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

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2:17 minutes

Problem 2

Textbook Question

After ACh attaches to its receptors at the neuromuscular junction, what is the next step?
a. Sodium channels open
b. Calcium binds to regulatory proteins on the thin filaments
c. Cross bridges attach
d. ATP is hydrolyzed

Verified step by step guidance

Step 1: Understand the role of acetylcholine (ACh) at the neuromuscular junction. ACh is a neurotransmitter that binds to receptors on the muscle cell membrane (sarcolemma), initiating a sequence of events leading to muscle contraction.

Step 2: Recognize that after ACh binds to its receptors, it triggers the opening of sodium channels in the sarcolemma. This allows sodium ions (Na⁺) to flow into the muscle cell, leading to depolarization of the membrane.

Step 3: Depolarization of the sarcolemma generates an action potential that travels along the muscle fiber and into the T-tubules, stimulating the release of calcium ions (Ca²⁺) from the sarcoplasmic reticulum.

Step 4: Calcium ions bind to regulatory proteins (troponin) on the thin filaments, causing a conformational change that exposes binding sites on actin for the myosin heads to attach, forming cross bridges.

Step 5: ATP is hydrolyzed by the myosin heads to provide energy for the cross-bridge cycling process, which leads to muscle contraction. This step occurs later in the sequence after calcium binding and cross-bridge formation.

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Key Concepts

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

Neuromuscular Junction

The neuromuscular junction is the synapse or connection point between a motor neuron and a muscle fiber. When a motor neuron releases acetylcholine (ACh), it binds to receptors on the muscle cell membrane, initiating a series of events that lead to muscle contraction. Understanding this process is crucial for determining the subsequent steps after ACh binding.

Action Potential and Sodium Channels

An action potential is an electrical signal that travels along the neuron and triggers the release of neurotransmitters like ACh. When ACh binds to its receptors, it causes sodium channels in the muscle cell membrane to open, allowing sodium ions to flow into the cell. This influx of sodium ions is essential for depolarizing the muscle cell and initiating contraction.

Muscle Contraction Mechanism

Muscle contraction involves a series of biochemical events, including the binding of calcium ions to regulatory proteins on the thin filaments, which allows cross-bridges to form between actin and myosin. This process is powered by ATP hydrolysis, which provides the energy necessary for muscle fibers to contract. Understanding this mechanism is vital for answering questions about the sequence of events following ACh binding.

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Textbook Question

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

A muscle fiber changes length during isotonic concentric and isotonic eccentric contractions.

Tell where each of the three types of muscle tissue would be found in the body. What is meant by the statement, 'Smooth muscles are involuntary in action'?

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Textbook Question

Linda's father suffers an apparent heart attack and is rushed to the emergency room of the local hospital. The doctor on call tells her that he has ordered some blood work and that he will be able to tell if her father actually had a heart attack by looking at the blood levels of CK and cardiac troponin. Why would knowing the level of CK and cardiac troponin help to indicate if a person suffered a heart attack?

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Textbook Question

Describe the events that occur from the time calcium ions enter the axon terminal at the neuromuscular junction until muscle cell contraction occurs.

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Textbook Question

Chemical A binds and blocks acetylcholine receptors of muscle cells. Chemical B floods the cytoplasm of muscle cells with calcium ions. Which chemical would make the best muscle relaxant, and why?

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Textbook Question

What structural feature of a skeletal muscle fiber propagates action potentials into the interior of the cell?

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Textbook Question

What forms of energy reserves do resting skeletal muscle fibers contain?

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Textbook Question

Areas of the body where you would not expect to find slow fibers include the