MUSCULAR SYSTEM BY: GROUP VI

MAJOR FUNCTIONS OF MUSCULAR SYSTEM MOVEMENT of the body. Contraction of skeletal muscles is responsible for the overall movements of the body. Ex: walking, running, and manipulating objects with the hands. MAINTENANCE of the posture. Skeletal muscles constantly maintain tone, which keeps us sitting or standing erect. PRODUCTION of body heat. When skeletal muscles contract, heat is given off as a by-product. This released heat is critical to the maintenance of body temperature.

MAJOR FUNCTIONS OF MUSCULAR SYSTEM COMMUNICATION. Skeletal muscles are involved in all aspects of communication. Ex: speaking, writing, typing, gesturing, and facial expression. CONSTRICTION of organs and vessels. The contraction of smooth muscle within the walls of internal organs. This constriction can help propel and mix food and water in the digestive tract, propel sections from organs, and regulate blood through vessels. CONTRACTION of the heart. The contraction of cardiac muscle causes the heart to beat, propelling blood to all part of the body.

 Skeletal muscle is so named because most of the muscles are attached to the skeletal system.  Also called striated muscle  Associated by connective tissue, constitutes approximately 40% of body weight. SKELETAL MUSCLE

CHARACTERISTICS OF SKELETAL MUSCLE 1.Contractility- is the ability of skeletal muscle to shorten with for - when skeletal muscles contract, they cause the structures to which they are attached to move. 2.Excitability- the capacity of skeletal muscle to respond to a stimulus. - normally, the stimulus is from nerves that we consciously control.

CHARACTERISTICS OF SKELETAL MUSCLE 3. Extensibility- means that skeletal muscles stretch. - after a contraction, skeletal muscles can be stretched to their normal resting length and beyond to a limited degree. 4. Elasticity- is the ability of skeletal muscles to recoil to their original resting length after they have been stretched.

SKELETAL MUSCLE STRUCTURE Epimysium- also called muscular fascia - a connective tissue sheath that surrounds the skeletal muscles. Perimysium- a loose connective tissue that subdivide each whole muscle. Fasciculi- numerous visible bundles. Endomysium- a loose connective tissue that then subdivide each fascicle into separate muscle cells called muscle fiber.

Muscle fiber- is a single cylindrical fiber, with several nuclei located at its periphery. - the largest human muscle fibers up to 30cm long and 0.15mm in diameter. Sarcolemma- the cell membrane of the muscle fiber. Transverse tubules or T tubules- are many tubelike invaginations along the surface of the muscle fiber. Sarcoplasmic reticulum- a smooth e.r that associates T tubules. MUSCLE FIBER STRUCTURE

Sarcoplasm- cytoplasm of muscle fiber. Myofibrils- a threadlike structures that extend from one end of the muscle fiber to other end. TWO MAJOR PARTS: 1.Actin myofilaments 2.Myosin myofilaments

MUSCLE FIBER STRUCTURE

MYOSIN MYOFILAMENTS or THICK MYOFILAMENTS - resemble bundles of minute golf clubs. - the parts of the myosin molecule that resemble golf club heads are referred to as myosin heads. IMPORTANT PROPERTIES OF MYOSIN HEADS: 1.The heads can bind to attachment sites on the actin myofilaments; 2.They can bend and straighten during contraction; and 3.They can break down ATP, releasing energy.

EXCITABILITY OF MUSCLE FIBERS

NERVE SUPPLY and MUSCLE FIBER STIMULATES

MUSCLE CONTRACTION

ENERGY REQUIREMENTS FOR MUSCLE CONTRACTION

FATIGUE

EFFECTS OF FIBER TYPE ON ACTIVITY LEVEL

TYPES OF MUSCLE CONTRACTION