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Human Form & Function > Muscle Physiology > Flashcards

Muscle Physiology Flashcards

1
Q

striated muscle cells

A

Voluntary

attached to bones or skin

very long, cylindrical

multinucleated

not self stimulated

no rhythmic contractions

fatigues easily

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2
Q

cardiac muscle cells

A

involuntary

branching

only in heart

self stimulated

striated

does not fatigue

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3
Q

cardiac muscles are…

A

striated
elongated
branched cells (linked via intercalated disks)

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4
Q

desmosomes (cardiac muscle cells)

A

specialized cell junctions along intercalated disks between cells “spot welds”

withstand high mechanical stress from myocardial beating

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5
Q

gap junctions (cardiac muscle cells)

A

provide electrical conduction that enables intercalated cells to beat as a single conductive unit (syncytium)

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6
Q

what enters cytoplasm from both the sarcoplasmic reticulum stores and extracellular sources

A

Calcium

  • L-type calcium channel enables Ca2+-induced calcium release
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7
Q

autorhythmicity

A

intrinsic pacemaker cells (cardiac muscle cells)

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8
Q

What type of respiration do cardiac muscle cells primarily use?

A

aerobic respiration

able to moderately resist fatigue (large mitochondria)

high myoglobin content for O2 storage

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9
Q

cardiac myocytes

A

don’t fatigue easily BUT they are very sensitive to ischemia/hypoxia

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10
Q

smooth muscle cell’s shape and nucleus?

A

spindle-shaped and mononucleated

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11
Q

T/F: smooth muscle cells form sheets on the walls of hollow organs and some blood vessels

A

TRUE

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12
Q

smooth muscle cells: voluntary or involuntary control?

A

involuntary control

slow, rhythmic (wave-like) contractions

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13
Q

T/F: smooth muscles cells are striated

A

FALSE:

smooth muscle cells are NOT striated (not organized into sarcomeres)

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14
Q

smooth muscle cell organization

A

thin (actin) fibers are attached to the cell wall and to dense bodies in the cytoplasm between myosin bundles

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15
Q

smooth muscle cell activation causes what?

A

When activated, thin actin fibers slide over the myosin bundles causing shortening of the cell walls

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16
Q

smooth muscle cells contracted vs contracted state

A

crumples up when contracted

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17
Q

motor unit

A

the functional unit of skeletal muscle

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18
Q

a motor unit is composed of…

A

composed of an alpha motor neuron and all the muscle fibers (myofibrils) it innervates

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19
Q

alpha motor neuron axon characteristics

A

synapse with up to thousands of muscle fibers BUT each muscle fiber is connected to only ONE alpha motor neuron

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20
Q

motor unit recruitment

A

the process by which more and more motor units are put into action

the greater the number/size of the motor units recruited, the more powerful the contraction

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21
Q

sarcomere

A

a structural unit of myofibril in striated muscle

gives Striated Muscle its “striped” appearance

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22
Q

sarcomere is composed of…

A

myosin (thick)
actin (thin)

both protein filaments

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23
Q

arrangement of sarcomere

A
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24
Q

sarcomere: what does the z-disk do?

A

anchor for actin filaments

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25
Q

sarcomere: what is the I-band?

A

space between A-bands containing only actin and z-disk

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26
Q

sarcomere: what is the H-zone?

A

forms the center (lightest part) of the A-band

contains myosin filaments only

shortens during contraction

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27
Q

sarcomere: M-line

A

middle/midline of the H-zone and the A-band

accessory proteins anchor myosin to M-line

28
Q

sarcomere: A-band

A

darker, thicker band containing both myosin and actin

length does not change during contraction

29
Q

sarcomere: titins

A

elastic filaments that anchor myosin to z-discs (springs)

30
Q

what sarcomere components shorten during muscle contraction?

A

I-band
H-zone

A-band does NOT shorten

31
Q

sliding filament theory

A

During contraction, the heads of each thick (myosin) filament form a cross-bridge with adjacent thin (actin) filaments.

During excitation-contraction coupling, the actin filaments slide toward the M-line (center) shortening the sarcomere

32
Q

sliding filament theory is a ______- dependent process

A

ATP-dependent process

33
Q

T/F: during muscle contraction, the length of the actin and myosin filaments shorten

A

FALSE: the length of the filaments do not shorten

the I-band and H-band shorten *actin and myosin are pulled together

34
Q

excitation-contraction coupling

A

Physiological conversion of electrical stimuli (action potential (APs )) to mechanical responses (contraction) at the neuromuscular junction

35
Q

6 steps of excitation-contraction coupling

A
36
Q

cross-bridge formation

A
37
Q

during relaxation is cytoplasmic Ca2+ low or high?

A

low Ca2+ in relaxation

38
Q

during muscle relaxation (low Ca2+), what blocks the myosin binding site on actin?

A

tropomyosin block binding site on actin (prevents contraction)

39
Q

during muscle contraction (high Ca2+), what is activated on actin?

A

troponin is activated by Ca2+

troponin pulls tropomyosin off the actin’s myosin binding site

myosin head is able to bind to actin and contract muscle

40
Q

what does high Ca2+ concentration do?

A

The higher the Ca2+ concentration, the greater the # of tropomyosin molecules moved to expose myosin binding sites

41
Q

cross-bridge cycle

A
42
Q

cross bridge cyle can continue as long as…

A
  1. muscle is activated
  2. ATP is available
  3. the physical limit of shortening the sarcomere has not been reached
43
Q

Main events of Skeletal muscle contraction

A
44
Q

sarcomere length-tension relationship

A

The lower limit of contractile ability (75% of resting length)

Optimaloperatinglength(80-120%)
—— muscle is slightly stretched with a slight overlap between myofibrils.

Maximal limit the sarcomere can stretch (170%).

45
Q

3 energy sources for muscle contraction

A
46
Q

muscle contraction: creatine phosphate

A

direct phosphorylation

energy source: CP

oxygen use: none

produces 1 ATP per CP

47
Q

muscle twitch

A

response of a muscle to a single action potential on its motor neuron

48
Q

muscle twitch threshold

A

minimum voltage necessary to produce contraction

a single brief stimulus at that voltage produces a quick all or nothing cycle of contraction & relaxation (i.e., a twitch)

49
Q

phases of muscle twitch

A

latent period
contraction phase
relaxation phase
refractory period

50
Q

multiple motor unit summation

A

“Recruitment”

Increasing the strength of the stimulus at a constant frequency to recruit additional motor units and thereby increase the tension developed

51
Q

tetanus

A

prolonged contraction without relaxation

NOT sustainable –> fatigue

51
Q

unfused (incomplete) tetanus

A

“staircase effect”/treppe

wave summating at a frequency sufficient to produce periods of incomplete relaxation between contractions

51
Q

wave summation

A

“temporal summation”

Increasing frequency of a stimulus held at a constant intensity

52
Q

tension vs load

A

tension: the force exerted on an object by a contracting muscle

load: the force exerted on the muscle by an object

53
Q

isometric contraction

A

load exceeds the tension (muscle doesn’t shorten)

53
Q

isotonic contraction

A

the tension (force) generated by the muscle is greater than the load (muscle shortens)

54
Q

fractionation

A

All motor units in a muscle do not need to activate

However, the more motor units activated, or the larger the motor units recruited, the greater the tension (i.e., force) achievable by the muscle

55
Q

Henneman’s “Size Principle”

A

Motor unit recruitment depends on the demand (i.e., load).

Motor units are recruited in the order of the size of the motor unit based on the force needed

56
Q

Size Principle: under increasing load

A

motor units are recruited from smallest to largest

Type I (slow) motor units are recruited first for light exercise then Type IIa (fast) then Type IIb (slow)

Type I (slow)
Type IIa (fast)
Type IIb (slow)

57
Q

slow vs fast twitch muscle fibers

A

slow (Type I)
Fast (Type II)

58
Q

reflex arc

A

neural pathway that controls a reflex

59
Q

somatic

A

skeletal muscle

60
Q

autonomic

A

smooth and cardiac muscle

61
Q

6 basic components of reflex arcs

A

sensory receptor
sensory (afferent) neuron
integration center (CNS)
interneuron
motor (efferent neuron)
effector (muscle)

62
Q

example of monosynaptic reflex

A

Knee jerk (stretch reflex)

*contraction of stretched muscle

63
Q

example of a disynaptic reflex

A

golgi (deep) tendon reflex

*relaxation of the contracted muscle

Human Form & Function (21 decks)

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