mr brannon thought you might enjoy a few colorful muscle slides

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Mr Brannon— Thought you might enjoy a few colorful muscle slides

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Page 1: Mr Brannon Thought you might enjoy a few colorful muscle slides

Mr Brannon—Thought you might enjoy a few colorful muscle slides

Page 2: 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.

Page 3: 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.

Page 4: Mr Brannon Thought you might enjoy a few colorful muscle slides

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

Page 5: Mr Brannon Thought you might enjoy a few colorful muscle slides

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

Page 6: Mr Brannon Thought you might enjoy a few colorful muscle slides

Type I fibers = redType II fibers = whiteCapillaries appear as blackdots around fibers

Capillary supply is highest in type I myofibers

Page 7: Mr Brannon Thought you might enjoy a few colorful muscle slides

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

Page 8: Mr Brannon Thought you might enjoy a few colorful muscle slides

Satellite cells are key players in growth and repair of muscle fibers

Satellite cell outside of musclefiber

Satellite cells isolatedfrom muscle in cell culture

Page 9: Mr Brannon Thought you might enjoy a few colorful muscle slides

Satellite cells fuse together during development and repair

Page 10: Mr Brannon Thought you might enjoy a few colorful muscle slides

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

Page 11: Mr Brannon Thought you might enjoy a few colorful muscle slides

I had to include my favorite cartoon…