The driving age should be raised up to 18 because teens can be a little careless. Driving at the age of 18 is a more mature age for teens because they can have more responsibility. Teens should not be driving at the age of 16 because they could be texting and driving or drinking and driving with some friends.
During contraction, the smooth-muscle cell's intermediate filaments help to draw the cell up, like closing a drawstring purse. Calcium ions regulate contraction in smooth muscle, but they do it in a slightly different way than in skeletal muscle: Calcium ions come from outside of the cell. Calcium ions bind to an enzyme complex on myosin, called calmodulin-myosin light chain kinase.
SKELETAL MUSCLE (most familiar) is controlled by the conscious mind & moves the bones of the skeleton so that the animal can move around. CARDIAC MUSCLE one place in the body -the heart. It starts the heart beating long before the animal is born & keeps it up until the animal dies. SMOOTH MUSCLE is found all over the body in places - eyes, air passageways in the lungs, stomach & intestines, urinary bladder, blood vessels, & reproductive tract. It carries out most of the unconscious, internal movements that the body needs to maintain itself in good working order.