The 650 skeletal muscles in the human body contract when they receive signals from motor neurons, which are triggered from a part of the cell called the sarcoplasmic reticulum. Motor neurons tell your muscles to contract and the better you become at having those signals tell your muscles to contract, the stronger you can get.
Answer:
Influenza is caused by viruses that can be spread through air or by contact from one individual to another
Explanation:
Pregnancy can contribute to morning sickness
Measles is a viral infection that's serious for small children but is easily preventable by a vaccine. it is a respiratory problem. this infection came into the us when people travel internationally.
Aerobic exercise stimulates the heart rate and breathing rate to increase in a way that can be sustained for the exercise session. In contrast, anaerobic ("without oxygen") exercise is activity that causes you to be quickly out of breath, like sprinting or lifting a heavy weight.
