| A | B |
|---|
| excitability | the ability of a muscle to receive nerve stimulation |
| elasticity | the flexibility of a muscle |
| endoskeleton | internal or inside skeleton |
| exoskeleton | external or outside skeleton |
| heat production | a function of the muscles |
| smooth muscle | involuntary muscle found in the digestive tract |
| cardiac muscle | found in the heart |
| innervation | attached to nerves; stimulated by nerves |
| skeletal muscle | voluntary muscle, like the biceps or triceps, that enables the bones to move |
| atrophy | decrease in muscle size due to lack of exercise |
| hypertrophy | increase in muscle size due to exercise |
| homologous structure | structure that is the same in a number of animals- like the spine or vertebrae |
| cranium | skull |
| patella | knee |
| phalanges | fingers and toes |
| femur | upper leg (thigh) |
| mandible | lower jaw |
| ribs | protects heart and lungs |
| natural selection | organisms best suited to the environment survive |
| calcium | mineral stored in the bone |
