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Neuromuscular Junction (NMJ)
Synapse where motor neurons stimulate skeletal muscles.
Acetylcholine (ACh)
Neurotransmitter at the NMJ for muscle contraction.
End Plate Potential
Local depolarization leading to action potentials.
Action Potential (AP)
Rapid electrical signal triggering muscle contraction.
Sarcoplasmic Reticulum
Organelle releasing Ca++ for muscle contraction.
Acetylcholinesterase (AChE)
Enzyme breaking down ACh to stop signaling.
Motor Unit
One motor neuron and its muscle fibers.
Wave Summation
Increased contraction strength from rapid stimuli.
Fused Tetanus
Sustained contraction without relaxation between stimuli.
Threshold Stimulus
Minimum stimulus for observable muscle response.
Maximal Stimulus
Strongest stimulus increasing contractile force.
Size Principle of Recruitment
Smaller motor units recruited before larger ones.
Isotonic Contraction
Muscle changes length while moving a load.
Eccentric Contraction
Muscle lengthens while generating force.
Concentric Contraction
Muscle shortens while generating force.
Isometric Contraction
Muscle tension increases without changing length.
Muscle Tone
Slight contraction of relaxed muscles for posture.
Motor Nerve
Nerve supplying at least one muscle.
Depolarization
Na+ influx causing membrane potential change.
Repolarization
K+ efflux restoring membrane potential.
Na+/K+ Pump
Maintains ion distribution across muscle cell membrane.
Length-tension relationship
Optimal muscle length for maximum tension generation.
Stored ATP
Immediate energy source for muscle contraction.
Creatine phosphate
High-energy molecule for rapid ATP regeneration.
Aerobic respiration
Produces 32 ATP, requires continuous oxygen.
Anaerobic glycolysis
Fast ATP production without oxygen, yields 2 ATP.
Muscle fatigue
Physiological inability to contract muscle effectively.
EPOC
Oxygen needed post-exercise for recovery processes.
Anaerobic threshold
Point where muscle shifts to anaerobic metabolism.
Aerobic endurance
Duration muscles can sustain aerobic metabolism.
Ion imbalances
Disruptions affecting muscle membrane potential and contraction.
Inorganic phosphate
Byproduct that may hinder calcium release in muscles.
Decreased ATP
Low ATP levels affect muscle contraction efficiency.
Glycogen depletion
Reduced glucose source impacting muscle energy supply.
Creatine kinase
Enzyme facilitating ATP regeneration from creatine phosphate.
Cori cycle
Liver process converting lactic acid to glucose.
ATP & CP system
Energy system for short, high-intensity activities.
Anaerobic pathway
Quick energy source, less ATP than aerobic.
Muscle contraction
Process where muscle fibers shorten to produce force.
Cross bridge cycling
Mechanism of muscle contraction involving myosin and actin.
Calcium pump
Regulates calcium levels for muscle relaxation.
Oxygen debt
Extra oxygen required to restore muscle function.
ATP-driven muscle contraction
20-25% efficient; rest dissipated as heat.
Slow oxidative fibers
Thin, fatigue-resistant fibers using fat for energy.
Fast glycolytic fibers
Pale, powerful fibers with high glycogen reserves.
Fast oxidative fibers
Red, fatigue-resistant fibers using oxygen for energy.
Mitochondria
Organelles producing ATP through aerobic respiration.
Myoglobin
Oxygen-binding protein in muscle fibers.
Aerobic enzymes
Enzymes facilitating energy production in oxygen-rich environments.
Fatigue-resistant
Ability to sustain activity without tiring quickly.
Powerful muscle contraction
High force output during muscle activity.
Smooth muscle
Involuntary muscle found in hollow organs.
Skeletal muscle
Voluntary muscle attached to bones for movement.
Caveolae
Plasma indentations rich in calcium channels.
Calmodulin
Protein binding calcium in smooth muscle contraction.
Gap junctions
Connections allowing electrical coupling between smooth muscle cells.
Unitary smooth muscle
Visceral muscle contracting as a functional unit.
Multiunit smooth muscle
Muscle fibers act independently, like skeletal muscle.
Peristalsis
Wave-like muscle contractions moving contents through organs.
Excitation-contraction coupling
Process linking electrical stimulation to muscle contraction.
Stretch response
Increased stretch leads to stronger muscle contraction.
Intermediate filaments
Noncontractile fibers providing structural support in smooth muscle.
Dense bodies
Structures anchoring thin filaments in smooth muscle.
Sarcoplasmic reticulum
Calcium storage organelle in muscle cells.
Fatigue
Inability to maintain muscle performance over time.
