Your answer is the nuclear envelope, The nuclear envelope is a double membrane of the nucleus that encloses the genetic material. It separates the contents of the nucleus from the cytoplasm.
Excitatory neurotransmitter? This question is too vague.
The warm-up period before a workout allows the persons muscles to stretch out, and work up to the more intense workout, without hurting, tearing, or injuring. It increases heart rate, which loosens up joints, and increases blood flow to muscles, all which prevents the person from getting hurt.
