Muscle physiology

Muscle Physiology

System	Muscular system

Muscle physiology is the study of the functions and properties of muscles, the tissues in the body responsible for movement. This field encompasses the molecular, cellular, and systemic aspects of how muscles operate, including muscle contraction, energy metabolism, and muscle growth and repair.

Types of Muscle Tissue

Muscle physiology primarily focuses on three types of muscle tissue:

• Skeletal muscle: These muscles are attached to bones and are responsible for voluntary movements. They are striated in appearance due to the regular arrangement of contractile proteins.
• Cardiac muscle: Found only in the heart, cardiac muscles pump blood throughout the body and operate involuntarily. They are also striated but differ in their connectivity and regulation.
• Smooth muscle: These muscles are found in the walls of hollow organs like the intestines and blood vessels. They are not striated and control involuntary movements such as the contraction of blood vessels and the gastrointestinal tract.

Muscle Contraction

Muscle contraction is a fundamental aspect of muscle physiology. It involves the interaction between the proteins actin and myosin, which generate force and movement. The process can be divided into:

• Excitation-Contraction Coupling: The process by which a nerve impulse triggers a muscle fiber to contract.
• Sliding Filament Theory: A model explaining how muscles change length by sliding actin and myosin filaments over each other.

Energy Metabolism

Muscles require energy to contract, which they derive from adenosine triphosphate (ATP). The sources of ATP in muscle cells include:

• Creatine phosphate: Provides a rapid but short-lived source of ATP.
• Glycolysis: The breakdown of glucose to pyruvate, which can generate ATP anaerobically.
• Oxidative phosphorylation: A process in mitochondria that produces ATP from oxygen and nutrients, suitable for prolonged muscle activity.

Muscle Growth and Repair

Muscle growth (hypertrophy) and repair are crucial for maintaining muscle function and occur through processes such as:

• Protein Synthesis: The creation of new muscle proteins to repair or enhance muscle fibers.
• Satellite Cells: Precursor cells that can differentiate and fuse with muscle fibers to facilitate growth and repair.

Pathophysiology

Understanding muscle physiology also involves studying muscle diseases and disorders, such as muscular dystrophy, myopathy, and muscle atrophy. These conditions can significantly impair muscle function and are a major focus of clinical research.

See Also

• Neuromuscular junction
• Motor unit
• Muscle fatigue
• Exercise physiology