Chapter 6A (The Muscular System)

Muscular System

System responsible for all types of body movement.

Skeletal Muscle

Muscle type attached to bones, voluntary and striated.

Cardiac Muscle

Involuntary muscle found only in the heart.

Smooth Muscle

Involuntary muscle found in the walls of hollow organs.

Skeletal Muscle Fiber

Elongated muscle cell; also known as muscle fiber.

Myofilaments

Thin (actin) and thick (myosin) filaments responsible for muscle contraction.

Myo-

Prefix referring to 'muscle'.

Sarco-

Prefix referring to 'flesh'.

Epimysium

Connective tissue that covers the entire skeletal muscle.

Perimysium

Connective tissue that wraps around a fascicle (bundle) of muscle fibers.

Endomysium

Connective tissue that encloses a single muscle fiber.

Fascia

Connective tissue structure that surrounds muscles.

Tendons

Cordlike structures that attach muscles to bones.

Aponeuroses

Sheet-like structures that attach muscles indirectly to bones or connective tissues.

Irritability

Ability of muscle cells to receive and respond to a stimulus.

Contractility

Ability of muscle cells to shorten forcibly when stimulated.

Extensibility

Ability of muscle cells to be stretched.

Elasticity

Ability of muscle cells to recoil and resume resting length after stretching.

Neuromuscular Junction

Association site of the motor neuron and muscle fiber.

Acetylcholine (ACh)

Neurotransmitter that stimulates skeletal muscle.

Action Potential

Electrical signal that triggers muscle contraction.

Sarcoplasmic Reticulum (SR)

Specialized endoplasmic reticulum that stores and releases calcium in muscle cells.

Sarcolemma

Specialized plasma membrane of muscle fibers.

Myofibrils

Long organelles inside muscle cells that contain the myofilaments.

Sarcomeres

The basic contractile unit of muscle fibers.

Myosin Heads

Projections on myosin filaments that link thick and thin filaments during contraction.

Sliding Filament Theory

Theory explaining muscle contraction through the sliding of actin and myosin filaments.

Graded Responses

Different degrees of muscle contraction based on strength and frequency of stimulation.

Muscle Fiber Contraction

'All-or-none' response where muscle fibers contract fully when adequately stimulated.

Muscle Twitch

A single, brief contraction of a muscle fiber.

Unfused Tetanus

Increased frequency of stimulation leading to stronger muscle contractions without complete relaxation.

Fused Tetanus

Rapid stimulation with no relaxation observed, resulting in smooth and sustained contractions.

Muscle Fatigue

Condition occurring due to strenuous and prolonged muscle activity.

Oxygen Deficit

Reduced oxygen availability that contributes to muscle fatigue.

Energy Supply (ATP)

Adenosine triphosphate, the energy currency required for muscle contractions.

Aerobic Exercise

Endurance exercise like jogging that increases muscle strength and flexibility.

Resistance Exercise

Weight lifting that increases muscle size and strength.

Myosin Filaments

Thick filaments composed of the protein myosin.

Actin Filaments

Thin filaments composed of the protein actin.

Z Disc

Midline interruption in the I band of a sarcomere.

A Band

Dark band of the sarcomere containing thick filaments.

I Band

Light band of the sarcomere containing thin filaments.

H Zone

Lighter central area within the A band.

M Line

Center line of the H zone within a sarcomere.

Calcium Ions (Ca2+)

Play a crucial role in muscle contraction by triggering the release of neurotransmitters.

Repolarization

Process of returning to the resting membrane potential after depolarization.

Sodium-Potassium Pump

Protein that helps maintain the concentration gradients of sodium and potassium ions.

Intercalated Discs

Specialized connections between cardiac muscle cells allowing synchronized contraction.

Muscle Spindle

A proprioceptor located within the belly of muscles that detects changes in muscle length.

Pacemaker

Cells in the heart that maintain the rhythm of heart contractions.

Lactic Acid

A byproduct of anaerobic respiration that contributes to muscle fatigue.

Metabolism

Chemical processes in the body that maintain life, including energy production.

Contraction Cycle

The series of events that occur during muscle contraction involving myosin and actin.

Muscle Fiber Types

Different types of muscle fibers that vary in strength, speed, and endurance.

Muscle Tone

The continuous and passive partial contraction of the muscles.

Eccentric Contraction

Lengthening of the muscle under tension.

Concentric Contraction

Shortening of the muscle under tension.