Lecture 11 - Skeletal Muscle And Exercise Flashcards
Gains in muscle strength are due to * and * adaptations to *
Muscular; neuronal; exercise
Define hypertrophy
Enlargement of a tissue from the increase in size of its cells
Describe the graph of progress (Y) versus training duration, for strength, hypertrophy and neuronal
Strength will increase as a slope
Neuronal will increase to a point (about halfway down strength’s line) and then plateau
Hypertrophy will take a bit longer to start increasing, but then increases to a point just above neuronal and then plateaus
Define autogenic inhibition
What is the receptor for this intrinsic inhibitory reflex?
Sudden relaxation of muscles/inhibition of contraction upon development of high tendon tension to protect against damage
Golgi tendon organs
What can training do to inhibitory impulses? Why is this?
Lower them
The trained muscle can generate more force
What does coactivation of agonists and antagonists do? What happens if you reduce this?
Normally antagonists oppose agonist force
Reduced coactivation may lead to strength gain
Muscle cells are *
What is the source of new nuclei due to hypertrophy?
Multinucleated
Myogenic stem (satellite) cells that fuse with muscle fibre
Myonuclei numbers * prior to * in ** cross sectional area (*)
Increase; increase; muscle fibre; hypertrophy
After atrophy, what is preserved?
What is this known as?
What else is preserved?
Myonuclei
Muscle memory
Neural adaptations
Describe the diagram of an untrained person’s myonuclei post first training and beyond, including atrophy
1) untrained > first training causes satellite cell fusion leading to a big muscle with many myonuclei
2) detraining causes atrophy of the muscle but the myonuclei number is retained
3) retraining increases muscle size again, with myonuclei number the same
Post exercise, resistance training increases * synthesis, though during exercise, it * synthesis and * degradation
Protein; decreases; increases
Muscle hypertrophy requires ** and * of mTOR (**)
Dietary protein
Activation
Mechanistic target of rapamycin
How is mTOR activated?
1) insulin produces Akt (+ve regulator of mTOR)
2) exercise produces phosphatidic acid (+ve regulator of mTOR) and contributes to amino acids
3) amino acids leucine and glutamine go through the transporter, with leucine being the +ve regulator of mTOR. Amino acids also contribute to Na/K transporter which helps
4) once Akt, phosphatidic acid and leucine +vely regulate mTOR (which is attached to a lysosome) this activates it and mRNA is transcribed which leads to protein synthesis and hypertrophy
What happens in fibre hyperplasia?
What contributes to hypertrophy? (2)
Intense strength training leads to fibre splitting, and an increase in fibre number
1) Fibre hyperplasia
2) Fusing of satellite cells
Describe the process of satellite cell fusion
1) Injury causes myogenic stem cell activation
2) Leads to chemotaxis (movement of stem cell)
3) More stem cells fuse into new fibres
4) Now a regenerated fibre that rests
