Sliding Filament Theory Muscle Structure and Function Sliding Filament Theory Sport Books Publisher

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Muscle Striations Sport Books Publisher

Components of skeletal muscle d) myofibril c) muscle fibre b) muscle fibre bundle a) Muscle belly Sport Books Publisher

How do muscles contract?

How do muscles contract? The muscular system and the nervous system work together to signal and receive signals from the brain to allow for muscular contraction. The link = neuromuscular junction

How do muscles contract? A muscle contraction results from a signal from a nerve impulse. The electrical impulse travels down the neuron and body of the nerve to the neuromuscular junction. (Where the nervous system and the muscle meet)

Neuromuscular Junction Axon Neurotransmitter acetylcholine (Ach) Sarcolemma Axon Terminal Synaptic Cleft Receptor ©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material. This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook. 9

How do muscles contract? Acetylcholine is released and receptors on the muscle fibers detect the chemicals presence and muscle contracts. Within a motor unit (bundle of muscle fibers), all fibers contract at the same time or all fibers are relaxed = all or none principle

Neuromuscular Junction Axon Neurotransmitter acetylcholine (Ach) Sarcolemma Axon Terminal Synaptic Cleft Receptor ©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material. This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook. 11

The Motor Unit Dendrites Neuron cell body Axon hillock Motor neuron Myelin sheath Direction of action potential Neurolemma Neuromuscular junction Terminal branches Motor end plate Muscle fibres ©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material. This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook. 12

How our muscle contracts once the message has been recieved Sliding Filament Theory

Muscle Structure A muscle is a collection of many microscopic fibers. Each muscle fiber consists of many small fibrils which are composed of even smaller protein filaments. (actin and myosin) Myosin = thicker Actin = thinner When a muscle contracts/shortens the finer/thinner actin filaments slide toward eachother and pass over the myosin filaments.

Longitudinal section of myofibril (a) At rest Sport Books Publisher

Sliding Filament Theory When a nerve impulse is received at the muscle (neuromuscular junction) it enters the interior of the fiber via a tuble. The impulse causes the release of calcium ions (Ca++). As a result, the myosin cross-bridges form a type of bond with selected sites on the actin filaments.

The Sliding Filament Theory ATP is split and the energy released allows the acting filaments to slide toward each other. Consequently the muscle fiber shortens by about one third of its resting length.

The Sliding Filament Theory ©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material. This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook. 18

The Sliding Filament Theory ©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material. This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook. 19

The Sliding Filament Theory Myosin crossbridges Results in the sliding or overlap of the actin and myosin filaments Causes sarcomere to contract (muscle contraction) ©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material. This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook. 20

Sliding Filament Theory In relaxation phase, the effect of the nerve impulse subsides, calcium ions are removed and the bond between myosin crossbrides and the actin filaments is broken.

Beef Muscle Contraction Video Contraction and Relaxation of muscle Beef Muscle Contraction

Contractile Machinery: Tendons, origin, insertion In order for muscles to contract, they must be attached to the bones to create movement Tendons: strong fibrous tissues at the ends of each muscle that attach muscle to bone Origin: the point of attachment of the muscle to the bone that does not move Insertion: the point of attachment of the muscle on the bone that moves Sport Books Publisher

Muscle Fibre Types Fast twitch fibres: Slow twitch fibres: Slow Oxidative (Type I) Fast twitch fibres: Fast Glycolytic (Type IIa) Fast Oxidative Glyc. (Type IIb) Sport Books Publisher

A. Slow Twitch Fibres Suited for repeated contractions during activities requiring a force output of less than 20 to 25 percent of max force output Examples: lower power activities, endurance events Sport Books Publisher

B) Fast Twitch Fibres Significantly greater force and speed generating capability than slow twitch fibres Well suited for activities involving high power Examples: sprinting, jumping, throwing Sport Books Publisher

Relative involvement of muscle fibre types in sport events. Sport Books Publisher

Muscle Biopsy Fast Twitch (Type II Fibres) Capillary Blood Slow Twitch Vessels Slow Twitch (Type I Fibres) Sport Books Publisher

Muscle Teamwork Agonist (prime mover): Antagonist: Synergist: - Muscle or group of muscles producing a desired effect Antagonist: - Muscle or group of muscles opposing the action Synergist: - Muscles surrounding the joint being moved Fixators: - Muscle or group of muscles that steady joints closer to the body axis so the desired action can occur Sport Books Publisher

Bending or straightening of the elbow requires the coordinated interplay of the biceps and triceps muscles. The triceps relaxes and the biceps contracts The triceps contracts and the biceps relaxes Sport Books Publisher

Agonist and Antagonist Pairs