The Muscle System. Muscles Found in every organ of body Three types Skeletal Cardiac Smooth.
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The Muscle System
Transcript of The Muscle System. Muscles Found in every organ of body Three types Skeletal Cardiac Smooth.
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
Anatomy of A Muscle
Single Muscle Fiber Fascicle
Muscle
Muscle Fiber
Muscle Fiber• Elongated
• Multinuleated
• Myofibrils running entire length
• SR surrounds each myofibril
•Mitochondria embedded throughout
Sarcomere
• The contractile unit
Anatomy of a Muscle
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
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 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 phosphate creatine
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
CO2 + H20
Muscle MetabolismStored ATP
Creatine Phosphate 1 ATP
Anaerobic MetabolismStored Glycogen 2 ATP
Aerobic MetabolismGlucose/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
•
Facial Hair in Women
•
Gynecomastia
•
Diseases and Disorders
• Muscular dystrophy
• Tetanus
• Muscle cramps
• Sprains/Strains
Diseases and Disorders of the Muscular System
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
insertioninsertion
origin
Antagonistic Pairs
Antagonistic muscles oppose each other
