Human Anatomy and Physiology Eleventh Edition Chapter 09 Part B Muscles and Muscle Tissue

Practice flashcards covering muscle tone, types of contractions, energy sources, fatigue, fiber types, and smooth muscle characteristics based on Chapter 09 Part B of the Human Anatomy and Physiology lecture notes.

Muscle Tone

Constant, slightly contracted state of all muscles due to weak, involuntary contractions of its motor units in response to input from stretch receptors.

Motor Unit

Consists of one motor neuron and all the muscle fibers (ranging from four to several hundred) it innervates.

Isotonic contractions

Muscle contractions where the muscle changes in length and moves a load.

Isometric contractions

Contractions where the load is greater than the maximum tension the muscle can generate, resulting in no change in muscle length.

Creatine phosphate (CP)

A molecule used for the direct phosphorylation of ADP to quickly regenerate ATP in muscle fibers.

Muscle Fatigue

The physiological inability to contract despite continued stimulation, potentially caused by ionic imbalances or increased inorganic phosphate ($P_i$).

Excess Postexercise Oxygen Consumption (EPOC)

The extra oxygen needed after exercise to replenish oxygen reserves, glycogen stores, ATP, and creatine phosphate reserves, and to convert lactic acid to pyruvic acid.

Slow oxidative fibers

Muscle fiber types best suited for low-intensity, endurance activities such as maintaining posture.

Fast oxidative fibers

Muscle fiber types best suited for medium-intensity activities like sprinting or walking.

Fast glycolytic fibers

Muscle fiber types designed for short-term, intense, or powerful movements such as hitting a baseball.

Recruitment

The factor of muscle contraction where the number of muscle fibers stimulated is increased; the more motor units recruited, the greater the force.

Hypertrophy

The increase in size of muscle cells, typically occurring with regular exercise.

Disuse atrophy

The degeneration and loss of muscle mass reaching up to $5\%$ loss of strength per day due to immobilization or loss of neural stimulation.

Aerobic (endurance) exercise

Activities like jogging or swimming that lead to increased muscle capillaries, number of mitochondria, and myoglobin synthesis.

Resistance exercise

Typically anaerobic activities like weight lifting that lead to muscle hypertrophy and increased myofilaments and glycogen stores.

Smooth Muscle

Involuntary, spindle-shaped fibers found in the walls of hollow organs (except the heart) that lack striations, sarcomeres, and T tubules.

Dense Bodies

Structures in smooth muscle fibers that, along with intermediate filaments, harness the pull generated by myosin cross bridges.