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Ch. 10 Muscle Tissue
Martini - Fundamentals of Anatomy and Physiology 12th Edition
Martini, Nath, Bartholomew12th EditionFundamentals of Anatomy and PhysiologyISBN: 9780137854011Not the one you use?Change textbook
All textbooksMartini, Nath, Bartholomew 12th EditionCh. 10 Muscle TissueProblem 8
Chapter 10, Problem 8

An action potential can travel quickly from one cardiac muscle cell to another because of the presence of
(a) Gap junctions
(b) Tight junctions
(c) Intercalated discs
(d) Both a and c

Verified step by step guidance
1
Step 1: Understand the structure of cardiac muscle cells and how they connect to each other. Cardiac muscle cells are connected by specialized structures that allow electrical signals to pass rapidly between cells.
Step 2: Identify the role of gap junctions. Gap junctions are channels that directly connect the cytoplasm of adjacent cells, allowing ions and small molecules to pass freely, which facilitates the rapid spread of action potentials.
Step 3: Recognize the function of intercalated discs. Intercalated discs are complex structures that include gap junctions and desmosomes; they physically and electrically connect cardiac muscle cells.
Step 4: Differentiate tight junctions from gap junctions. Tight junctions create a seal between cells to prevent leakage of extracellular fluid, but they do not facilitate electrical conduction.
Step 5: Conclude that the rapid transmission of action potentials in cardiac muscle cells is due to both gap junctions and intercalated discs working together, making option (d) the correct choice.

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Key Concepts

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

Action Potential in Cardiac Muscle

An action potential is an electrical signal that triggers muscle contraction. In cardiac muscle, it propagates rapidly to ensure coordinated heartbeats, enabling the heart to pump blood efficiently.
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Cardiac Action Potentials Example 3

Gap Junctions

Gap junctions are specialized connections between cardiac muscle cells that allow direct electrical communication. They enable ions and small molecules to pass quickly, facilitating rapid transmission of action potentials.
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Cell Junctions

Intercalated Discs

Intercalated discs are complex structures that connect cardiac muscle cells. They contain gap junctions and desmosomes, providing both mechanical strength and electrical connectivity for synchronized contraction.
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Structure of the Sarcomere: Bands, Zones, Discs & Lines
Related Practice
Textbook Question

Identify the structures in the following figure.

a. ___

b. ___

c. ___

d. ___

e. ___

f. ___

g. ___

h. ___

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Textbook Question

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

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Textbook Question

Which of the following statements about myofibrils is not correct?

(a) Each skeletal muscle fiber contains hundreds to thousands of myofibrils.

(b) Myofibrils contain repeating units called sarcomeres.

(c) Myofibrils extend the length of a skeletal muscle fiber.

(d) Filaments consist of bundles of myofibrils.

(e) Myofibrils are attached to the plasma membrane at both ends of a muscle fiber.

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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 three layers of connective tissue are part of each muscle? What functional role does each layer play?

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