1. Chapter 6 Muscular System Prefixes that refer to muscle: myo-, mys- = muscle; sarco- = flesh

2. Body movements (see pg 198-199) Flexion – decreases joint angle – brings bones closer Ex. Knee, elbow, bending forward at hip Extension – increases joint angle – moves bones apart Ex. Straightening knee, elbow Hyperextension – greater than 180 degrees Rotation – movement around longitudinal axis Abduction – movement of limb away from midline Adduction – movement of limb toward midline Circumduction – proximal end is still; distal end moves in a circle Dorsiflexion – flexing foot Plantar flexion – pointing foot Inversion – turn sole of foot medially Eversion – turn sole of foot laterally Supination – forearm rotates laterally – palms anterior – radius and ulna are parallel Pronation – forearm rotates medially – palms posterior – radius and ulna cross Opposition – touching thumb to fingertips

3. Muscle types Skeletal Multinucleate Made of skeletal muscle fibers – largest Attach to skeleton Aka striated or voluntary muscle

4. Endomysium – connective tissue around each fiber Perimysium – fibrous membrane around several fibers Forms a bundle called a fascicle Epimysium – tougher connective covering around several fascicles Blends into tendons or aponeuroses

5. Smooth Aka visceral, nonstriated, involuntary muscle Single nucleus Found in hollow visceral organs Layered: circular layer and longitudinal layer Alternately contract and relax Causes movement of material inside organ

6. Cardiac Aka striated, involuntary muscle Branching fibers joined by intercalated discs

7. Muscle functions Producing movement Maintaining posture Stabilizing joints Generating heat – byproduct

8. Skeletal muscle anatomy Sarcolemma – plasma membrane Microfibrils – fill cytoplasm

9. Have light (I) bands and dark (A) bands Made of units called sarcomeres Has 2 types of myofilaments  Thick filaments – made of myosin  Thin filaments – made of actin  Anchored to Z disc  H zone (bare zone) center where thin filaments do not meet

10. Skeletal Muscle Activity Two properties that allow muscles to function Irritability – ability to receive/respond to stimuli Contractility – ability to shorten Motor unit – a neuron and the muscle cells it stimulates Axons (extensions of neuron) branch into axon terminals which form neuromuscular junctions with muscle cells Don’t actually touch at junction – synaptic cleft (gap) filled with interstitial fluid

11. Nerve impulse triggers release of neurotransmitter acetylcholine (Ach) which diffuses across synaptic cleft and attaches to sarcolemma Allows Na ions to move into the cell and K ions to move out More Na enters causing an electrical current – action potential Current moves across muscle cell and causes contraction

13. Sliding filament theory Myosin heads attach to the thin filaments pulling them inward The heads attach and release several times gripping a farther point on the thin filament each time.

14. Energy Production Phosphorylation of ADP by creatine phosphate (CP) CP is found only in muscle cells CP transfers a phosphate to ADP to make ATP Aerobic respiration 95% of ATP production Oxidative phosphorylation in mitochondria Breakdown of glucose, fatty acids, proteins Anaerobic glycolysis/lactic acid fermentation

15. Graded responses Muscle cells follow the “all-or-none” law – if stimulated the entire cell will contract Muscles are thousands of cells and have graded responses – different degrees of shortening Graded reactions are produced in 2 ways Changing frequency of muscle stimulation Muscle twitches – single, brief contractions Unfused (incomplete) tetanus – is a time to relax between impulses Fused (complete) tetanus – rapid impulses with no relaxation between – contractions are sustained Changing the number of muscle cells stimulated Contractions are slight or vigorous depending on what work has to be done

16. Muscle fatigue – muscle is unable to contract even though it is being stimulated Results from oxygen debt Muscle contractions Isotonic contractions – filaments slide, muscle shortens and movement occurs Ex. Bending knee, rotating arms, smiling Isometric contractions – filaments are unable to slide, tension increases Muscle tone – state of continuous partial contractions

17. Exercise Aerobic/endurance – result in stronger, more flexible muscles – more resistant to fatigue Blood supply increases, cells form more mitochondria, store more oxygen Resistance/isometric – causes muscles to increase in size – pits muscles against an (nearly) immovable object

18. 5 golden rules of skeletal muscle activity All muscles cross at least one joint (with a few exceptions) The bulk of the muscle lies proximal to the joint crossed All muscles have at least 2 attachments: the origin and the insertion Origin – attachment to an immovable or less movable bone Insertion – attachment to the movable bone Muscles only pull; never push. During contraction, the muscle insertion moves toward the origin.

19. Interaction of muscles Prime mover – major responsibility for a movement Antagonists – oppose or reverse a movement These 2 may interchange – biceps and triceps moving elbow Synergists – help stabilize prime movers which cross numerous joints You can make a fist without bending wrist Fixators – stabilize the origin of prime movers

20. Naming muscles Direction of muscle fibers Rectus – straight; oblique – slanted Size of muscle Minimus, maximus, longus Location of muscle Named for bone which they are associated with Number of origins Biceps, triceps, quadriceps Location of origin and insertion Sternocleidomastoid – origin is sternum and clavicle; insertion is mastoid process Shape of muscle Deltoid – triangular Action of muscles Flexor, extensor, adductor

21. Fascicle arrangement – determines range of motion and power (see pg 203) Circular – arranged in concentric rings – sphincters Convergent – have a single insertion – triangular/fan- shaped Parallel – straplike Fusiform – spindle-shaped with expanded belly Pennate – short fascicles attach obliquely to a central tendon Unipennate – insert into 1 side of tendon Bipennate – insert into opposite sides of tendon Multipennate – insert into several sides of tendon