Starter On the flipchart paper, write down everything you know about the skeletal system. What helps the skeleton to move?

Muscle Structure and Function Level 3 Anatomy and Physiology for Exercise and Health

By the end of this session you will be able to: Learning outcomes By the end of this session you will be able to: Explain the cellular structure of muscle fibres Describe sliding filament theory Explain the effects of different types of exercise on muscle fibre types Describe the ability of muscle fibres to adapt to training

What are the different types of muscle tissue? Smooth Cardiac Skeletal What are the different sources of energy for muscles? Fat Carbs Protein When does fat become the main energy source for muscles? After carbs

Myocardium (cardiac muscle) Only found in the heart. Actin and myosin filaments are arranged similar to the skeletal muscle. 3 differences: Cannot be controlled (involuntary muscle) Muscle cells ae connected via intercalated discs to form a single coordinated unit. This is so they can share nutrients equally as well as communicate with each other quickly. Cells contact in a specially organised sequence – single contraction. Only generated by oxygen

Smooth Muscles Found in the tubes of the body. (digestive, reproductive, respiratory, blood vessels and urinary tracts. Involuntary muscle. Contraction leads to decreased in diameter (constriction), whist relaxation leads to an increase (dilation)

Skeletal muscle Bring all the movement of the skeleton and is largely voluntary, though some movements are continuous involuntary and are the postural muscles which adjust skeletal alignment.

Muscle structure and function

Skeletal muscle structure A muscle is a large collection of individual fibres packaged together and protected by connective tissues. Mainly composed by protein collagen fibres, with some elastic tissue. Muscles are bound together by different fasic made of dense irregular connective tissue. Composed by mainly collage fibres which run in different directions. The fascia of the muscle eventually converge to the tendon which attaches to the bone.

The tendon is made of dense regular connective tissue. Collagen fibres in the tendon run in one direction to create a strong connection for the muscle in the direction of pull. A cover of endomysium surrounds each and every cell. The endomysium is continuous with the fibres membrane. Many fibres are then bundled together and wrapped in the perimyosin. The bundle of fibres is referred to as the fascicle. The outer covering of the muscle then surrounds several of these bundles. This is called the epimysium. Towards the ends of the muscle the irregular collagen fibres of the fascia become more regularly aligned and thickened to form the muscle tendon. The tendon then fuses with the periosteum of the bone to which it is connected. All the connective tissue in a muscle are continuous with each other.

It is this tissue that transmit the pulling forces generated inside the muscle cell to the bony leavers, bringing about movement. All muscles are well supplied with blood vessels carrying nutrients and oxygen, and nerve fibres that convey the stimulus.

Fascia Location Endomysium Around each muscle cell (fibre) Perimysium Around the fascicles (bundles of fibres) Epimysuim Around the outside of the muscle An easy way to remember the types of facia is that the epimysium is ‘epic’ as it is the largest layer around the whole muscle; endomysium is the ‘end’ because it is the last and smallest layer; perimysium is simple the one in the middle.

Muscle structure Muscle fibre Myofibril Myofilament

Muscle Cell Structure The muscle fibres (cells) are the approximate width of a human hair and often run the full length of a muscle. They are composed of smaller elements known as myofibrils. Myofibrils are divided along their length into repeating units called sarcomeres. The sarcomeres given skeletal muscle the striped appearance and shorten to bring about muscle contraction.

Muscle structure and function

Sliding filament theory Occurs within the sarcomere The ‘unit’ of muscular contraction Requires calcium and ATP Nervous stimulus causes the myosin heads to attach to the actin forming cross bridges Myosin heads pivot and pull actin towards the centre of the sarcomere Process is repeated and myosin attaches further along the actin

Motor units and recruitment

Task Draw a motor unit. What is the ‘all or none’ law?

Motor units and recruitment The strength of a muscular contraction will be affected by: The frequency of nerve impulses coming into the muscle cell The number of motor units activated

Fast glycolytic fibres Muscle fibre types Slow twitch fibres Fast twitch fibres Type 1 Type 2 Slow oxidative fibres Fast glycolytic fibres Red in colour White in colour Contain large numbers of mitochondria Contain low numbers of mitochondria Endurance type activities Strength / anaerobic type activities

Muscle fibre types The 2 fibres subdivide: Type 2a – Fast oxidative glycolytic (FOG) Type 2b – Fast glycolytic (FG)