Muscle Anatomy PDF

The Muscular System ▪Muscles are responsible for all types of body movement ▪Three basic muscle types are found in the body ▪Skeletal muscle ▪Cardiac muscle ▪Smooth muscle Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Characteristics of Muscles ▪M...

The Muscular System ▪Muscles are responsible for all types of body movement ▪Three basic muscle types are found in the body ▪Skeletal muscle ▪Cardiac muscle ▪Smooth muscle Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Characteristics of Muscles ▪Muscle cells are elongated (muscle cell = muscle fiber) ▪Contraction of muscles is due to the movement of microfilaments ▪All muscles share some terminology ▪Prefix myo refers to muscle ▪Prefix mys refers to muscle ▪Prefix sarco refers to flesh Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Characteristics ▪Most are attached by tendons to bones ▪Cells are multinucleated ▪Striated – have visible banding ▪Voluntary – subject to conscious control ▪Cells are surrounded and bundled by connective tissue Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Connective Tissue Wrappings of Skeletal Muscle * ▪Endomysium – around single muscle fiber ▪Perimysium – around a fascicle (bundle) of fibers Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.1 Connective Tissue Wrappings of Skeletal Muscle ▪Epimysium – covers the entire skeletal muscle ▪Fascia – on the outside of the epimysium Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.1 Skeletal Muscle Attachments ▪Epimysium blends into a connective tissue attachment ▪Tendon – cord-like structure ▪Aponeuroses – sheet-like structure ▪Sites of muscle attachment ▪Bones ▪Cartilages ▪Connective tissue coverings Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle Characteristics ▪Has no striations ▪Spindle-shaped cells ▪Single nucleus ▪Involuntary – no conscious control ▪Found mainly in the walls of hollow organs Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.2a Cardiac Muscle Characteristics ▪Has striations ▪Usually has a single nucleus ▪Joined to another muscle cell at an intercalated disc ▪Involuntary ▪Found only in the heart Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.2b Function of Muscles ▪Produce movement ▪Maintain posture ▪Stabilize joints ▪Generate heat Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle * ▪Cells are multinucleated ▪Nuclei are just beneath the sarcolemma Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.3a Microscopic Anatomy of Skeletal Muscle ▪Sarcolemma – specialized plasma membrane ▪Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum that stores Ca for final “go” signal for contraction Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.3a Microscopic Anatomy of Skeletal Muscle ▪Myofibril ▪Bundles of myofilaments (cytoskeleton = actin and myosin) ▪Myofibrils are aligned to give distinct bands ▪ I band = light band = actin filaments ▪ A band = dark band = actin + myosin filaments Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.3b Microscopic Anatomy of Skeletal Muscle * ▪Sarcomere ▪Contractile unit of a muscle fiber Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.3b Microscopic Anatomy of Skeletal Muscle ▪Organization of the sarcomere ▪Thick filaments = myosin filaments ▪ Composed of the protein myosin ▪ Has ATPase enzymes Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.3c Microscopic Anatomy of Skeletal Muscle ▪Organization of the sarcomere ▪Thin filaments = actin filaments ▪ Composed of the protein actin Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.3c Microscopic Anatomy of Skeletal Muscle ▪Myosin filaments have heads (extensions, or cross bridges) ▪Myosin and actin overlap somewhat Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.3d Microscopic Anatomy of Skeletal Muscle ▪At rest, there is a bare zone (AKA: H zone) that lacks actin filaments ▪Sarcoplasmic reticulum (SR) – for storage of calcium Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.3d Properties of Skeletal Muscle Activity ▪Irritability – ability to receive and respond to a stimulus ▪Contractility – ability to shorten when an adequate stimulus is received Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Stimulus to Muscles (on the test) ▪Skeletal muscles must be stimulated by a nerve to contract ▪Motor unit ▪One neuron ▪Muscle cells stimulated by that neuron Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.4a Nerve Stimulus to Muscles ▪Neuromuscular junctions – association site of nerve and muscle Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.5b Nerve Stimulus to Muscles ▪Synaptic cleft – gap between nerve and muscle ▪Nerve and muscle do not make contact ▪Area between nerve and muscle is filled with interstitial fluid Figure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 6.5b Transmission of Nerve Impulse to Muscle ▪ Neurotransmitter – chemical released by nerve upon arrival of nerve impulse ▪ The neurotransmitter for skeletal muscle is acetylcholine* (on test) ▪ Neurotransmitter attaches to receptors on the sarcolemma ▪ http://www.youtube.com/watch?v=7_frccgVAWQ&feature=r elated ▪ http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it =swf::535::535::/sites/dl/free/0072437316/120107/bio_c.swf: :Function of the Neuromuscular Junction ▪ Sarcolemma becomes permeable to sodium (Na+) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of Nerve Impulse to Muscle ▪Sodium rushing into the cell through sarcolemma generates an action potential (electrical current) ▪Once action potential is started, it travels over the entire surface of the sarcolemma. ▪ muscle contraction cannot be stopped http://www.youtube.com/watch?v=SCasruJT-D U Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings