mr brannon thought you might enjoy a few colorful muscle slides
TRANSCRIPT
Mr Brannon—Thought you might enjoy a few colorful muscle slides
Figure 8.2. Exercise Physiology, 4th Ed. SK Powers & ET Howley. McGraw-Hill 2001.
Figure 8.2. Exercise Physiology, 4th Ed. SK Powers & ET Howley. McGraw-Hill 2001.
Summary: Early steps in skeletal muscle development
Portion of dorsal mesoderm
Divides into tissue blocks (somites)
Activin B
Portion of somitic mesoderm committed to form muscle
MyoDMyf-5MyogeninMyf-6
Proliferation of myoblasts
Activin BFGFsTGF-BImmediate early genes (fos, myc, jun)
Differentiation and fusion to form myotubes
MyoDMyf-5MyogeninMyf-6
Maturation to myofibers
Muscle assembly and fiber type determination
Review of Primary Fiber TypesReview of Primary Fiber TypesVariable Type I Type IIa Type IIx
Twitch time Slow Fast Fast
Motor unit threshold Low Moderate High
Glycolytic capacity Low High-Moderate
High
Oxidative capacity High High Low
Resistance to fatigue High Moderate Low
Specific Tension 20% higher 20% higher
Shortening velocity Low Intermediate Highest
Myosin heavy chain MHCI MHCIIa MHCIIx
I
IIa IIx
Type I fibers = redType II fibers = whiteCapillaries appear as blackdots around fibers
Capillary supply is highest in type I myofibers
Mixture of small (atrophied) fibersand large (hypertrophied) fibers.The small ones are dying and theenlarged ones are compensating.
Comparison of normal vs. diseased muscle
Normal healthy sample
Muscle fibers are similar in size
Diseased
Copper = type I muscle fibersGreen = type IIa muscle fibersBlack = type IIx muscle fibers
Satellite cells are key players in growth and repair of muscle fibers
Satellite cell outside of musclefiber
Satellite cells isolatedfrom muscle in cell culture
Satellite cells fuse together during development and repair
Myostatin is a negative regulator of muscle mass and it is important during development to ensure that muscle develops normally.This is what happens when the “anti-growth” factor myostatin fails (genetic mutation)
Belgian Blue 7 mo. male
I had to include my favorite cartoon…