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Biol 223 > Chapter 10 > Flashcards

Chapter 10 Flashcards

1
Q

The three types of cells in muscle tissue are

A
  1. skeletal
  2. cardiac
  3. smooth
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2
Q

What function do all three muscle tissue types share in common?

A

generate muscle tension

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3
Q

What are some other functions of muscle tissue?

A

creates movement, maintains posture, stabilizes joints, generates heat, and regulates the flow of materials through hollow organs.

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4
Q

What do skeletal muscle cells and cardiac muscle cells have in common?

A

they are both striated

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5
Q

What makes smooth muscle different from skeletal and cardiac muscle tissues?

A

no striations

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6
Q

Define contractility

A

the ability of proteins within a cell to draw together. Contraction does not mean shorten

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7
Q

Define excitability.

A

muscle cells are responsive to stimuli

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8
Q

Define conductivity.

A

when a muscle cell is excited, the electrical changes rapidly conduct along the entire length of the plasma membrane

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9
Q

Define extensibility

A

stretching of muscle cells up to 3 x’s their length

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10
Q

Define elasticity

A

the ability for cells to return to their original shape after stretching

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11
Q

What are myocytes? What is the sarcoplasm? What is the sarcolemma?

A

muscle cells. sarcoplasm is a myocytes cytoplasm. sarcolemma is the myocytes plasma membrane (phospholipid bylayer)

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12
Q

What does the sarcoplasmic reticulum store and release?

A

calcium

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13
Q

which is the most abundant organelle of skeletal muscle cells, and is made up of contractile proteins?

A

myofibrils

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14
Q

What surrounds the myofibrils and stores and releases calcium ions?

A

sarcoplasmic reticulum

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15
Q

Transverse tubules (T-tubules) are deep inward extensions of…………. that are filled with extracellular fluid.

A

sarcolemma

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16
Q

Terminal cisternae are enlarged sections of …………. found flanking each T- tubule. Two terminal cisternae and their corresponding T-tubule form a …………….

A

sarcoplasmic reticulum. Triad

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17
Q

What are the 3 types of myofilaments?

A

thick, thin, and elastic

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18
Q

Thick filaments are composed of bundles of…………

A

many molecules of the contractile protein, myosin

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19
Q

What 3 proteins are thin filaments composed of?

A

actin, tropomyosin, troponin

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20
Q

Tropomyosin is a long rope-like regulatory protein that twists around ………… , covering up its active sites.

A

the 2 actin strands so it covers up the active sites, while at rest.

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21
Q

Troponin is a small globular regulatory protein that holds …………. in place and assists with turning contractions on and off.

A

tropomyosin

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22
Q

Elastic filaments are composed of a single massive, spring-like structural protein called ………… that stabilizes the myofibril structure and resists excessive stretching force.

A

titin

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23
Q

Striations appear microscopically as alternating light, or I, bands, where only …………. filaments are found and dark, or A, bands, where both
…………… and ………….. filaments are found.

A

thin, thick and thin

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24
Q

In the middle of the A band where only thick filaments exist is the……….. The …………. line is a dark line in the middle of the A band made up of structural proteins. The ……… disc is found in the middle of the I band and is composed of structural proteins.

A

H zone. M line. Z disc

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25
Q

what is a sarcomere? A sarcomere extends from one ………….. to the next.

A

z disc. It is the functional unit where contraction occurs.

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26
Q

During a contraction, both the …………. and the ……….. narrow while the A band remains unchanged.

A

I bands and the H zone

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27
Q

Myosin heads attach to actin to pull the thin filaments towards the M line, which brings …………… closer together, shortening the sarcomere.

A

z discs

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28
Q

What are membrane potentials due to?

A

an unequal distribution of ions near the plasma membrane resulting in a polarized resting state.

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29
Q

What is the resting membrane potential? How many milivolts does it measure?

A

the electrical potential across the sarcolemma of a resting muscle fiber. 70 millivolts

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30
Q

when does resting membrane potential change?

A

when the barrier to ion movement is removed from the plasma membrane.

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31
Q

What are action potentials?

A

are brief, temporary changes in the membrane potential of a cell from a resting negative value to a value, and then back to its resting negative value.

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32
Q

Action potentials are generated by

A

opening gated ion channels in the plasma membrane.

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33
Q

two types of gated channels are?

A
  1. Ligand

2. voltage

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34
Q

What do ligand gated channels open in response to?

A

The presence of certain chemicals called ligand

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35
Q

What do voltage gated channels open in response to?

A

In resone to changes in the membrane potential across the plasma membrane

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36
Q

What is depolarization?

A

A stage in action potential. In response to stimulus, voltage gated sodium ion channels open, and sodium ions enter the cell, making membrane potential less negative (rises to +30 mlV)

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37
Q

What is repolarization?

A

A step in action potential that is triggered by the closing of the voltage gated sodium ion channel. Simultaneously, the voltage gated potassium channel opens, letting potassium out of the cell, and repolarizing the cell to its -85mlV charge.

38
Q

The NMJ (neuromuscular junction) is where a single motor neuron communicates with many ………… fibers. What is another name for the NMJ?

A

Muscle. Synapse

39
Q

What are chemicals that trigger changes in a target tissue when released allowing for cell to cell communication?

A

Nero transmitters

40
Q

What is the neurotransmitter released from a motor neuron stimulates a muscle fiber?

A

Acetylcholine

41
Q

What are the three components of the neuromuscular junction?

A
  1. The axon terminal
  2. The synaptic cleft
  3. The motor end plate
42
Q

What is the ligand that opens the gates that allow sodium to diffuse into the cell?

A

Acetylcholine

43
Q

What are the three faces of muscle contraction?

A

Excitation phase, Excitation contraction coupling, and the contraction phase

44
Q

Summarize how the excitation phase begins

A

An action potential arrives at the axon terminal. The synaptic vesicles release acetylcholine into the synaptic cleft. Acetylcholine binds to the ligand gated ion channels in the motor end plate.

45
Q

What is an end plate potential?

A

It is a local depolarization in the area of the motor end plate.

46
Q

How is an end plate potential accomplished?

A

Entry of sodium ions into the myocyte depolarizes the sarcolemma locally which produces an end plate potential.

47
Q

How is a functional muscle contraction produced?

A

Multiple end plate potential’s must be generated

48
Q

Which enzyme rapidly degrades acetylcholine In the synaptic cleft

A

Acetylcholinesterase

49
Q

And end plate potential leads to the opening of voltage gated………..channels in the sarcolemma surrounding the motor end plate, which triggers an action potential

A

Sodium ion

50
Q

Action potentials propagate down the …….. , which signals to terminal cisternae to open voltage gated calcium ion channels releasing calcium ions into the cytosol

A

T-tubules

51
Q

How does the contraction phase begin?

A

Calcium ions bind to troponin. The tropomyosin moves and the active sites of actin are exposed. When the active site of actin are exposed the myosin heads are able to bind tightly to them this is known as cross bridging

52
Q

When is a myosin head cocked?

A

When The ATP that was bound to it is hydrolyzed

53
Q

What does the myosin head bind to once it is cocked?

A

Actin

54
Q

What is a power stroke? What promotes it?

A

When the myosin pivots and pulls the actin toward the center of the sarcomere. It is promoted by the removal of ADP and phosphate

55
Q

What is required for the cross bridge cycle to repeat?

A

ATP must break the attachment of myosin to Actin

56
Q

Muscle relaxation occurs in two separate steps. First, Motor neuron action potentials stop signaling for the release of ………. from axon terminals. Any acetylcholine left in the synaptic cleft is rapidly degraded by the enzyme ……….. Since acetylcholine can no longer bind to the motor end plate, the end plate potential stop as ligand gated ………….. channels close.

A

Acetylcholine. Acetylcholineesterase.

Ion

57
Q

How does repolarization occur?

A

The Acetylcholine degrades into substances that can’t stimulate the muscle. Without stimulation the gated ion channels close on the end plate

58
Q

How do the positions of troponin and tropomyosin change in the absence of calcium ions, and how does this make the muscle relax?

A

Troponin returns to its original position pushing tropomyosin back to where it blocks the active sites of the actin, which prevents myosin heads from binding to it.

59
Q

The main immediate energy is stored as …………..in the muscle fiber and is rapidly consumed during muscle contraction.

A

ATP

60
Q

Creatine phosphate concentration in the cytosol is 5-6 times higher than ATP; can immediately regenerate enough ATP for about seconds of maximum muscle activity.

A

10 seconds

61
Q

Glycolysis is a series of reactions that occurs in the cytosol all cells. Glycolysis breaks ……….. down into ……………and provides energy (ATP) for muscle contraction once immediate sources of energy are depleted.

A

glucose. 2 ATP

62
Q

Glycolysis, or anaerobic catabolism, does not require

A

oxygen

63
Q

What happens to pyruvate if oxygen is abundant? What happens to pyruvate if oxygen is not abundant?

A

it will enter the mitochondria for oxidative catabolism. It will be converted into 2 lactic acid molecules.

64
Q

Oxidative catabolism, or aerobic catabolism, requires oxygen directly. Oxidative catabolism allows for longer lasting muscle contractions because these reactions produce many more…………. molecules than glycolysis.

A

ATP

65
Q

Oxidative catabolism is the predominant energy source after ………….. minute of contraction and provides nearly 100% of ATP after several minutes.

A

1

66
Q

Some oxygen is supplied by the blood but the majority is bound to the oxygen- carrier .

A

myoglobin

67
Q

When glucose levels are exhausted, what molecules can be catabolized to generate ATP?

A

fatty acids and amino acids

68
Q

A ……….. is the smallest unit of muscle contraction.

A

muscle twitch

69
Q

What are the 3 phases of a twitch?

A
  1. latent period:
  2. contraction period:
  3. relaxation period:
70
Q

The ………… period begins at the onset of the latent period and ends at the beginning of the contraction period. During this time the muscle fiber is unable to respond to further stimuli.

A

refractory

71
Q

Repeated stimulation of a fiber results in progressively greater tension production. Calcium ion levels remain elevated in the …………. as SR pumps cannot keep up with successive stimuli. Waves of contractions have additive effects known as ……………. The tension produced depends on the frequency of motor neuron stimulation resulting in two possibilities: ………….. or ………….

A

cytosol, wave summation, unfused tetanus (roughly 80%), or fused tetanus (highest tension nearly 100%)

72
Q

The length-tension relationship states that the optimal length of a sarcomere is about 100-120% of the natural length of the sarcomere. At this natural length a sarcomere can generate the greatest tension. The length of the sarcomere must be short enough to allow for a generous zone of overlap between thin and thick filaments. But the length of the sarcomere must be long enough for the thick filaments to pull the thin filaments toward the ……….. line without running into the ………….-discs.

A

m-line, z discs

73
Q

What are two main classes of skeletal muscle fibers, and how are they classified?

A
  1. Type 1: fibers are small diameter, slow-twitch fibers that contract slowly to produce less force for a longer period of time.
  2. Type II fibers are large diameter, fast twitch fibers that fatigue quickly.
74
Q

Compare the number of mitochondria, myoglobin and the blood supply in fast-twitch fibers to slow-twitch fibers

A

Slow-twitch fibers have low myosin ATPase activity, rely on oxidative catabolism and have large numbers of mitochondria, a well-developed blood supply, and myoglobin molecules; this gives them a characteristic “dark meat” red color.

Fast-twitch fibers have high myosin ATPase activity, less myoglobin, few mitochondria, white meat b/c less oxygenated blood.

75
Q

What is a motor unit?

A

A single motor neuron and all the muscle fibers that it innervates

76
Q

Motor units are considered either slow, composed of ………… fibers only; or fast, composed of ………. fibers only.. The number of fibers varies depending on the motor unit’s function. Muscles requiring fine motor control have ………. motor units, and those requiring less control have ………. motor units.

A

type 1, type 2, small, large

77
Q

As greater force is required more motor units must be stimulated, a process known as…………

A

recruitment

78
Q

What is muscle tone? Why is muscle tone is vital?

A

A baseline level of involuntary activation of motor units. It stabilizes joints, maintains posture, generates heat, and ensures that muscles are ready to go when needed.

79
Q

What are the 3 types of muscle contractions?

A
  1. Isotonic concentric
  2. Isotonic eccentric
  3. Isometric
80
Q

List the changes, primarily biochemical that result from endurance training.

A

able to better utilize fatty acids in ATP production, increased resistance to fatigue.

81
Q

What is fatigue, and what causes it?

A

The inability to maintain a given level of intensity of a particular exercise. Caused by:

  1. depletion of metabolites
  2. decreased oxygen to muscle fibers.
  3. accumulation of certain chemicals.
  4. environmental conditions
82
Q

What is EPOC and what causes it?

A

a mechanism that allows the body to recover from exercise-induced homeostatic imbalances. It’s caused by the body’s need to release heat, to restore cell’s ion concentration, and restoration of blood pH

83
Q

what are 3 functions of smooth muscle?

A
  1. peristalis
  2. formation of sphincters
  3. regulation of flow
84
Q

In smooth muscle cells, both thick and thin filaments are longer, and the thin filament lacks………. Myosin heads are found along the entire length of the thick filament.

A

troponin

85
Q

What two things do smooth muscle cells lack?

A

motor-end plates, and t-tubules

86
Q

Smooth muscle cells respond to multiple stimuli including:

A

mechanical, hormonal, nervous system, and local pacemaker cell

87
Q

Contraction of smooth muscle involves influx of extracellular calcium ions that bind to

A

calmodulin

88
Q

the calcium ion and calmodulin complex activate an enzyme called?

A

myosin-light chain kinase (MLCK)

89
Q

what is a latch state?

A

a state in which the smooth muscle cell maintains tension while consuming very little ATP

90
Q

What are the 2 types of smooth muscle?

A
  1. Single unit smooth muscle: found in all hollow organs.

2. Multi-unit smooth muscle cell: the more rare type, found in the uterus and eyes, made for precision

91
Q

What is a pacemaker cell in cardiac tissue, and what is its function?

A

cells that provide the electrical stimulation to the heart (since it isn’t stimulated by the nervous system). Allows heart to be autorhythmic (sets its own pace).

Biol 223 (13 decks)

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