Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

9. Muscle Tissue

Steps of Muscle Contraction

Anatomy & Physiology

9. Muscle Tissue

Steps of Muscle Contraction

Previous problemNext problem

1:52 minutes

Problem 18

Textbook Question

Explain what is meant by the term excitation-contraction coupling.

Verified step by step guidance

Understand that excitation-contraction coupling refers to the physiological process that links the electrical excitation of a muscle fiber (action potential) to its mechanical contraction (shortening of the muscle). This process is essential for muscle function.

Begin by recognizing that the process starts with an action potential traveling along the sarcolemma (the muscle cell membrane) and into the T-tubules, which are invaginations of the sarcolemma that penetrate into the muscle fiber.

Learn that the action potential in the T-tubules triggers the release of calcium ions (Ca²⁺) from the sarcoplasmic reticulum (SR), a specialized organelle that stores calcium. This release is mediated by voltage-sensitive proteins in the T-tubules that interact with calcium release channels in the SR.

Understand that the released calcium ions bind to troponin, a regulatory protein on the actin filaments. This binding causes a conformational change in the troponin-tropomyosin complex, exposing the myosin-binding sites on actin filaments.

Finally, recognize that the exposure of myosin-binding sites allows myosin heads to attach to actin, forming cross-bridges. This initiates the sliding filament mechanism, where myosin heads pull actin filaments toward the center of the sarcomere, resulting in muscle contraction.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Excitation-Contraction Coupling

Excitation-contraction coupling refers to the physiological process by which an electrical signal (action potential) in a muscle cell leads to muscle contraction. This process involves the transmission of the action potential along the sarcolemma and into the T-tubules, triggering the release of calcium ions from the sarcoplasmic reticulum, which ultimately initiates the contraction of the muscle fibers.

Role of Calcium Ions

Calcium ions play a crucial role in excitation-contraction coupling by binding to troponin, a regulatory protein on the actin filaments. This binding causes a conformational change that moves tropomyosin away from the myosin-binding sites on actin, allowing myosin heads to attach and perform the power stroke necessary for muscle contraction.

Action Potential

An action potential is a rapid, temporary change in the electrical membrane potential of a cell, which is essential for initiating muscle contraction. In muscle cells, the action potential is generated when the cell membrane depolarizes, leading to the opening of voltage-gated ion channels and the subsequent influx of sodium ions, which propagates the signal along the muscle fiber.

Watch next

Master Overview of Muscle Contraction with a bite sized video explanation from Bruce Bryan

Start learning

Related Videos

Related Practice

Textbook Question

The ions that enter the skeletal muscle cell during the generation of an action potential are

a. Calcium ions

b. Chloride ions

c. Sodium ions

d. Potassium ions

Myoglobin has a special function in muscle tissue. It:

a. Breaks down glycogen

b. Is a contractile protein

c. Holds a reserve supply of oxygen in the muscle

Aerobic exercise results in all of the following except:

a. More capillaries surrounding muscle fibers

b. More mitochondria in muscle cells

c. Increased size and strength of existing muscle cells

d. More myoglobin

What is the importance of acetylcholinesterase in muscle cell contraction?

Define and draw a motor unit.

a. Describe the structure of a sarcomere and indicate the relationship of the sarcomere to myofilaments.

b. Explain the sliding filament model of contraction using appropriately labeled diagrams of a relaxed and a contracted sarcomere.

Explain how a slight (but smooth) contraction differs from a vigorous contraction of the same muscle. Use the concepts of multiple motor unit summation.

Muscle-relaxing drugs are administered to a patient during major surgery. Which of the two chemicals described next would be a good skeletal muscle relaxant and why?

• Chemical A binds to and blocks ACh receptors of muscle cells.

• Chemical B floods the muscle cells' cytoplasm with Ca²⁺.

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap