Anatomy- Skeletal Muscles

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Muscle Test #1 Study Guide
1. What are the primary functions of muscles? What are skeletal muscles made of? Five Skeletal Muscle Functions
1.Produce movement of the skeleton
•By pulling on tendons that then move bones
2.Maintain posture and body position
3.Support soft tissues
•With the muscles of the abdominal wall and the pelvic floor 4.Guard entrances and exits
•In the form of sphincters
5.Maintain body temperature
•When contraction occurs, energy is used and converted to heat Skeletal muscles are organs Made of:
•Connective tissue
•Blood vessels
•Nerves
•Skeletal muscle tissue
2. List and describe the three layers of connective tissue associated with muscles. 1.Epimysium
•Covers the entire muscle
2.Perimysium
•Divides the muscle into bundles called fascicles
•Blood vessels and nerves are contained in the perimysium
3.Endomysium
•Covers each muscle fiber and ties fibers together
•Contains capillaries and nerve tissue
3. Describe a sarcomere. Where is it found? What does it do? How is it “defined” within the muscle? What is it made of? Sarcomeres
•Smallest functional unit of skeletal muscle fiber
•Formed by repeating myofilament arrangements
•Each myofibril has about 10,000 sarcomeres
•Thick and thin filament arrangements are what produce the striated appearance of the fiber •Overlapping filaments define lines and bands
4. How does calcium interact with troponin and tropomyosin? What does this do? Where is this calcium stored? Steps of Contraction
1.Calcium released from Sarcoplasmic Reticulum (around myofibril) 2.Calcium binds to troponin
3.Change of troponin shape causes tropomyosin to move away from active sites 4.Myosin heads bind to active site, creating cross-bridges, rotate and cause actin to slide over myosin 5. How are skeletal muscle cells different from other cells?5.) Skeletal muscle fibers are quite different from the typical cells. One obvious difference is size: Skeletal muscle fibers are enormous.A second obvious difference is that skeletal muscle fibers are multinucleate: Each skeletal muscle fiber contains hundreds of nuclei just internal to the cell membrane.

6. How do muscle cells regulate tension?
The Contraction Cycle
•Action potential causes release of calcium from the Sarcoplasmic Reticulum •Calcium binds to troponin and the contraction cycle starts Contraction Produces Tension
•As sarcomeres contract, so does the entire muscle fiber
•As fibers contract, tension is created by tendons pulling on bones •Movement will occur only if the tension is greater than the resistance •Compression is a force that pushes objects
•Muscle cells create only tension, not compression
Contraction Produces Tension
•Individual fibers
•Are either contracted or relaxed
•"On" or "off"
•Tension is a product of the number of cross-bridges a fiber contains • Variation in tension can occur based on:
•The amount of overlap of the myofilaments
•The frequency of stimulation
•The more frequent the stimulus, the more Ca2+ builds up, resulting in greater contractions Contraction Produces Tension
•Whole skeletal muscle organ
•Contracts with varying tensions based on:
•Frequency of muscle fiber stimulation
•Number of fibers activated
7. Describe Isometric and isotonic contractions.
•Isotonic contraction
•When the length of the muscle changes, but the tension remains the same until relaxation •For example, lifting a book
•Isometric contraction
•When the whole muscle length stays the same, the tension produced does not exceed the load •For example, pushing against a wall
8. What is oxygen debt? The Recovery Period
•Requires "repaying" the oxygen debt by continuing to breathe faster •Even after the end of exercise, and recycling lactic acid •Heat production occurs during exercise
•Raising the body temperature
•Blood vessels in skin will dilate; sweat covers the skin and evaporates •Promoting heat loss
9....
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