74 Questions
What is the primary mechanism that transports glucose to skeletal muscle?
Movement of GLUT4 to the plasma membrane
At what exercise intensity would plasma fatty acids be the dominant fuel sources?
50%
What is the rate-limiting enzyme in glycolysis?
Phosphofructokinase
During exercise, why does glucose uptake into tissues other than working muscle decrease?
Increased insulin concentration
Which intensity of exercise can be sustained for many hours?
30%
What is the effect of a rise in insulin concentration after a meal?
Decreased glucose uptake by muscle
What happens to insulin concentrations during exercise?
Decrease
What is the main reason behind the failure to recruit motor units during fatigue?
Reduction in 'arousal' in the central nervous system
What is the primary reason for the decrease of intracellular potassium ions during high frequency muscle stimulation to fatigue?
Inability of Na+/K+ pump to pump potassium into the muscle
What is responsible for depolarization and a reduction in action potential amplitude during fatigue?
Failure to pump potassium back into the cell
Which ion is most likely to increase during heavy exercise due to its relationship with generation of lactate and decline in pH?
Hydrogen
What molecule inhibits attached cross-bridges from moving to a strong binding state during fatigue?
Inorganic Phosphate
Which mechanism is NOT responsible for the onset of peripheral fatigue?
Loss of sodium ions from the cell
Why is calcium not lost from the muscle during fatiguing contractions?
'Arousal' levels decrease
What is the enzyme responsible for the subsequent splitting of ATP in the cross-bridge cycle?
Myosin ATPase
What accounts for approximately 70% of the ATP demand during exercise?
Myosin ATPase action
Which process is dependent on ATP and requires the activity of Ca2+ ATPase?
Calcium reuptake into sarcoplasmic reticulum
What is responsible for maintaining the resting membrane potential of muscle fibers by pumping Na+ out and K+ in?
Na+/K+-ATPase
Which process occurs passively through the glucose transporter GLUT4 and is not dependent on ATP?
Glucose transport into muscle cells
During exercise, which enzyme's activity increases to regain the resting membrane potential following contraction?
Na+/K+-ATPase
What enzyme is mostly responsible for resynthesizing ATP during intense exercise lasting less than 10 seconds?
Creatine kinase
What is the main determinant of end-diastolic volume (EDV)?
Venous return
What effect does stretching the ventricles have on ventricular contraction strength?
Increases contraction strength
Which mechanism helps enhance venous return during muscle contraction?
Venoconstriction
Which physiological phenomenon plays a key role in directing blood flow to working skeletal muscles during exercise?
Decreased flow to organs of the digestive system
What happens to skin blood flow during maximal exercise?
Decreases slightly
How does the Frank-Starling Effect relate to ventricular contraction?
It increases ventricular contraction strength
What maintains or increases blood volume to the brain during exercise?
Similar CO but reduced blood flow to the brain
What is the primary role of muscle contraction in enhancing venous return?
Exerting rhythmic pressure on vessels
What is the main limitation to VO2 max according to the text?
Maximal cardiac output
How does elevated capillary density affect O2 extraction?
Reduces blood transit time
What determines an individual's VO2max?
Genetics and aging
Why is it important for body temperature to be kept within a narrow range?
To prevent protein and enzyme dysfunction
How does body temperature affect ATP generation?
High temperatures can lead to ATP generation failure
What impact does a body temperature below 34 have?
Arrhythmias and potential death
How does biological sex typically affect VO2max?
Decreases VO2max in females
What effect does endurance training frequency have on VO2max?
Increase in VO2max depends on duration and intensity
What is the role of T Tubules in muscle fibers?
Rapidly distribute action potentials throughout all sarcomeres
What is the function of the sarcoplasmic reticulum in muscle contraction?
Uptakes calcium from the cytosol
How does the Triad structure contribute to muscle contraction?
Facilitates transmission of action potential to release calcium
Where is calcium stored in the muscle for contraction?
Sarcoplasmic Reticulum
What is the main purpose of Excitation Contraction Coupling in muscle physiology?
To generate force by cross-bridge formation
What is the significance of junctional folds in muscle fibers?
Contain receptors for acetylcholine
Why are Terminal Cisternae important in muscle contraction?
Release calcium into the cytosol to initiate contraction
How do Longitudinal Tubules contribute to muscle function?
Uptake calcium from the cytosol
What is the primary cause of depolarization and a reduction in action potential amplitude during fatigue?
Accumulation of extracellular potassium ions
Which ion is implicated in the mechanism that inhibits attached cross-bridges from transitioning to a strong binding state during fatigue?
Inorganic Phosphate (Pi)
What contributes to the generation of lactate and decline in pH during heavy exercise?
Elevated hydrogen ion concentrations
During fatiguing contractions, what contributes to potassium accumulation outside the cell?
Failure of the Na+/K+ pump to pump potassium into the muscle at a sufficient rate
Which mechanism is related to changes in the central nervous system and reductions in 'arousal' during fatigue?
Failure to recruit motor units
What contributes to the depolarization and reduction in action potential amplitude during high frequency muscle stimulation to fatigue?
Decrease of intracellular potassium ions
What is the main molecule responsible for inhibiting cross-bridges from moving to a strong binding state during fatiguing contractions?
Hydrogen ions
What is most likely to increase during heavy exercise due to its relationship with generation of lactate and decline in pH?
Potassium
What system is heavily relied upon during 30-second exercise bouts?
Phosphagen system
Which stores the most calories in the human body according to the text?
Adipose tissue
What is required for PCr to be replenished following sprint exercise?
Donation of a phosphate from ATP
What is the primary fuel source during an all-out sprint?
Anaerobic glycolysis
How long of a rest period is required to replenish PCr to approximately 80%?
40 seconds
What contributes to delayed fatigue onset in sprint training?
Conversion to type 2a muscle fibers
What is mainly responsible for resynthesizing ATP during high-intensity exercise lasting less than 10 seconds?
Phosphagen system
Where are carbs primarily stored for energy use?
Muscle glycogen
What is the role of carnitine proteins in fatty acid transport into the mitochondria?
Transport fatty acids across mitochondrial membranes
Why does an increase in oxygen demand during exercise lead to an increase in oxygen utilization?
Increase in aerobic metabolism
What is the final form of fatty acids before they can undergo oxidation within the mitochondria?
Fatty acid acyl-CoA
How does the movement of FFA transporters during exercise contribute to FFA oxidation?
Enhances FFA uptake into the mitochondria
What is the primary function of acyl-carnitine in fatty acid metabolism?
Transport fatty acids into mitochondria
In what form do fatty acids enter the mitochondria for oxidation?
Fatty acid acyl-CoA
What is the significance of an increase in plasma FFA uptake during exercise?
Facilitates FFA oxidation in muscles
How do carnitine proteins assist in fatty acid metabolism within the mitochondria?
Transport fatty acids across mitochondrial membranes
What process within the muscle largely contributes to the increase in energy consumption during dynamic exercise?
Cross bridge cycling
During high-intensity sprinting, which energy system is primarily relied upon for ATP resynthesis?
Phosphagen system
What is the primary result of pyruvate in the context of exercise?
Formation of lactate
Which energy system tends to be more utilized during prolonged endurance exercise?
Aerobic energy system
What is the mechanism that primarily helps maintain sodium and potassium balance during exercise?
Ionic cycling
Test your knowledge on the mechanisms of neuromuscular fatigue. Learn about the role of central nervous system changes, intracellular potassium ions, and the Na+/K+ pump during fatiguing contractions.
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