muscular function Flashcards
What is necessary for muscle contraction?
ATP is necessary for muscle contraction
ATP is primarily needed to move and detach cross bridges and to pump Ca2+ back into the sarcoplasmic reticulum (SR)
How long can muscles store enough ATP for contraction?
Muscles can store enough ATP for 4-6 seconds of contraction
What are the three pathways for ATP regeneration in muscle?
- Direct phosphorylation
- Anaerobic pathway
- Aerobic pathway
What is creatine phosphate’s role in muscle metabolism?
Creatine phosphate provides rapid energy for muscle contraction for up to 15 seconds
What does glycolysis produce from one molecule of glucose?
Glycolysis produces 2 pyruvates and 2 ATP molecules
What happens to pyruvate if there is insufficient oxygen during glycolysis?
Pyruvate is converted to lactic acid
What is required for aerobic cellular respiration?
Aerobic cellular respiration requires oxygen and carbon substrates
What are the products of aerobic cellular respiration?
- CO2
- H2O
- Heat
What is muscle fatigue?
Muscle fatigue is the inability to contract forcefully after prolonged activity
What are some triggering factors for muscle fatigue?
- Less Ca2+ in the sarcoplasm
- More Mg2+
- Less ATP
- Increased Pi
- Decreased glycogen
What needs to occur for a muscle to return to its pre-exercise state?
- Oxygen reserves replenished
- Lactic acid reconverted to pyruvic acid
- Glycogen stores replenished
- ATP and creatine phosphate stores resynthesized
What are the main types of muscle fibers based on speed of shortening?
- Slow oxidative (SO)
- Fast oxidative-glycolytic (FOG)
- Fast glycolytic (FG)
What are the characteristics of slow oxidative fibers?
Slow oxidative fibers are small diameter, red, fatigue resistant, and primarily use oxidative ATP production
What type of exercise increases the size and strength of fast glycolytic fibers?
Strength (resistance) exercise increases size and strength of fast glycolytic fibers
What is an isotonic contraction?
An isotonic contraction occurs when force is constant and the muscle shortens
What is an isometric contraction?
An isometric contraction occurs when length is constant and the force varies
What are the phases of muscle contraction observed in an isometric fiber?
- Latent period
- Contraction period
- Relaxation period
What is graded muscle contraction?
Graded muscle contraction allows for smooth variations in muscle contraction strength
What are the two ways to grade muscle contractions?
- Temporal summation
- Recruitment
What is temporal summation in muscle contraction?
Temporal summation refers to increased contraction strength with higher frequency of action potentials
What is recruitment in muscle contraction?
Recruitment is the process of increasing contraction strength by recruiting more motor units
What is the maximal stimulus?
Maximal stimulus is the point at which all muscle motor units are recruited
What is sarcopenia?
Sarcopenia is the slow progressive loss of skeletal muscle mass after the age of 30
What effect does aging have on muscle fiber composition?
The relative number of slow oxidative fibers tends to increase with aging
What can help slow down muscle changes associated with aging?
Endurance and strength training can help slow down changes due to aging
