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Physiology Exam 2 > Skeletal Muscle 1 > Flashcards

Skeletal Muscle 1 Flashcards

1
Q

What type of fibers are the lower motor neurons?

A

A alpha fibers

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2
Q

Big to small, what is the anatomical organization of skeletal muscle?

A

-whole muscle
-muscle fascicles
-muscle fibers
-myofibrils
-myofilaments arranged in sarcomeres

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3
Q

What is the functional unit of skeletal muscle?

A

sarcomere

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4
Q

What is the dark band in the sarcomere?

A

A band

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5
Q

What is the light band in the sarcomere?

A

I band

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6
Q

Which of the two bands shorted during contraction?

A

H zone and I band

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7
Q

What band stays the same length during muscle contraction?

A

A band
-only thick filament so does not move

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8
Q

What is the H zone?

A

the space between the two thin filaments next to each other

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9
Q

What is the A band?

A

entire length of thick filament

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10
Q

What is the I band?

A

only thin filament

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11
Q

What is the H zone?

A

only thick filaments

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12
Q

What is the Z line?

A

thin filaments anchored here

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13
Q

What is the M line?

A

link the central regions of the thick filament

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14
Q

What is the thin filament?

A

made of actin, tropomyosin, and troponin

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15
Q

What are the 3 subunits of troponin?

A

T- tropomyosin binds
C- calcium binds
I- actin binds

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16
Q

What is the thick filament?

A

myosin filament that has multiple cross-bridges where the heads can bind to the G actin molecules

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17
Q

What type of activity of myosin have?

A

ATPase activity

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18
Q

What does tropomyosin do during rest?

A

blocks the actin binding site

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19
Q

What is the dystrophin-glycoprotein complex?

A

-connects thin filament to glycoprotein in sarcolemma
-provides scaffolding for sarcomeres

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20
Q

What can happen if dystrophin is messed up?

A

the complex is not maintained in the membrane
-this does not provide the stability that the muscle cell needs
-the cell membrane breaks and muscles cells die
-leads to many different types of muscular dystrophies that have varying severities and modes of inheritances

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21
Q

What does the alpha motor neuron release into the synapse?

A

release Ach to bind to nicotinic receptors on the muscle fibers

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22
Q

What does botulinim toxin A cause?

A

inhibits the release of Ach into the neuromuscular junction

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23
Q

What are t-tubules?

A

invaginations of the skeletal muscle memrbane that increases the surface area that Ach can act on on the membrane
-allows the message to get into the inside of the muscle as well

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24
Q

Where does the Ca needed for muscle contraction come from?

A

sacroplasmic reticulum

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25
Q

What blocks the binding of myosin to actin in a resting state?

A

tropomyosin

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26
Q

When troponin binds to Ca, waht happens?

A

tropomyosin is pulled away from the myosin binding site and allows for the power stroke

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27
Q

What is the terminal cisternae?

A

portion of SR that contacts the T tubule

28
Q

What are the steps that occur for Ca to be released from the SR?

A

-AP moves down the membrane
-down T tubules
-activate DHP receptors in plasma membrane
-open ryanodine receptors (calcium channels) on the SR
-Ca does into the sarcoplasm

29
Q

What does ATP binding to the mysoin head do?

A

break the cross bridging

30
Q

What does the energy from ATP hydrolysis do?

A

provide energy for cocking the myosin head back into resting position

31
Q

How much ATP do muscle cells have?

A

enough for 8 twitches

32
Q

What are the sources of ATP in muscle?

A

aerobic and anaerobic metabolism and phosphocreatine

33
Q

What does CK presence help determine?

A

if damage to the muscle tissues has occurred

34
Q

What happens to fatigued muscles?

A

-decreased tension generation
-take longer to contract
-relax more slowly and may not completed relax

35
Q

What are theories for why muscles fatigue?

A

-changes in membrane potential
-decreased ACH
-blockage of blood flow
-central fatigue
-increased metabolic byproducts
-depleted glycogen

36
Q

What is the rigor state of cross bridge cycling?

A

myosin and actin are tightly bound

37
Q

When ATP binds myosin, what happens?

A

myosin affinity to bind with actin decreases and actin and myosin separate

38
Q

When the myosin head moves toward the Z line, waht happens?

A

ATP is hydrolyzed

39
Q

When ADP is released, waht happens?

A

actin and myosin resume the brief rigor state

40
Q

How long does cross-bridge cycling occur?

A

until you run out of ATP or calcium E

41
Q

What must happen for relaxation of skeletal muscle?

A

alpha motor neuron stop firing and cytosolic Ca must decrease

42
Q

What are the steps of muscle relaxation?

A

-calcium ATPase on SR to remove calcium from cytosol
-tropomyosin moves, and covers actin’s myosin binding site
-actin slowly slides back to its original resting place and sacromere returns back to original length

43
Q

Without the presense of ATP, what occurs?

A

the rigor state is maintained
-this is why rigor mortis occurs
-no more energy to break the cross bridge

44
Q

Characteristics of Type I muscle fibers?

A

slow twitch
oxidative phosphorylation for ATP creation
high myoglobin
slow myosin ATPase activity
moderate calcium capacity
small
moderate glycolytic capacity
high oxidative capacity
slow to fatique

45
Q

Characteristics of Type IIA muscle fibers?

A

fast twitch
-oxidative phosphorylation and glycolysis
high myoglobin
-fast myosin ATPase activity
-fast SR Ca ATPase activity
-moderate diameter
high glyocolytic activity
moderate oxidative capacity
fast resistant

46
Q

Charactertistics of Type IIB muscle fibers?

A

fast twitch
glycolytic
white (low myoglobin)
fast myosin ATPase activity
fast SR Ca capacity
large diameter
high glycolytic activity
low oxidative capacity
fast and fatigable

47
Q

What are the changes in size of skeletal muscles that can occur?

A

-hypertrophy (increase in size)
-atrophy (decrease in size)
-sarcopenia (decrease in size due to age)

48
Q

What type of fibers are present in the jaw muscles?

A

usually a homogenous mixture of type I and II fibers

49
Q

What can occur in the fibers in the muscles of the jaw?

A

-the fiber types can change with age
-type I fibers tend to decrease and type II fibers increase

50
Q

What is unique about the type of fibers in the jaw?

A

the type II fibers are smaller than the type I fibers (typically, type II is bigger than type I)

51
Q

What are isometric contractions?

A

force produced is less than the load
-there is no movement
-no shortening of the muscle occurs

52
Q

What is isotonic contractions?

A

force produced is great enough to move the load

53
Q

What is the usually progression of muscle contractions?

A

the isometric contractions will continue until enough force is built to create an isotonic contraction (isotonic contractions not always possible though)

54
Q

What is an example of isometric exercise?

A

plank

55
Q

What is an example of isotonic exercise?

A

bicep curl

56
Q

Is the max force used in every isotonic contraction?

A

absolutely not
-the amount of force needed to move the object is used, no more
ex) something weighing 5 pounds will only use 5 pounds of force

57
Q

What are ways to increase the total force of contraction?

A

-increase the number of muscle fibers contracting
-increasing the frequency of fiber activation

58
Q

How are motor units recruited?

A

in order of size
-small recruited first because smaller motor units control fewer fibers

59
Q

What happens when an increase in the number of motor units get activated?

A

the total tension created by the contraciton of the muscle increases
-spatial summation

60
Q

What is asynchronous recruitment?

A

random motor units are activated in random manners
-alternates so the same motor units are not used every time
-try to resist fatigue

61
Q

What are small motor units made of?

A

slow twitch oxidative fibers
-lowest threshold for firing and are recruited first

62
Q

What are larger motor units made of?

A

fast twitch glycolytic gibers (IIB)
-highest threshold and are recruited last

63
Q

What happens when the twitches are close together? q

A

the Ca from the first twitch is still present in the sacroplasm when the second twitch is activated
-not complete relaxation between stimuli

64
Q

What happens when there is max tension?

A

the cross bridges are saturated

65
Q

What alters tension in a single muscle twitch?

A

sarcomere lenght

66
Q

What is the optimal length?

A

the best degree of overlap between the thick and thin filament

67
Q
A

Physiology Exam 2 (6 decks)

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