The document contains multiple choice questions about the human body systems including: - Muscular system - largest muscle is the gluteus maximus, about 40-50% of body weight is muscle - Nervous system - brain has around 100 billion neurons, 4% are active, brain loses about 1 gram per year as we age - Urinary system - includes 4 organs, adult produces about 1.5 quarts of urine daily, sphincter muscle prevents accidental urination - Digestive system - digestion begins in mouth with saliva and chewing, stomach juices aid digestion - Endocrine system - pineal gland affects sleep, thyroid controls energy levels, diabetes is from low insulin - Integumentary