1. Skeletal Muscle Tissue

2. Hierarchy
Muscle (belly) → fasciculus → myofiber (cell) → myofibril → myofilaments

3. Myoneural (neuromuscular) Junction
Where nerves meet the muscle to give message

4. Color Code: Anatomy of Muscle
Tendon-connects muscle to periostium
b/c. belly is surrounded by epimysium
fasciculus-bundle of fibers surrounded by perimysium
Myofibers-surrounded by endomysium
f/g. myofibril- made up of myofilaments

7. Muscle Size The number of myofibers doesn’t change
a. Atrophy: decrease in size due to lack of use in extended atrophy, the fiber will actually die.
If you don’t use it, it will shut down!

9. Atrophy can be reversed unless it is permanent damage!!!!!

10. Hypertrophy
Increase in number and size of myofibrils

11. Testosterone Stimulates hypertrophy
Steroid-synthetic testosterone hormone to artificially build muscle.
Do boys and girls have it?
Yes-boys produce more than females!!

12. Maintenance of muscle mass and strength
Maintenance of bone density and strength
Libido and clitoral engorgement/penile erection frequency.
Mental and physical energy
Excessive testosterone in males can lead to an increased risk of prostate cancer

15. Anatomy of Myofiber Sarcolemma: Cell membrane
Sarcoplasm: muscle cytoplasm, contains myoglobin & mitochondria, glycogen-stored glucose.

16. Sarcoplasmic Reticulum (SR):
surrounds myofibrils
stores calcium ions Ca ++
(important for muscle contraction)
a. Cisternae: calcium storage area
b. T Tubules: transverse tubules, connect sarcolemma to sarcoplasm.

18. Anatomy of Myofibril Responsible for contraction
2 myofilaments: actin- the thin one
myosin- the thick one
Sarcomeres: functional unit of contraction; area between 2 z-lines
10,000 or more sarcomeres along each myofiber.

19. g. I Band: Light region, actin only
f. A Band: dark region, both actin and myosin
h. H Zone: center of the A band, myosin only

20. j. Z line: dark zig-zag line in center of I band
k. Actin: thin myofilament
They have active sites (handles) if calcium is present.

22. l. Myosin: thick myofilament
m. Cross Bridges: part of myosin, attach to actin in the presence of calcium

23. Sliding Filament Theory
Actin filaments slide past myosin
Z lines get closer together
Sarcomere shortens-neither actin or myosin get shorter.