Muscle structure and adaptation

Pregunta	Respuesta
How do muscle fibres grow?	By diameter, not number
Which 2 factors increase muscle strength?	1. Fibre diameter 2. Muscle mass
What is MHC?	Myosin Heavy Chain
What are the MHC isoforms whose genes are found in a cluster? (5)	1. MHC 2A 2. MHC 2B 3. MHC X/d 4. Neonatal MHC 5. Embryonic MHC
What is the other MHC isoform and where is it's gene found?	MHC 1 is on chromosome 14q
What are the differences between the MHC isoforms?	Their ATPases work to hydrolyse ATP at different rates
Which are the fastest fibres and why?	MHC 2B are the fastest, because they rely on anaerobic glycolysis to provide fast ATP, and have no myoglobin
Which are the slowest fibres and why?	MHC I are the slowest fibres, as they obtain their energy from the slower, oxygen-requiring processes of the Krebs cycle and oxidative phosphorylation, which give a higher yield of ATP and are more resistant to fatigue. They have lots of myoglobin
How could a stain showing the level of ATPase activity help diagnose a myopathy?	The stain can show the level of ATPase activity in each fibre, so in fibres in which ATPases are not working at all (myopathy), it would be visible
How do muscles grow when exercised?	Through a system of repair and regeneration. When exercising, the muscles undergo injuries, which causes satellite progenitor cells to be activated and they proliferate. They are attracted to the sites of injury, become myoblasts and fuse with the muscle fibre, adding mass to the muscle.
What hormones are involved in muscle and bone growth?	GHRH is released from the hypothalamus which stimulates the release of GH from the pituitary gland, which works on the liver to release IGF-1, which induces muscle and bone growth
During exercise, what autocrine function helps muscle hypertrophy?	Muscle fibres make their own IGF-1 when exercising, which induces their growth
What is a motor unit?	A motor neuron and all the muscle fibres it supplies
What is motor unit recruitment?	How many motor neurons are activated, thus how many fibres are activated and so how strong the contraction is.
What happens to the motor units as the demand for force increases?	Larger motor units are recruited and they recruit larger fibres, so a larger force of contraction can be achieved
Which type of muscle fibres do marathon runners predominantly build up?	MHC I fibres, which have high oxidative capacity and resist fatigue
Which type of muscle fibres do sprinters predominantly build up?	MHC 2A and 2B fibres which give rapid bursts of energy from glycolysis and are easily fatigued
What are the cellular adaptations during endurance training?	Mitochondria replicate and grow larger, increasing the oxidative capacity. Levels of myoglobin also increase, which help produce more energy during long periods of exercise
What happens in ageing muscle? (5)	1. Muscle fibres die 2. Muscles atrophy 3. Muscles get weaker 4. Motor units remodel and nerve connections are lost 5. Muscles contract more slowly

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	Creado por Hannah Tribe hace alrededor de 10 años