Textbook Question
Why is it difficult to lift a heavy object when the elbow is at full extension?
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Ch. 11 The Muscular System
Martini, Nath, Bartholomew11th EditionFundamentals of Anatomy & PhysiologyISBN: 9780136874089
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Table of contents
- Ch. 1 An Introduction to Anatomy and Physiology26
- Ch. 2 The Chemical Level of Organization34
- Ch. 3 The Cellular Level of Organization30
- Ch. 4 The Tissue Level of Organization24
- Ch. 5 The Integumentary System17
- Ch. 6 Bones and Bone Structure36
- Ch. 7 The Axial Skeleton11
- Ch. 8 The Appendicular Skeleton17
- Ch. 9 Joints13
- Ch. 10 Muscle Tissue12
- Ch. 11 The Muscular System28
- Ch. 12 Nervous Tissue18
- Ch. 13 The Spinal Cord, Spinal Nerves, and Spinal Reflexes22
- Ch. 14 The Brain and Cranial Nerves20
- Ch. 15 Sensory Pathways and the Somatic Nervous System17
- Ch. 16 The Autonomic Nervous System and Higher-Order Functions30
- Ch. 17 The Special Senses16
- Ch. 18 The Endocrine System20
- Ch. 19 Blood31
- Ch. 20 The Heart31
- Ch. 21 Blood Vessels and Circulation29
- Ch. 22 The Lymphatic System and Immunity31
- Ch. 23 The Respiratory System12
- Ch. 24 The Digestive System18
- Ch. 26 The Urinary System31
- Ch. 27 Fluids & Electrolytes32
- Ch. 28 The Reproductive System12
- Ch. 29 Development and Inheritance23
Martini, Nath, Bartholomew11th EditionFundamentals of Anatomy & PhysiologyISBN: 9780136874089Not the one you use?Change textbook
Chapter 11, Problem 26
Why can a pennate muscle generate more tension than can a parallel muscle of the same size?
Verified step by step guidance1
Understand the basic difference in muscle fiber arrangement: a parallel muscle has fibers running parallel to the force-generating axis, while a pennate muscle has fibers arranged at an angle to this axis.
Recognize that the force a muscle can generate is proportional to its physiological cross-sectional area (PCSA), which accounts for the total area of all muscle fibers perpendicular to their length.
Note that in pennate muscles, because fibers are angled, more fibers can be packed into the same muscle volume compared to parallel muscles, increasing the PCSA.
Use the relationship that the total force generated by the muscle is the sum of the forces produced by all fibers, so a greater PCSA means greater total force despite the angle of fibers.
Conclude that although each fiber in a pennate muscle contributes less force along the muscle's line of action due to the angle, the increased number of fibers (and thus greater PCSA) allows the pennate muscle to generate more overall tension than a parallel muscle of the same size.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Muscle Architecture
Muscle architecture refers to the arrangement of muscle fibers relative to the force-generating axis. Pennate muscles have fibers oriented at an angle to the tendon, allowing more fibers to pack into a given volume, while parallel muscles have fibers aligned along the force axis.
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Introduction to Muscles and Muscle Tissue Example 1
Physiological Cross-Sectional Area (PCSA)
PCSA is the total cross-sectional area of all muscle fibers perpendicular to their direction. Pennate muscles have a larger PCSA than parallel muscles of the same size, enabling them to generate greater force because tension is proportional to PCSA.
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Force Generation and Fiber Angle
In pennate muscles, fibers pull at an angle, so individual fiber force contributes less directly to tendon force. However, the increased number of fibers compensates for this, resulting in higher overall tension compared to parallel muscles where fibers pull directly along the tendon.
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Related Practice
Textbook Question
Why does a convergent muscle exhibit more versatility when contracting than does a parallel muscle?
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Textbook Question
Elongated bursae that reduce friction and surround the tendons that cross the posterior and anterior surfaces of the wrist form___.
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Textbook Question
Mary sees Jill coming toward her and immediately contracts her frontalis and procerus. She also contracts her right levator labii. Is Mary glad to see Jill? How can you tell?
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Textbook Question
Mary's newborn is having trouble suckling. The doctor suggests that it may be a problem with a particular muscle. What muscle is the doctor probably referring to?
(a) Orbicularis oris
(b) Buccinator
(c) Masseter
(d) Risorius
(e) Zygomaticus
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Textbook Question
The muscles of the vertebral column include many posterior extensors but few anterior flexors. Why?
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