Muscle Physiology Quiz

Muscle Contraction

• Muscle contraction is the process by which muscle cells generate force
• It occurs when the muscle fiber shortens, resulting in muscle movement
• Contraction is a result of the sliding of actin and myosin filaments over each other
• There are three types of muscle contractions:
  • Isotonic contraction: muscle shortens while maintaining constant tension
  • Isometric contraction: muscle generates tension without changing length
  • Eccentric contraction: muscle lengthens while maintaining constant tension

Neuromuscular Junction

• The neuromuscular junction (NMJ) is the site where a motor neuron terminates and forms a synapse with a muscle fiber
• The NMJ is responsible for transmitting the signal from the motor neuron to the muscle fiber
• The process of transmission involves:
  • Release of neurotransmitters (acetylcholine) from the motor neuron
  • Binding of neurotransmitters to receptors on the muscle fiber
  • Generation of an action potential in the muscle fiber

Sliding Filament Theory

• The sliding filament theory explains how muscle contraction occurs
• It proposes that muscle contraction is a result of the sliding of actin and myosin filaments over each other
• The theory states that:
  • Actin filaments are thin filaments that make up the muscle fiber
  • Myosin filaments are thick filaments that make up the muscle fiber
  • During contraction, the myosin filaments slide along the actin filaments, resulting in muscle shortening

Excitation-Contraction Coupling

• Excitation-contraction coupling is the process by which an action potential in the muscle fiber leads to muscle contraction
• The process involves:
  • The action potential depolarizing the muscle fiber membrane
  • The release of calcium ions from the sarcoplasmic reticulum
  • The binding of calcium ions to troponin and tropomyosin, allowing the myosin head to bind to actin
  • The contraction of the muscle fiber

Muscle Fatigue

• Muscle fatigue is the decline in muscle force and velocity over time
• It is a result of:
  • Depletion of energy stores (ATP and CP)
  • Accumulation of metabolic byproducts (lactic acid and potassium ions)
  • Changes in the neuromuscular junction and muscle fiber properties
• There are two types of muscle fatigue:
  • Peripheral fatigue: fatigue that occurs in the muscle fiber itself
  • Central fatigue: fatigue that occurs in the central nervous system (CNS)