Muscle Physiology

Question 1

How many skeletal muscles are in the human body?

Answer 1

600

Question 2

What are the functions of skeletal muscle?

Answer 2

Movement
Stability
control of body openings/passages
generates heat

Question 3

40. Muscle produce up to ____ of one’s body heat.

Answer 3

85%

Question 4

41. What determines the origin and insertion of a muscle?

Answer 4

Origin: remains relatively fixed during muscle contraction,
Insertion: attachment site that moves towards the origin during muscle contraction

Question 5

42. Name the 5 characteristics of muscle tissue.

Answer 5

Excitability
Conductivity
Contractibility
Extensibility
Elasticity

Question 6

43. What makes up the striations of skeletal muscle? Which bands are associated with dark and light?

Answer 6

Sarcomeres make up striations
A-Band makes up dark
I-Band makes up light

Question 7

44. What is a sarcomere?

Answer 7

Z-Disk to Z-Disk
or
Basic function unit of muscle

Question 8

46. What is the function of z-disc?

Answer 8

acts as an anchor for actin filaments

Question 9

47. What is the sliding filament theory? Do the thick or thin filaments change length during contraction?

Answer 9

thin filaments slide past the thick filaments, causing the sarcomere to shorten and the muscle to contract
Neither change in length

Question 10

48. Which bands of the sarcomere change size during contraction?

Answer 10

I band and the H zone of the sarcomere decrease in size while the A band remains constant in size.

Question 11

49. What 2 proteins are considered contractile proteins? Regulatory proteins?

Answer 11

Contractile: Actin and Myosin
Regulatory: Troponin and Tropomyosin

Question 12

50. What are the components of the thin filament? Thick filament?

Answer 12

Thin: Actin, Tropomyosin, and Troponin
Thick: Myosin

Question 13

51. Sarcoplasmic reticulum is the main storage site for what ion?

Answer 13

Calcium

Question 14

52. What makes up the Triad? What part of the triad does the AP go down into?

Answer 14

A T-tubule and two terminal cisternae
The action potential goes down the T-tubule

Question 15

53. What is the function of dystrophin? What happens if there are genetic defects to this protein?

Answer 15

-maintaining the structural integrity of muscle cells.
helps anchor the actin filaments of the muscle fiber to the sarcolemma
-absence of functional dystrophin leads to progressive muscle weakness, wasting, and eventual loss of muscle function.

Question 16

54. Is muscular dystrophy more common in males or females?

Answer 16

males

Question 17

55. What is considered a motor unit? What is the difference between small and large?

Answer 17

single motor neuron and all the muscle fibers it innervates
Small: muscles that require fine control and precision
large: muscles that require more force

Question 18

56. What histologically does muscle tissue look like when contracted and at rest?

Answer 18

Contracted: muscle to appear darker under the microscope
At Rest: gives the muscle a striated appearance

Question 19

57. What is rigor mortis? What is the main cause of this stiffness? How long does it last?

Answer 19

• occurs after death where the muscles become stiff and difficult to move
• due to the depletion of ATP in the muscle fibers, required for the separation of the myosin and actin filaments during muscle relaxation.
• begins within 2-6 hours after death and peaks around 12 hours, lasting for approximately 24-48

Question 20

58. What prevents Ach from escaping the neuromuscular junction? What breaks down Ach at the neuromuscular junction?

Answer 20

-Synaptic cleft: narrow space between the motor neuron terminal and the muscle fiber
-Acetylcholinesterase (AChE): breaks down Ach into acetyl and choline.

Question 21

59. What is the role of the junctional folds at the neuromuscular junction?

Answer 21

increase surface area

Question 22

60. What two things can cause flaccid paralysis? What are their mechanisms?

Answer 22

• Curare and Botulism
• preventing the release of acetylcholine or by blocking the receptors for acetylcholine causing for immobile

Question 23

61. What two things can cause spastic paralysis? What are their mechanisms?

Answer 23

• Insect Venom and tetanus
• leads to excessive muscle activity and spasticity

Question 24

62. During excitation-contraction coupling, what happens at the neuromuscular junction?

Answer 24

• End plate potential
• Action potential
• T-tubules
• Ca is released
• contraction
• Ca is pumped back to SR

Question 25

63. What are the two roles of Ca++ during excitation contraction coupling?

Answer 25

- increases the concentration of Ca++ in the sarcoplasm of the muscle fiber - conformational change in tropomyosin, which exposes the binding sites on actin molecules for the myosin heads.

Question 26

64. How does contraction stop and relaxation occur?

Answer 26

occurs when the action potential that triggered the release of calcium from the sarcoplasmic reticulum stops

Question 27

65. Explain the length tension relationship in the muscle.

Answer 27

the amount of tension a muscle can generate is dependent on the length of the muscle fiber at the time of contraction.

Question 28

66. What two things does temporal summation cause?

Answer 28

- Increased force of muscle contraction - Increased frequency of muscle contraction

Question 29

67. Describe the 4 different types of muscle stimulation.

Answer 29

- Twitch contraction: single, brief contraction - Summation: Repeated stimulation of a muscle fiber - Tetanus: sustained contraction of a muscle fibe - Recruitment: increasing the number of motor units

Question 30

68. What is the difference between isometric and isotonic?

Answer 30

Isometric: muscle generates tension without changing its length Isotonic: the muscle generates tension while changing its length

Question 31

69. What is the difference between concentric an eccentric?

Answer 31

Concentric: muscle shortens while generating tension (Upward curl) Eccentric: muscle lengthens while generating tension (Downward motion)

Question 32

70. When would the muscle use anaerobic fermentation? Aerobic respiration?

Answer 32

Anaerobic Ferm: short-term, high-intensity demand for energy, such as during intense exercise Aerobic Res: sustained, low-intensity demand for energy, such as during moderate exercise

Question 33

71. Know the difference between fast-twitch and slow-twitch muscle fibers. Which process is aerobic and which is anaerobic? What types of activities recruit each?

Answer 33

Fast-twitch: contract more quickly and with greater force, rely on anaerobic (weightlifting) Slow-twitch: contract more slowly and with less force, rely on aerobic (running)

Question 34

72. How is cardiac muscle stimulated to contract? Smooth muscle?

Answer 34

Cardiac: by an electrical signal from the sinoatrial (SA) node, which is located in the right atrium of the heart. Smooth: neurotransmitters, hormones, and changes in the local environment (such as stretch or pH).

Question 35

73. How does cardiac muscle get its ATP?

Answer 35

through aerobic respiration using oxygen and glucose

Question 36

74. Why is smooth muscle smooth? Where does it get its calcium?

Answer 36

-smooth because it lacks striations, which are present in skeletal and cardiac muscles. -gets its calcium from both extracellular and intracellular sources

Question 37

76. What is the difference between slow twitch fibers, fast-twitch oxidative glycolytic fibers, and fast-twitch fibers? What energy pathways do each use? What gives rise to their colors? Which has the greatest force production? Which has greatest fatigue resistance?

Answer 37

Slow-twitch: aerobic respiration generates ATP and has a large number of mitochondria and myoglobin, a reddish appearance. (greatest fatigue resistance) Fast-twitch oxidative glycolytic fibers: aerobic respiration and glycolysis to generate ATP, a moderate number of mitochondria and myoglobin, pink appearance Fast-twitch: anaerobic glycolysis to generate ATP and fewer mitochondria and myoglobin, white in appearance. ( Greatest force production)

Question 38

77. Why do muscles fatigue?

Answer 38

- accumulation of lactic acid - depletion of energy stores (ATP) - decrease in calcium ion availability

Question 39

62. During excitation-contraction coupling. What neurotransmitter is involved?

Answer 39

AHc