STRUCTURAL BASIS OF MUSCLE CONTRACTION MUSCLE TYPES OF

STRUCTURAL BASIS OF MUSCLE CONTRACTION

MUSCLE TYPES OF MUSCLE: § Smooth muscle § cardiac muscle § skeletal muscle Ø SMOOTH MUSCLE: The muscle of all internal organs viscera and blood vessels except heart is called smooth muscle. These muscles are found in the blood vessels digestive tract and many other organs.

DISTRIBUTION OF SMOOTH MUSCLE • • Non-striated & involuntary. Present in almost all the organs in the form of sheets, bundles or sheets around their tissue Structure in which smooth muscle fibers are present. Wall of organ like esophagus, stomach and intestine in the GIT. Ducts of digestive glands Wall of the blood vessel in circulatory system. Ureter, urinary bladder in excretery system

Function of smooth muscle • In Respiratory system: Contraction and relaxation of smooth muscle of air passage regulate inflow and outflow of air. • In Digestive system: Helps in the movement of food substances mixing it with digestive juices and elimination of unwanted substances. • In Renal system: Regulate renal blood flow and glomerular filtration. • In cardiovascular system: Around the blood vessels regulate blood pressure and blood flow

Structure of smooth muscles • Fusiforms or elongated cells 2 -5 microns in diameter & 50 -200 microns in length • Single & elongated nucleus, centrally placed • Contractile proteins, actin, myosin & tropomyosin. • Dense bodies- formed by the proteins desmin. Attached to thin filament. Scattered in a sarcoplasm. Not arranged in straight line. • Thick filaments formed by myosin & thin filaments are formed by actin and tropomyosin

Types of smooth muscle Single-unit • In an organ smooth muscle fibers function as one unit • Fibers have many interconnecting gap junction. • Its presence is more common in the body then multi-unit smooth muscle. • Fibers are arranged in sheets or bundles • Control of actin myogenic

MULTI-UNIT SMOOTH MUSCLE • • Indiviual fibers Function independently No gap junctions each muscle fiber is innervated by single nerve ending. Outer membrane made up of glycoprotein. Individual fiber: Control of action , neurogenic. No spontaneous contraction.

CARDIAC MUSCLE • • The muscle of the vertebrates heart is called cardiac muscle. Just like skeletal muscle also appears striated because it consist of sarcomeres. These are muscles of the heart. They constitute most of the mass of heart wall. STRUCTURE: Heart muscle is composed of chains of single cells. Each cell has its own muscles. The chains of the cell are organized to fibers

• Many of the sarcomeres are connected end-to-end to form myofibrils • cardiac muscle also contains the sarcolemma with deep invaginations called T-tubules. • cardiac muscle cells are connected to one another via structure called intercalated discs • . these connecting discs contain gap junctions. • These gap junctions allow action potentials between cells quickly and efficiently by allowing the movement of ions between adjacent cardiac muscles cells

SKELETAL MUSCLES • The muscles that are attached with the skeleton and associated with the movement of bones are called skeletal muscles. • The skeletal muscle are consciously control & therefore are called voluntary muscles. • These are also striped or striated muscles because they show alternate light & dark bands. • e. g. triceps and biceps

STRUCTURE OF MUSCLE FIBRE • . Each end of the muscle is attached to the bone by • means of modified connective tissue tendon The structural and functional unit of skeletal muscle is called skeletal muscle fibre • Each muscle consists of muscle bundles. • Each muscle bundle is further composed of muscle fibre or cells. Each muscle fibre is about 10 -100 mm in diameter. • The muscle fiber from the side, they show a pattern of cross banding or striations this pattern gives rise to other common name for skeletal muscle, striated muscle