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BIOS4001 - Skeletomuscular System > Common Muscle Disorders > Flashcards

Common Muscle Disorders Flashcards

1
Q

What do muscle fibers use for contraction?

A

Muscle fibers use ATP for contraction

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2
Q

How is ATP generated by the muscle cell?

A

ATP is generated by the muscle cell from:
- creatine phosphate
- glucose & glycogen
- fatty acids

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3
Q

What is direct phosphorylation?

A

The transfer of a phosphate group from creatine phosphate to ADP, which generates ATP.

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4
Q

What is oxidative metabolism?

A

The primary energy source for muscle through oxidative phosphorylation, which generates 34 ATP per glucose.

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5
Q

What is glycolytic metabolism?

A

The primary energy source for muscle through anaerobic glycolysis, which generates 2 ATP per glucose.

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6
Q

What happens if the muscle doesn’t have enough oxygen delivered to it by myoglobin?

A

If the effort is strong and sustained:
- the muscle might not have enough oxygen delivered to it by myoglobin
- resulting in anaerobic glycolysis
- with only 2 ATP formed per glucose and synthesis of lactic acid

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7
Q

What is the demand for ATP in a resting muscle fiber?

A

The demand for ATP is low in a resting muscle fiber

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8
Q

How is ATP generated in a resting muscle fiber?

A

By the breakdown of fatty acids in the mitochondria

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9
Q

What is the fate of glucose in a resting muscle fiber?

A

Some of the mitochondrial ATP is used to convert glucose to glycogen

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10
Q

What is creatine phosphate (CP)?

A

Creatine phosphate (CP) is a high-energy molecule that can be rapidly converted to ATP.

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11
Q

What is the role of mitochondria in a resting muscle fiber?

A
  • generate ATP from the breakdown of fatty acids
  • use some of this ATP to convert glucose to glycogen & creatine to creatine phosphate
  • thus building up energy reserves in the muscle
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12
Q

What happens to the demand for ATP during moderate activity?

A

The demand for ATP increases

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13
Q

Is there still enough oxygen for the mitochondria to meet the increased demand during moderate activity?

A

Yes, there is still enough oxygen for the mitochondria to meet the increased demand

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14
Q

Is excess ATP produced during moderate activity?

A

No, there is no excess ATP produced during moderate activity

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15
Q

What is the primary source of ATP generation during moderate activity?

A

ATP is generated primarily by aerobic metabolism of glucose from stored glycogen

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16
Q

What happens if the glycogen reserves are low during moderate activity?

A

If the glycogen reserves are low, the muscle fiber can also break down other substrates, such as fatty acids.

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17
Q

What is all of the ATP being generated during moderate activity used for?

A

All of the ATP being generated is used to power muscle contraction.

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18
Q

What happens to the demand for ATP during peak activity?

A

The demand for ATP is enormous

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19
Q

Why can’t oxygen diffuse into the muscle fiber fast enough during peak activity?

A

Oxygen cannot diffuse into the fiber fast enough for the mitochondria to meet the enormous demand for ATP.

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20
Q

How much of the cell’s ATP needs can be met by the mitochondria during peak activity?

A

Only a third of the cell’s ATP needs can be met by the mitochondria during peak activity.

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21
Q

Where does the rest of the ATP come from during peak activity?

A

The rest of the ATP comes from glycolysis

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22
Q

What happens when pyruvate is produced faster than the mitochondria can utilize it during peak activity?

A

The pyruvate builds up in the cytosol

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23
Q

What happens to pyruvate in the cytosol during peak activity?

A

The pyruvate is converted to lactate

24
Q

Why do hydrogen ions from ATP hydrolysis not get absorbed by the mitochondria during peak activity?

A

mitochondria is not able to keep up with the rate of H+ production

25
Q

What is the consequence of the buildup of hydrogen ions during peak activity?

A

The buildup of hydrogen ions increases cytosol acidity, which inhibits muscle contraction, leading to rapid fatigue.

26
Q

Question: What are slow fibers?

A

Muscle fibers that have:
- a smaller diameter
- appear darker due to myoglobin
- have lots of mitochondria; fatigue resistant
- extra capillaries

27
Q

What are fast fibers?

A

Muscle fibers that have:
- a larger diameter
- appear paler in color; less myoglobin
- are easily fatigued due to fewer mitochondria and do more glycolysis
- fewer capillaries

28
Q

What is muscle fatigue?

A

A decline in the ability of the muscle to sustain the strength of contraction.

29
Q

What are the causes of muscle fatigue?

A
  • rapid build-up of lactic acid
  • decreased neurotransmitter at the synapse
  • decrease in oxygen supply
  • decrease in energy supply (glucose, glycogen, fatty-acids)
  • psychological causes
30
Q

How does exercise affect muscles?

A

Exercise increases:
- muscle size
- strength
- endurance

31
Q

What is the effect of aerobic (endurance) exercise on muscles?

A

Aerobic exercise promotes increased oxidative capacity of the muscle fiber, resulting in:
- increased blood vessel supply
- increased mitochondria
- stronger, more flexible muscles with greater resistance to fatigue

32
Q

What is the effect of resistance exercise (weight lifting) on muscles?

A

Resistance exercise increases glycolytic activity, which leads to:
- increased synthesis of glycolytic enzymes & myofibrils
- increased muscle size & strength

33
Q

What hormones affect muscle growth?

A
  • testosterone
  • growth hormone (GH)
  • insulin-like growth factor-1 (IGF-1)
  • insulin
34
Q

How does growth hormone (GH) affect muscle growth?

A
  • produced by the pituitary gland
  • stimulates the release of insulin-like growth factor 1 (IGF-1)
  • which promotes muscle growth & increasing bone density
35
Q

How does testosterone affect muscle growth?

A

Increases muscle mass and strength

36
Q

What are ‘Double-Muscled’ animals?

A

Animals that have been selectively bred for increased muscle mass and a double-muscling phenotype

37
Q

What is myostatin?

A

Myostatin is a protein that regulates muscle growth by inhibiting proliferation (cell growth)

38
Q

What happens when myostatin is inhibited?

A

When myostatin is inhibited, muscle growth is increased

39
Q

Why are some animals naturally double-muscled?

A

Because they have mutations that either reduce myostatin production or block its activity

40
Q

What could cause muscle disorders?

A

Muscle disorders can be caused by:
- failures in signaling in the NS
- problems with synaptic transmission
- issues with the muscle itself

41
Q

How are muscle cramps caused?

A

Muscle cramps are caused by hyperexcitability of the somatic motor neuron controlling the muscle

42
Q

How can muscle cramps be relieved?

A

Stretching the muscle relieves muscle cramps by sending sensory information back to the CNS to inhibit the motor neurons

43
Q

What are some consequences of muscle overuse and trauma?

A

Muscle overuse can result in muscle fatigue and trauma can cause tearing of the muscle tissue

44
Q

What is muscle disuse?

A

Muscle disuse occurs when a muscle is not used or immobilized for an extended period

45
Q

How can muscle disuse affect muscles?

A

Causes muscle atrophy

46
Q

What is mucle atrophy?

A

Where the muscle fibers get smaller, and the blood supply to the muscle diminishes.
- muscle atrophy longer than a year is permanent

47
Q

What are some examples of acquired muscle disorders?

A

Acquired disorders can result from:
- infectious diseases (e.g., influenza)
- poisoning by toxins (e.g., botulinum toxin)
- tetanus (e.g. tetanus toxin)

48
Q

What are inherited muscle disorders?

A

Include:
- muscular dystrophy
- biochemical defects in glycogen & lipid storage

49
Q

What is Duchenne muscular dystrophy?

A

Duchenne muscular dystrophy is a genetic disorder that results in the absence of the cytoskeletal protein dystrophin

50
Q

What are the consequences of Duchenne muscular dystrophy’s absence of dystrophin?

A

Leads to tiny tears in the muscle fibers:
- which allow Ca ions to enter & activate enzymes
- that break down fiber components
- resulting in muscle weakness and degeneration

51
Q

What is myasthenia gravis?

A

An autoimmune disease where antibodies are produced against the ACh receptors

52
Q

What are the consequences of the autoimmune response against Ach receptors?

A

Results in a reduction in the number of Ach receptors at the neuromuscular junction, leading to muscle weakness and fatigue

53
Q

What is the effect of curare on skeletal muscle?

A

Curare is a compound that binds to the ACh receptor without activating it, which results in the inhibition of muscle contraction and paralysis

54
Q

What is the effect of botulism toxin on the synapse?

A

Botulism toxin prevents the release of the neurotransmitter into the synapse, resulting in the inhibition of muscle contraction and paralysis.

55
Q

What is the effect of nerve gas on the synapse?

A
  • inhibits AChE present in the synapse
  • which leads to the accumulation of ACh & overstimulation of the muscle
  • resulting in muscle spasm, convulsions, & paralysis
56
Q

What is the effect of nerve gas on the synapse?

A
  • inhibits acetylcholinerestase (AChE) present in the synapse
  • which leads to the accumulation of Ach & overstimulation of the muscle
  • resulting in muscle spasm, convulsions, & paralysis

BIOS4001 - Skeletomuscular System (13 decks)

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