A&p Chapter 10 - Muscular Tissue

Excitability refers to the ability of muscle cells to respond to stimuli and generate electrical signals. This is a fundamental characteristic of muscle cells that allows them to contract and produce movement. When a muscle cell receives a stimulus, such as a nerve impulse, it responds by generating an electrical signal called an action potential. This electrical signal then triggers a series of events that lead to muscle contraction. Therefore, the statement that the ability of muscle cells to respond to stimuli and produce electrical signals is known as excitability is true.

A single somatic motor neuron and all of the muscle fibers it stimulates is known as a motor unit.

The given answer is true because it accurately describes the sequence of events that occur during skeletal muscle contraction. First, a nerve impulse is generated, which triggers the release of the neurotransmitter acetylcholine. This neurotransmitter then stimulates the generation of a muscle action potential. The muscle action potential leads to the release of calcium ions from the sarcoplasmic reticulum. These calcium ions then bind to troponin, which allows for the power stroke to occur. During the power stroke, actin and myosin bind and release, resulting in muscle contraction.

The synaptic end bulbs of somatic motor neurons contain synaptic vesicles filled with the neurotransmitter acetylcholine. Acetylcholine is the primary neurotransmitter involved in transmitting signals from motor neurons to muscle fibers, allowing for muscle contraction and movement. When an action potential reaches the synaptic end bulb, it triggers the release of acetylcholine from the synaptic vesicles into the synaptic cleft, where it binds to receptors on the muscle fiber, initiating a muscle contraction. Therefore, acetylcholine plays a crucial role in the communication between motor neurons and muscles.

The latent period in muscle physiology refers to a brief delay that occurs between the application of a stimulus and the beginning of contraction. This delay is necessary for the excitation-contraction coupling process to occur, where the electrical signal from the stimulus is transmitted to the muscle fibers and triggers the release of calcium ions. These calcium ions then bind to the contractile proteins in the muscle, initiating the contraction. Therefore, the latent period represents the time it takes for this process to happen before the muscle actually starts to contract.

The correct answer is 1,2,3, and 4. Creatine phosphate, glycolysis, anaerobic cellular respiration, and aerobic cellular respiration are all sources of ATP for muscle contraction. Creatine phosphate is used as a quick source of ATP during short bursts of intense activity. Glycolysis breaks down glucose to produce ATP in the absence of oxygen. Anaerobic cellular respiration also produces ATP from glucose, but without the need for oxygen. Aerobic cellular respiration is the most efficient way to produce ATP and requires oxygen. Acetylcholine is a neurotransmitter that is involved in muscle contraction, but it is not a direct source of ATP.

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If ATP were suddenly unavailable after the sarcomere had begun to shorten, the myosin heads would be unable to detach from actin. ATP is required for the detachment of myosin heads from actin during muscle contraction. Without ATP, the myosin heads would remain bound to actin, preventing the relaxation of the muscle and leading to a continuous state of contraction.

During muscle contraction, several events occur. Cross-bridges are formed when the energized myosin head attaches to actin's myosin-binding site. ATP undergoes hydrolysis to provide energy for muscle contraction. Calcium concentration in the cytosol increases, which is necessary for the contraction process. The Z discs are drawn toward each other, causing the muscle to shorten. However, the thick filaments do not slide inward toward the M line during muscle contraction. Instead, the thin filaments slide over the thick filaments, resulting in the muscle contraction.

Sarcomeres are the basic contractile units of muscle fibers. When sarcomeres shorten, it means that the muscle is contracting. During contraction, the thick and thin filaments slide past each other, causing the sarcomeres to shorten. As the sarcomeres shorten, the tension in them increases, leading to muscle contraction and the generation of force. Therefore, the statement "if sarcomeres shorten, the tension in them increases" is true, as it aligns with the basic principles of muscle contraction.

Muscular atrophy refers to the wasting away or decrease in size of muscle tissue due to lack of use or physical activity. This can occur as a result of immobilization, prolonged bed rest, or certain medical conditions. On the other hand, fibrosis is the replacement of skeletal muscle fibers with scar tissue. This can happen as a result of chronic inflammation, injury, or certain diseases. Fibrosis can lead to decreased muscle function and flexibility.