Anatomy & Physiology Ms. Cohen The Muscular System Anatomy & Physiology Ms. Cohen

Do Now At your table is a picture of a muscle that can be found in the body. Where do you think this muscle is found? Name 5 things your body can do using this muscle.

What are the functions of muscles? Movement, posture, heat production

Where do you find muscle tissue? Skeletal, smooth, cardiac

Muscle Histology Striations Branches

How does a muscle move? Motor Unit muscles must be stimulated by nerve impulses (motor neuron) Point of contact between nerve and muscle is a neuromuscular junction

Muscle Organization Myofilaments The muscle can be broken into long bundles of proteins called muscle fibers. These fibers are made up of fine, threadlike structures called myofilaments which contain two types of proteins: thick - myosin, and thin - actin

Sarcomere - functional contractile unit of a muscle fiber The SARCOMERE is the functional contractile unit of the muscle fiber. This is where all the “action” happens! Striations

How does a muscle contract?

Video of muscle contraction http://www.youtube.com/watch?v=83yNoEJyP6g&feature=results_video&playnext=1&list=PL883809E1FEECC629

What is happening between the muscle proteins? During contraction, the thick and thin myofilaments attach to form cross bridges These bridges act as levers to ratchet filaments past each other Calcium must be present for bridges to form Any idea why rigor mortis sets in when people have died?

sarcomere

http://www.youtube.com/watch?v=WRxsOMenNQM&feature=related

Sarcomere - functional contractile unit of muscle Sarcolemma - cell membrane of skeletal muscle, receives nerve impulses Sarcoplasmic reticulum - smooth ER in muscle cell. Stores calcium ions Myofibrils - muscle fibers Myofilaments - proteins that make up myofibrils Actin - thin protein in muscle that makes contraction Myosin - thick protein in muscle that makes contraction Myoglobin - red pigment which binds to and stores oxygen in muscle cells. Troponin - regulatory protein that turns contraction on Tropomysin - regulatory protein that turns contraction off Calcium - ion binds to troponin-tropomysin molecule, thus changing shape of molecule and turning contraction ON.