Sarcomere Patterns and Contraction

This section explains the organization and changes in sarcomere structure during muscle contraction.

Definition: The repeating pattern of light and dark bands in a sarcomere creates the striated appearance of skeletal muscle.

Highlight: During contraction, the sarcomere length changes while maintaining its basic structural organization.

Types of Muscles

The human body contains three main types of muscles, each with unique characteristics and functions:

Skeletal Muscle Skeletal muscles are the most abundant type of muscle tissue in the body. They are responsible for voluntary movements and make up the bulk of our visible muscles.

Highlight: Skeletal muscles are striated, under conscious control, and contract rapidly.

Cardiac Muscle Cardiac muscle is found exclusively in the heart. It has a specialized structure that allows for coordinated contraction.

Vocabulary: Myogenic - Cardiac muscle cells can contract without nervous stimulation, allowing for regular heartbeats.

Smooth Muscle Smooth muscle, also known as involuntary muscle, is found in various organs throughout the body.

Example: Smooth muscle is present in the walls of the stomach, bladder, and blood vessels. It aids in processes like peristalsis in the digestive tract.

The structure of skeletal muscle is complex and highly organized:

• Muscle fibers are enclosed in a membrane called the sarcolemma
• Each fiber contains multiple nuclei and is filled with sarcoplasm
• Myofibrils are long, cylindrical structures within the muscle fibers
• Sarcoplasmic reticulum stores calcium ions necessary for muscle contraction

Definition: Sarcolemma - The plasma membrane that surrounds a muscle fiber.