1. Unit: Muscular System

2. Please, help me out!
If there are things throughout this unit you do not like, please write it down and explain why.
If you feel I could have done something differently that would have been more effective for you, please record it.
At the end of the unit I will ask you to answer these questions on sheet of paper. Thanks for your help!!

3. What you will learn: Review Muscle types
I can label the major parts of skeletal muscle
I can describe how skeletal muscle contracts (sliding filament model)
I can identify the origin and insertion points of major muscles within the human body.
I can describe the functions of skeletal muscle
I can identify the parts of a motor unit
I can describe a muscle stimulus (all-or-none)
I can identify the types of skeletal muscle contractions (tonic, twitch, tetanic, isotonic, isometric)
I can explain why a muscle fatigues
Learn the name, location, function, insertion and origin points of the major muscles in the body (cat dissection, Yeah!)

4. Lets get started: Review
Take five minutes to recall and record in your journal:
The three types of muscle tissue
Identify two distinguishing characteristics for each.

5. Muscle Tissues
Smooth
Cardiac
Skeletal

6. Smooth Muscle Cells are tapered at each end Have a single nucleus
Lack cross striations
Involuntary
Important in blood vessel walls and in many hollow internal organs (such as gut, urethra, and ureter)

7. Cardiac Muscle Composes the heart Cross striations Involuntary
Intercalated disks - where the membranes of adjacent cardiac fibers come in contact with each other.

8. Skeletal Muscle Voluntary Many cross striations Multi-nucleated
Attached to bone and when contracted allow for movement.

9. Skeletal Muscle Voluntary Many cross striations Multi-nucleated
Attached to bone and when contracted allow for movement.

10. Do you know:
Do you know why the muscular system is classified as a system?
- What makes it a system?
- Take a moment to describe why it is classified as system in your electronic journal.

11. Do you know (cont.):
The muscular system is an organ system consisting of skeletal, smooth and cardiac muscles. It permits movement of the body, maintains posture, and aids in blood circulation.
-Multiple muscles interact with each other to produce body movements.
- Synergists: (Muscles of the truck External oblique, Internal oblique, Transverse abdominis compress abdomen)
- Antagonist: (Triceps brachii vs. Biceps brachii aides in extension and flexion)

12. Function of Skeletal Muscle:
1. Movement – as skeletal muscle becomes shorter as fibers contract, the bones to which the muscle/s attach move closer together causing movement.
- Voluntary muscular movement is smooth and free of jerks because skeletal muscles generally work in teams.
- Several muscles contract, while others relax
- Prime mover: of all the muscles contracting simultaneously, the one that is mainly responsible for producing the movement is the PM.

13. Function of Skeletal Muscle:
2. Posture or muscle tone – we are able to maintain our body position because of a specialized type of skeletal contraction called tonic.
- Tonic contraction: do not move any body parts but hold muscles in position (muscle tone maintains posture through constant tension).

14. Function of Skeletal Muscle:
3. Heat Production – contraction of muscle fibers produces most of the heat required to maintain a constant body temperature.
- the energy for muscle contractions comes form ATP (powerhouse of the cell) and is used to shorten the muscle fibers.
- hypothermia: any decrease below normal (below 98.6 ◦F) - Why is this significant?

15. Structure of Skeletal Muscle:
Skeletal muscle is an organ composed mainly of striated muscle cells and connective tissue.
Skeletal muscles attach to two bones that have a moveable joint between them.
- recall the three classifications of joints, synarthroses, amphiarthroses, diarthroses
- example: deltoid muscle

16. Structure of Skeletal Muscle:
One bone is more stationary in a given movement than the other.
The muscles attachment to this more stationary bone is called its origin point.
The attachment to the more movable bone is called the muscles insertion point.
- Think Biceps brachii - origin: scapula (supraglenoid tubercle & coracoid process, insertion: radius)

17. Structure of Skeletal Muscle:

18. Movements Produced by Skeletal Muscle Contractions:
Muscles acting on some joints produce movement in several directions, whereas only limited movement is possible at other joints.
1) Flexion - is a movement that makes the angel between two bones at their joint smaller than it was at the beginning of the movement.
- ex. Hamstring group
2) Extension – makes the angle between two bones at their joint larger.
- ex. Quadriceps group

19. Movements Produced by Skeletal Muscle Contractions:
3) Abduction - means moving a part away from the midline of the body.
- ex. Moving arm out to the side
4) Adduction – means moving a part toward the midline.
- ex. Bring your arm down to your side, toward midline
5) Rotation – movement around a longitudinal axis.
- ex. Head rotates on cervical axis.

20. Movements Produced by Skeletal Muscle Contractions:
Refers to hand positions that result from rotation of the forearm.
6) Supination – hand position with the palm turned to the anterior position (as in the anatomical position)
- Supine: means lying face up
7) Pronation – hand position with the palm facing posteriorly.
- Prone: means lying face down

21. Movements Produced by Skeletal Muscle Contractions:
Refers to ankle movements.
8) Dorsiflexion – the dorsum or top of the foot is elevated with the toes pointing upward.
9) Plantar Flexion – bottom of foot is directed downward, as if standing on toes.

22. Structure of Skeletal Muscle:
Body – all the muscle, except the two ends
Tendons – anchor muscles firmly to bones. Made of dense fibrous connective tissue in the shape of heavy cords, have great strength but less mobility.
Bursae – are small flexible sacs that lie between tendons and bone and are lined with synovial membrane. Aides in tendon movement over bone when it the tendon shortens (contracts).
Synovial Membrane - secretes a slippery lubricating fluid that fills the bursa.

23. Structure of Skeletal Muscle:

24. Note: Microscopic Structure of Muscle

25. Microscopic Structure of Muscle (see handout):

26. Microscopic Structure of Muscle:
Muscle Fibers – specialized contractile cells that are grouped together and arranged in a highly organized way.
- Each muscle fiber contains multiple myofibrils that house sarcomeres (the basic functional contractile unit of skeletal muscle) arranged end to end within the myofibril.
- Each sarcomere is filled with two kinds of very fine and threadlike structures: thick and thin myofilaments.

27. Microscopic Structure of Muscle:
Muscle Fibers – specialized contractile cells that are grouped together and arranged in a highly organized way.
- Each muscle fiber contains multiple myofibrils that house sarcomeres (the basic functional contractile unit of skeletal muscle) arranged end to end within the myofibril.
- Each sarcomere is filled with two kinds of very fine and threadlike structures: thick and thin myofilaments.

28. Microscopic Structure of Muscle:
Thick myofilaments – are formed from a protein called myosin.
Thin myofilaments – are composed mostly of protein called actin. (Note: Z-lines denote new sarcomere)

29. Sliding Filament Model:
The Sliding filament model describes a process used by muscles to contract. It is a cycle of repetitive events that cause a thin filament to slide over a thick filament and generate tension in the muscle thus shortening the sarcomere and the muscle.
- Note: That even in a relaxed state, the thick and thin filaments still over lap.

30. Sliding Filament Model:
During a contraction the thick and thin myofilaments in a muscle fiber first attach to one another by forming cross-bridges.
- This acts as levers to ratchet or pull the myofilaments past each other.
- Form properly only when calcium is present.
- Calcium is stored in the endoplasmic reticulum in the muscle cell.
- Is released into the cytoplasm, only when the cell is simulated by a nerve impulse.
- Energy (ATP) also needs to be present in order to shorten the muscle.

31. Microscopic Structure of Muscle:

32. Microscopic Structure of Muscle (see handout):

33. Muscle Fatigue:
Occurs when muscle cells are stimulated repeatedly with inadequate periods of rest.
-During exercise ATP is depleted through cellular respiration.
- The body tries to replenish the oxygen debt, through increased oxygen intake (increased inhalation; aerobic respiration).
- However, when that is not enough the body produces lactic acid through lactic acid fermentation (anaerobic).
-This is only temporary, and the build up of lactic acid can cause muscle soreness after exercise.

34. Muscle Fatigue:
- Therefore, the strength of muscle contractions decreases which results in muscle fatigue.
- Eventually muscle contraction will no longer occur (cease).
- After exercise, labored breathing will persist in order to “pay the debt” for the metabolic effort. This is an example of your body trying to maintain homeostasis (bringing your body back into a stable internal environment).