1. Chapter 10: Anatomy of the Muscular System

2. INTRODUCTION
The body contains more than 600 skeletal muscles (Figures 10-5 and 10-6)
From 40% to 50% of body weight is skeletal muscle
Muscles, along with the skeleton, determine the form and contour of the body

5. SKELETAL MUSCLE STRUCTURE (cont.)
Attachment of muscles (Figure 10-3)
Origin: point of attachment that does not move when the muscle contracts
Insertion: point of attachment that moves when the muscle contracts

7. SKELETAL MUSCLE STRUCTURE (cont.)
Muscle actions (Figure 10-4)
Most movements are produced by the coordinated action of several muscles; some muscles in the group contract while others relax
Prime mover: a muscle that directly performs a specific movement
Agonists: any “mover” muscle that directly performs a movement, including the prime mover
Antagonist: muscles that, when contracting, directly oppose prime movers; relax while the prime mover (agonist) is contracting to produce movement; provide precision and control during contraction of prime movers
Synergists: muscles that contract at the same time as the prime movers; facilitate prime mover actions to produce a more efficient movement
Fixator muscles: joint stabilizers (type of synergist)

9. HOW MUSCLES ARE NAMED
Muscle names can be in Latin or English (this text uses English)
Muscles are named according to one or more of the following features:
Location, function, shape (Tables 10-2 to 10-4)
Direction of fibers: named according to fiber orientation (Table 10-5)
Number of heads or divisions (Table 10-5)
Points of attachment: origin and insertion points
Relative size: small, medium, or large (Table 10-6)
Hints on how to deduce muscle actions

23. 1. Which of these usually is under conscious control?
A. Cardiac muscle
B. Smooth muscle
C. Skeletal muscle
Chapter: 10
Answer: C
Discussion: This item presents a good opportunity to discuss the term “voluntary muscle,” meaning under conscious control. Some will argue that smooth or cardiac muscle can be altered by biofeedback, meditation, etc., but really that is the conscious mind influencing subconscious processes—a good point of discussion. Also, one could argue that quiet breathing usually is a subconscious process, as is the knee-jerk reflex, but both involve skeletal muscles—another good discussion point.

24. 2. A good example of an antagonist is the ________ .
A. Rectus abdominis
B. Gluteus maximus
C. Pectoralis major
D. Deltoid
Chapter: 10
Answer: B
Discussion: During flexion of the hip, the three iliopsoas muscles are the prime movers and the gluteus maximus acts as the antagonist. The other muscles are agonists.
Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc., an affiliate of Elsevier Inc.

25. 3. Contraction of the “prayer muscles” prevents the…
A. Head from falling backward.
B. Hands from losing grip.
C. Knees from becoming overextended.
D. Vertebral column from extreme flexion.
Chapter: 10
Answer: A
Discussion: The two ropelike sternocleidomastoids, or “prayer muscles,” contract to bring the head forward and down, bowing the head.
Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc., an affiliate of Elsevier Inc.

26. 4. When doing a full-body push-up, your body acts as a ____-class lever.
A. First
B. Second
C. Third
Chapter: 10
Answer: B
Discussion: A full-body push-up is a second-class lever in which the foot is the fulcrum, the body weight is the load, and the force is applied by the hands against the ground.
Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc., an affiliate of Elsevier Inc.

27. B. Causes you to stand on your toes.
5. Plantar flexion...
A. Bends the elbow.
B. Causes you to stand on your toes.
C. Causes you to stand on your heels.
D. Bends the wrist.
E. Moves the leg out to the side of the body.
Chapter: 10
Answer: B
Discussion: C is dorsiflexion. Follow-up: ask which terms describe each of the other actions, then ask which muscles are involved in each action.
Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc., an affiliate of Elsevier Inc.

28. 6. Which of the following is NOT a consequence of poor posture?
A. Poor respiration
B. Spinal deformities
C. Strained ligaments
D. Increased muscle fatigue
E. Increased abdominal cavity volume
Chapter: 10
Answer: E
Discussion: Poor posture causes the volume of the abdominal cavity to decrease, which can make digestion more difficult.
Mosby items and derived items © 2010, 2007, 2003 by Mosby, Inc., an affiliate of Elsevier Inc.

29. Chapter 11: Physiology of the Muscular System

30. INTRODUCTION
The muscular system is responsible for moving the framework of the body
In addition to movement, muscle tissue performs various other functions

31. GENERAL FUNCTIONS
Movement of the body as a whole or movement of its parts
Heat production
Posture

32. Overview of the muscle cell (Figures 11-1 and 11-2)
Muscle cells are called fibers because of their threadlike shape
Sarcolemma: plasma membrane of muscle fibers
Sarcoplasmic reticulum (SR)
T tubules: network of tubules and sacs found within muscle fibers
Membrane of the SR continually pumps calcium ions from the sarcoplasm and stores the ions within its sacs for later release (Figure 11-3)

35. FUNCTION OF SKELETAL MUSCLE TISSUE (cont.)
Muscle fibers contain many mitochondria and several nuclei
Myofibrils: numerous fine fibers packed close together in sarcoplasm
Sarcomere
Segment of myofibril between two successive Z disks
Contractile unit of muscle fibers
Striated muscle (Figure 11-4)
Dark stripes called A bands; light H zone runs across the midsection of each dark A band
Light stripes called I bands; dark Z disk extends across the center of each light I band

37. FUNCTION OF SKELETAL MUSCLE TISSUE (cont.)
T tubules
Transverse tubules extend across the sarcoplasm at right angles to the long axis of the muscle fiber
Formed by inward extensions of the sarcolemma
Membrane has ion pumps that continually transport calcium ions inward from the sarcoplasm
Allow electrical impulses traveling along the sarcolemma to move deeper into the cell
Triad
Triplet of tubules; a T tubule sandwiched between two sacs of SR
Allows an electrical impulse traveling along a T tubule to stimulate the membranes of adjacent sacs of the SR

38. FUNCTION OF SKELETAL MUSCLE TISSUE (cont.)
Myofilaments (Figures 11-5 and 11-6)
Each myofibril contains thousands of thick and thin myofilaments
Four different kinds of protein molecules make up myofilaments
Myosins
Makes up almost all the thick filament
Myosin “heads” are chemically attracted to actin molecules
Myosin “heads” are known as cross bridges when attached to actin
Actin: globular protein that forms two fibrous strands twisted around each other to form the bulk of the thin filament
Tropomyosin: protein that blocks the active sites on actin molecules
Troponin: protein that holds tropomyosin molecules in place
Thin filaments attach to both Z disks (Z lines) of a sarcomere and extend partway toward the center
Thick myosin filaments do not attach to the Z disks

41. FUNCTION OF SKELETAL MUSCLE TISSUE (cont.)
Mechanism of contraction
Excitation and contraction (Figures 11-7 to 11-13; Table 11-1)
A skeletal muscle fiber remains at rest until stimulated by a motor neuron
Neuromuscular junction: motor neurons connect to the sarcolemma at the motor endplate
Neuromuscular junction is a synapse where neurotransmitter molecules transmit signals
Acetylcholine: the neurotransmitter released into the synaptic cleft that diffuses across the gap, stimulates the receptors, and initiates an impulse in the sarcolemma
Nerve impulse travels over the sarcolemma and inward along the T tubules, which triggers the release of calcium ions (Ca++)
Ca++ binds to troponin, which causes tropomyosin to shift and expose active sites on actin

49. FUNCTION OF SKELETAL MUSCLE TISSUE (cont.)
Excitation and contraction (cont.)
Sliding filament model
When active sites on actin are exposed, myosin heads bind to them
Myosin heads bend and pull the thin filaments past them
Each head releases, binds to the next active site, and pulls again
The entire myofibril shortens
Relaxation
Immediately after Ca++ is released, the SR begins actively pumping it back into the sacs
Ca++ is removed from the troponin molecules, thereby shutting down the contraction

50. FUNCTION OF SKELETAL MUSCLE TISSUE (cont.)
Energy sources for muscle contraction (Figure 11-14)
Hydrolysis of adenosine triphosphate (ATP) yields the energy required for muscular contraction
ATP binds to the myosin head and transfers its energy there to perform the work of pulling the thin filament during contraction
Muscle fibers continually resynthesized ATP from the breakdown of creatine phosphate
Catabolism by muscle fibers requires glucose and oxygen (O2)
At rest, excess O2 in the sarcoplasm is bound to myoglobin (Box 11-4)
Red fibers: muscle fibers with high levels of myoglobin
White fibers: muscle fibers with little myoglobin
Aerobic respiration
Occurs when adequate O2 is available from blood (Figure 11-15)
Slower than anaerobic respiration; thus supplies energy for the long term rather than the short term

53. FUNCTION OF SKELETAL MUSCLE TISSUE (cont.)
Anaerobic respiration (Figure 11-16)
Very rapid, providing energy during first minutes of maximal exercise (Figure 11-16)
May occur when low levels of O2 are available
Results in the formation of lactic acid, which requires O2 to convert back to glucose, the producing of an “oxygen debt,” or excess postexercise O2 consumption
Glucose and O2 supplied to muscle fibers by blood capillaries (Figure 11-15)
Skeletal muscle contraction produces waste heat that can be used to help maintain the set point body temperature (Figure 11-17)

61. GRADED STRENGTH PRINCIPLE
Skeletal muscles contract with varying degrees of strength at different times
Factors that contribute to the phenomenon of graded strength (Figure 11-26):
Metabolic condition of individual fibers
Number of muscle fibers contracting simultaneously; the greater the number of fibers contracting, the stronger the contraction
Number of motor units recruited
Intensity and frequency of stimulation (Figure 11-23)

66. GRADED STRENGTH PRINCIPLE (cont.)
Isotonic contraction
Contraction in which the tone or tension within a muscle remains the same as the length of the muscle changes
Concentric: muscle shortens as it contracts
Eccentric: muscle lengthens while contracting
Isotonic means “same tension”
Isometric contraction
Contraction in which muscle length remains the same while muscle tension increases
Isometric means “same length”
Most body movements occur as a result of both types of contractions

68. FUNCTION OF CARDIAC AND SMOOTH MUSCLE TISSUE
Cardiac muscle (Figure 11-28; Table 11-1)
Found only in the heart; forms the bulk of the wall of each chamber
Also known as striated involuntary muscle
Contracts rhythmically and continuously to provide the pumping action needed to maintain constant blood flow

70. FUNCTION OF CARDIAC AND SMOOTH MUSCLE TISSUE (cont.)
Cardiac muscle resembles skeletal muscle but has unique features related to its role in continuously pumping blood
Each cardiac muscle contains parallel myofibrils (Figure 11-28)
Cardiac muscle fibers form strong, electrically coupled junctions (intercalated disks) with other fibers; individual cells also exhibit branching
Cardiac muscle does not run low on ATP or experience fatigue
Cardiac muscle is self-stimulating

72. FUNCTION OF CARDIAC AND SMOOTH MUSCLE TISSUE (cont.)
Smooth muscle is composed of small, tapered cells with single nuclei (Figure 11-30)
No striations because thick and thin myofilaments are arranged differently than in skeletal or cardiac muscle fibers; myofilaments are not organized into sarcomeres