MACRO AND MICRO STRUCTURE OF MUSCLE Module 1: Anatomy and Physiology

Big Picture Things to Remember  Each skeletal muscle is an organ that contains muscle tissue, connective tissue, nerves, and blood vessels.  Connective tissue names have the suffix -mysium.  Connective tissue is always on the outside of a bundle or cell.  The whole muscle is a bundle of bundles of muscle cells.  Muscle cells contain bundles of the contractile proteins along with all of the other structures you'd expect to find in a cell (nuclei, mitochondria, etc.).  The terms myo- and sarco- refer to muscle.

Muscle’s Connective Tissue Epimysium- covers the entire muscle Perimysium- surrounds the fasciculus (group of muscle fibers) Endomysium-surrounds individual muscle cell

Muscle Cell Structure

Myofibrils  Muscle cells are made up of many (hundreds) myofibrils  Myofibrils contain myofilaments (contractile proteins)  Two myofilaments are:  Actin  Myosin

Actin  Thin filaments  Contain troponin and tropomyosin  Anchored to the Z lines

Myosin  Thick filaments  Have globular heads, called cross-bridges, that stick out at regular intervals  Anchored at the M Bridge (at the center of the H zone)

Sarcomere  The functional (or contractile) unit of a muscle

Motor Unit  Motor Unit is the motor nerve (neuron) and all the muscle fibers that it innervates