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

18. The Heart

Cardiac Action Potentials

Anatomy & Physiology

18. The Heart

Cardiac Action Potentials

Previous problemNext problem

Problem 8e

Textbook Question

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.
Open sodium ion channels cause hyperpolarization in pacemaker cells, which triggers HCN channels to open and begins a new action potential.

Verified step by step guidance

Step 1: Understand the role of sodium ion channels in pacemaker cells. Sodium ion channels typically allow sodium ions (Na⁺) to flow into the cell, leading to depolarization rather than hyperpolarization. Hyperpolarization occurs when the membrane potential becomes more negative, which is usually caused by potassium ion (K⁺) efflux or chloride ion (Cl⁻) influx.

Step 2: Review the function of HCN (hyperpolarization-activated cyclic nucleotide-gated) channels. These channels open in response to hyperpolarization, allowing sodium ions to enter the cell and contribute to the gradual depolarization that initiates a new action potential in pacemaker cells.

Step 3: Analyze the statement provided. The statement claims that open sodium ion channels cause hyperpolarization, which is incorrect. Sodium ion channels cause depolarization, not hyperpolarization.

Step 4: Correct the false statement. A true version of the statement would be: 'Open sodium ion channels cause depolarization in pacemaker cells, which triggers HCN channels to open and begins a new action potential.'

Step 5: Verify the corrected statement by reviewing the physiology of pacemaker cells and their action potential cycle, ensuring the explanation aligns with established scientific understanding.

Verified video answer for a similar problem:

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

Play a video:

Was this helpful?

Key Concepts

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

Hyperpolarization

Hyperpolarization refers to an increase in the membrane potential of a cell, making it more negative than the resting potential. In pacemaker cells, this occurs when ion channels, such as sodium channels, open, allowing positive ions to flow out or negative ions to flow in, which can inhibit the generation of action potentials.

Pacemaker Cells

Pacemaker cells are specialized cardiac cells that generate electrical impulses to regulate heart rhythm. They are primarily located in the sinoatrial node and are responsible for initiating the heartbeat by undergoing spontaneous depolarization, which leads to action potentials that trigger heart contractions.

HCN Channels

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are ion channels that open in response to hyperpolarization. They play a crucial role in pacemaker activity by allowing sodium ions to enter the cell, contributing to the depolarization phase of the action potential and facilitating the rhythmic firing of pacemaker cells.

Watch next

Master Introduction to Action Potential in Cardiac Cells with a bite sized video explanation from Bruce Bryan

Start learning

Related Videos

Related Practice

Textbook Question

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

The rapid depolarization phase of the contractile cell action potential is due to the opening of voltage-gated potassium ion channels.

456

views

Textbook Question

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

Pacemaker cells lack a distinct plateau phase.

431

views

Textbook Question

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

The plateau phase in contractile cells is due to the influx of calcium ions through calcium ion channels.

513

views

Textbook Question

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

The repolarization phase of the contractile cell is due to the potassium ions rushing into the cell through potassium ion channels.

475

views

Textbook Question

What are the effects of the plateau phase of the contractile cell action potential?

451

views

Textbook Question

An experimental toxin makes the refractory period of cardiac muscle cells equal in length to that of skeletal muscle fibers. Predict the consequences of this toxin.

384

views

Multiple Choice

The absolute refractory period refers to the time during which __________.

The noncontractile cardiac muscle cells that initiate their own depolarization and cause depolarization of the rest of the heart are called __________.

1373

views

rank