Muscle Structure and Function

1. Muscle Structure and Function

2. Skeletal muscle Cardiac muscle Smooth muscle Types of Muscle • The human body is comprised of over 600 muscles • Muscle makes up 30-35% (in women) and 42-47% (in men) of body mass. Three types of muscle:

3. Key Terms Tendons - tough bands of connective tissue thatjoin muscle to bone • Aponeurosis – asheet-like membrane that serves as a fascia to bind muscles together or to connect muscle to bone • ex. Palmaraponeurosis • Fascia – connective tissue that covers, supports, and separates muscles • ex. Fascia lata (thigh), brachial fascia (upper arm) Tissue- masses of cells that have similarfunction and form Muscle tissue - collection of cells that shorten duringcontraction, therefore creating tension that results inmovement

4. A. Skeletal (Striated) Muscle Muscles that are attached to the bones via connective tissue tendons • During muscle contraction, skeletal muscle shortens and moves various parts of the skeleton • We have voluntary control of our muscles, meaning they are activated through signals carried to the them via nerves • Referred to as striated, because their appearance is a series of alternating light and dark stripes (myofilaments) • Repetitive contraction leads to fatigue

5. B. Smooth Muscle Muscles surrounding your body’s internal organs, as well as your blood vessels, respiratory tract, iris (eye) & gastro-intestinal tract • The contractions are slow and uniform and can remain for long periods of time • Activation is involuntary • Fatigue resistant • Fibres are arranged in dense sheets, therefore appearing smooth

6. C. Cardiac Muscle Muscles found only in the heart. • Functions to provide the contractile activity of the heart (pumping blood to the rest of the body) • Is very fatigue resistant • Activation of cardiac muscle is involuntary • Striated

7. Components of skeletal muscle a) Muscle b) Fascicle c) Muscle fiber d) Myofibril

8. Muscle Structure • Beginning at the muscle (superficial to deep): • Epimysium: connective tissue surrounding the whole muscle (many fascicles) • Perimysium: connective tissue surrounding each fascicle • Fascicle: perimysium wrapped muscle fibres • Endomysium: connective tissue surrounding each muscle fibre • Muscle fiber: muscle cell • Sarcolemma: a plasma membrane beneath the endomysium that contains the cells • sarcoplasm • Sarcoplasm: similar to cytoplasm of other cells, containing large amounts of glucose & • myoglobin (protein that stores oxygen)

9. Muscle Structure Cont’d • Myofibrils: rodlike contractile elements, that occupy most of the muscle cell • and are composed of sarcomeres arranged end to end • Sarcomeres: a contractile unit composed of myofilaments (actin & myosin) • Myofilaments: • Myosin (thick): made up of a “head” (attachment site for actin) & “tail” • Actin (thin): • tropomyosin: arranged along the actin filament, and when relaxed • prevent myosin head from binding to actin • troponin: binding site for calcium

10. Properties of a Muscle Fibre • Irritability - ability of muscle to respond to stimulus • Conductivity - ability to transmit nerve impulses • Contractibility - ability to shorten in length • Extensibility - ability to extend in length • Elasticity - ability to stretch and return to normal position

11. Muscle Teamwork Agonist (prime mover): • the muscle or group of muscles producing a desired effect Antagonist: • the muscle or group of muscles opposing the action • lengthens when the agonist muscle contracts

12. Contractile Machinery: Origin & Insertion In order for muscles to contract, they must be attached to the bones to create movement. Origin: the end of the muscle attached to the bone that does not move (proximal attachment) Insertion: the point of attachment of the muscle on the bone that moves (distal attachment)