muscle (Pt. 2) Flashcards
Q: What is the “marbling effect” in aging muscle?
A: The gradual infiltration of fat into muscle tissue, similar to marbling seen in meat, where fat appears between and within muscle fibers.
Q: What are the causes of the marbling effect in aging muscle?
A: Natural aging process, decreased physical activity, hormonal changes, and reduced muscle protein synthesis.
Q: How does the marbling effect impact muscle quality and function?
A: It reduces muscle quality, decreases muscle strength, impacts muscle function, and increases the risk of mobility issues.
Q: What are some prevention and management strategies for the marbling effect?
A: Regular exercise (especially strength training), proper nutrition, adequate protein intake, and maintaining physical activity levels.
Q: How is the marbling effect related to sarcopenia?
A: It is part of sarcopenia (age-related muscle loss) and can be partially prevented or slowed through lifestyle interventions.
Q: What nutritional factor is important for preventing the marbling effect?
Q: What type of exercise is particularly beneficial for managing the marbling effect?
A: Adequate protein intake.
A: Strength training.
Q: How does muscle mass differ between young and old muscle?
A: Young muscle has higher mass and density for greater strength, while old muscle shows loss of mass (sarcopenia) and decreased strength.
Q: What is the difference in fat content between young and old muscle?
A: Young muscle has lower intramuscular fat levels, while old muscle shows increased fat infiltration (marbling effect).
Q: How does fiber composition differ between young and old muscle?
A: Young muscle has a balanced mix of fast and slow-twitch fibers, while old muscle shows decreased fast-twitch fibers.
Q: What is the difference in regenerative capacity?
(young vs. old muscle)
A: Young muscle has greater ability to recover and regenerate, while old muscle has reduced regenerative capacity due to fewer satellite cells.
Q: How does functional performance compare?
(young VS. Old muscle)
A: Young muscle performs better in strength and endurance activities, while old muscle may struggle with daily activities.
Q: What impacts quick, explosive movements in older muscle?
A: The decrease in fast-twitch fibers.
Q: Why is recovery slower in older muscle?
A: Due to reduced regenerative capacity and fewer satellite cells.
Q: What is sarcopenia?
A: Sarcopenia is the age-related loss of muscle mass and strength.
Q: What role does oxidative stress play in sarcopenia?
A: Oxidative stress damages cellular structures, contributing to muscle deterioration.
Q: How do hormonal changes affect sarcopenia?
A: Alterations in hormones and growth factors impact muscle growth and repair.
Q: What is the effect of satellite cell dysfunction in sarcopenia?
A: Impaired satellite cells reduce muscle repair and regeneration capacity.
Q: How do neural changes contribute to sarcopenia?
A: Loss of motor neurons and changes in neural plaques weaken muscle function.
Q: What is the role of mitochondrial dysfunction in sarcopenia?
A: Reduced energy production in muscle cells affects overall muscle health.
Q: What impact does inactivity have on sarcopenia?
A: Inactivity leads to muscle degradation and accelerates sarcopenia.
Q: How does an imbalance in protein metabolism contribute to sarcopenia?
A: Disruption in protein synthesis and breakdown reduces muscle quality and function.
Q: What is the effect of chronic inflammation on muscle tissue in sarcopenia?
A: Chronic inflammation negatively affects muscle health and accelerates muscle loss.
Q: How does apoptosis influence sarcopenia?
A: Increased cell death leads to loss of muscle fibers over time.
Q: What are microvascular changes in sarcopenia?
A: Reduced blood supply adversely impacts muscle health and regeneration.
Q: What fiber types are present in young, healthy muscles?
A: Type I (Slow Oxidative) and Type IIa (Fast Oxidative-Glycolytic)
Q: What are the main factors that cause muscle fiber transitions?
A: Aging, inactivity, disease, exercise/training, and hormonal changes
Q: What fiber transition occurs with aging and inactivity?
A: Type IIa fibers transition to Type I fibers, with loss of fast-twitch fibers
Q: What is the functional impact of age-related fiber transitions?
A: Decrease in power and strength due to loss of fast-twitch fibers
Q: How does training affect muscle fiber types?
A: Can maintain Type IIa fibers, improve fiber characteristics, and shift fiber properties based on training type
Q: Can training prevent age-related fiber transitions?
A: Yes, training can help maintain Type IIa fibers and their characteristics
Q: How can fiber properties be modified?
A: Through specific types of training and exercise
Q: What are the main changes in fiber types with aging?
A: Decrease in Type IIa (fast-twitch) fibers, increase in Type I (slow-twitch) fibers, and loss of total fiber number
Q: What are the five main performance impacts of age-related fiber changes?
A: 1. Reduced power output 2. Decreased strength 3. Slower movement speed 4. Better endurance capacity 5. Lower explosive force
Q: How does endurance capacity change with aging?
A: It may improve due to increased proportion of Type I (slow-twitch) fibers
Q: Why does explosive force decrease with age?
A: Due to loss of Type IIa (fast-twitch) fibers and reduced total fiber number
Q: What type of training is most important for maintaining Type IIa fibers?
A: Resistance training and high-intensity exercise
Q: What role do motor units play in age-related muscle changes?
A: Their loss contributes to decreased muscle function and fiber type changes
Q: What type of muscle fibers do fast-twitch motor neurons connect to?
A: Fast-twitch (FT) muscle fibers
Q: What are fast-twitch fibers responsible for?
A: Quick, powerful movements
Q: What type of muscle fibers do slow-twitch motor neurons connect to?
A: Slow-twitch (ST) muscle fibers
Q: What are slow-twitch fibers designed for?
A: Endurance and sustained activities
Q: What is the relationship between motor neurons and muscle fiber types?
A: Fast-twitch neurons connect to fast-twitch fibers, and slow-twitch neurons connect to slow-twitch fibers
Q: How do motor neurons determine muscle fiber function?
A: The type of motor neuron (fast or slow) determines whether the muscle fiber will be used for quick movements or endurance activities
Q: What is the main functional difference between fast and slow-twitch fibers?
A: Fast-twitch fibers provide power and speed, while slow-twitch fibers provide endurance
Q: What happens when a fast-twitch motor neuron is lost?
A: Loss of nerve connection to fast-twitch muscle fibers, leading to denervation
Q: What happens to slow-twitch motor neurons during this process?
A: They remain functional and maintain connections with slow-twitch fibers; may reinnervate some former fast-twitch fibers
Q: What are the immediate effects of fast-twitch fiber denervation?
A: Muscle fibers lose nerve supply, leading to reduced strength and power, and increased reliance on slow-twitch fibers
Q: What happens to a denervated muscle fiber?
A: It becomes “orphaned,” begins to atrophy, loses strength and function, and may die if not reinnervated
Q: What are the possible outcomes for denervated fast-twitch fibers?
A: They may die completely, get “adopted” by slow-twitch motor neurons, or change characteristics to match new nerve type
Q: How does reinnervation by slow-twitch neurons affect muscle fibers?
A: Fibers become more slow-twitch in nature, changing their characteristics
Q: What are the functional impacts of fast-twitch denervation?
A: Reduced power output, decreased strength, slower contractions, and changed muscle characteristics
Q: What is the overall effect on muscle performance?
A: Decrease in power and speed capabilities, with greater reliance on slow-twitch characteristics
Q: What is the key difference between initial denervation and complete denervation?
A: Initial denervation shows loss of nerve supply while fibers remain organized; complete denervation shows disorganized and degrading muscle fibers
Q: What happens to muscle fibers immediately after losing nerve supply?
A: They remain present and organized initially, but begin losing function
Q: What happens to muscle fibers over time without nerve input?
A: They become disorganized, begin to degrade, and may eventually die off completely
Q: What can prevent complete muscle fiber death after denervation?
A: Reinnervation by other motor neurons (typically slow-twitch)
Q: How does muscle fiber structure change during denervation?
A: It progresses from organized to disorganized, with eventual deterioration of fiber structure
Q: What is the final outcome if denervated muscle fibers are not reinnervated?
A: Complete degradation and death of the muscle fibers
Q: Why is nerve input essential for muscle fiber survival?
A: Without nerve input, muscle fibers cannot maintain their structure and function, leading to deterioration
Q: What is the progression of denervation effects?
A: Loss of nerve supply → loss of organization → degradation of structure → potential fiber death
Q: What is reinnervation in muscle fibers?
A: The process where slow-twitch motor neurons extend new connections to denervated muscle fibers
Q: What happens to reinnervated fibers over time?
A: They may transition to behave more like slow-twitch fibers
Q: What is the neuromuscular junction (NMJ)?
A: The structure where motor neurons connect and communicate with muscle fibers to enable contraction
Q: How do slow-twitch motor neurons compensate for motor neuron loss?
A: They extend new connections to innervate denervated muscle fibers
Q: What is the functional significance of reinnervation by slow-twitch neurons?
A: It preserves muscle fiber function but changes the fiber characteristics to slow-twitch properties
Q: What structure must be rebuilt during reinnervation?
A: The neuromuscular junction (NMJ)
Q: What is the primary purpose of the NMJ?
A: To enable communication between motor neurons and muscle fibers for muscle contraction
Q: What is the main functional change after fiber type conversion?
A: Increased endurance capacity but reduced power and speed
Q: What does a mix of fiber types indicate about muscle function?
A: It suggests varied functional capabilities, balancing endurance and strength/power
Q: Why is fiber type diversity important in muscle tissue?
A: It allows muscles to perform both endurance and power-based activities effectively
Q: What functional advantage does having mixed fiber types provide?
A: It enables muscles to handle both sustained low-intensity and brief high-intensity activities
Q: What are the possible causes of increased slow-twitch fiber proportion?
A: Aging, inactivity leading to fiber type conversion, or adaptation to endurance-focused activities
Q: What types of activities might cause adaptation?
A: Endurance-focused activities or exercises, or lack of high-intensity activities
Q: What does this fiber type distribution suggest about muscle function?
A: The muscle is better suited for endurance activities than power activities
Q: What are the primary contributors to skeletal muscle atrophy?
A: Inactivity, aging, inflammation, insulin resistance, critical illness, and anabolic resistance
Q: How do inactivity and aging contribute to muscle atrophy?
A: They affect microvasculature, reduce satellite cell function, increase inflammation, and lead to anabolic resistance, reducing muscle regeneration
Q: What is anabolic resistance?
A: A reduced responsiveness of muscle tissue to anabolic stimuli like protein and exercise, making it harder to build and maintain muscle mass
Q: How does insulin resistance contribute to muscle atrophy?
A: It impairs cell glucose/nutrient uptake, reducing muscle building and increasing muscle breakdown
Q: What is the role of myoblasts in muscle health?
A: Myoblasts help repair muscles, but their activity is reduced due to satellite cell decline with aging
Q: Name three lifestyle interventions to prevent age-related muscle loss.
A:
Resistance training
High-protein diet
Load-bearing cardio (e.g., running, walking, and hiking)
Q: Why is building muscle during youth important?
A: It creates a “muscle bank,” maximizing muscle mass to mitigate the impact of natural muscle loss with aging
Q: What role does inflammation play in muscle atrophy?
A: Chronic inflammation increases anabolic resistance, reducing the ability to build and maintain muscle
Q: What critical life changes can decrease physical activity between ages 30-60?
A: Work/job demands, raising children, financial constraints, and retirement
Q: What is the relationship between physical activity and anabolic resistance?
A: Regular activity, especially resistance training, reduces anabolic resistance and promotes muscle health
Q: What is the current government recommended dietary allowance (RDA) for protein?
A: 0.8 grams per kg of body weight per day
Q: Why is the current RDA for protein considered inadequate?
A: Research shows protein intakes less than 1.0g per kg leads to rapid muscle loss and dysfunction; 0.8g/day only maintains nitrogen balance
Q: What is nitrogen balance?
A: The state where protein intake supports tissue growth and repair without having too much or too little nitrogen in your system
Q: Why is 0.8g/kg protein insufficient for muscle health?
A: It’s only the bare minimum to maintain nitrogen balance, not enough to build or maintain optimal muscle mass
Q: What’s problematic about the current protein RDA for older adults?
A: It doesn’t account for increased protein needs during aging to prevent muscle loss
Q: Why do older adults need more protein than the RDA suggests?
A: To prevent rapid muscle loss and maintain proper muscle function during aging
How much protein should you ingest per day?
1.6-2.2 grams/kg
How much protein should you ingest per meal if < 40 years of age?
0.25 grams/kg
How much protein should you ingest per meal if > 40 years of age?
0.40 grams/kg
When is the best time to consume protein for muscle growth and recovery?
Doesn’t matter
