Download Chapter 11 Muscular System

CHAPTER 12
MUSCULAR SYSTEM
BEHAVIORAL OBJECTIVES
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List the functions of skeletal muscle. [12.1, p.226]
Describe the anatomy of a whole muscle. [12.1, pp.226-227, Fig. 12.2]
Describe muscular attachments and antagonistic pairs. [12.1, p.227, Fig. 12.3]
Name the major muscles of the body, and know their actions. [12.1, p.228, Fig. 12.4, Tables 12.1 & 12.2]
Describe the anatomy of a muscle fiber. [12.1, p.226 & p.231, Figs. 12.2 & 12.5]
Explain how the sarcomere shortens during muscle contraction. [12.2, pp.230-231, Fig. 12.5]
Describe the neuromuscular junction, and explain how impulses are transferred to the muscle sarcolemma.
[12.2, p.232, Fig. 12.7]
Explain the role of calcium in muscle contraction. [12.2, p. 233, Fig. 12.8]
Describe the basic laboratory observations on whole muscle contraction. [12.3, p.234, Fig. 12.9]
Explain how muscle tone is maintained. [12.3, p.234]
Describe the benefits of physical exercise. [12.3, Health Focus, p.235]
List the energy sources available within a muscle fiber, and explain the circumstances in which each is used.
[12.4, pp.236-239, Fig. 12.10]
Discuss the events leading to oxygen debt. [12.4, p.236, Fig. 12.10]
Describe how exercise can increase muscle size. [12.4, p.238]
Contrast the functions of slow-twitch and fast-twitch fibers. [12.4, p.238, Fig. 12.11]
List a number of muscular disorders. [12.4, p. 240, Fig. 12.12]
Discuss how the muscular system works with other body systems to maintain homeostasis. [12.5, p.240-241,
Human Systems Work Together]
Describe the role of the muscular system in homeostasis. [12.5, p.240-241]
Understand and use the bold-faced and italicized terms included in this chapter. [Understanding Key Terms,
p.243]
EXTENDED LECTURE OUTLINE
12.1 Skeletal Muscles
Muscles have various functions. Skeletal muscles maintain posture, cause movement, produce heat, and assist in
movement within cardiovascular and lymphatic vessels. The contraction of cardiac muscle causes the heart to pump
blood. The contraction of smooth muscle propels food in the digestive tract and urine in the ureters.
The Structure of Muscles
Skeletal muscles are covered by fascia that extends beyond their ends as tendons. A muscle fiber contains many
contractile structures called myofibrils.
Muscles Work in Pairs
The origin of a muscle is the end attaching to the immovable bone; the insertion of a muscle is the end attaching to
the movable bone. Muscles are frequently grouped as synergists and antagonists. The muscle that works hardest is
the prime mover.
Skeletal Muscles of the Body
Skeletal muscles are named according to their size, shape, location, direction of fibers, number of attachments, or
action. Names and functions of the major muscles of the body are listed in Tables 12.1 and 12.2.
Mader VRL CD-ROM
Image 0225l.jpg (Fig. 12.1)
Image 0226l.jpg (Fig. 12.2)
Image 0227l.jpg (Fig. 12.3)
Image 0228al.jpg (Fig. 12.4)
Image 0228bl.jpg (Fig. 12.4)
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Mader VRL CD-ROM, con’t.
Image 0228cl.jpg (Fig. 12.4)
Image 0228dl.jpg (Fig. 12.4)
Image 0228el.jpg (Fig. 12.4)
Image 0228fl.jpg (Fig. 12.4)
Dynamic Human 2.0 CD-ROM
Muscular/Anatomy/Body Regions
Muscular/Anatomy/Cardiac Muscle
Muscular/Anatomy/Skeletal Muscle
Muscular/Anatomy/Smooth Muscle
Muscular/Explorations/Muscle Action Around a Joint
Life Science Animations VRL 2.0
Muscular/Clinical Concepts/MRI of Rotator Cuff
Animal Biology/Support and Movement/ How a Muscle Moves
Mader ESP Modules Online
Animals/Support and Locomotion/Muscles
Transparencies
169 (Fig. 12.2)
170 (Fig. 12.3)
171 (Fig. 12.4a)
172 (Fig. 12.4b)
12.2 Mechanism of Muscle Fiber Contraction
Overview of Muscular Contraction
The plasma membrane of a muscle fiber is its sarcolemma. Its endoplasmic reticulum is called the sarcoplasmic
reticulum, which stores calcium. The sarcolemma invaginates into T tubules that contact the sarcophasmic
reticulum. Within muscle fibers are the contractile myofibrils.
Myofibrils and Sarcomeres
Myofibrils are cylindrical structures within muscle fibers. Myofilaments that make up myofibrils are
arranged such that they exhibit striations. Striations are grouped into contractile units called sarcomeres.
Within sarcomeres, thick filaments are made up of myosin, and thin filaments are made up of actin.
Sliding Filaments
When a nervous impulse reaches a muscle fiber, the sarcoplasmic reticulum releases its stored calcium, and
the fiber contracts. The myosin filaments have cross-bridges that pull on the actin myofilaments, causing
them to slide past each other. The sliding filament theory states that the filaments do not change in length
as the sarcomere shortens.
Muscle Innervation
The region where a motor neuron contacts a muscle fiber is called the neuromuscular junction. A motor nerve fiber
expands into a synaptic end bulb as it approaches a muscle fiber. When a nerve impulse travels down the neuron,
synaptic vesicles storing a neurotransmitter acetylcholine (ACh) move to the end of the bulb, releasing the ACh into
the synaptic cleft.
The muscle fiber receives the neurotransmitter at receptor sites. The sarcolemma generates impulses that travel over
the sarcolemma to the T tubules and sarcoplasmic reticulum. Stored calcium is released to the cell, triggering
contraction.
Two proteins, troponin and tropomyosin, occur in conjunction with the actin filaments. Calcium binds with the
troponin, exposing a myosin-binding site.
Myosin cross-bridges bind to the revealed site on the actin filaments. ATP supplies energy to form the cross-bridges.
When ADP + P are released from mysoin, the cross-bridges change their position and pull the thin filaments toward
the middle of the sarcomere.
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Mader VRL CD-ROM
Image 0229al.jpg (Fig. 12.5)
Image 0229bl.jpg (Fig. 12.5)
Image 0229cl.jpg (Fig. 12.5)
Image 0230l.jpg (Fig. 12.6)
Image 0231l.jpg (Fig. 12.7)
Image 0232al.jpg (Fig. 12.8)
Image 0232bl.jpg (Fig. 12.8)
Dynamic Human 2.0 CD-ROM
Muscular/Explorations/Neuromuscular Junction
Muscular/Explorations/Sliding Filament Theory
Muscular/Histology/Cardiac Muscle
Muscular/Histology/Smooth Muscle
Muscular/Histology/Skeletal Muscle: Cross-Section
Muscular/Histology/Skeletal Muscle:Longitudinal
Muscular/Histology/Neuromuscular Junction
Life Science Animations VRL 2.0
Animal Biology/Support and Movement/ Contraction of a
Muscle
Animal Biology/Support and Movement/ Role of Calcium and
Myosin and Muscle Contraction
Animal Biology/Support and Movement/ Striated Muscle
Contraction
Animal Biology/Support and Movement/ Muscle Contraction
Action Potential
Animal Biology/Support and Movement/ Detailed Striated
Muscle Contraction
Animal Biology/Support and Movement/ Actin-Myosin
Crossbridges
Mader ESP Modules Online
Animals/Support and Locomotion/Muscle Cell Function
Transparencies
173 (Fig. 12.5)
174 (Fig. 12.7)
175 (Fig. 12.8a)
176 (Fig. 12.8b)
12.3 Whole Muscle Contraction
Basic Laboratory Observations
A myogram is the visual pattern generated from the recorded contraction of a muscle. A muscle twitch or single
contraction is divided into a latent period, a period of contraction, and a relaxation period. When a muscle receives a
rapid series of stimuli, it cannot relax between contractions. It contracts (summates) until it reaches a sustained
contraction, called tetanus.
Muscle Tone in the Body
Muscle tone results when portions of muscles are contracting while other portions relax. Maintenance of muscle
tone requires receptors called muscle spindles.
Recruitment and the Strength of Contraction
When a nervous impulse is received, all muscle fibers within the motor neuron contract together in a motor unit.
When more impulses are received, more motor units within a muscle contract (recruitment).
Mader VRL CD-ROM
Image 0233l.jpg (Fig. 12.9)
Transparencies
177 (Fig. 12.9)
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12.4 Energy for Muscle Contraction
ATP can be supplied to muscle in three different ways: One anaerobic pathway uses creatine phosphate to
regenerate ATP. A second anaerobic pathway, fermentation, provides energy without using oxygen. Fermentation
ends with lactic acid, which changes muscle pH, leading to fatigue. Aerobic respiration supplies muscles with most
of their energy. In people that exercise regularly, the number of mitochondria per muscle cell increases.
Oxygen Debt
Oxygen debt occurs when cells have used up available supplies of oxygen. Repaying oxygen debt means
replenishing creatine phosphate and converting lactic acid back to pyruvate.
Athletes and Muscle Contraction
Exercise and Size of Muscles
Atrophy occurs when muscles are unused. Forceful exercise (weight lifting) increases the number of
myofibrils in a muscle, leading to hypertrophy.
Slow-Twitch and Fast-Twitch Muscle Fibers
Slow-twitch fibers have more endurance and supply their energy aerobically. Fast-twitch fibers are
anaerobic and designed for strength but not endurance. They can develop maximum tension rapidly but
fatigue quickly.
Muscular Disorders
Tendonitis occurs when a tendon is inflamed and painful, and is due to physical strain. Muscular dystrophy is a
group of disorders in which there is a progressive degeneration of muscles. Myasthenia gravis is an autoimmune
disease in which antibodies destroy acetylcholine receptors. Muscular cramps and spasms are annoying, but not
serious, muscular disorders.
Mader VRL CD-ROM
Image 0234l.jpg (Fig. TA12.1)
Image 0235l.jpg (Fig. TA12.2)
Image 0236l.jpg (Fig. TA12.3)
Image 0237al.jpg (Fig. 12.10)
Image 0237bl.jpg (Fig. 12.10)
Image 0237cl.jpg (Fig. 12.10)
Image 0238l.jpg (Fig. 12.11)
Image 0239l.jpg (Fig. 12A)
Image 0240l.jpg (Fig. 12.12)
Dynamic Human 2.0 CD-ROM
Muscular/Explorations/Contraction: Isometric/Isotonic
Case Studies Online
Sports and Fitness
Transparencies
178 (Fig. 12.10)
179 (Fig. 12.11)
12.5 Homeostasis
The Human Systems Work Together box illustrates how the muscular system works with other body systems to
maintain homeostasis.
Mader VRL CD-ROM
Image 0241al.jpg (Fig. TA12.4)
Image 0241bl.jpg (Fig. TA12.4)
Image 0242l.jpg (Fig. TA12.5)
Transparencies
180 (Fig. TA12.1)
181 (Fig. TA12.2)
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SEVENTH EDITION CHANGES
New/Revised Text:
This was chapter 11 in the previous edition.
12.4 Energy for Muscle Contraction introductory paragraphs have been rewritten for clarity. The
discussion entitled Muscular Disorders is completely new and discusses muscle spasms and cramps, tendonitis,
tetanus, muscular dystrophy, and myasthenia gravis.
New/Revised Figures:
12.7 Neuromuscular junction; 12.12 Myasthenia gravis.
STUDENT ACTIVITIES
Physical Therapy As a Career
1. Invite a physical therapist or PTA to your classroom. Ask them to discuss the educational and vocational
requirements needed to become a physical therapist or PTA. Then ask them to describe the types of physical
therapy they use for different types of patients. Have them explain what activities they might do during a typical
day and invite students to ask questions.
Athletic Department Weight Room
2. Take your students to your local Althetic Department weight room and have an athletic trainer show some of
the muscle-building exercises that aer suggested for different sports. Have them show your students how to
work different muscle groups, being sure to name muscles and discuss how muscles work in groups.
Exercise Specialist
3. Ask a campus coach, athletic trainer, or aerobic dance instructor to come to your class and discuss the
importance of aerobic exercise. Request that the speaker includes such topics as: what type of exercise to begin
if you do not exercise at all; the importance of stretching, as well as types and duration of stretches before and
after exercise; the need for a minimum of 20 minutes of aerobic activity; how to determine whether you are
achieving aerobic activity; and muscle toning. Demonstrations are useful for this topic. Include a discussion of
Table 12A, “A Checklist for Staying Fit”.
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