Muscular System X

The Muscular System Main function of a muscle: Contraction (shortening) Because muscles can contract: The main functions of the muscular system are: Movement Maintains Posture Stabilizes Joints Generates Heat Controls Openings (sphincters) Expressions Protection (reflexes)

Characteristics of Muscles Skeletal and smooth muscle cells are elongated ***(a muscle cell is also referred to as a muscle fiber) Some skeletal muscle cells can be up to a foot long in length All muscles share some terminology If you see myo- mys- or sarc- you think MUSCLE! Prefixes myo and mys refer to “muscle” Prefix sarco refers to “flesh”

Three basic muscle types are found in the body Skeletal muscle Cardiac muscle Smooth muscle

Skeletal (Striated) Muscle Under voluntary control. Thin cells that extend the entire length of muscle; multinucleated. Location: Attached to bones through entire body Function: Body movement, heat production

Cardiac Muscle Striated; involuntary control Single cells with intercalated disks – cell to cell attachment points for communication. Location: Heart Function: Blood movement via heart contraction

Smooth Muscle Unstriated, under involuntary control. Cells are longer but tapered at the ends; single nucleated, nucleus located in the middle of cell Location: Walls of organs, blood vessels, eyes, glands, and skin Function: Move products internally

Comparison of Skeletal, Cardiac, and Smooth Muscles Table 6.1 (1 of 2)

Comparison of Skeletal, Cardiac, and Smooth Muscles Table 6.1 (2 of 2)

Terminology Review Endo- Inside, Within (endoskeleton) Peri- Around, surround (perimeter) Epi- On, over, above (epidermis)

Our Focus: SKELETAL MUSCLE (Striated)

Skeletal Muscle Characteristics Attached to the skeleton Attached by tendons to bones (or aponeuroses) Cells are multinucleate (many nuclei) Striated (have visible banding) Strong force Tire easily (muscle fatigue) Voluntary—you control them (exception = reflexes)

Connective Tissue Wrappings of Skeletal Muscle Cells are surrounded and bundled by connective tissue Endomysium—encloses a single muscle fiber Perimysium—wraps around a group of muscle fibers forming a fascicle (bundle of muscle fibers) Epimysium—covers the entire skeletal muscle (many fascicles)

Connective Tissue Wrappings of Skeletal Muscle Figure 6.1

Skeletal Muscle Attachments Epimysium blends into a connective tissue attachment at the ends of muscles 2 Types Aponeuroses—sheet-like structures of connective tissue (sometimes referred to as fascia) Attach muscles to bones, cartilages, or connective tissue coverings

Skeletal Muscle Attachments Tendons—cord-like structures Mostly collagen fibers Often cross a joint due to toughness and small size