Skeletal Muscle Structure and Function

Myofibrils are composed of thick and thin filaments and are the basic functional unit of a muscle fiber.

The basic functional unit of a myofibril, and the contractile unit of muscle. It contains myosin and actin.

<p>Tropomyosin twists around actin and attaches to both actin and troponin at regular intervals.</p> Signup and view all the answers

<p>Troponin attaches to both actin and tropomyosin, and contains the binding site for calcium.</p> Signup and view all the answers

<p>An alpha motor neuron is a nerve that connects and innervates with skeletal muscle fibers, causing muscle contraction.</p> Signup and view all the answers

<p>Calcium binds to troponin, causing a conformational change in tropomyosin and exposing the active binding site on actin, allowing myosin heads to bind to actin.</p> Signup and view all the answers

<p>tilting</p> Signup and view all the answers

<p>Glucose.</p> Signup and view all the answers

<p>ATP provides the energy required for the muscle contraction. It is also used to pump calcium back into the sarcoplasmic reticulum after contraction, allowing the muscle to relax.</p> Signup and view all the answers

<p>ATPase is an enzyme located on the myosin head that breaks down ATP to yield ADP and inorganic phosphate, releasing energy that powers the power stroke of the myosin head.</p> Signup and view all the answers

<p>Type I</p> Signup and view all the answers

<p>Type IIb</p> Signup and view all the answers

<p>True</p> Signup and view all the answers

<p>Less force is generated, as there is less overlap between actin and myosin, resulting in fewer cross-bridge interactions.</p> Signup and view all the answers

<p>Fat</p> Signup and view all the answers

<p>Enzymes speed up chemical reactions by lowering the activation energy required for the reaction to occur, but they do not start or control the rate of the reaction.</p> Signup and view all the answers

<p>A rate-limiting enzyme is an enzyme that controls the rate of a metabolic pathway. It is usually found at the beginning of the pathway and is regulated by negative feedback.</p> Signup and view all the answers

<p>The three main energy systems are the ATP-PCr system, glycolysis, and oxidative phosphorylation.</p> Signup and view all the answers

<p>The ATP-PCr system is the fastest energy system and produces 1 ATP molecule. It is the primary source of energy for activities lasting less than 15 seconds.</p> Signup and view all the answers

<p>Glycolysis is the breakdown of glucose to pyruvate. It produces 2 ATP molecules from glucose and 3 ATP molecules from glycogen. It is the primary source of energy for activities lasting 2-3 minutes.</p> Signup and view all the answers

<p>Oxidative phosphorylation is the process of producing ATP by utilizing oxygen. It takes place in the mitochondria and produces 32 ATP molecules from glucose and 33 ATP molecules from glycogen. It is the primary source of energy for sustained aerobic exercise.</p> Signup and view all the answers

<p>The electron transport chain is a series of protein complexes located in the inner mitochondrial membrane. It is responsible for creating a concentration gradient of hydrogen ions, ultimately leading to the production of ATP.</p> Signup and view all the answers

<p>The major players in oxidative phosphorylation are NADH, FADH2, protein complexes, and ATP synthase.</p> Signup and view all the answers

<p>Beta oxidation is a process that breaks down fatty acids into acetyl-CoA, a molecule that can be used in the Krebs cycle to produce energy. It is an important source of energy, particularly during prolonged, low-intensity exercise.</p> Signup and view all the answers

<p>Beta oxidation involves four phases: 1. fatty acid activation, 2. fatty acid transport into the mitochondria, 3. the beta oxidation cycle itself, and 4. the production of acetyl-CoA.</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>The crossover concept describes the shift in primary energy source from fat to carbohydrates during exercise. The crossover point is usually at about 60% of maximal oxygen uptake for fat, and above 75% for carbohydrates.</p> Signup and view all the answers

<p>The two main divisions of the peripheral nervous system are the sensory division and the motor division.</p> Signup and view all the answers

<p>The five steps include: 1) stimulus, 2) sensory neuron activation, 3) CNS processing, 4) motor neuron activation, and 5) muscle contraction.</p> Signup and view all the answers

<p>The endocrine system is primarily responsible for regulating metabolism, maintaining homeostasis, and controlling growth and development.</p> Signup and view all the answers

<p>Steroid hormones are lipid-soluble hormones produced by the adrenal cortex, ovaries, testes, and placenta.</p> Signup and view all the answers

<p>Non-steroid hormones are water-soluble and cannot pass through cell membranes. They bind to receptors on the cell membrane, triggering a series of events that lead to cellular changes.</p> Signup and view all the answers

<p>Downregulation refers to a decrease in the number of hormone receptors on a cell, while upregulation refers to an increase in the number of hormone receptors. These processes are regulated by the body to maintain appropriate hormone levels and cellular responses.</p> Signup and view all the answers

<p>Growth hormone stimulates protein and muscle growth, and it also accelerates fat metabolism, which can help to increase exercise intensity.</p> Signup and view all the answers

<p>The thyroid gland produces the hormones T3 and T4, which play a crucial role in regulating metabolism, influencing protein synthesis, carbohydrate utilization, and overall energy expenditure.</p> Signup and view all the answers

<p>The adrenal medulla produces catecholamines (epinephrine and norepinephrine) and corticosteroids (cortisol). Catecholamines are involved in the 'fight-or-flight' response to stress, increasing heart rate and blood pressure, while cortisol helps regulate blood sugar levels and promotes protein breakdown.</p> Signup and view all the answers

<p>The pancreas produces insulin and glucagon. Insulin lowers blood sugar levels by promoting glucose uptake into cells, while glucagon raises blood sugar levels by stimulating the breakdown of glycogen and the production of glucose by the liver.</p> Signup and view all the answers

<p>The two main methods for measuring energy expenditure are direct calorimetry and indirect calorimetry.</p> Signup and view all the answers

<p>The respiratory exchange ratio (RER) is the ratio of carbon dioxide produced to oxygen consumed. It is used to determine the primary fuel source being utilized during exercise.</p> Signup and view all the answers

<p>Basal metabolic rate (BMR) is the minimum amount of energy required to keep the body functioning at rest. It is typically measured under specific conditions, such as after a 12-hour fast and in a thermoneutral environment.</p> Signup and view all the answers

<p>Resting metabolic rate (RMR) is similar to BMR but is a more practical measure, as it does not require strict fasting or a thermoneutral environment. It is often used to estimate daily energy expenditure.</p> Signup and view all the answers

<p>VO2max is the maximum amount of oxygen that the body can utilize during maximal exercise. It is a crucial indicator of aerobic fitness.</p> Signup and view all the answers

<p>Lactate threshold is the point during exercise where the accumulation of lactate in the blood begins to increase significantly. It is often used as a measure of anaerobic threshold, as it signifies the point at which the body starts to rely more heavily on anaerobic metabolism.</p> Signup and view all the answers

<p>True</p> Signup and view all the answers

<p>Fatigue can be caused by a variety of factors, including inadequate energy delivery, accumulation of metabolic by-products, impaired muscle fiber contractile mechanisms, and alterations in neural control of muscle contraction.</p> Signup and view all the answers