Muscle Growth Flashcards
What is muscle fiber number affected by?
1) Animal-Animal variation
2) Muscle
3) Species
4) Nutrition
5) Age
6) Breed and selection
7) Sex
8) Genetic conditions
True or False: Low muscle weight results in low muscle fiber
True!
True or False: Males have a smaller number of muscle fibers at birth than females.
False! - Males have a smaller number of muscle fibers at birth than do females.
True or False: Increased muscle mass between an elephant and a mouse is due to an increase in muscle fiber numbers.
True!
What does the myostatin gene (MSTN) promote?
What’s another name for this gene?
Promotes protein degradation. Results in more fibers, larger fibers, and less fat.
Myostatin gene is also known as Growth/Differentiation factor 8 (GDF8).
___________ affects developing and adult skeletal muscle.
Myostatin
Myostatin is expressed in _________ of ________.
Myotome, somites
True or False: Myostatin is a positive regulator of muscle growth.
False - Myostatin is a negative regulator of muscle growth.
What is considered normal for when the receptor for myostatin in myogenesis is activated?
When the receptor is activated, there will be an increase in the expression of protein that promotes withdrawal from the cell cycle. As a result, this limits myoblast proliferation, hyperplasia, and muscle growth.
What happens when a mutated myostatin sends an inactive/little signal to the receptor?
The receptor will not activate and the cells will continue to enter the cell cycle. This leads to a continuation of myoblast proliferation, hyperplasia, and muscle growth.
How do muscles grow postnatally?
Muscle fiber hypertrophy! This causes an accumulation of myofibrillar proteins, which increases in length and increases in diameter.
When muscles grow postnatally, which causes the increase in length?
It’s caused by the addition of sarcomeres and stretch-induced hypertrophy.
When muscles grow postnatally, which causes the increase in diameter?
It’s caused by the addition of myofibrils, splitting of myofibrils, addition of myofilaments, and work- or exercise-induced hypertrophy.
What does protein accumulation depend on?
Protein synthesis and degradation
When muscles are growing, are old proteins replaced by new proteins?
Yes
How do we accumulate more protein?
Through diet because we can control the amount of consumption of protein.
Muscle DNA accumulates postnatally through what kind of cells?
Satellite Cells
What are satellite cells?
Cells that fill in and proliferate when there’s damage. They surround the muscle fibers to prevent damage.
How are satellite cells recruited?
Satellite cells (in G0) can be activated, can proliferate and fuse with myofibers and contribute to DNA.
What do satellite cells provide? What does that do?
They provide additional DNA, which increases capacity for protein synthesis and hypertrophy.
What do satellite cells do when there’s muscle damage?
When there’s muscle damage, satellite cells are activated and proliferate, then bridge the damaged area, and then the muscle fiber regenerates and is repaired.
Name the enzyme systems involved in protein degradation.
1) Caspases
2) Lysosomal proteases
3) Calpain protease system
4) Ubiquitin proteasome
What do caspases do?
They control inflammation and cell depth
What do lysosomal proteases do?
They are enzymes breaking down proteins in lysosomes
