BackAnatomy & Physiology: Muscle and Joint Fundamentals
Terms in this set (28)
Muscle tension is the force produced when muscle fibers contract and depends on how many fibers are stimulated.
A motor unit consists of one motor neuron and all the muscle fibers it controls, allowing coordinated muscle contraction.
Recruitment is the gradual increase in muscle tension by activating more motor units, starting with small units and progressing to larger ones.
Muscle tone is the continuous, low-level tension in resting muscles that helps maintain posture and stabilize joints.
Isotonic contractions change muscle length while producing tension; includes concentric (muscle shortens) and eccentric (muscle lengthens) types.
A concentric contraction occurs when muscle tension exceeds the load and the muscle shortens, like lifting a dumbbell.
An eccentric contraction occurs when muscle tension is less than the load and the muscle lengthens while controlling movement, like lowering a dumbbell.
Isometric contractions produce tension without changing muscle length, such as holding a weight steady without movement.
ATP provides the direct energy for muscle contraction and must be continuously regenerated during activity.
Creatine phosphate stores high-energy phosphate groups to quickly regenerate ATP during short, intense muscle activity.
Glycolysis is an anaerobic process breaking down glucose into pyruvate, producing 2 ATP quickly but less efficiently than aerobic metabolism.
Aerobic metabolism uses oxygen in mitochondria to produce ATP efficiently, supporting prolonged, moderate muscle activity.
Hypertrophy is the increase in muscle size due to repeated high-tension stimulation, increasing fiber diameter and contractile proteins.
Atrophy is the decrease in muscle size, tone, and strength caused by disuse or injury.
DOMS is muscle soreness starting hours after exercise, often from eccentric contractions, caused by microtears and inflammation.
Intercalated discs connect cardiac muscle cells with gap junctions for electrical signals and desmosomes for mechanical strength.
Plasticity is smooth muscle's ability to adjust length while maintaining contractile ability, important for organs like the bladder.
Electrical signals trigger the sarcoplasmic reticulum to release calcium, which binds troponin, moving tropomyosin and allowing myosin to bind actin.
The length–tension relationship describes how muscle fibers produce maximum tension at an optimal resting length due to optimal actin-myosin overlap.
Tetanus is a sustained muscle contraction caused by rapid, repeated stimulation, with complete tetanus showing no relaxation between stimuli.
The sliding-filament theory explains muscle contraction as thin actin filaments sliding past thick myosin filaments, shortening sarcomeres.
Synovial joints include plane (gliding), hinge, pivot, condylar, saddle, and ball-and-socket, each allowing specific movement types.
Flexion decreases joint angle; extension increases joint angle, returning a limb toward anatomical position.
Abduction moves a body part away from the midline; adduction moves it toward the midline.
Pronation rotates the forearm so the palm faces backward; supination rotates it so the palm faces forward.
The ACL prevents anterior tibial displacement; the PCL prevents posterior tibial displacement in the knee joint.
Osteoarthritis is degenerative cartilage wear; rheumatoid arthritis is an autoimmune inflammatory joint disease.
Muscle fatigue results from energy depletion, muscle damage, and pH changes interfering with contraction processes.