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SF1 - Test 2 > 2 - Green - Muscle Physiology > Flashcards

2 - Green - Muscle Physiology Flashcards

1
Q

bHLH

A

Basic helix-loop-helix

Structural region on MyoD that is required for activity and dimerization

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2
Q

E-box

A

Binding site in DNA for myogenic factors

Required to activate transcription

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3
Q

Excitation-Contraction Coupling

A

Pysiological process of converting an electrical stimulus to the muscle into a contraction

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4
Q

Power Stroke

A

Molecular intractions between actin and myosin that lead to muscle contraction

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5
Q

Satellite Cells

A

Stem Cells found in skeletal muscle fibers that promote repair and regeneration

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6
Q

SERCA

A

Sarcoendoplasmic reticulum calcium ATPase

Pump located in sarcoplasmic reticulum (SR) that transports Ca2+ from the cytoplasm into the SR

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7
Q

Summation Contraction

A

Short duration contraction caused consecutive action potentials

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8
Q

Tetanus Contraction

A

Steady, prolonged contraction caused by continuous stimulation

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9
Q

Twitch Contraction

A

Single muscle contraction caused by one action potential

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10
Q

How are myotubes formed? What is uniqe anout thoe organelle structure?

A

Single cell myoblasts fuse to form multinucleated myotubules

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11
Q

What transcription factors drive fusion of myogenic cells?

A

MyoD

myogenin

myf-5

MRF-4/herculin/myf-6

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12
Q

MyoD Structure

A

Nuclear phosphoprotein

Contains bHLH region

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13
Q

How are transcription factors utilized to drive myogenic fusion?

A

Dimers

homodimers okay, but hetero-dimers with E2 proteins best

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14
Q

What is present in most muscle-specific enhancers in multiple copies?

A

E-boxes

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15
Q

E2 Family of Genes

A

E2A

E2-2

HEB

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16
Q

How is transcription activated?

If no E-boxes are present, how are these regulated?

Where does specificity reside?

What affect doe MyoD initiate have on the regulatory regions?

A

MyoD complexes must bind two or more upstream E-Boxes

Intermediate proteins

Specificity resides in the basic region

MyoD initiates chromatin remodeling

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17
Q

Do differentiated muscle cells continue to divide?

A

No

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18
Q

What are the early and late myogenic proteins?

A

MyoD, Myf5 = Early

Myogenin, MRF4 = Late

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19
Q

What can a loss of Myostatin result in?

A

Hughed Jacked Man

Yolked diesel cows

20
Q

What is the chief negative regulator of muscle growth?

By what mechanism does it work?

How is it activated?

A

Myostatin

Inhibits myoblast proliferation, inhibits progression of myoblasts from G1 to S

Activated by MyoD binding to E-box in myostatin promoter

21
Q

Gain of Function (GoF)

vs

Loss of Function (LoF)

[Myostatin]

A

GoF = Overexpression = Fewer Muscle Cells

LoF = Underexpression = Jacked and Tan

22
Q

What are recruited to repair and regenerate muscle?

What do they act on?

Where are they located?

A

Satellite cells are recruited to supply myoblasts for repair and regeneration

located on surfact of muscle fiber, beneath basal lamina

23
Q

What is the status of satellite cells on a regular basis?

How are they activated?

A

Quiescent until needed

Activated by immune response to injury

24
Q

How does weight training increase muscle mass?

What regulates this activity?

What androgen may play a role in this?

A

Microtrauma activates satellite cells

Growth factors and hormones regulate–stimulate increase in protein and glucose uptake

testosterone may have direct regulatory effect on satellite cells

25
Q

2 Light Chains

2 Heavy Chains

A

Essential and Regulatory

Ea/ has globular head and filamentous tail

26
Q

Myosin Cross Bridge

A

Composed of head, project from thick filament, links thick and thin myofilaments

27
Q

What does myosin act as biologically?

What does it bind to?

Where are these properties located?

A

ATPase, releases chemical energy for contraction

Binds to actin

Globular head

28
Q

Tropomyosin

A

Lies in groove between two strands of actin

Regulatory function and provides structural rigidity to actin; blocks active sites

29
Q

Troponin

A

Complex of three proteins:

T - binds troponin to tropmyosin

C - high/low affinity for Ca2+

I - Inhibits interaction between actin and myosin

30
Q

Titin

A

Spring like molecule that extends from M-line to Z-disc, keeps myosin filaments centered in sarcomere and maintain resting tension that allows muscle to snap back if overextended

31
Q

Nebulin

A

Associated with actin

regulates assembly and alignment of actin filaments

32
Q

Free cytostolic Calcium levels in relaxed muscle?

What happens upon stimulation?

What does it bind to? Result?

A

Low

Levels greatly rise

Binds to troponin C to change conformation and open binding sites

33
Q

What leads to E-C Coupling?

What does this result in?

A

Excitation of motor end plate by nerve leads to influx of sodium ions

Results in depolarization of muscle plasma membrane (sarcolemma), open V.G. Sodium Channels.

34
Q

Once the action potential initiates a wave of depolarization, how does it travel?

What do these contain?

What is the result?

A

T-tubular system of sarcolemma

Voltage gated calcium channels (dihydropyridine - DHP)

Calcium release

35
Q

How is Calcium released from the sarcoplasmic reticulum?

What causes these to open?

A

Through channels with Ruanodine receptor 1 or RyR1

Activated through protein-protein interaction with DHP channels in T-tubule membrane

36
Q

What recaptures Ca2+ in the cytoplasm?

Where is it returned?

A

Sarcoendoplasmic Reticulum Calcium ATPase (SERCA)

Terminal cisternae

37
Q

What “cocks” the myosin head?

A

Myosin-Actin + ATP -> M-ATP + A

ATPase on myosin hydrolzyes ATP

Conformational change of M-ATP to M*-ADP-Pi

M* = high energy state

38
Q

What are last two steps of myosin-actin interaction, and what is the result?

A

Pi and ADP are released sequentially, causing ratchet movement

  • power stroke
39
Q

Movements during power stroke?

A

Actin towards M-line of sarcomere

Z-bands toward eachother

Sarcomere shortening (contracting)

40
Q

Rigor mortis

A

No ATP

Actin not released from myosin

41
Q

Analogy for Actin-Myosin interaction?

A

ATP Cocks Myosin trigger

Actin+Myosin pulls trigger

Stored energy released

42
Q

Chloride Channel (CIC-1)

A

Responsible for large resting chloride conductance of skeletal muscle

Stabilizes resting membrane potential preventing false action potentials

Repolarizes membrane following contraction

43
Q

Why is calcium readily pumped back into SR cisternae by SERCA during relaxation?

What protein helps clear this calcium?

A

Ca2+ has higher affinity for pumps than for troponin C

Calsequestrin

44
Q

What are three sources to replenish ATP?

A

(In this order)

  1. Creatine Phosphate
  2. Glycolysis
  3. Oxidative Phosphorylation
45
Q
A

SF1 - Test 2 (13 decks)

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