Anatomy & Physiology: The Unity of Form and Function, 7th Edition

Published by McGraw-Hill Education
ISBN 10: 0073403717
ISBN 13: 978-0-07340-371-7

Chapter 19 - Section 19.3 - Cardiac Muscle and the Cardiac Conduction System - Before You Go On - Page 722: 10

Answer

Cardiac muscle and skeletal muscle are two different types of muscle tissues in the human body. They have distinct characteristics and functions, and their cellular structures reflect these differences. Here's a comparison of the development of organelles in cardiac and skeletal muscles: **Less Developed Organelles in Cardiac Muscle:** 1. **Sarcoplasmic Reticulum (SR):** The sarcoplasmic reticulum is an organelle in muscle cells responsible for storing and releasing calcium ions, which play a critical role in muscle contraction. In cardiac muscle, the SR is less developed compared to skeletal muscle. This can lead to a slower calcium release and reuptake process in cardiac muscle cells. **More Developed Organelles in Cardiac Muscle:** 1. **Mitochondria:** Cardiac muscle cells have a higher density of mitochondria compared to skeletal muscle cells. Mitochondria are responsible for producing energy (ATP) through cellular respiration. This increased mitochondrial density in cardiac muscle is essential because the heart requires a continuous supply of energy to maintain its rhythmic contractions. **Functional Significance of Differences:** 1. **Sarcoplasmic Reticulum (SR) Difference:** The less developed SR in cardiac muscle contributes to a slower and more prolonged contraction and relaxation process. This is important for ensuring adequate filling and ejection of blood from the heart chambers, allowing the heart to efficiently pump blood throughout the body. The prolonged contraction also prevents the heart from reaching tetanus (sustained contraction) and allows the heart muscle to relax between beats. 2. **Mitochondrial Density Difference:** The higher density of mitochondria in cardiac muscle provides the energy required for continuous and sustained contraction. Unlike skeletal muscles, which can experience fatigue during prolonged activity, the heart must contract rhythmically without tiring. The abundant mitochondria support the oxidative metabolism needed to generate ATP efficiently, allowing the heart to function reliably. In summary, the differences in organelle development between cardiac and skeletal muscles are closely related to their distinct functions. Cardiac muscle's less developed SR and higher mitochondrial density are adaptations that support its specialized role in maintaining the heart's continuous pumping action and preventing fatigue during constant rhythmic contractions.

Work Step by Step

Cardiac muscle and skeletal muscle are two different types of muscle tissues in the human body. They have distinct characteristics and functions, and their cellular structures reflect these differences. Here's a comparison of the development of organelles in cardiac and skeletal muscles: **Less Developed Organelles in Cardiac Muscle:** 1. **Sarcoplasmic Reticulum (SR):** The sarcoplasmic reticulum is an organelle in muscle cells responsible for storing and releasing calcium ions, which play a critical role in muscle contraction. In cardiac muscle, the SR is less developed compared to skeletal muscle. This can lead to a slower calcium release and reuptake process in cardiac muscle cells. **More Developed Organelles in Cardiac Muscle:** 1. **Mitochondria:** Cardiac muscle cells have a higher density of mitochondria compared to skeletal muscle cells. Mitochondria are responsible for producing energy (ATP) through cellular respiration. This increased mitochondrial density in cardiac muscle is essential because the heart requires a continuous supply of energy to maintain its rhythmic contractions. **Functional Significance of Differences:** 1. **Sarcoplasmic Reticulum (SR) Difference:** The less developed SR in cardiac muscle contributes to a slower and more prolonged contraction and relaxation process. This is important for ensuring adequate filling and ejection of blood from the heart chambers, allowing the heart to efficiently pump blood throughout the body. The prolonged contraction also prevents the heart from reaching tetanus (sustained contraction) and allows the heart muscle to relax between beats. 2. **Mitochondrial Density Difference:** The higher density of mitochondria in cardiac muscle provides the energy required for continuous and sustained contraction. Unlike skeletal muscles, which can experience fatigue during prolonged activity, the heart must contract rhythmically without tiring. The abundant mitochondria support the oxidative metabolism needed to generate ATP efficiently, allowing the heart to function reliably. In summary, the differences in organelle development between cardiac and skeletal muscles are closely related to their distinct functions. Cardiac muscle's less developed SR and higher mitochondrial density are adaptations that support its specialized role in maintaining the heart's continuous pumping action and preventing fatigue during constant rhythmic contractions.
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