|MadSci Network: Anatomy|
Decreasing temperature will cause muscles to have less strength and to contract more slowly. This is because they are made of physical molecules, like most other things. When they are colder, the molecules do not move as fast as when they are warm. In addition, nerves are colder. They do not conduct nerve impulses as fast. In effect, the muscles might not work as well as usual because the nerves are numb. Plus, the distribution of blood is different, which a lot blood vessels constricting, to preserve body heat (of course, how much depends on warm the body is, with a lot less vasoconstriction when the body is warm). This will also affect the way muscles work, especially with repeated activity, like writing the same thing over and over. Finally, all of these changes will decrease the amount of coordination that the person has. This is because the brain is used to having nerve impulses travel at certain speeds; the brain is also used to feedback arriving from muscles at certain intervals. So one might expect that the effects of decreasing temperature would decrease coordination. One must remember that the motion of writing is not just the activity of muscles. There is a large element of visual feedback in controlling activities like writing. Various types of sensory feedback, such as spindles in the muscles and receptors in the skin (for example, measuring the strength of the grip) also play a role. All of these things (except the visual feedback) will be affected by the changes in temperature, not jsut the strength of the muscles.
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