Muscle Physiology: Exploring the World of Body Movement

Muscle Physiology: Exploring the World of Body Movement

Muscles are essential components that allow the body to move, maintain posture, and perform numerous other functions. To better understand muscles, we need to classify them based on various criteria.

Muscle Classification:

• By Location and Function:

• Skeletal Muscle: Attached to bones, enabling body movement and actions.

• Smooth Muscle: Found in the walls of internal organs such as the stomach, intestines, bladder, etc., helping regulate the functions of these organs.

• Cardiac Muscle: Located in the heart, working automatically to pump blood throughout the body.

• By Structure:

• Striated Muscle (Skeletal and Cardiac Muscle): Exhibits a striated appearance due to the orderly arrangement of actin and myosin protein filaments.

• Smooth Muscle: Lacks striations, with actin and myosin filaments arranged in a less organized manner.

• By Activation and Regulation Mechanism:

• Voluntary Muscle: Controlled by the central nervous system, muscles can contract and relax at will.

• Involuntary Muscle: Functions automatically, not under conscious control, including cardiac and smooth muscle.

Muscle Functions:

• Response Mechanism: Muscles act as a response mechanism to signals from the nervous system and bodily fluids, generating appropriate reactions.

• Biological Machine: Participate in mechanical work, heat generation, posture maintenance, etc.

• Activity Regulation: Muscles help regulate the functions of internal organs, such as digestion, excretion, circulation, etc.

Characteristics of Striated Muscle Cells:

• Structure: Striated muscle cells contain multiple nuclei, mitochondria, lysosomes, and vacuoles containing lipids.

• Contents: The cytoplasm contains glycogen, glycogen-degrading enzymes, creatine phosphate, amino acids, etc.

• Myoglobin: Myoglobin plays a role in oxygen transport and storage within striated muscle cells.

Motor Unit:

• Concept: A motor neuron along with all the muscle fibers it innervates.

• Characteristics:

• Muscle fibers within a motor unit can be scattered throughout the muscle mass.

• Fast motor unit (white muscle): Muscles contract very quickly, suitable for rapid movements, such as sprinting.

• Slow motor unit (red muscle): Muscles maintain posture, have high oxidative processes, are sensitive to oxygen deficiency, have abundant capillaries, myoglobin, and are less prone to fatigue.

Comparing Motor Units of Force-Generating and Posture-Maintaining Muscles with Muscles Performing Precise Movements:

• Large, Force-Generating and Posture-Maintaining Muscles: Each neuron controls hundreds to thousands of muscle fibers.

• Muscles Performing Precise Movements: Each neuron controls a few muscle fibers, and each muscle fiber receives only one terminal branch.

Understanding the structure, function, and activity of muscles is key to protecting and improving our health, as well as enhancing our body’s movement capabilities.