Sometimes you may have atrial flutter that develops into atrial fibrillation and vice versa. The risk factors for and the symptoms and causes of atrial flutter are similar to those of atrial fibrillation. For example, strokes are also a concern in someone with atrial flutter. As with atrial fibrillation, atrial flutter is usually not life-threatening when it's properly treated.
Nerves and Nerve Types. There three types of nerves in the central nervous system: motor neurons, sensory neurons and autonomic neurons. Motor nerves send impulses or signals from the brain and spinal cord to all of the muscles in the body.
Nerve cells are INVOLUNTARY (you can't control nerve impulses) while muscle cells are VOLUNTARY (you can often control what your muscles do) 2. Muscle cells go through cell division easily and swiftly -- which is why when you exercise, your muscles grow back stronger within a few days.