MUSCLE

Skeletal Muscle Muscle attaches to bones by tendons at both ends –The less movable end (anchor) is called the origin –The end where bones moves is called the insertion

Skeletal Muscle (cont.) –Contraction pulls the insertion towards the origin –The middle is called the BELLY.

Skeletal Muscle (cont.) Limb Muscles which cause angles to decrease are called Flexors Muscles that cause an angle in increase are called extensors. Abductors – lift limb away from center Adductors – pull limb towards body.

Skeletal Muscle (cont.) Each Muscle is surrounded by a connective sheath called EPIMYSIUM. This sheath is continuous with tendons. With in the muscle, bundles of fibers are bound together by sheaths called PERIMYSIUM.

Skeletal muscle (cont.)

Muscle -> Epimysium Fasicle ->Perimysium, endomysium Muscle Fiber -> Sarcolema Myofibril -> striations, sarcomere, actin, myosin.

Sarcomere

Sarcomere Cell membrane of muscle fiber called Sarcolemma. –Muscle fibers contain long parallel Myofibrils. –Myofibrils made up of repeating subunits calls Sarcomeres. –These repeating bundles are seen as striations.

Sarcomere (cont.) A sarcomere is a cylinder made up of actin(thin) and myosin(thick) Filaments. –These protein fibers cause the contraction –Myosin filaments have protrusions called crossbridges.

Zones Multiple zones are identified within the sarcomere. –“H zone” mysoin filaments not overlapped by actin. –“A band” entire are occupied by myosin

Zones –“I band” on either end of “A” where actin is, but not myosin connected to adjacent sarcomere. –“Z line” marks the end of sarcomere. Actin attached to. –“M line” middle of Sarcomere. This is what gives striations.

Sliding filament model

Sliding Filament Model ATP bonds to cross- bridges setting them in a cocked position. Nerve signal allows Ca + to flood into sarcoplasm Ca + ions attach to binding sites on actin. ATP energizes crossbridge moving the filaments. ATP is broken down and released as cross bridge releases

Sliding filament model

Muscle Contraction Must have Ca+ ions –Used to bond with actin site causing activation –Allows crossbridges to bond –Source is Diet/bone storage –Lack causes muscle cramps or Charlie Horses.

Muscle Contraction(cont) Must have ATP molecules –Used to energize and flex mysin crossbridges. –Source is Cellular respiration in mitochondria –Lack of ATP and muscles cannot contract.

ATP for Muscles Remember? C 6 H 12 O 6 + 6O 2 -> 6CO 2 + 6H 2 O + ATP ADP + P + “e” -> ATP(38)

ATP –Glucose and O 2 necessary for respiration to take place. –Cells that are activated excessively and cannot supply O 2 fast enough go into O 2 debt. –Cells will react and contract, but use Anaerobic Respiration. C 6 H 12 O 6 -> 2C 3 H 6 O 3 + 2ATP

ATP (anaerobic) –Results in “Oxygen Debt” or lactic acid formation –Causes Muscle Fatigue –More lactic acid = more pain = more fatigue –Recovery allows more O2, which breaks down lactic acid, decreasing pain and increasing ATP synthesis. –Body changes hrt and Resp rates to bring in more glucose and O 2