Anatomy Chapter 8: Muscular System Quiz

Types of Muscular Tissue

• Three types of muscular tissue: skeletal, cardiac, and smooth.
• Skeletal muscle: attached to bones, striated, and under voluntary control.
• Cardiac muscle: found in heart walls, striated, and involuntary.
• Smooth muscle: located in viscera, non-striated, and involuntary.

Functions of Muscular Tissue

• Produces body movements and stabilizes body positions.
• Regulates organ volume and facilitates movement of substances within the body.
• Generates heat as a byproduct of muscle activity.

Connective Tissue in Muscles

• Epimysium: covers the entire muscle.
• Perimysium: encases fascicles, or bundles of muscle fibers.
• Endomysium: surrounds individual muscle fibers.

Muscle Attachments and Energy Supply

• Tendons serve as extensions of connective tissue, attaching muscle to bone.
• Nerves and blood vessels deliver nutrients and oxygen necessary for muscle contraction.

Muscle Fiber Structure

• Each skeletal muscle fiber is encased in a sarcolemma.
• Muscle fibers contain sarcoplasm, multiple nuclei, mitochondria, myoglobin, and sarcoplasmic reticulum.

Sarcomeres and Filament Composition

• Sarcomeres are the functional units of myofibrils, composed of thick (myosin) and thin (actin, tropomyosin, troponin) filaments.

Muscle Contraction Mechanism

• Muscle contraction occurs when myosin heads walk along thin filaments, pulling them toward the center.
• The neuromuscular junction is the synapse between a motor neuron and a muscle fiber.
• A motor unit consists of a motor neuron and the muscle fibers it stimulates.

Mechanisms and Types of Contraction

• The sliding filament mechanism describes how filaments slide past each other to shorten muscle fibers.
• Muscle contraction is controlled by calcium ions; a decrease in Ca2+ stops the contraction cycle.
• Muscle tone results from the continuous involuntary activation of some motor units.

ATP Production Sources

• Muscle fibers generate ATP through creatine phosphate, anaerobic, and aerobic respiration.
• Creatine phosphate and ATP support maximal contraction for about 15 seconds.
• Anaerobic respiration provides ATP for 30-40 seconds of intense activity.
• Sustained activity beyond one minute relies on aerobic respiration.

Muscle Fatigue and Recovery

• Muscle fatigue refers to the inability to contract forcefully after prolonged activity.
• Recovery oxygen uptake involves increased oxygen consumption following exercise.

Muscle Contraction Patterns

• Twitch contraction results from a single action potential.
• Myograms record muscle contractions, showing the latent, contraction, and relaxation periods.
• Wave summation increases contraction strength with successive stimuli.
• Unfused tetanus exhibits partial relaxation, while fused tetanus maintains a strong, sustained contraction.

Skeletal Muscle Fiber Classification

• Skeletal muscle fibers are classified into slow oxidative (SO), fast oxidative-glycolytic (FOG), and fast glycolytic (FG) fibers.
• Recruitment order of fibers: SO, then FOG, then FG fibers.
• Aerobic exercises can transform FG fibers into FOG fibers.
• Strength training enhances FG fiber size and strength.

Muscle Movement Principles

• Skeletal muscles move by pulling on tendons attached to bones.
• Muscles have an origin (stationary attachment) and an insertion (movable attachment).
• Prime movers (agonists) perform the primary action; antagonists provide opposing actions.
• Synergists assist prime movers, and fixators stabilize the origin for efficient action.

Muscle Aging and Development

• Major skeletal muscles are categorized based on region and characteristics.
• Skeletal muscle names often reflect their features.
• Muscle loss occurs around age 30, typically replaced by fibrous connective tissue and fat.
• Aging is associated with decreased strength, slower reflexes, and reduced flexibility.