose from its store, and the fat cells release fat. The digestive system shuts down to permit all the body's systems to serve the muscles and nerves. With all action systems at peak efficiency, the body can respond with amazing speed and strength to whatever threatens it.
A phylogeny showing the major modern angiosperm lineages
Valgus Stress Test
world as i would like it
Selected Biological Response Modifiers
Linear dose-response curve
People who are color-blind see colors differently. (a) Those with normal vision see the red leaves.