Lecture B

Muscle fiber contraction

Muscle fiber contraction

The process of skeletal muscle fibers shortening.

All or none

The principle that muscle fiber contraction occurs fully or not at all.

Graded responses

Different degrees of skeletal muscle shortening produced by changing the frequency of muscle stimulation or the number of muscle cells being stimulated at one time.

Twitch

A single, brief contraction of a muscle fiber.

Tetanus

A series of contractions where one contraction is immediately followed by another, resulting in a sustained muscle contraction.

Unfused tetanus

Contractions with some relaxation occurring between them, resulting in summed effects.

Fused tetanus

Contractions with no evidence of relaxation before the following contractions, resulting in a sustained muscle contraction.

Muscle force

The strength of muscle contraction, which depends on the number of fibers stimulated.

Energy for muscle contraction

Initially, muscles use stored ATP for energy, but other pathways must be utilized to produce ATP after ATP stores are depleted.

Direct phosphorylation

The process of reattaching a phosphate to ADP by creatine phosphate to regenerate ATP.

Aerobic respiration

The breakdown of glucose into carbon dioxide and water, releasing energy (ATP) in the presence of oxygen.

Anaerobic glycolysis

The breakdown of glucose without oxygen, producing ATP and lactic acid.

Muscle fatigue

Inability of a muscle to contract even with a stimulus, often caused by oxygen debt and accumulation of lactic acid.

Isotonic contractions

Contractions where myofilaments can slide past each other, resulting in muscle shortening and movement.

Isometric contractions

Contractions where tension in the muscles increases, but the muscle is unable to shorten or produce movement.

Muscle tone

The state of some fibers being contracted even in a relaxed muscle, providing stability and readiness for movement.

Effect of exercise on muscles

Exercise increases muscle size, strength, and endurance, with aerobic exercise improving flexibility and resistance to fatigue, and resistance exercise increasing muscle size and strength.

Phosphorylation

The process of reattaching a phosphate to ADP to recreate ATP.