Stress causes tension in muscles that are very painful. This is how stress affects the musculoskeletal system.
Explanation:
Stress affects the musculoskeletal system causing muscle tension. Muscles can be so tight that they lead to a painful frame of muscle spasm. The back and neck muscles are particularly more sensitive to the effects of stress.
The slightest muscle strain can be the "drop of water" in a stressed person. For example, if the spinal nerves are restricted by scar tissue or calcium deposits, they can lead to minimal muscle tension that compresses the nerves and causes pain. Another example is sciatica, which can become much greater when the person feels stressed.
When the body is stressed, muscles tense up. Muscle tension is almost a reflex reaction to stress — the body's way of guarding against injury and pain. With sudden onset stress, the muscles tense up all at once, and then release their tension when the stress passes.
In general, negative selection eliminates from the population very harmful changes to proteins that kill or stop reproduction. ... The authors also found a correlation between genes predicted to be under negative selection and genes implicated in certain hereditary diseases
