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

11. Nervous Tissue and Nervous System

Change in Membrane Potential

Anatomy & Physiology

11. Nervous Tissue and Nervous System

Change in Membrane Potential

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5:01 minutes

Problem 17

Textbook Question

Describe the steps involved in the generation of an action potential.

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Step 1: Resting membrane potential is established. The neuron is at rest, and the inside of the cell is negatively charged relative to the outside. This is maintained by the sodium-potassium pump, which actively transports 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell, and by the selective permeability of the membrane to K⁺ ions.

Step 2: Depolarization begins when a stimulus causes voltage-gated sodium (Na⁺) channels to open. Sodium ions rush into the cell due to the concentration gradient and electrical gradient, making the inside of the cell less negative. If the membrane potential reaches the threshold (approximately -55 mV), an action potential is triggered.

Step 3: Rapid depolarization occurs as more Na⁺ channels open, allowing a large influx of sodium ions. The membrane potential becomes positive, reaching a peak of approximately +30 mV.

Step 4: Repolarization begins as voltage-gated sodium channels close and voltage-gated potassium (K⁺) channels open. Potassium ions exit the cell, restoring the negative charge inside the cell and bringing the membrane potential back toward the resting level.

Step 5: Hyperpolarization occurs because the potassium channels close slowly, allowing excess K⁺ ions to leave the cell. This causes the membrane potential to temporarily become more negative than the resting potential. The sodium-potassium pump and leak channels then restore the resting membrane potential.

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Key Concepts

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

Resting Membrane Potential

The resting membrane potential is the electrical charge difference across the neuronal membrane when the neuron is not actively firing. Typically around -70 mV, this potential is maintained by the sodium-potassium pump, which actively transports sodium ions out of the cell and potassium ions into the cell, creating a polarized state that is crucial for the generation of action potentials.

Depolarization

Depolarization is the initial phase of an action potential, where the neuron's membrane potential becomes less negative, moving towards zero. This occurs when voltage-gated sodium channels open in response to a stimulus, allowing sodium ions to rush into the cell. If the depolarization reaches a certain threshold, it triggers the full action potential.

Repolarization

Repolarization is the process that follows depolarization, restoring the membrane potential back to its resting state. This occurs when voltage-gated potassium channels open, allowing potassium ions to exit the cell, which helps to counteract the influx of sodium ions. This phase is essential for resetting the neuron's electrical state, enabling it to fire again.

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Related Practice

Textbook Question

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

A depolarization is a change in membrane potential that makes the potential less negative.

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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 local potential is a change in membrane potential that conducts the long-distance signals of the nervous system.

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Textbook Question

A drug that blocks Na⁺ channels in neurons does so not only in the axon but also in the dendrites and cell body. What overall effect would this have on action potential generation?

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Textbook Question

What would happen if the drug blocked K⁺ channels instead?

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Multiple Choice

Why does depolarization occur in a neuron during an action potential?

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Multiple Choice

Which of the following would be likely to cause depolarization of a neuron?