1. Anatomy of skeletal muscle ppt #1 Unit 4 Muscles
Pgs , Chapter 11.1

2. Muscular System Chapter 11

3. Muscle Intro Functions of muscles
Movement: respiration, circulation, defecation
Stability: resists gravity and provides tension to tendons
Communication
Heat Production: muscle provides 85% of body heat

4. Types of Muscle Skeletal – striated & voluntary Smooth – involuntary
Cardiac - heart
The word “striated” means striped. Skeletal muscle appears striped under a microscope.

5. Connective Tissues of Muscle
Skeletal muscles are composed of muscular AND connective tissues.
A skeletal muscle can be about 100um in diameter BUT up to 30cm in length!!
Muscle Cell=Muscle Fiber
Muscle fiber is surrounded by connective tissue, Endomysium
(allows for nerves and blood capillaries to to reach each fiber)
Muscle fibers are bundled into Fascicles
(can be seen by naked eye, looks like strands)

6. Muscles and Muscle Fiber Structure
Muscles are composed of many FIBERS that are arranged in bundles called FASCICLES

7. --Each Fascicle is separated (wrapped) from other fascicles by a connective tissue sheath, Perimysium
--The entire muscle as a whole is surrounded by another connective tissue layer, Epimysium
--The Epimysium gradually becomes connective tissue sheaths called Fascia
Fascia thickens and becomes Deep Fascia (no fat) between adjacent muscles.
--This becomes even thicker and becomes Superficial fascia between muscles and skin. Some places like buttocks and abdomen is very adipose.(fat)

8. EPIMYSIUM = outermost layer, surrounds entire muscle.
PERIMYSIUM = separates and surrounds fascicles (bundles of muscle fibers)
ENDOMYSIUM = surrounds each individual muscle fiber(cell)
This model of the muscles uses straws to represent fibers.
Green = endomysium Yellow = perimysium Blue = epimysium

9. Epimysium
Perimysium
Endomysium

10. Muscle Layers
Muscle Fiber
Endomysium
Perimysium
Epimysium

11. Individual muscles are separated by FASCIA, which also forms tendons

13. How are muscle cells created?
In embryonic development, STEM CELLS called Myoblasts fuse to produce each muscle fiber.
Muscle Cell Organization:
Each muscle fiber, (1 muscle cell) has: many myofibrils (protein bundles)
Each muscle fiber has: many flattened or sausage shaped nuclei pushed
against the plasma membrane
Each muscle fiber (cell) has: plasma membrane= Sarcolemma
Each muscle fiber (cell) has: cytoploasm = Sarcoplasm
Each muscle fiber (cell) has: many Mitochondria

14. Nucleus
Sarcolemma
Mitochondrion
Sarcoplasm
Myofibril

15. The Sarcoplasm also contains lots of Glycogen (stored carb) which provides energy and the red pigment Myoglobin
which stores Oxygen.
Other organelles are packed into the spaces between the myofibrils like:
Sarcoplastic Reticulum: has channels to release FLOOD of Ca+ Forms a network around each myofibril .
T Tubules= Transverse tubules which signal the SR to release Ca+ Mitochondria: Produces ATP from O2 and glucose (cellular respiration)

16. Structure of a Skeletal Muscle Fiber
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Muscle fiber
Nucleus
A band
I band
Z disc
Mitochondria
Openings into transverse tubules
Sarcoplasmic reticulum T
riad: T
erminal cisternae T
ransverse tubule
Sarcolemma
Myofibrils
Sarcoplasm
Figure 11.2
Myofilaments

17. Structure of Myofibrils
Myofibrils are the long protein cords that fill most of the muscle cell
Each Myofibril is a bundle of parallel protein microfilaments called:Myofilaments
3 kinds of Myofilaments:
Thick Filaments: hundreds of strands of proteins called :
MYOSIN looks like golf clubs

18. THICK FILAMENTS Single myosin
Hundreds
of myosin

19. Tropomyosin and Troponin are Regulatory proteins
Thin Filaments: 2 intertwined strands of protein called:
Fibrous ACTIN
Fibrous Actin (F actin) with “globs” of Globular Actin (G actin)
* each G-Actin (globular Actin)has an active site that binds to the
head of myosin
Thin Filaments also have protein strands of Tropomyosin
When muscle is relaxed, the tropomyosin blocks the G actins and prevents myosin from binding.
Thin filaments also have Troponin: a Ca+ binding protein
Tropomyosin and Troponin are Regulatory proteins
Myosin and Actin are Contractile Proteins

21. Thin Myofilaments
G act
(c) Thin filament
Figure 11.3c

22. Elastic Filaments: made of huge springy proteins called
Elastic Filaments: made of huge springy proteins called Titan, this helps stabilize the thick filaments and helps prevent overstretching.
flank each thick filament and anchor it to the Z disc
helps stabilize the thick filament
center it between the thin filaments
prevents over stretching

23. Accessory Proteins include(more than 20 dif proteins) Dystrophin)
1. Links actin in outermost myofilaments and
2. transfers forces of muscle contraction to
connective tissue around muscle cell
Genetic defects in dystrophin produce the
disease muscular dystrophy.

24. Myofibrils are made of 1. MYOSIN = thick filaments
ACTIN = thin filaments
Elastic filaments

25. Filament organization
Actin and Myosin are in all cells and control motility .
In muscle cells they areContractile proteins (act to shorten muscle fibers)
Actin and Myosin are organized in a precise array which then is seen as striations in the muscle.
Striated muscle has DARK A bands
alternating with light I bands

26. Myofilaments ACTIN (thin) and MYOSIN (thick)
  form dark and light bands
A band = dArk • thick (myosin)
I band = lIght • thIn (actin)

27. Overlap of Thick and Thin Filaments
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Thick filament
Thin filament
Bare zone
Portion of a sarcomere showing the overlap
of thick and thin filaments
Figure 11.3d

28. Bands in muscle myofibrils:
A bands= thick filaments lying side by side
- very dark where thick and thin overlap
H bands= lighter region with no overlap of
thick and thin…just thick
I Bands = is region with only thin filaments and is
anchored to Z disc by elastic filaments
Z disc = Protein disc to which thin and elastic filaments
are anchored
Sarcomere= segment of myofibril from one Z disc to the
next Z disc

30. A muscle shortens because individual sarcomeres shorten and pull the z discs closer to each other. As discs are pulled closer they pull on the sarcolemma to achieve shortening of the cell.

31. Striations and Sarcomeres
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Nucleus
Sarcomere 5
Z disc
M line 4
H band
Individual myofibrils 3
I band
A band
I band 2 1
(a)
Visuals Unlimited
Figure 11.5a
sarcomere – functional contractile unit of the muscle fiber
muscle shortens because individual sarcomeres shorten
pulls z discs closer to each other

34. It is important to remember the hierarchy
fasicles
myofibrils
myofilaments
actin
myosin