Muscle Tissue Anatomy & Physiology - Chapter 10B

This set of vocabulary flashcards covers muscle tissue physiology, including the stages of excitation-contraction coupling, crossbridge cycling, metabolic pathways for ATP production, and the classification of muscle fiber types.

End-plate potential (EPP)

A local change in membrane potential at the motor end plate that occurs when ACh binds to chemically gated receptors, allowing $Na^+$ to diffuse into the cell until the potential reaches the threshold of $-65\,mV$.

Depolarization

The phase of an action potential characterized by a rapid rise in membrane charge from $-65\,mV$ to $+30\,mV$ as $Na^+$ diffuses into the cell through voltage-gated channels.

Repolarization

The phase of an action potential where the membrane potential returns to $-90\,mV$ as voltage-gated $Na^+$ channels close and voltage-gated $K^+$ channels open, allowing $K^+$ to diffuse out of the cell.

Refractory period

The brief time during which a muscle cell is depolarizing and repolarizing and is unable to respond to another stimulation.

Triad

A functional unit consisting of a T-tubule and the two adjacent terminal cisternae of the sarcoplasmic reticulum.

Ca2+ release channels

Channels in the terminal cisternae of the sarcoplasmic reticulum that open in response to a shape change in voltage-sensitive calcium channels in the T-tubule membrane.

Troponin

A protein on thin filaments that, when bound by $Ca^{2+}$, undergoes a conformational change that moves tropomyosin to expose myosin binding sites on actin.

Crossbridge formation

The step in contraction where myosin heads in the cocked position bind to exposed binding sites on actin.

Power stroke

A movement where the myosin head swivels toward the center of the sarcomere, pulling the thin filament, while $ADP$ and $P_i$ are released.

Myosin ATPase

An enzyme that splits $ATP$ into $ADP$ and $P_i$ to provide the energy needed to reset the myosin head to the cocked position.

Sliding filament theory

The description of muscle contraction involving the repetitive movement of thin filaments sliding past thick filaments, resulting in the narrowing of the H zone and I band.

Tetanus

A condition characterized by spastic paralysis caused by a toxin from $Clostridium$ $tetani$ that blocks the release of inhibitory neurotransmitters in the spinal cord.

Botulism

Muscular paralysis caused by a toxin from $Clostridium$ $botulinum$ that prevents the release of ACh at synaptic knobs.

Acetylcholinesterase

An enzyme that facilitates muscle relaxation by hydrolyzing ACh in the synaptic cleft, terminating the end plate potential.

Myokinase

An enzyme that helps maintain $ATP$ levels during intense exertion by transferring a phosphate from one $ADP$ to another $ADP$ to produce $ATP$ and $AMP$.

Creatine phosphate

A high-energy molecule that can transfer its phosphate to $ADP$ to form $ATP$ via creatine kinase, providing an additional $10-15\,seconds$ of energy.

Glycolysis

An anaerobic metabolic process in the cytosol that converts glucose to two pyruvate molecules and yields $2\,ATP$ per glucose.

Aerobic cellular respiration

A process occurring in the mitochondria that requires oxygen and produces greater amounts of $ATP$ by oxidizing pyruvate, fatty acids, or amino acids.

Lactic acid cycle

The process where lactate is transported to the liver, converted back to glucose, and then returned to the muscle for energy.

Oxygen debt

The amount of additional oxygen required after exercise to replace oxygen on hemoglobin/myoglobin, replenish glycogen, and convert lactic acid back to glucose.

Slow oxidative (SO) fibers

Type I skeletal muscle fibers that are fatigue-resistant, red in color, and utilize aerobic respiration for slower, less powerful contractions.

Fast glycolytic (FG) fibers

Type IIx skeletal muscle fibers that are large and white, utilizing anaerobic respiration for fast, powerful, but brief contractions.

Fast oxidative (FO) fibers

Type IIa intermediate fibers that are light red and produce fast, powerful contractions primarily through aerobic respiration.