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Structure and Function Test 1 > Muscle Physiology 2 > Flashcards

Muscle Physiology 2 Flashcards

1
Q

Induces an upregulation in 1) mitochondrial number and function, 2) ATP and phosphocreatine content, 3) enhanced levels of intramuscular glycogen stores, and 4) an increase in intramuscular triglyceride levels

A

Exercise

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2
Q

Muscle fibers express type β2 adrenoceptors. Acute adrenergic stimulation causes an

A

Increase in forceful contraction of Type 2b fibers

Decrease in force develops in Type 1 fibers

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3
Q

Chronic stimulation of the skeletal muscle adrenoreceptor system via a β2 agonist (ex: albuterol) exerts and

A

Anabolic effect

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4
Q

Controls various aspects of muscle metabolism by controlling SERCA

-upregulates rate of contraction and relaxation but does NOT increase contractile force

A

Thyroid hormone

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5
Q

The effects of thyroid hormone are most profound in

A

Type 1 muscle

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6
Q

Although the rate of contraction-relaxation is augmented by thyroid hormone, the overall efficiency of energy turnover is

A

Decreased

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7
Q

Age associated loss in muscle mass

A

Sarcopenia

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8
Q

The process of sarcopenia actually begins sometime around age 30 years, after which muscle loss can approach

A

3-8% per decade

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9
Q

Decrease proteogenesis and the rate of amino acid transport and inhibit IGF-1 expression

A

Glucocorticoids (ex: prednisone and dexamethasone)

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10
Q

A transcription factor required for satellite cell differentiation into myofibers

-inhibited by glucocorticoids

A

Myogenin

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11
Q

Functions as an endocrine organ

A

Muscle

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12
Q

Aerobic and anaerobic muscle work is correlated with the secretion of growth factors and immune mediators from muscle fibers, collectively known as

A

Myokines

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13
Q

Can modulate muscle hypertrophy and myogenesis

A

Myokines

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14
Q

Consists of 1) a motor neuron and relatively few muscle fibers and/or 2) numerous motor neurons innervating single and/or small groups of muscle fibers.

A

One motor unit in muscles mediating fine control (i.e. hands)

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15
Q

These small diameter fibers are extremely well vascularized (hence the bright red appearance), and can effectively utilize oxidative metabolism for energy

A

Type 1 muscle fibers

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16
Q

Type 1 muscle fibers contain an abundance of

A

Myoglobin and mitochondria

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17
Q

Function as a hybrid between type 1 and type 2b fibers

A

Type 2a fibers

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18
Q

Are relatively large in diameter, this giving them a greater potential for force of contraction

A

Fast fibers

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19
Q

Fast fibers have a relatively low complement of mitochondira, but an extensive

A

SR

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20
Q

What are the two types of efferent neurons that innervate skeletal muscle fibers?

A

α and ƴ motor neurons

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21
Q

Mediate essentially all of the voluntary contractile responses of skeletal muscle

A

α neurons

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22
Q

Smaller, slower neurons that innervate the intrafusal muscle fibers within the muscle spindles

A

ƴ neurons

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23
Q

Contain sensory receptors that are designed to detect changes in muscle length and the rate of change of length

A

Muscle spindles

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24
Q

Intrafusal fibers run in parallel to the force generating extrafusal fibers. The intrafusal fiber ends are innervated by

A

Type II afferent fibers and ƴ motor neurons

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25
Q

The ends (chain) of intrafusal fibers can be stimulated to contract in response to

A

ƴ motor neuron activity

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26
Q

In contrast, the central portion of intrafusal fibers (bag) can not contract but is sensitive to

A

Stretch

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27
Q

Have receptors that encircle the center of the intrafusal fibers

-Impulses are continually being transmitted via
these sensory neurons to the spinal cord

A

Type 1a afferent neurons

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28
Q

Stretch and/or an increase in the rate of stretch can up-regulate the number and frequency of APs transmitted by

A

Type 1a afferent neurons

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29
Q

During muscle contraction, the bag region of
muscle spindles initially go slack, and type II and Ia activity is suppressed. If sustained contraction is required, descending (motor) tracts stimulate

A

ƴ motor neuron activity

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30
Q

ƴ motor neurons then stimulate contraction of the

A

Intrafusal muscle ends

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31
Q

Contraction of the fiber ends causes stretch within the

center (bag) portion of intrafusal fibers, and this stretch reactivates

A

Type 1a afferent activity

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32
Q

What happens when the limit of contraction/re-stretch of intrafusal fibers is reached?

A

Isotonic muscle contraction ceases

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33
Q

Continuously provides the CNS with information about muscle length and rate of change in length in order to allow and sustain the full range of skeletal muscle contraction

A

The muscle spindle

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34
Q

Located in musculotendon junctions where they serve as an early warning system to the CNS that muscle tension has suddenly increased

-serve as a protective mechanism against muscle tear

A

Golgi tendon organs (GTOs)

35
Q

If load (due to passive stretch or active contraction) causes an increase in tension in the muscle, the activity of GTOs is up-regulated, and there is an increase in the frequency of

A

Type 1b action potentials

36
Q

Activation of type 1b muscle fibers stimulates

A

Decrease in muscle tension

37
Q

Stimulate inhibitory interneurons and antagonistic muscles

A

Type 1b afferents

38
Q

Defined as a reversible decrease in contractile force in

response to an increase in stimulation frequency or duration

A

Muscle fatigue

39
Q

Force generation is especially restrained due to a breakdown in pCr, attributing to an insufficient rate of ADP phosphorylation and the accumulation of

A

Inorganic phosphate

40
Q

What are the differences between smooth and skeletal muscle cells?

A

Smooth muscle cells:

  1. ) are smaller
  2. ) have 1 central nucleus
  3. ) unstriated
  4. ) small SR
  5. ) high actin to myosin ratio (15:1)
41
Q

Smooth muscles have many dense bodies, some of which are attached to the cell membrane. Dense bodies serve the same function as

A

Skeletal Z-discs

42
Q

Connected by gap junctions which allow innervation of only a few muscle fibers to result in excitation of all muscle fibers in a region

A

Visceral smooth muscle

43
Q

Visceral smooth muscle acts as a

A

Single unit

44
Q

What contains more vascular smooth muscle, arteries or veins?

A

Arteries

45
Q

The contraction and relaxation of vascular smooth muscle (i.e. vascular smooth muscle tone) is under the
control of the

A

Sympathetic nervous system

46
Q

Contraction of smooth muscle occurs by a

-similar to skeletal muscle

A

Sliding filament mechanism

47
Q

Because actin filaments are attached to dense bodies within the cell membrane, fiber shortening pulls the cell membrane inward causing the muscle cell to appear

A

Crinkled

48
Q

With smooth muscle, as with skeletal muscle, the contractile system is activated by an increase in

A

Sarcoplasmic Ca2+

49
Q

In smooth muscle, Ca2+ is obtained from extracellular sources following cell depolarization and activation of

A

Voltage-gated Ca2+ channels

50
Q

Can each activate Ca2+ channels in the SR membrane through which SR stores of Ca2+ enter the sarcoplasm in smooth muscle cells

A

Ca2+-induced Ca2+ release and/or IP3-mediated signal transduction

51
Q

In smooth muscles, when sarcoplasmic Ca2+ concentrations are sufficiently elevated, Ca2+ binds the calcium sensor known as

A

Calmodulin

52
Q

The Ca2+/Calmodulin complex then activates

A

Myosin light chain kinase (MLCK)

53
Q

Activation of MLCK causes phosphorylation of myosins, which gives them a very high affinity for

A

Actin

54
Q

Dephosphorylates myosin in smooth muscle cells, resulting in the cessation of contration

A

MLCK phosphatase

55
Q

Prolonged in comparison to skeletal muscle contraction

A

Smooth muscle contraction

56
Q

In order to accomplish these relatively long duration contractions, smooth muscle utilizes

A

Oxidative metabolism

57
Q

Slow, sustained contraction is caused by slow cycling of the

A

Myosin crossbridges

58
Q

In smooth muscle cells, contraction requires very little

A

ATP

59
Q

MLCK phosphatase is activated, crossbridge cycling ceases, and muscle relaxation occurs when

A

Ca2+/Calmodulin levels fall

60
Q

In contrast to skeletal muscle, smooth muscle can shorten from 50% to 75% of its relaxed length
without altering the overlapping of

A

Myosin and actin filaments

61
Q

As opposed to the linear contraction of skeletal muscle, smooth muscle can contract upon itself in

A

Multiple dimensions

62
Q

In smooth muscle, stretch of the smooth muscle fibers results in Ca2+ inflix, which activates the

A

Contractile system (increases active tension)

63
Q

The elastic properties of smooth muscle aids in the process of

  • allows for an alleviation in pressure, which follows an increase in volume
  • especially advantageous to hollow organs
A

Stress relaxation

64
Q

What is Laplace’s Law?

A

P = T/r

where,

P = pressure
T = tension
r = radius
65
Q

The concept of stress relaxation is especially important in the

-less important in vascular tissues

A

Bladder

66
Q

ANS post ganglionic neurons have axons which have swollen areas called

-in close proximity to the smooth muscles they innervate

A

Varicosities

67
Q

Function as diffuse neuromuscular junctions

A

Variscosities

68
Q

Have vesicles containing the neurotransmitter, ACh (parasympathetic nervous system), or norepinephrine (sympathetic nervous system)

A

Variscosities

69
Q

There are different types of action potentials that can be generated by smooth muscle. The main type of potential is called a

A

Slow wave potential

70
Q

Not action potentials, but are rhythmic, subthreshold, pacemaker-type changes in membrane depolarization and repolarization

A

Slow wave potentials

71
Q

The depolarization phase of a slow wave is induced by the opening of Ca2+ channels. These Ca2+ channels can be

A

Ligand- or voltage-gated

72
Q

Slow waves set what is known as the

A

Basal electrical rythm of the gut

73
Q

Smooth muscle potential which is similar to skeletal muscle APs.

-Depolarization is mediated by activation of Ca2+ and/or Na+ chanels

A

Spike potential

74
Q

Both outward IK+ and ICa2+ can be involved in repolarization of

A

Spike potentials

75
Q

100-1000 msec slower than spike potentials due to delayed repolarization.

-Like spike potentials, depolarization is mediated by inward ICa2+ and/or INa+

A

Plateau potentials

76
Q

In a plateau potential, depolarization is followed by a transient repolarization phase, which is dependent on

A

Outward IK+

77
Q

An example of a tissue that utilizes both spike potentials and plateau potentials

A

Myometrium

78
Q

Ion flux is different in

A

Smooth muscle than in skeletal

79
Q

In smooth muscle, the RMP is

A

-50 to -60 mV

80
Q

In smooth muscle, the threshold potential is

A

-30 to -35 mV

81
Q

Stimulation of smooth muscle increases Na+ influx, this in turn initiates

A

Membrane depolarization

82
Q

The depolarization phase of a spike potential is due

predominantly to

A

Ca2+ influx

83
Q

Participates not only in the depolarization phase of the AP in smooth muscle, but also in the initiation of smooth muscle contraction

A

Ca2+

Structure and Function Test 1 (61 decks)

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