YMCA L3 Anatomy - Musculoskeletal System

Long-term strength training will lead to hypertrophy of type 2 muscle fibers. Hypertrophy refers to an increase in the size and volume of muscle cells, resulting in stronger and larger muscles. This occurs as a response to the stress and strain placed on the muscles during strength training exercises. Type 2 muscle fibers are primarily responsible for generating power and strength, and they are more likely to undergo hypertrophy compared to type 1 muscle fibers, which are more involved in endurance activities. Therefore, long-term strength training will cause type 2 muscle fibers to grow and become stronger.

When a myosin head attaches to an actin filament, it forms a connection called a cross-bridge. This cross-bridge allows for the sliding of actin filaments past myosin filaments, resulting in muscle contraction. The myosin head binds to the actin filament, undergoes a conformational change, and then releases, allowing for the next cross-bridge to form. This repeated formation and release of cross-bridges is essential for muscle contraction and movement.

The trapezius muscle is a type of skeletal muscle tissue that is voluntary, meaning it is under conscious control. It is located in the upper back and neck region and is responsible for movements such as shrugging the shoulders and rotating the head. Unlike smooth muscle tissue found in the arterial wall, digestive tract, and heart, the trapezius muscle can be consciously contracted and relaxed.

The alternative given to skeletal muscle tissue is striated. This is because skeletal muscle tissue is characterized by the presence of striations, which are alternating light and dark bands that give the muscle a striped appearance. Striated muscle tissue is also under voluntary control, meaning that it can be consciously controlled by the individual. Cardiac muscle tissue, on the other hand, is also striated but is involuntary, meaning that it is not under conscious control. Smooth muscle tissue, while also involuntary, does not have striations.

The digestive tract is an example of smooth, involuntary muscle because it is composed of smooth muscle tissue that is not under conscious control. Smooth muscle is found in the walls of organs and structures such as the digestive tract, blood vessels, and uterus. It functions involuntarily to control movements such as peristalsis in the digestive system and contractions in the uterus. In contrast, the heart is an example of cardiac muscle, which is also involuntary but has a striated appearance. The biceps and latissimus dorsi are examples of skeletal muscle, which is under conscious control.

Actin and Myosin are the two main proteins responsible for muscle contraction. Actin is a thin filament while Myosin is a thick filament. During muscle contraction, Myosin binds to Actin and pulls it, causing the muscle fibers to shorten. This sliding filament mechanism is the basis for muscle contraction. Tendons and ligaments are connective tissues that attach muscles to bones and bones to each other, respectively. Perimysium and Epimysium are connective tissue layers that surround and protect muscle fibers. Calcium and Tropomyosin are also involved in muscle contraction, but they do not directly bring about contraction like Actin and Myosin do.

Type I muscle fibers, also known as slow-twitch fibers, generate ATP slowly. These fibers are rich in mitochondria and have a high oxidative capacity, which allows them to produce ATP through aerobic metabolism. Type I fibers are fatigue-resistant and are well-suited for endurance activities such as long-distance running or cycling. They rely primarily on oxidative phosphorylation to generate ATP, which is a slower process compared to glycolysis used by other muscle fiber types. Therefore, Type I fibers generate ATP slowly.

Type I muscle fibers, also known as slow-twitch fibers, are predominantly used during low intensity activities. These muscle fibers are more resistant to fatigue and are efficient in using oxygen to produce energy. They are responsible for endurance activities such as long-distance running or cycling at a steady pace. Type I fibers have a higher number of mitochondria and myoglobin content, which allows them to sustain prolonged contractions without fatigue. On the other hand, Type II muscle fibers (Type IIa and Type IIb) are predominantly used during high intensity activities that require explosive power and strength.

Type IIb muscle fibers, also known as fast-twitch fibers, are characterized by their thicker size and high firing threshold. These fibers are designed for quick and powerful contractions, making them well-suited for activities that require bursts of strength and speed, such as sprinting or weightlifting. The high firing threshold means that they require a greater amount of stimulation to activate compared to other muscle fiber types. This allows them to generate a large amount of force but also makes them more prone to fatigue.

Smooth muscle fibers form the walls of blood vessels. Unlike skeletal and cardiac muscle fibers, smooth muscles are not striated, meaning they do not have the striped appearance. Smooth muscles are involuntary muscles, meaning they are not under conscious control. They are responsible for controlling the diameter of blood vessels and regulating blood flow throughout the body.

Cardiovascular activities are used to predominantly train type 1 muscle fibers. These activities, such as running, swimming, or cycling, involve continuous and repetitive movements over a prolonged period of time. Type 1 muscle fibers are slow-twitch fibers that are highly resistant to fatigue and are responsible for endurance activities. Therefore, cardiovascular exercises that focus on aerobic endurance are most effective in training and strengthening these type 1 muscle fibers. Muscular strength activities, interval training, and yoga may also have benefits for overall fitness, but they do not predominantly target type 1 muscle fibers.

During every 'crossbridge', only one ATP molecule is used. This is because ATP is hydrolyzed by the myosin head to provide energy for the crossbridge cycle in muscle contraction. The energy released from the hydrolysis of ATP allows the myosin head to detach from the actin filament, reposition itself, and bind to a new actin binding site, generating force and causing muscle contraction. Therefore, only one ATP molecule is required for each crossbridge cycle.

The sarcomere is the basic unit of muscle contraction and is responsible for generating force. It is composed of both actin and myosin filaments, which interact with each other to create muscle contractions. The other options, myofilament, fascicle, and perimysium, do not specifically refer to the structure that contains both actin and myosin. Therefore, the correct answer is sarcomere.

Epimysium is the broad protective sheath that surrounds the entire muscle. It is a dense connective tissue layer that encases the entire muscle, providing support and protection. It helps to maintain the shape of the muscle and allows for smooth movement by reducing friction between the muscle and surrounding tissues. The epimysium also connects the muscle to the surrounding structures, such as tendons and bones, allowing for effective transmission of force during muscle contraction.

Type IIa muscle fibers are used in both aerobic and anaerobic energy production. These muscle fibers have a combination of characteristics of both Type I (slow-twitch) and Type IIb (fast-twitch) fibers. They have a high capacity for aerobic metabolism, allowing them to use oxygen efficiently for energy production. At the same time, they also have a high capacity for anaerobic metabolism, enabling them to generate energy quickly without oxygen. This versatility makes Type IIa fibers suitable for activities that require both endurance and power, such as sprinting or long-distance running.

A motor unit is responsible for coordinating the contractions of a single muscle. It consists of a motor neuron and the muscle fibers it innervates. When the motor neuron receives a signal from the brain, it stimulates the muscle fibers to contract, resulting in movement. The motor unit ensures that the muscle fibers contract in a synchronized manner, allowing for smooth and coordinated muscle movements.

The term used to describe the connective tissue which surrounds each bundle of muscle fibers is perimysium.

The endomysium surrounds each individual muscle fiber. It is a layer of connective tissue that provides support and protection to the muscle fiber. It also contains blood vessels and nerves that supply the muscle fiber with nutrients and signals for contraction. The endomysium helps to maintain the structural integrity of the muscle fiber and allows for efficient muscle function.

The correct order of the skeletal muscle components, from largest to smallest, is muscle, fascicle, muscle fibre, myofibril, sarcomere, myofilament.

During the process of muscle contraction, calcium plays a crucial role by revealing the binding site on the actin. This allows the myosin heads to attach to the actin filaments, forming cross-bridges. As a result, the myosin pulls the actin filaments towards the center of the sarcomere, causing muscle contraction. Without calcium, the binding site on actin would remain blocked, preventing the interaction between actin and myosin and inhibiting muscle contraction.