Post on 13-Dec-2015
Myogenesis! The formation of muscle fibers and muscles in
embryonic development Due to
Satellite cells
Myogenic pathways
Hormones
Satellite cells
Population of cells located in adult skeletal muscle
Are responsible for muscle growth and regeneration
Located in the indentation between sarcolemma and basal lamina
Satellite cells become activated and expressed and then become myoblasts
These cells fuse together to generate new myofibers during regeneration of torn and damaged skeletal muscle
Myogenic pathways
In the early development of an embryo, myoblasts can either proliferate, or differentiate into a myotube. Differenitiation- When an undifferentiated cell is
given the features of a specific cell
Proliferation- Duplication through cell division
“Skeletal myogenesis is then initiated in myogenic cells originating form the dermomyotome lips that differentiate to form primary muscle fibers (see [1] for review). Subsequently, a progenitor population that expresses Pax3 and Pax7 arise from the central portion of the dermomyotome and is maintained throughout embryogenesis within the developing skeletal muscles “
Myogenic proteins
MyoD and Myf5 Have defined specific roles in satellite cell
biology
MyoD is required for the differentiation potential of skeletal myoblasts
Myf5 regulates their proliferation rate and homeostasis
What happens to the cell
Hypertrophy- An increase in the size of existing muscle cells This occurs with consistently applied external
loads and an abundance of nutrients.
Atrophy- Decrease in muscle cell size. Can occur from disease, lack of physical activity,
aging and lack of nutrients.
Hyperplasia- An increase in the numbers of cells/fibers in a normal tissue or organ.
Hypertrophy
Neuroelectrical activity with greater impulses over short periods of time signal growth.
Different growth factors are secreted during muscle repair among which insulin-like growth factors (IGFs) are the only ones that promote both muscle cell proliferation and differentiation and that play a key role in muscle regeneration and hypertrophy.
Myostatin is a protein that limits muscular hypertrophy.
Criteria for Hypertrophy
1. Progressive Overload Resistance Training
2. Proper Nutrition Carbohydrates and Protein
3. Genetics
4. Hormone Secretion Testosterone
HgH
Androgens
IGF-1
Atrophy
Neuroelectrical activity of low-intensity signal input over longer periods of time signal for greater muscular efficiency, decreasing the size (therefore, energy needs) of the muscle cells.
Decreased protein kinase signaling
Protein degradation via ubiquitin-proteosome pathway
AMP-activated protein kinase (AMPK) pathway, which can lead to decreased muscle protein synthesis.
References
Farrel, P. A., Joyner, M. J., & Caiozzo, V. J. (2012). ACSM's Advanced Exercise Physiology (2nd ed.). Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.
Le Grand, F., & Rudnicki, M. A. (2007). Skeletal muscle satellite cells and adult myogenesis. Current Opinion in Cell Biology, 19(6), 628–633. http://doi.org/10.1016/j.ceb.2007.09.012
Skeletal muscle hypertrophy and regeneration: Interplay between the myogenic regulatory factors (MRFs) and insulin-like growth factors (IGFs) pathways. Available from: http://www.researchgate.net/publication/236103945_Skeletal_muscle_hypertrophy_and_regeneration_Interplay_between_the_myogenic_regulatory_factors_(MRFs)_and_insulin-like_growth_factors_(IGFs)_pathways [accessed Sep 6, 2015].
THOMAS J. HAWKE1 AND DANIEL J. GARRY1,21Department of Internal Medicine and 2Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
www.muscle.ucsd.edu/musintro/hypertrophy.html
www.nlm.nih.gov/medlineplus/ency/article/003441.htm
www.physiologyonline.physiology.org/content/23/3/160