Comp Vert Chapter 10 (Exam 2)

1. What are the seven major functions of muscles?

Locomotion, posture, circulation, digestion, respiration, sphincter control, and heat production.

2. What are the three types of muscle tissue?

Skeletal, cardiac, and smooth muscle.

3. What are the characteristics of skeletal muscle?

Striated, generally voluntary, long fibers, and multiple nuclei.

4. What are the characteristics of cardiac muscle?

Striated, involuntary, often branched cells, and intercalated discs.

5. What are the characteristics of smooth muscle?

Nonstriated, involuntary, spindle-shaped cells with one nucleus.

6. Where is cardiac muscle found?

In the heart, where it pumps blood through rhythmic contractions.

7. What is the function of smooth muscle?

Controls movements of internal organs, blood vessels, and digestive structures.

8. What are intercalated discs?

Connections between cardiac muscle cells that help coordinate contractions.

9. What is the organization of skeletal muscle from largest to smallest?

Whole muscle → fascicle → muscle fiber → myofibril → sarcomere → myofilaments.

10. What is a fascicle?

A bundle of muscle fibers.

11. What is a muscle fiber?

An individual muscle cell.

12. What is a myofibril?

A long contractile structure containing repeating sarcomeres.

13. What is a sarcomere?

The repeating contractile unit of skeletal muscle.

14. What are the two major contractile proteins?

Actin and myosin.

15. What is the difference between actin and myosin?

Actin forms thin filaments; myosin forms thick filaments.

16. What is endomysium?

Connective tissue surrounding an individual muscle fiber.

17. What is perimysium?

Connective tissue surrounding a fascicle.

18. What is epimysium?

Connective tissue surrounding an entire muscle.

19. What is the sarcolemma?

The plasma membrane of a muscle cell.

20. What is the sarcoplasmic reticulum?

Specialized smooth endoplasmic reticulum that helps regulate contraction.

21. What are T-tubules?

Extensions of the sarcolemma that carry electrical excitation deep into muscle fibers.

22. What is a motor unit?

A motor neuron and all muscle fibers it innervates.

23. What is the motor end plate?

The specialized region where a motor neuron communicates with a muscle fiber.

24. What is a tendon?

Strong connective tissue that transmits muscle force to skeletal elements.

25. What is the difference between an aponeurosis and fascia?

An aponeurosis is a broad, flat tendon; fascia surrounds and supports body structures.

26. What is the sliding filament mechanism?

Myosin interacts with actin, causing filaments to slide past one another and shorten sarcomeres.

27. Do actin and myosin filaments shorten during contraction?

No. They slide past one another, increasing overlap.

28. What is a cross-bridge?

A temporary connection between myosin and actin during contraction.

29. What is the role of T-tubules during contraction?

They transmit excitation into the muscle fiber to help initiate contraction.

30. At what muscle length is active tension greatest?

At an optimal intermediate length with favorable actin-myosin overlap.

31. Why does an overstretched muscle produce less active tension?

There is insufficient overlap between actin and myosin to form many cross-bridges.

32. Why does an excessively shortened muscle produce less active tension?

Excessive filament overlap interferes with effective cross-bridge activity.

33. What is red muscle specialized for?

Sustained activity and endurance.

34. What are the characteristics of red muscle?

High myoglobin, rich blood supply, and strong fatigue resistance.

35. What is myoglobin?

An oxygen-storing protein found in muscle.

36. What is white muscle specialized for?

Rapid, forceful contractions during short bursts of activity.

37. What are the characteristics of white muscle?

Lower myoglobin, less extensive blood supply, and faster fatigue.

38. What is the difference between tonic and twitch fibers?

Tonic fibers sustain slow contractions; twitch fibers produce relatively rapid contractions.

39. What are slow-twitch (S) fibers?

Fibers that develop force slowly and resist fatigue.

40. What are fast-twitch fatigable (FF) fibers?

Fibers that generate high force rapidly but fatigue quickly.

41. What are fast-twitch fatigue-resistant (FR) fibers?

Fibers that contract rapidly and resist fatigue better than FF fibers.

42. What are fast-twitch intermediate (FI) fibers?

Fast fibers with intermediate force and fatigue characteristics.

43. What is the general muscle fiber recruitment sequence?

Slow-twitch → fast fatigue-resistant → fast fatigable, as force demand increases.

44. What is passive tension?

Resistance generated when a relaxed muscle is stretched.

45. What is active tension?

Force generated by actin-myosin interactions in contracting muscle.

46. What is the formula for total muscle tension?

Total tension = Active tension + Passive tension.

47. How do you calculate active tension?

Active tension = Total tension − Passive tension.

48. What are the two main ways muscles increase force?

Recruiting more motor units and increasing stimulation frequency.

49. How does physiological cross-sectional area affect muscle force?

Greater physiological cross-sectional area generally increases force-producing capacity.

50. What is the main advantage of parallel muscles?

Greater shortening distance and velocity.

Question

Answer

51. What is the main advantage of pinnate muscles?

Greater force production due to more contractile fibers packed into a given volume.

52. How are muscle fibers arranged in parallel muscles?

Fibers run along the long axis of the muscle.

53. How are muscle fibers arranged in pinnate muscles?

Fibers attach at an angle to a tendon.

54. What is the advantage of sarcomeres arranged in series?

Greater shortening distance and absolute shortening speed.

55. What is the advantage of muscle fibers arranged in parallel?

Greater force production.

56. What is a lever system in skeletal movement?

Bones act as levers, joints as pivots, and muscles provide force against a load.

57. What is the advantage of a proximal muscle insertion?

A shorter moment arm generally favors movement speed and range.

58. What is the advantage of a more distal muscle insertion?

A longer moment arm can increase joint torque and mechanical advantage.

59. What is an agonist or prime mover?

The muscle mainly responsible for producing a particular movement.

60. What is a synergist?

A muscle that works with another muscle to produce a movement.

61. What is an antagonist?

A muscle that produces movement opposing another muscle.

62. What is a fixator?

A muscle that stabilizes a structure or joint during movement.

63. What is the difference between muscle origin and insertion?

The origin is relatively fixed; the insertion is relatively movable.

64. What is the function of the geniohyoid?

Moves the hyoid forward or helps depress the mandible when the hyoid is stabilized.

65. What is flexion versus extension?

Flexion bends a joint; extension straightens a joint.

66. What is adduction versus abduction?

Adduction moves toward the midline; abduction moves away.

67. What is protraction versus retraction?

Protraction moves a structure forward; retraction moves it backward.

68. What is muscle homology?

Muscles sharing a common evolutionary origin.

69. What are important criteria for identifying homologous muscles?

Similar attachments, function, innervation, and embryonic origin.

70. Why is innervation important when studying muscle homology?

Nerve supply may remain conserved despite evolutionary changes in muscle shape or function.

71. What is paraxial mesoderm?

Embryonic tissue beside the neural tube contributing to much of the skeletal musculature.

72. What are somites?

Paired, segmented embryonic structures that contribute to skeletal, dermal, and muscular tissues.

73. What are the three main components of a somite?

Sclerotome, dermatome, and myotome.

74. What does the sclerotome develop into?

Vertebral skeletal structures.

75. What does the dermatome develop into?

The dermis.

76. What does the myotome develop into?

Skeletal musculature.

77. What are somitomeres?

Cranial embryonic structures associated with development of head muscles.

78. What are epaxial muscles?

Dorsal axial muscles involved in vertebral movement and stabilization.

79. What are hypaxial muscles?

Ventral and lateral axial muscles involved in body-wall movement, support, and respiration.

80. What separates epaxial and hypaxial muscles in jawed fishes?

The horizontal septum.

81. What is the primary locomotor role of axial muscles in fishes?

Generating lateral undulations that produce swimming thrust.

82. What happened to appendicular musculature during tetrapod evolution?

It became larger and more specialized as limbs gained importance in movement and support.

83. What are the three major epaxial muscle groups in amniotes?

Transversospinalis, longissimus, and iliocostalis.

84. Name the major hypaxial muscle groups emphasized in the study guide.

Subvertebralis, longus colli, transversus abdominis, obliques, intercostals, and rectus abdominis.

85. What is the muscular sling?

Muscles that suspend and stabilize the trunk between the forelimbs.

86. Which four muscles contribute to the pectoral muscular sling?

Trapezius, rhomboideus, serratus ventralis, and levator scapulae.

87. What are the major dorsal forelimb muscle derivatives?

Deltoid, latissimus dorsi, triceps, and forearm extensors.

88. What are the major ventral forelimb muscle derivatives?

Pectoralis, supracoracoideus derivatives, biceps brachii, and forearm flexors.

89. What are the major dorsal hindlimb muscle derivatives?

Gluteal complex, iliacus, psoas, quadriceps, sartorius, and tibialis anterior.

90. What are the major ventral hindlimb muscle derivatives?

Adductor femoris, gracilis, hamstrings, and gastrocnemius.

91. What three muscles make up the hamstring group?

Semimembranosus, semitendinosus, and biceps femoris.

92. Why do running animals concentrate muscle mass close to the trunk?

It reduces distal limb mass and improves running efficiency.

93. What is the function of the pectoralis in bird flight?

Produces the powerful wing downstroke.

94. What is the function of the supracoracoideus in bird flight?

Elevates the wing during the upstroke through a pulley-like tendon arrangement.

95. What is branchiomeric musculature?

Muscles associated with embryonic pharyngeal arches, involved in jaw, gill, and facial movements.

96. What is hypobranchial musculature?

Muscles originating from trunk somites that migrate toward the jaw, hyoid, throat, and tongue regions.

97. Which mammalian jaw muscles evolved from adductor mandibulae derivatives?

Masseter, temporalis, and pterygoid muscles.

98. Which cranial nerves control the six major extrinsic eye muscles?

CN III controls most; CN IV controls superior oblique; CN VI controls lateral rectus.