1 Only appointments for producers with active licenses on PDB will be renewed. 2  Appointment Renewal Invoices and the list of appointment renewals due will be available on the NIPR website beginning 8:00 AM Central Time, November 1, 2015 through 4:00 PM Central Time December 31, 2015. 3  NIPR website link is: www.nipr.com.
Myofibrils are composed of long proteins including actin, myosin, and titin, and other proteins that hold them together. These proteins are organized into thick and thin filaments called myofilaments, which repeat along the length of the myofibril in sections called sarcomeres.
Looking at one myofibril, we see that it is divided into segments called sarcomeres. These are the contractile units of a muscle. A dark stripe called a Z disc marks the ends of one sarcomere and the beginning of the next. Sarcomeres are composed of thick filaments and thin filaments.The thin filaments are attached at one end to a Z disc and extend toward the center of the sarcomere.tructure and Function of Skeletal Muscle. Let's begin by working our way down through levels of organization in a skeletal muscle until we reach the contractile units that actually generate the force.