Problem 23 - Anatomy and Physiology of Animals

Question

Which of the following statements is false? a. Slow fibers have a small network of capillaries. b. Slow fibers contain the pigment myoglobin. C. Slow fibers contain a large number of mitochondria. d. Slow fibers contract for extended periods.

Step-by-Step Solution

Answer

Statement a is false.

Step 1: Identify the characteristics of slow fibers

Slow fibers, also known as slow-twitch muscles, are designed for endurance and prolonged activity. They are rich in capillaries, contain myoglobin, and have many mitochondria.

Step 2: Analyze option a

Option a states that slow fibers have a small network of capillaries. This statement contradicts the known fact that slow fibers have a large network of capillaries to support oxygen supply for endurance activities.

Step 3: Analyze option b

Option b states that slow fibers contain the pigment myoglobin. This is true, as myoglobin allows these fibers to efficiently store and utilize oxygen.

Step 4: Analyze option c

Option c states that slow fibers contain a large number of mitochondria. This is correct, as mitochondria are crucial for energy production in slow-twitch muscle fibers.

Step 5: Analyze option d

Option d states that slow fibers contract for extended periods. This is true, as slow-twitch fibers are designed for sustained, endurance-based actions.

Key Concepts

Slow-Twitch Fibers

Slow-twitch fibers, also known as type I muscle fibers, are specialized for endurance and long-lasting performance. These fibers are crucial in activities like running, cycling, and swimming, where sustained energy is key. Slow-twitch fibers contract slowly but are resistant to fatigue, making them ideal for prolonged exertion.

• They generate less force than fast-twitch fibers but can maintain contractions for longer periods.
• They are heavily involved in aerobic respiration, using oxygen to produce the energy needed for endurance activities.

Understanding the role of slow-twitch fibers helps in training and exercise planning, especially for endurance athletes.

Myoglobin

Myoglobin is a vital protein found within muscle cells, playing a key role in oxygen storage and transport. It gives muscles their red color and is particularly abundant in slow-twitch fibers.

• Myoglobin binds to oxygen molecules, aiding in the supply of oxygen to the mitochondria during muscle activity.
• This process is essential for efficient energy production through aerobic metabolism.

The high myoglobin content in slow-twitch fibers allows these muscles to perform effectively during extended periods of activity by maintaining an adequate oxygen supply.

Capillaries

Capillaries are tiny blood vessels that form an extensive network throughout the muscle tissue, providing a critical supply line for blood, nutrients, and oxygen. In slow-twitch fibers, the capillary network is particularly dense.

• This high capillary density ensures an abundant oxygen supply, supporting aerobic energy metabolism.
• Efficient waste removal, such as carbon dioxide and lactic acid, is also facilitated by the capillary network.

A well-developed capillary system is essential for endurance activities, as it helps maintain muscle function during prolonged periods of exertion.

Mitochondria

Mitochondria are often called the "powerhouses" of the cell because they are responsible for producing energy. In slow-twitch muscles, there is a high density of mitochondria.

• The main role of mitochondria is to convert nutrients into ATP, the primary energy currency used by cells.
• They support aerobic respiration by breaking down glucose and fatty acids in the presence of oxygen to produce energy.

A large number of mitochondria in slow-twitch fibers enables these cells to efficiently produce energy over long durations, which is crucial for sustaining endurance activities.