Muscle Physiology 2

Question 1

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

Answer 1

Exercise

Question 2

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

Answer 2

Increase in forceful contraction of Type 2b fibers

Decrease in force develops in Type 1 fibers

Question 3

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

Answer 3

Anabolic effect

Question 4

Controls various aspects of muscle metabolism by controlling SERCA

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

Answer 4

Thyroid hormone

Question 5

The effects of thyroid hormone are most profound in

Answer 5

Type 1 muscle

Question 6

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

Answer 6

Decreased

Question 7

Age associated loss in muscle mass

Answer 7

Sarcopenia

Question 8

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

Answer 8

3-8% per decade

Question 9

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

Answer 9

Glucocorticoids (ex: prednisone and dexamethasone)

Question 10

A transcription factor required for satellite cell differentiation into myofibers

-inhibited by glucocorticoids

Answer 10

Myogenin

Question 11

Functions as an endocrine organ

Answer 11

Muscle

Question 12

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

Answer 12

Myokines

Question 13

Can modulate muscle hypertrophy and myogenesis

Answer 13

Myokines

Question 14

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.

Answer 14

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

Question 15

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

Answer 15

Type 1 muscle fibers

Question 16

Type 1 muscle fibers contain an abundance of

Answer 16

Myoglobin and mitochondria

Question 17

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

Answer 17

Type 2a fibers

Question 18

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

Answer 18

Fast fibers

Question 19

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

Answer 19

SR

Question 20

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

Answer 20

α and ƴ motor neurons

Question 21

Mediate essentially all of the voluntary contractile responses of skeletal muscle

Answer 21

α neurons

Question 22

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

Answer 22

ƴ neurons

Question 23

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

Answer 23

Muscle spindles

Question 24

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

Answer 24

Type II afferent fibers and ƴ motor neurons

Question 25

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

Answer 25

ƴ motor neuron activity

Question 26

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

Answer 26

Stretch

Question 27

Have receptors that encircle the center of the intrafusal fibers -Impulses are continually being transmitted via these sensory neurons to the spinal cord

Answer 27

Type 1a afferent neurons

Question 28

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

Answer 28

Type 1a afferent neurons

Question 29

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

Answer 29

ƴ motor neuron activity

Question 30

ƴ motor neurons then stimulate contraction of the

Answer 30

Intrafusal muscle ends

Question 31

Contraction of the fiber ends causes stretch within the | center (bag) portion of intrafusal fibers, and this stretch reactivates

Answer 31

Type 1a afferent activity

Question 32

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

Answer 32

Isotonic muscle contraction ceases

Question 33

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

Answer 33

The muscle spindle

Question 34

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

Answer 34

Golgi tendon organs (GTOs)

Question 35

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

Answer 35

Type 1b action potentials

Question 36

Activation of type 1b muscle fibers stimulates

Answer 36

Decrease in muscle tension

Question 37

Stimulate inhibitory interneurons and antagonistic muscles

Answer 37

Type 1b afferents

Question 38

Defined as a reversible decrease in contractile force in | response to an increase in stimulation frequency or duration

Answer 38

Muscle fatigue

Question 39

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

Answer 39

Inorganic phosphate

Question 40

What are the differences between smooth and skeletal muscle cells?

Answer 40

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

Question 41

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

Answer 41

Skeletal Z-discs

Question 42

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

Answer 42

Visceral smooth muscle

Question 43

Visceral smooth muscle acts as a

Answer 43

Single unit

Question 44

What contains more vascular smooth muscle, arteries or veins?

Answer 44

Arteries

Question 45

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

Answer 45

Sympathetic nervous system

Question 46

Contraction of smooth muscle occurs by a -similar to skeletal muscle

Answer 46

Sliding filament mechanism

Question 47

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

Answer 47

Crinkled

Question 48

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

Answer 48

Sarcoplasmic Ca2+

Question 49

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

Answer 49

Voltage-gated Ca2+ channels

Question 50

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

Answer 50

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

Question 51

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

Answer 51

Calmodulin

Question 52

The Ca2+/Calmodulin complex then activates

Answer 52

Myosin light chain kinase (MLCK)

Question 53

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

Answer 53

Actin

Question 54

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

Answer 54

MLCK phosphatase

Question 55

Prolonged in comparison to skeletal muscle contraction

Answer 55

Smooth muscle contraction

Question 56

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

Answer 56

Oxidative metabolism

Question 57

Slow, sustained contraction is caused by slow cycling of the

Answer 57

Myosin crossbridges

Question 58

In smooth muscle cells, contraction requires very little

Answer 58

ATP

Question 59

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

Answer 59

Ca2+/Calmodulin levels fall

Question 60

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

Answer 60

Myosin and actin filaments

Question 61

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

Answer 61

Multiple dimensions

Question 62

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

Answer 62

Contractile system (increases active tension)

Question 63

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

Answer 63

Stress relaxation

Question 64

What is Laplace's Law?

Answer 64

P = T/r where, ``` P = pressure T = tension r = radius ```

Question 65

The concept of stress relaxation is especially important in the -less important in vascular tissues

Answer 65

Bladder

Question 66

ANS post ganglionic neurons have axons which have swollen areas called -in close proximity to the smooth muscles they innervate

Answer 66

Varicosities

Question 67

Function as diffuse neuromuscular junctions

Answer 67

Variscosities

Question 68

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

Answer 68

Variscosities

Question 69

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

Answer 69

Slow wave potential

Question 70

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

Answer 70

Slow wave potentials

Question 71

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

Answer 71

Ligand- or voltage-gated

Question 72

Slow waves set what is known as the

Answer 72

Basal electrical rythm of the gut

Question 73

Smooth muscle potential which is similar to skeletal muscle APs. -Depolarization is mediated by activation of Ca2+ and/or Na+ chanels

Answer 73

Spike potential

Question 74

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

Answer 74

Spike potentials

Question 75

100-1000 msec slower than spike potentials due to delayed repolarization. -Like spike potentials, depolarization is mediated by inward ICa2+ and/or INa+

Answer 75

Plateau potentials

Question 76

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

Answer 76

Outward IK+

Question 77

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

Answer 77

Myometrium

Question 78

Ion flux is different in

Answer 78

Smooth muscle than in skeletal

Question 79

In smooth muscle, the RMP is

Answer 79

-50 to -60 mV

Question 80

In smooth muscle, the threshold potential is

Answer 80

-30 to -35 mV

Question 81

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

Answer 81

Membrane depolarization

Question 82

The depolarization phase of a spike potential is due | predominantly to

Answer 82

Ca2+ influx

Question 83

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

Answer 83

Ca2+