A&P1 Ch. 10 Homework

Chapter 10, Muscle Homework

1. List 4 important functions of muscle tissue.

Four important functions of muscle tissue are: to produce body movement, stabilize joints, maintain posture, and to generate heat.

2. Describe the microscopic structure and functional roles of the myofibrils, sarcoplasmic reticulum, and T tubules of skeletal muscle fibers.

Myofibrils: Tightly packed in the muscle fiber, made up of actin (thin) and myosin (thick) filaments. Contains sarcomere, which are contractile elements. Myofibrils are broken up in to parts, Z-discs, H Zone, I-band, A-band, and M-line.

Sarcoplasmic Reticulum: Interconnecting tubules surrounding the myofibril. It regulates levels of Ca. It’s a smooth ER and houses many mitochondria, and glycogen granules. Communicates with H-Zone, terminal cisternae.

T-tubules: Run between paired terminal cisternae at I A-band junction where they encircle sarcomere. Functions to increase muscle surface area, as a nerve pathway, and signals release of calcium from terminal cisternae.

3. Describe the sliding filament model of muscle contraction.

During a contraction, both the I-band and the H-zone narrow, while the A-band remains unchanged. /myosin heads attach to actin to pull the thin filaments toward the M-line, which brings Z-discs closer together, shortening the sarcomere. Sarcomeres are arranged end to end within each myofibril and when simultaneously contracted, shorten the whole muscle fiber.

4. Explain how muscle fibers are stimulated to contract by describing events that occur at the neuromuscular junction.

An action potential arrives at the axon terminal, calcium is let in the axon terminal, calcium then stimulates the synaptic vesicles to exocytize acetylcholine in to the synaptic cleft. Acetylcholine binds to the receptors on sarcolemma and open the channels for the consumption of sodium and the expulsion of potassium.

5. Follow the events of excitation-contraction coupling that lead to cross bridge...