The Muscle System
Muscles Found in every organ of body Three types Skeletal Cardiac Smooth
Function of Muscles Movement Tension Heat generation
Muscle Anatomy
Anatomy of A Muscle
Single Muscle FiberFascicle Muscle
Muscle Fiber
Elongated Multinuleated Myofibrils running entire length SR surrounds each myofibril Mitochondria embedded throughout
Sarcomere The contractile unit
Anatomy of a MuscleMuscle Fascicle Single Muscle Fiber Muscle Fascicle Muscle Cell
Muscle Movement
Muscle Contraction All muscles work the same way –Contract and relax –All muscles are excitable: Nerves stimulate Muscle contracts
Mechanism of Nerve Stimulation 1. Nerve impulse reaches terminal 2. ACh released 3. ACh diffuses across cleft 4. ACh attaches to receptors 5. Sarcolemma becomes permeable to Na+ 6. Action Potential (charge) travels down cell
1. Calcium released from SR, triggering exposure of binding sites on actin 2. Myosin binds with actin 3. The power stroke: Actin filaments pulled - slide past myosin 4. ATP binds to cross bridge, disconnects from actin 5. ATP re-energizes cross bridge 6. Calcium ions go back to SR Mechanism of Muscle Contraction
Muscle Metabolism
ATP used to: –Energize myosin cross bridge –Disconnect myosin cross bridge from actin –Energize calcium pump
ATP: The Energy Source Adenine P P P Adenine P + Energy
Muscle cells use stored ATP Within seconds, stored ATP is used up The First Seconds of Contraction
20-ish Seconds of Contraction creatine phosphatecreatine ATP
40-ish Seconds of Intense Contraction pyruvic acid glycogen glucose 2 ATP lactic acid Anaerobic metabolism
Long Term Muscle Activity Aerobic metabolism glycogen glucose 36 ATP CO 2 + H 2 0
Muscle Metabolism Stored ATP Creatine Phosphate 1 ATP Anaerobic Metabolism Stored Glycogen 2 ATP Aerobic Metabolism Glucose/glycogen 36 ATP
Contraction Strength and Control
Motor Units A neuron and all the cells it stimulates All cells of motor unit contract together Size of motor unit determines precision
Recruitment Muscle recruitment: more motor units are activiated
Summation Summation: Rate of muscle stimulation is increased
White or Dark Muscle: Slow or Fast Twitch
Fast Twitch: White Muscle Rapid, powerful response Depend on anaerobic pathways Packed with actin and myosin Muscles fatigue rapidly
Slow Twitch: Red Muscle Contract slowly, but with great endurance Depend on aerobic pathways Packed with mitochondria, myoglobin
Strength training –Builds more fast-twitch myofibrils Aerobic training –Builds endurance –Increases blood supply to muscle cell Exercise and Training
Anabolic – induces muscle growth Mimic testosterone Stimulates protein formation in muscle cells May cause: –Increase in muscle strength without increase in tendon strength –Liver/heart disease –Sterility Anabolic Steroids
Androgenic Steroids Androgenic steroids – male/female hormones Andro – testosterone precursor
Side Effects of Steroids
Side Effects of Steroids
Facial Hair in Women
Gynecomastia
Diseases and Disorders
Muscular dystrophy Tetanus Muscle cramps Sprains/Strains Diseases and Disorders of the Muscular System
Muscular Dystrophy
Tetanus
Muscle Cramps
Sprains/Strains
Strength versus Size
Moving Bones
Skeletal Muscle Moves Bones More than 600 skeletal muscles Origin: attachment to stationary bone Insertion: attachment to moving bone origin insertion origin
Antagonistic Pairs Antagonistic muscles oppose each other