D5.2 - Muscles, Health, and Homeostasis

Study Notes

Muscular Dystrophy: A group of hereditary conditions leading to muscle degeneration, weakness, and replacement with fatty/fibrous tissue. Muscle function decline is accelerated.
Botulism: A potentially fatal condition caused by a toxin from bacteria. It prevents the release of neurotransmitters, causing paralysis.
Cramps: Painful muscle spasms resulting from strenuous exercise, cold, dehydration, electrolyte imbalance, low blood sugar, or reduced blood flow.
Contractures: Abnormal muscle shortening not caused by nerve stimulation. Can result from issues with removing calcium ions from cells or scar tissue formation.
Fibromyalgia: Chronic muscular pain and tenderness often associated with fatigue, sleep issues, and potentially other causes.
Crush Syndrome: A shock-like state following severe muscle trauma, often seen in severe accidents or natural disasters. Associated with high fever and kidney failure.
Delayed Onset Muscle Soreness (DOMS): Pain, stiffness, and tenderness appearing hours or a day after strenuous exercise. Caused by muscle damage, inflammation, and increased levels of enzymes.
Myositis: Muscle inflammation and weakness, often stemming from infection or autoimmune disease.

Muscles can lose function due to lack of use.
Atrophy is the reduction in muscle size, tone, and power due to inactivity and lack of use of the muscle.
Muscle atrophy is reversible if the inactivity isn't severe or long-lasting
If muscle fibers die, loss of muscle tissue is permanent.

Regular exercise strengthens and improves the efficiency of the use of energy.
Hypertrophy is the increase in muscle size.
Regularly used muscles increase in size, primarily due to increased muscle fiber size, and contain more mitochondria, enabling efficient use of energy and more resistance to lactic acid buildup.
- More substantial blood vessels mean better supply to the working parts
White meat and dark meat contain differing levels of blood vessels
Glycogen is stored in muscles after exercise.

Muscle twitches are brief, rapid contractions of a muscle.
Repeated stimulation causes summation, leading to more prolonged contraction and tetanus (maximum sustained contraction).
Muscle fatigue occurs when the muscle no longer responds to stimulation due to depleted energy reserves.
Muscle twitches are divided into three stages:
- Latent period: time between stimulus and contraction start
- Contraction period: time muscle shortens,
- Relaxation period: time muscle returns to its original length

Myograms are graphs showing the force of muscle contraction over time.
Summation shows that successive twitches combine to create larger and longer contractions.
Tetanus represents a sustained maximal muscle contraction.
Muscle fatigue signals the point where the muscle can no longer contract with stimulation.

Slow-twitch (Type I) fibers: Contract slowly, resist fatigue, and have high endurance. Rely on aerobic metabolism. Have large amounts of myoglobin.
Fast-twitch (Type II) fibers: Contract quickly and generate powerful contractions but fatigue quickly. Primarily rely on anaerobic metabolism. Have low levels of myoglobin.

Intermediate fibers are a blend of fast and slow twitch fibers. They resist fatigue moderately and are more resistant to fatigue compared to fast twitch fibers. Endurance training increases the proportion of intermediate fibers.

The muscular system plays a significant role in maintaining homeostasis by generating heat and regulating blood flow.
Muscles contribute to body temperature regulation.
Many bodily processes rely on the movement and action of muscles.