1. muscles contract or relax when they receive signals from question 1 options: the cardiovascular system. the nervous system. the respiratory system. the integumentary system. 2. muscles aid in which of the following? question 2 options: circulating blood running breathing all of the above 3. there are three muscle types: cardiac, smooth, and skeletal. which is responsible for the movement of your bones and is voluntary? question 3 options: cardiac smooth skeletal none of these are voluntary. 4. type i muscle fibers have high amounts of mitochondria and are ideal for lower forces and speed. which activity would not use mostly type i fibers? question 4 options: low impact aerobics