Photograph by Rich Reid. Tundras are among Earth's coldest, harshest biomes. Tundra ecosystems are treeless regions found in the Arctic and on the tops of mountains, where the climate is cold and windy and rainfall is scant. Tundra lands are snow-covered for much of the year, until summer brings a burst of wildflowers.
Muscle is a soft tissue found in most animals. Muscle cells contain protein filaments of actin and myosin that slide past one another, producing a contraction that changes both the length and the shape of the cell. The statement that the tongue is the strongest muscle in the body appears frequently in lists of surprising facts, but it is difficult to find any definition of strength that would make this statement true. 2  Note that the tongue consists of eight muscles, not one.
Three types of muscles. The muscular system can be broken down into three types of muscles: skeletal, smooth and cardiac, according to the NIH. Skeletal muscles are the only voluntary muscle tissue in the human body and control every action that a person consciously performs.Most skeletal muscles are attached to two bones across a joint, so the muscle serves to move parts of those bones closer to each other, according to The Merck Manual.he heart's natural pacemaker is made of cardiac muscle that signals other cardiac muscles to contract. Like visceral muscles, cardiac muscle tissue is controlled involuntarily. While hormones and signals from the brain adjust the rate of contraction, cardiac muscle stimulates itself to contract.