Muscle Structure and Function

Muscle Structure and Function

• Muscles enable bodily responses to the environment.
• The nervous system (fast, short-lived) and hormones (slower, widespread) are the two primary response mechanisms.
• Nerves act rapidly (milliseconds) and target specific areas.
• Hormones affect the entire body simultaneously.
• Muscles are generally controlled by nerves, allowing for specific actions.
• Muscles can only contract or shorten.
• Different muscle orientations provide movement in various directions (e.g., abdominal muscles).
• Antagonists (opposing muscles) are necessary for movement in opposite directions.
• The biceps and triceps are an example of an antagonist pair
• Muscles and the skeletal system collaborate for movement; muscles attach to bones via tendons.
• Skeletal muscles are consciously controlled.
• Muscles in organs like the intestines function autonomously.

Tissue and Cellular Structure

• Both bones and tendons have significant intercellular space filled with matrix.
• Bone cells communicate through channels in the hard matrix via gap junctions.
• Tendons consist largely of collagen, arranged in a triple helix structure that provides elasticity.
• The elasticity of tendons, especially the Achilles tendon, aids movement by storing and releasing energy.
• The gastrocnemius muscle (calf) connects to the metatarsal bone via the Achilles tendon.
• The gastrocnemius muscle is important for running.
• Usain Bolt can run at a top speed of 44 km per hour
• Birds also have the muscle gastrocnemius

Muscle Types

• There are three types: smooth, striated, and cardiac, and they differ in structure and control.
• Smooth muscle lines autonomous organs like the intestines with fibers not aligned in one direction.
• Striated muscle is consciously controlled, with fibers in one direction for specific movements.
• Cardiac muscle is involuntary with aligned fibers.
• A Microscopic view of striated muscle shows clear directional alignment.

Nervous System Control

• The cerebrum controls voluntary muscle actions, and the cerebellum coordinates muscle movements.
• Coordinate muscle function with each other
• The brainstem manages involuntary functions such as intestinal movement and heart muscle.
• A nerve impulse travels to a muscle where a nerve cell connects to multiple parts of a muscle fiber.
• One muscle fiber has multiple nuclei

Muscle Fiber Structure

• Muscle fibers contain myofibrils made of actin and myosin protein filaments.
• Muscles contract or expand; they are either contracted or relaxed
• Myosin filaments "walk" along actin using ATP, causing the muscle to contract.
• Muscles are high energy consumers because of the many ATP
• Muscles are full with mitochondrion
• A skeletal muscle consists of bundles of muscle bundles.
• Inside muscle bundles contain cells inside each cell are fillaments
• A sarcomere is a section with actin and myosin that is able to slide over each other

Actin and Myosin

• Actin is a pink part of the muscle
• Myosin is a blue part of the muscle
• Myosin can move by clicking of from the actin using ATP
• A muscle that gets hard use gets damage and results in muscle pain
• Your body compenstates that you can handle the damage next time because it will make more fiber in the muscle

Explore the structure and function of muscles in enabling bodily responses. Learn about the nervous system and hormones as response mechanisms. Understand muscle contraction, orientation, and the role of antagonists like biceps and triceps for movement.