Muscular System Functions Support the body by allowing us to stay upright Allow for movement by attaching to the skeleton Help maintain a constant body temperature Assist in movement in the cardiovascular and lymphatic vessels Protect internal organs and stabilize joints How skeletal muscles arrange Attachments: Tendon connects muscle to bone Origin attachment of a muscle on a stationary bone Insertion attachment of a muscle on a bone that moves Action: Antagonistic muscles that work in opposite pairs Synergistic muscles working in groups for a common action 3 types of muscle tissue Name SMOOTH CARDIAC SKELETAL Location Hollow organs and vessels Walls of the heart Skeletal muscle Action Involuntary Involuntary Voluntary Aspect fibers Spindle-shaped and smooth fibers (Non striated) Striated and branched fibers Striated and tubular fibers 1
Muscles of the human body Remember muscles action is always Antagonistic muscles work in opposite pairs, the always pull, they never push! Synergistic muscles work in groups for a common action How muscle fibers (cells) organize (1) (2) (2) (3) (4) Terminology for structure within a whole muscle Muscle fibers (cells) are arranged in bundles called fascicles (1) Fascicles are composed of myofibrils (2) Myofibrils are bundles of myofilaments (3) that run the length of a fiber Myofilaments are proteins ( and ) that are arranged in repeating units Sarcomeres (4) are the repeating units of and found along a myofibril 2
Muscle contraction (1) Nerve impulses travel down motor neurons to a neuromuscular junction (2) Acetylcholine (ACh) is released from the neurons and binds to receptors in the muscle fibers Motor neuron Muscle fiber Acetylcholine (ACh) Ca++ (calcium) stored in the sarcoplasmic reticulum (3) This binding stimulates fibers causing calcium to be released to the cytoplasm of the fibers (cells) Fiber s membrane (4) (5) Ca++ allows to bind to ATP binds to heads and releases the head from the Ca++ Myosin filament Myosin head calcium ATP (6) The energy from ATP allows and fibers to slide over one another contraction now occurs! Ca++ Muscle relaxation Happens when Ca++ availability decreases A Ca++ pump actively returns Ca++ to the endoplasmic reticulum sacomere CONTRACTION 3
Rigor mortis (stiffening of the body after death) ATP is needed to attach and detach the heads from After death muscle cells continue to produce ATP through fermentation and muscle cells can continue to contract When ATP runs out some heads are still attached and cannot unattach = rigor mortis Body temperature and rigor mortis helps to estimate the time of death Fuels sources for exercise Stored in the muscle: Glycogen Fat Stored in the blood: Glucose Fatty acids calcium ATP If we want to lose weight which one should we burn??? Plasma (blood) fatty acids because adipose tissue is the source for these ATP sources for muscle contraction The amount of ATP stored in the body (about 85g or 3oz) is only about enough to perform maximum exercise for several seconds ATP cannot be supplied by way of blood from other tissues (1) Creatine phosphate (2) Fermentation pathway (CP) Cellular respiration Builds up when a muscle is without O 2 resting, ATP reservoir (Anaerobic) Fastest way to acquire ATP but fast-g but only sustains a cell for seconds; results in lactate builds up when a muscle is build up resting High intensity exercise that lasts less than 5 seconds! Uses carbs Lactate builds up (cramps) (3) Aerobic Cellular Respiration Not an immediate source of ATP but the best long term source Can use carbs and fats mitochondria If we want to lose weight exercise at low intensity and for a long period of time you body will be using mostly ATP produced by (3) 4
Muscle fibers come in two forms Fast-twitch fibers Slow-twitch fibers Designed for strength Explosive power Designed for endurance Steady power 1- CP, fermentation, or aerobic cellular respiration? rely on CP and fermentation (anaerobic) Rely on aerobic respiration Few mitochondria) 2- Number of mitochondria in cells? Many mitochondria Fewer blood vessels than slow-twitch 3- Amount of blood vessels? Many blood vessels 4- Amount of Myoglobin (Oxygen transporting protein)? Few or none myoglobin molecules Many myoglobin molecules Bioethical focus: Anabolic steroids? Anabolic steroids are a group of steroids that usually increase protein production Most common side effects are high blood pressure, jaundice, acne and great increased risk of cancer Abuse of these drugs may also cause impotence and shrinking of the testicles May lead to increased aggressiveness and violent mood swings Are they worth the risk? Should they be legal to use in athletics? 5