1. Muscular System

2. Functions: 1.Movement 2.Stabilization 3.Storing and moving substances internally 4.Thermogenesis

3. Properties:  Excitability  Contractility  Extensibility  Elasticity

4. Skeletal Muscle Striated Multiple Nuclei Long fibers Tendons and bones Voluntary movement

5. Cardiac Muscle Striated Intercalated discs Branched fibers Heart Involuntary movement

6. Smooth Muscle Not striated Spindle shaped fibers Walls of hollow organs Involuntary movement

7. Muscle Names  Direction of fascicles (ex. Rectus, transverse, oblique)  Size (ex. Maximus, longus, latissimus)  Shape (ex. Deltoid, trapezius, orbicularis)  Action (ex. Flexor, abductor, pronator)  Number of origins (ex. Biceps, triceps)  Location (ex. Temporalis, frontalis)  Origin and insertion (ex. Sternocleidomastoid)

10. Deep Fascia  Epimysium – superficial  Perimysium – surrounds fascicles  Endomysium – surrounds fibers  Join to form tendons and aponeuroses

14. Motor units  Motor neuron and all the fibers contacted  “All or nothing”  Neuromuscular junction - synapse between neuron and motor end plate  Acetylcholine (ACh)

17. Excitation-contraction coupling  Action potential moves down T- tubules to SR  SR releases calcium through release channels  Ca 2+ binds to troponin - moves complex and opens binding sites  Contraction begins  Ca 2+ pumps and calsequestrin

19. Sliding Filament Mechanism  Ca 2+ binds to troponin  Myosin binding sites open  ATP hydrolysis energizes myosin  Crossbridges form  Power stroke (ADP released)  Detachment (New ATP binds)

21. Muscular control  Precision vs. power - how many fibers are in the motor unit?  Twitch contraction  Refractory period

22. Muscular control  Wave summation due to increased frequency of stimulation  Tautness of elastic components + partial filament contraction  Tetanus (unfused and fused)

24. Muscular control  Motor unit recruitment - more active units  Tone - small numbers of motor units always active (weak, involuntary contractions)

25. Muscle Action Origin/Insertion Muscles work in groups: Agonist Antagonist Synergist

26. Isotonic vs. Isometric  Isotonic -muscle changes length (generates movement)  Isometric - muscle holds position