The document describes the different types of muscles: skeletal, cardiac, and smooth, highlighting their characteristics and functions. It outlines key roles such as movement, posture maintenance, stability, heat production, circulation, respiration, and protection of organs. Additionally, it details the structure of skeletal muscle, including muscle fibers, sarcolemma, myofibrils, sarcomeres, tendons, and nuclei.

1. Muscles and Their Types

2. What Are Muscles?
Skeletal Muscle: Cardiac Muscle
Involuntary, found only in the
heart, striated.
Smooth Muscle
Involuntary, found in organs, non-
striated.
Muscles are soft tissues responsible
for generating force and movement.
Voluntary, attached to bones,
striated appearance.

3. Functions of Muscles:
 1. Movement: Muscles contract to move bones and body parts.
 2. Posture: Help maintain body posture and alignment.
 3. Stability: Stabilize joints and prevent unwanted movement.
 4. Heat Production: Generate heat through contractions, regulating
body temperature.
 5. Circulation: Cardiac muscles pump blood, while smooth muscles
help move blood and fluids in vessels.
 6. Breathing: Muscles like the diaphragm control respiration.
 7. Protection: Provide a layer of protection for internal organs.

4. Skeletal Muscle: Structure
and Function
Attached to bones, voluntary control, makes up 40% of body weight.
Striated due to the arrangement of actin and myosin filaments.
 1. Muscle Fiber (Cell): Long, cylindrical cells that make up the muscle.
 2. Sarcolemma: The membrane surrounding each muscle fiber.
 3. Myofibrils: Thread-like structures inside muscle fibers, made of actin and myosin
filaments.
 4. Sarcomeres: The functional unit of a muscle, where contraction occurs (made up
of actin and myosin).
 5. Tendons: Connect the skeletal muscle to bones, enabling movement.
 6. Nuclei: Each muscle fiber has multiple nuclei for controlling its function.