Skeletal muscle basics

Identify the four (4) functions of muscular tissue.

1. Stabilizing body positions.

2. Producing body movement.

3. Storing and moving materials in and out of the body.

4. Generating heat.

Identify the three (3) types of muscular tissue.

Skeletal, cardiac, and smooth muscle.

Identify the five (5) common properties of muscles.

1. Excitability

2. Conductivity

3. Contractility

4. Elasticity

5. Extensibility

Define skeletal muscle.

Skeletal muscle is a collection of muscle cells or fibers.

Define skeletal fibers.

Skeletal fibers are long, cylindrical multinucleated cells.

What is the muscle equivalent of a muscle cell?

Muscle fiber

What is the muscle equivalent of a cell membrane?

Sarcolemma

What is the muscle equivalent of a cytoplasm?

Sarcoplasm

What is the muscle equivalent of a modified endoplasmic reticulum?

Sarcoplasmic reticulum

Identify the three (3) layers of muscular connective tissue (mysia) from most superficial to deep.

1. Epimysium (around the entire muscle)

2. Perimysium (around the fascicle)

3. Endomysium (around the muscle fiber)

Identify the following structures.

1. Bone

2. Tendon

3. Epimysium

4. Blood vessel

5. Perimysium

6. Endomysium

7. Muscle fiber (Sarcolemma?)

8. Epimysium

9. Perimysium

10. Fascicle

11. Endomysium

What is myofibril?

Myofibril are the long, rod-shaped organelles inside muscle fibers that drive muscle contraction and relaxation.

• Myofibrils are composed of actin and myosin.

• Each myofibril is divided into repeating functional units called sarcomeres.

Identify and describe the filaments that comprise myofibrils.

Myofibrils are composed of actin and myosin:

• Myosin (thick filament): Thick filamentous motor proteins responsible for movement.

• Actin (thin filament): Globular proteins (G-actin) that form long filamentous chains called F-actin.

Identify the following structures.

1. Endomysium

2. Muscle fiber/cell

3. Myofibril

4. Myofibrils

5. Sarcoplasm

6. Nuclei

7. Mitochondria

8. Terminal cisternae

9. Sarcolemma

10. Nucleus

11. Zone of overlap

12. H-zone

13. M-line

14. Z-disc

15. Z-disc

16. Myofibril

17. I-band

18. A-band

19. I-band

20. Sarcomere

21. Thick filament (myosin)

22. Thin filament (actin)

23. Sarcoplasmic reticulum

24. Triad

25. Mitochondria

26. T-tubules

What is the neuromuscular junction?

The neuromuscular junction is a specialized synapse that connects motor neurons and skeletal muscle fibers, enabling muscle contraction and relaxation.

• Contraction: Process that enables the production of force; requires ATP.

• Relaxation: Release of tension created by contraction.

Define atrophy.

Atrophy is characterized by a reduction in muscle size and power after a long period of no use.

Define hypertrophy.

Hypertrophy is characterized by an increase in muscle size and contractile activity.

True or false: Muscle cells contain centrioles.

False. Skeletal muscle cells do not contain centrioles, and thus cannot participate in cell division.

• They can however, increase or decrease in size.

Identify the four (4) broad categories of muscle fiber arrangements.

Parallel, convergent, pennate, and circular muscles.

Identify the three (3) types of parallel muscles.

1. Typical parallel muscles

2. Parallel muscles with tendinous bands

3. Wrapping muscles

Identify the three (3) types of pennate muscles.

1. Unipennate muscle

2. Bipennate muscle

3. Multipennate muscle

Identify the three (3) types of fiber types.

1. Slow oxidative: dark, speckled; mitochondria-rich with high oxidative activity.

2. Fast oxidative: medium gray; intermediate oxidative capacity.

3. Fast glycolytic: pale; least oxidative.

What is the origin and insertion of a muscle?

• Origin: The end of the muscle attached to a fixed, stabilized bone; immovable.

• Insertion: The moveable end of the muscle that attaches to the bone being pulled.

What is an agonistic muscle?

Muscle that accomplishes a certain action.

What is an antagonistic muscle?

Muscle that acts in opposition to the agonist.

What are the shortcuts to identify the origin and insertion of a muscle?

For muscles that extend between a broad aponeurosis and a narrow tendon, the aponeurosis is the origin while the tendon is the insertion.

For muscles where there are several tensons on one end and only one on the other end, the region with multiple tendons is the origin, while the region with the single tendon is the insertion.

What is synergistic?

Groups of muscles working together.

What is fixator?

Muscles that holds one bone in place relative to the body while a distal bone is moved by another muscle.