Skeletal Muscle and Movement PDF

Skeletal Muscle and Movement Learning objectives At the end of this lecture, you should be able to: Introduce and describe the basic types of muscle tissues and their properties Describe the macroscopic arrangement of muscles and how this...

Skeletal Muscle and Movement Learning objectives At the end of this lecture, you should be able to: Introduce and describe the basic types of muscle tissues and their properties Describe the macroscopic arrangement of muscles and how this relates to movements Describe the microscopic function of muscle tissues and how this relates to their function Apply the lever system to predict and interpret movements Examine the histology and function of bone Resources: Try A&P textbooks – e.g. Ross & Wilson ‘Anatomy and Physiology in Health and Illness’ Chapter 16 for bone and muscle Skeletal Muscle and Movement 1  Three types of muscle tissue: Smooth Involuntary No striations Irregular fibres Mono-nucleated Responds to: nerve impulses, hormones, local stimuli Cardiac Involuntary Striated Regular fibres 1-2 nuclei Responds to: nerve impulses, hormones, local stimuli Skeletal Skeletal Muscle and Movement 2  Voluntary Striated Regular Fibres Multinucleated Responds to: nerve impulses only Skeletal muscle: Functions Generates movement Maintains posture Provides protection Heat production Promotes blood flow Properties Excitability – responds to nerve stimulus Conductivity – stimulus spreads throughout whole muscle Contractability – muscle cells can forcefully shorten Elasticity – ability to return to original length (recoil) Extensibility – capable of stretching Muscular connections Muscles usually connect bone to bone Crossing joints = movement Some exceptions – e.g. muscles of facial expression Attach via tendons Regular dense fibrous connective tissue Tough, inelastic Skeletal Muscle and Movement 3  Origin - Attachment to the stationary (or less mobile) bone Insertion - Attachment the movable (or more mobile) bone Skeletal Muscle and Movement 4  Building a muscle Each muscle tissue layer is surrounded by connective tissues (epimysium) Muscle Fascicle: Small packets of muscle cells Surrounded by perimysium Muscle Fibre: Muscle cells: myocytes (multinucleated) Surrounded by endomysium Sarcomeres are the smallest functional unit in muscle fibres Skeletal Muscle and Movement 5  Tendons connect muscle to bone Tough, inelastic Ligaments connect bone to bone Flexible, highly elastic The Skeleton Provides framework for body ~ 206 bones (in the adult) Multiple functions: Support / movement Protection Metabolism Skeletal Muscle and Movement 6  Anatomy of a Bone Bone is not ‘static’ / inert Metabolically active, under constant renovation Skeletal Muscle and Movement 7  Mixture of organic and inorganic components Mineral: hydroxyapatite (calcium phosphate) Organic: collagen (mainly Type I) Bone Tissue Two types of bone: Compact / Spongy Cortical / Compact Rigid, tightly-packed Formed of cylindrical structures - osteons Trabecular / Spongy / Cancellous Loosely-arranged struts Skeletal Muscle and Movement 8  Bone Development Two types of Bone development Intramembranous Forms directly in soft tissue (mesenchyme) Endochondral Cartilage template forms first Skeletal Muscle and Movement 9  Endochondral Ossification Bones form in stages Primary ossification centre (in-utero) Secondary ossification centres (post-natal) Growth plates separate these areas: Cartilaginous region Skeletal Muscle and Movement 10  Creating and Co-ordinating movement Muscle Shape and Structure Form affects function Mass = magnitude Arrangement of fasciles = direction of action Length of fibres = range of motion Arrangement of fascicles Skeletal Muscle and Movement 11  Lever Systems Muscles, bones and joints = levers Allow movement in set plane Skeletal Muscle and Movement 12  Lever = bone Fulcrum / axis = joint Applied force = muscle attachment site Skeletal Muscle and Movement 13 Skeletal Muscle and Movement 14