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 L3.4

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.

Verified step by step guidance

Understand the refractory period: The refractory period is the time during which a cell cannot initiate another action potential. In cardiac muscle cells, the refractory period is much longer than in skeletal muscle fibers, ensuring that the heart has time to contract and relax fully before the next contraction.

Compare cardiac and skeletal muscle refractory periods: Cardiac muscle cells have a refractory period lasting almost as long as the contraction itself, preventing tetanus (sustained contraction). Skeletal muscle fibers, on the other hand, have a much shorter refractory period, allowing for rapid and repeated contractions.

Predict the effect of the toxin: If the toxin shortens the refractory period of cardiac muscle cells to match that of skeletal muscle fibers, the heart could potentially experience tetanic contractions. This would disrupt the normal rhythmic pumping action of the heart, as the heart would not have time to relax between contractions.

Consider physiological consequences: Tetanic contractions in the heart would impair its ability to pump blood effectively, leading to reduced oxygen and nutrient delivery to tissues and potentially causing severe cardiovascular complications, such as heart failure or arrhythmias.

Relate to clinical implications: This scenario highlights the importance of the long refractory period in cardiac muscle cells for maintaining proper heart function. Any disruption to this mechanism, such as through toxins or diseases, could have life-threatening consequences.

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.

Refractory Period

The refractory period is the time during which a cell is unable to respond to a second stimulus after an initial action potential. In cardiac muscle cells, this period is longer than in skeletal muscle fibers, preventing tetanus and allowing the heart to fill with blood between beats. If the refractory period is equalized with that of skeletal muscle, it could lead to continuous contractions, compromising the heart's ability to pump effectively.

Cardiac Muscle Physiology

Cardiac muscle is specialized for continuous, rhythmic contractions and has unique properties, including automaticity and a prolonged refractory period. This allows the heart to maintain a steady rhythm and prevents arrhythmias. Altering the refractory period to match that of skeletal muscle could disrupt this rhythm, leading to potentially fatal arrhythmias or ineffective heart function.

Tetanus in Muscle Contraction

Tetanus refers to a sustained muscle contraction resulting from rapid stimulation without relaxation. In skeletal muscle, this can enhance force production, but in cardiac muscle, it is detrimental. If cardiac muscle cells experience tetanus due to a shortened refractory period, the heart would not relax properly, leading to inadequate blood flow and severe cardiovascular complications.

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 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

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.

471

views

Textbook Question

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

451

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 __________.

Which of the following correctly identifies a difference between action potentials in cardiac and skeletal muscle?

Calcium ion channels open in response to changes in membrane potential. What type of opening mechanism do calcium ion channels in cardiac muscle exhibit?

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap