Muscle Anatomy and Physiology Quiz

Animal Locomotion: Skeleton & Muscles

• Animal skeletons categorized into hydrostatic, exoskeleton, and endoskeleton
• Hydrostatic skeletons are fluid-filled compartments providing support and movement
• Exoskeletons are rigid external coverings that need to be shed (ecdysis) for growth, providing limited protection and support
• Endoskeletons are internal rigid structures, providing support and protection; in vertebrates they are the primary skeletal system
• Bone tissue is a complex organ composed of nerves, blood vessels, and bone tissue
• Compact bone, the outer layer of bone, has few microscopic spaces
• Spongy bone, the inner layer, has open spaces filled with marrow

Bone Tissue

• Two types of marrow: red, which produces red blood cells; yellow, which is adipose tissue with limited life span
• Calcium and phosphate ions are constantly deposited and withdrawn from bones.
• Hormonal controls regulate Ca2+ ions at optimal levels in blood and extracellular fluids. This is known as homeostasis

Types of Muscles

• Vertebrates have three types of muscles: skeletal, cardiac, and smooth
• Skeletal muscles are voluntary, striated, and neurogenic, stimulated by the nervous system; these are responsible for movement of the body
• Cardiac muscle is involuntary, striated, and myogenic, stimulated by the muscle itself
• Smooth muscle is involuntary, unstriated, and myogenic, stimulated by the muscle itself

Skeletal Muscle Structure

• Skeletal muscles are bundles of elongated muscle fibers. Individual muscle fibers are composed of multiple myofibrils
• Muscle fibers contain multiple nuclei
• Myofibrils are composed of many sarcomeres, the repeating functional units of a muscle and within a sarcomere are myosin and actin filaments. Organized protein arrangement creates the striated appearance
• The interaction between actin and myosin proteins results in muscle contraction. The sliding filament theory describes how these interactions create muscle contraction. The motor neuron stimulates the contraction of the muscle
• Muscle contraction is stimulated by motor neurons from the somatic nervous system
• Actin, myosin, and other proteins are involved in muscle contraction

Muscle Physiology

• Muscle shortening generates force & movement, dependent on the location where the muscle is attached to the skeleton (as if on a lever)
• Skeletal muscle actively shortens but passively relaxes
• Muscles generally grouped as antagonistic pairs around joints
• Muscles can be attached proximal (closer) ot the joint or distal from the joint; proximal insertion favors speed while distal favors strength