1. Parts of a Muscle

2. Structure of Skeletal Muscle
Muscles are made up of muscle cells and connective tissue
Most muscles attach at two places and crosses a joint.
Attachment at the more stationary end is the origin.
Attachment at the moveable end is the insertion.

3. Structure of Skeletal Muscle

4. Structure of Skeletal muscles
Skeletal muscles are composed of clusters of muscle cells.
Myocytes Myofibers Muscle fibers

5. Myocytes Known as a muscle cell or muscle fiber Cell structure
Muscles cells contain many nuclei
The plasma membrane→ sarcolemma
The cytoplasm→ sarcoplasm
Length
ranges from 0.1cm to more the 30cm in length
Diameter
ranges from 0.001cm to 0.01cm in diameter

6. Myofibrils
Each muscle fiber contains myofibrils, which are very long chains of sarcomeres, the contractile units of the cell
Muscle fibers align in parallel arrangements to look like long strands of fibers

8. Endomysium
Sheath of connective tissue that surrounds each muscle fiber.

9. Fascicles
A bundle of muscle fibers (myoctes)

10. Perimysium
Sheath of connective tissue that holds fascicles together.

11. Epimysium
Sheath of connective tissue that surrounds the entire muscle.
Also known as deep fascia

12. Movement of Muscles
Muscles move due to neurons and impulses through those neurons.

13. Specifically…..Brachial Plexus
The brachial plexus is a network of nerves that originate near the neck and shoulder.
These nerves begin at the spinal cord in the neck and control the hand, wrist, elbow, and shoulder
These are both motor and sensory neurons.

14. Muscle Fibers and Nerves – It’s All About the Charge!
Nerves can stimulate muscle fibers
Inside the fibers, there is a negative charge
When stimulated, the resting membrane potential changes
Channels open in the membrane allowing sodium ions to rush in creating an action potential

15. Muscle Fibers and Nerves
The nerves that stimulate muscles are called motor neurons and originate from the spinal cord.
When the action potential is created, the muscle fiber contracts.
How does this happen?
content/muscle.html
video

16. Contraction of Muscles
Each myofibril is made up of arrays of parallel protein filaments.
Myosin (protein) = thick filaments
Actin (protein) = thin filaments
Also contain a small amount of
troponin
tropomyosin.
These fibers make up a sarcomere – from a Z line to a Z Line (disc).

19. In the sarcomere of the myofibril, there are alternating thick and filaments that overlap.
Where they overlap is called the A band
This band appears dark when looking at the striations within a muscle
H zone is where there is no overlap of thick filaments

20. I bands are where only thin filaments occur
Appears as the lighter band when looking at the striations within the muscle
Z lines are where the different sarcomeres meet up
M Line center of the H zone

21. http://highered. mcgraw- hill
hill.com/sites/ /student_view0/chapter10/animation__sarcomere_contraction.html

23. Lines Really Have Structure

24. Sliding Filament Theory/Mechanism
Before a stimulus is received, a muscle is at rest.
Calcium ions are being stored within the sarcoplasmic reticulum (cytoplasm of the myocyte)
ATP molecules are chemically bound to thin filaments (myosin)
The thin filament has all three proteins (actin, troponin) and tropomyosin) attached
The fiber is ready to contract if a stimulus from a nerve were to occur.

25. Stimulus from a motor neuron is received
It becomes more permeable to calcium ions.
The calcium is released into the sarcomere.
Calcium binds to troponin in the thin filaments.
Actin and troponin undergo a shape change.
This exposes binding sites on thin filaments.
When these sites are exposed, portions of thick filaments called cross bridges bind forming a connection between thin and thick filaments.

26. When these cross bridges occur, calcium causes a breakdown of ATP that is bound to the thick filaments.
ATP is ready to be broken down….
ATP is broken down into ADP and phosphate and energy.
The energy that is released is used to move the cross bridges and some is released as heat.
Movement of the cross bridges causes the thin filaments to be drawn toward the center of the sarcomere.
When this action is completed, another ATP molecule binds to myosin causing the thick filament’s cross bridge to break from the attachment with the thin filament.

27. Once the thick filament position is restored, the cross bridge reforms its attachment to a binding site on the thin filament.
This cycle occurs again and again resulting in a continual movement of thin filaments toward the center of the sarcomere causing the sarcomere to shorten.
This gives muscle contraction!
pter10/animation__action_potentials_and_muscle_contraction.html

31. http://highered. mcgraw-hill

32. Rigor Mortis!

33. What Happens? When you die, ATP becomes unavailable.
The cross bridges that are formed (because the ATP is already attached) when you die are not released and the body is “frozen” in a certain position.
Conversion to ADP does not occur.
Rigor mortis can happen quickly after death.
It lasts form hours after death (depending on external conditions)
Release occurs due to the break down of tissues in the body.