Musculoskeletal system, with clicker questions (1)

MUSCULOSKELETAL SYSTEM CHAPTER 48 OVERVIEW Muscle movement was a key innovation in the evolution of animals. Muscle tissue is composed of cells that contract. The three major muscle tissues (smooth, cardiac, skeletal) have different structures and functions. Muscle forces and shape changes are transmitted to other parts of the body via the skeleton. The muscles and skeleton allow for diverse types of locomotion among animals. ANIMAL MOVEMENT Muscles generate movement by exerting force and causing shape changes. Muscle and skeletal systems work together to produce movement. Movement falls into two general categories: 1. Movement of the entire organism relative to its environment. Locomotion, movement of an animal under its own power, enables animals to seek food, shelter, etc. 2. Movement of one part of the animal relative to other parts. Movement not involved in locomotion include gill ventilation, beating of the heart, etc. MUSCLE CONTRACTION Vertebrate skeletal and cardiac muscle tissue is composed of long, slender cells called muscle fibers. Within each muscle fiber are many small strands called myofibrils, which may be striped or striated. Striped or striated myofibrils are made up of light and dark areas known as sarcomeres. • The sarcomere becomes shorter as the myofibril contracts and longer when the sarcomere relaxes. • Sarcomeres are made up of two types of proteins: actin (thin filaments) and myosin (thick filaments). .........................................CONTINUED.....................................................