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MSK Test 1 > LEC-2 Skeletal Muscle Physiology > Flashcards

LEC-2 Skeletal Muscle Physiology Flashcards

1
Q

Skeletal muscle makes up __% of one’s body mass.

A

40%

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2
Q

Smooth muscle makes up __% of one’s body mass.

A

~5%

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3
Q

Cardiac muscle makes up __% of one’s body mass.

A

~5%

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4
Q

(T/F) Skeletal muscle is able to be controlled via hormones.

A

False. Skeletal muscle is not able to be controlled via hormones.

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5
Q

(T/F) Smooth muscle is able to be controlled via hormones.

A

True.

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6
Q

(T/F) Cardiac muscle is able to be controlled via hormones.

A

True.

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7
Q

A(n) _____________ is a structural myofibril unit and also the distance between two Z discs.

A

Sarcomere

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8
Q

What are the three components of a troponin molecule?

A
  • Troponin C - Binds to calcium ions to produce a conformational change in Troponin I
  • Troponin T - Binds to tropomyosin, interlocking them to form a troponin-tropomyosin complex
  • Troponin I - Binds to actin in thin myofilaments to hold the troponin-tropomyosin complex in place
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9
Q

Troponin (I/C/T) binds to tropomyosin, interlocking them to form a troponin-tropomyosin complex.

A

Troponin T

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10
Q

Troponin (I/C/T) binds to actin in thin myofilaments to hold the troponin-tropomyosin complex in place. It also serves to inhibit the association of actin and myosin.

A

Troponin I

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11
Q

Troponin (I/C/T) binds to calcium ions to produce a conformational change in the troponin complex.

A

Troponin C

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12
Q

Myosin exists as a hexamer consisting of __ heavy chains and __ light chains.

A
  • 2 heavy chains
  • 4 light chains
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13
Q

There are __ thin filaments surrounding each thick filament

A

6

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14
Q

(T/F) F-actin molecules exist as single globular proteins that polymerize to form G-actin.

A

False. G-actin molecules exist as single globular proteins that polymerize to form F-actin (filamentous actin).

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15
Q

What is the shape of F-actin?

A

Double helix

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16
Q

What polymerizes to cover the active sites of F-actin?

A

Tropomyosin

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17
Q

__________ serves to attach F-actin to the Z-line.

A

α-actinin

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18
Q

__________ serves to terminate G-actin polymerization

A

β-actinin

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19
Q

__________ is a structural protein that imparts elasticity to the sarcomere.

A

Titin

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20
Q

Describe the general mechanism of muscle contraction.

A
  1. An action potential travels along a motor neuron to a group of muscle fibers.
  2. At the neuromuscular junction the nerve releases a small amount of ACh.
  3. ACh binds to its receptors and opens local cation channels.
  4. Large quantities of Na+ ions diffuse inside the muscle fiber, causing local depolarization and opening of additional Na+ channels.
  5. The AP travels along the muscle fiber membrane and travels to the center of the muscle through T-tubules. Upon reaching the sarcoplasmic reticulum, it releases large amounts of calcium ions.
  6. Calcium ions initiate attractive forces between actin and myosin filaments, causing them to slide in the contractile process.
  7. After a fraction of a second, the calcium ions are pumped back into the SR by a Ca2+ membrane pump and remain there until a new AP.
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21
Q

Removal of calcium ions from myofibrils causes the muscle contraction to (speed up/slow down/cease)

A

Cease

22
Q

What is an isometric contraction?

A

A contraction that results when tension on the muscle is allowed to increase, but the muscle length remains constant throughout. For example, trying to lift a car or push against a door frame.

23
Q

What is an isotonic contraction?

A

A contraction that results when tension placed upon the muscle remains constant throughout the motion, but the muscle length changes. For example, a weight lifter performing a bicep curl with a 25lb. weight.

24
Q

___________ tension is tension that develops in muscle while stretching the muscle to different lengths.

A

Passive

25
Q

__________ tension is tension caused by stimulating the muscle to contract at differing lengths.

A

Total

26
Q

(T/F) You may calculate active tension by adding passive and total tension together.

A

False. Active tension is the difference between total and passive tension.

27
Q

The denervation/re-innervation of a motor unit by another motor neuron (increases/decreases) the subsequent size of the new motor unit.

A

Increases

28
Q

Motor units for a motion are recruited in order of size from (largest/smallest) to (largest/smallest).

A

Recruited in order of size from smallest (first) to largest (last)

29
Q

What are the two mechanisms of increased tension development in skeletal muscle?

A
  • Multiple fiber summation or recruitment of additional motor units
  • Wave summation (increased firing frequency of a single motor neuron)
30
Q

The amount of ATP consumed by contracting muscle depends on what two factors?

A
  • The load placed on the muscle
  • The rate at which the muscle contracts
31
Q

Short-term regeneration of ATP may be accomplished by transferring a phosphate from a phosphocreatine molecule to an ADP molecule. This process is done by the enzyme _________________.

A

Creatine kinase

32
Q

Short-term regeneration of ATP may be accomplished by transferring a phosphate group from a single ADP molecule to another ADP molecule, resulting in AMP + ATP. This process is done by the enzyme ______________.

A

Adenylate kinase

33
Q

What are the three methods of long-term regeneration of ATP within muscle?

A
  1. Aerobic glycolysis
  2. TCA cycle and oxidative phosphorylation
  3. β-oxidation of fats and ketone bodies
34
Q

Type (I/IIA/IIB) skeletal muscle fiber is defined as red and fast oxidative.

A

IIa (best for running an intermediate sprint)

35
Q

Type (I/IIA/IIB) skeletal muscle fiber is defined as red and slow oxidative.

A

I (best for running a marathon)

36
Q

Type (I/IIA/IIB) skeletal muscle fiber is defined as white and fast glycolytic.

A

IIb (best for running a short sprint)

37
Q

What are the three determinants of muscle fiber type?

A
  • Genetics
  • Training
  • Motor nerve innervation
38
Q

_____ is a member of the TGF-β superfamily that functions as a negative regulator of muscle growth.

A

Myostatin (GDF8)

39
Q

_____________________ are members of a family of proteins called ligand-gated ion channels that are found in skeletal muscle and synapse between pre- and post-ganglionic fibers in SNS.

A

Nicotinic acetylcholine receptors

40
Q

The nicotinic acetylcholine receptor is comprised of ___ subunits.

A

5

41
Q

Which subunits of the ACh receptor bind to ACh?

A

The two α-subunits

42
Q

The ________________ is the membrane potential generated on the postsynaptic side of the neuromuscular junction.

A

Endplate potential

43
Q

The ____________ receptor is a voltage-dependent channel located within the T-tubule. It is in close relation to the __________ receptor located on the sarcoplasmic reticulum. Together, these receptors propagate calcium release from the SR.

A
  • Dihydropyridine receptor is a voltage-dependent channel.
  • Ryanodine receptor is located on SR
44
Q

What are the immediate effects of a motor nerve section?

A
  • Paralysis; loss of voluntary and reflex contractions
  • Muscle fasciculations due to irregular release of ACh
45
Q

What are the effects 2 hours after a motor nerve section?

A
  • Failure of distal end of motor neuron to elicit muscle contraction (despite presence of ACh vesicles)
  • Disappearance of MEPPs, followed by a return 1 week later
46
Q

What are the effects 2 weeks after a motor nerve section?

A
  • Muscle becomes increasingly sensitive to ACh
  • ACh receptors appear outside neuromuscular junction again
  • Spontaneous fibrillations in response to circulating ACh
  • Eventually re-innervation and restoration of the severed NMJ will occur
47
Q

__________ and __________ are used to inhibit AChE which increases ACh levels within the synaptic cleft. These are used to treat glaucoma and myasthenia gravis.

A

Pyridostigmine and neostigmine

48
Q

__________ are chemicals that irreversibly inhibit AChE. They are present in nerve gases and insecticides.

A

Organophosphates

49
Q

__________ are CNS depressants that decrease activity of the reticular formation through manipulation of GABA receptors. They function by increasing the frequency of opening for the inhibitory GABA receptor.

A

Benzodiazepines

50
Q

_________ is a drug that inhibits Ca2+ release by the sarcoplasmic reticulum.

A

Dantrolene

51
Q

Complete the following table.

A

Complete the following table.

52
Q

Complete the following table:

A

Complete the following table.

MSK Test 1 (11 decks)

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