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Human Physiology > Human Phys 2.4 > Flashcards

Human Phys 2.4 Flashcards

1
Q

Walk along theory of contraction steps

A
  1. Myosin head is stuck attached to actin in a rigor configuration
  2. An ATP molecule binds to the myosin allowing the head to detach from the actin filament
  3. The ATP is then broken down into a phosphate and ADP and this allows the head to return to normal position to get ready to bind again
  4. A weak binding of myosin head to actin causes the release of a phosphate and this release triggers a powerstroke
  5. In the course of the power stroke the ADP is lost and it is back in the attached rigor position
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2
Q

What are the four classes of muscle cells?

A

Skeletal muscle fibers

Heart muscle cells

Bundle of smooth muscle cells

Myoepithelial cell

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3
Q

The cross bridges of the sarcomere in skeletal muscle are made up of what?

A

Myosin

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4
Q

What does each muscle fiber do in muscles?

A

Extends the whole length of the muscle

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5
Q

What is each fiber in a muscle innervated by?

A

Single nerve ending

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6
Q

How long is each fiber in a muscle?

A

2-3 cm long and 100 um in diameter

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7
Q

What are myofibrils composed of?

A

3000 actin filaments and 1500 myosin filaments

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8
Q

What does endomysium surround?

A

Muscle fibers

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9
Q

What does perimysium surround?

A

Muscle fascicles

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10
Q

What does the epimysium surround?

A

Whole muscle

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11
Q

Where are blood vessels and nerves that supply the muscle fibers found?

A

Within the perimysium

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12
Q

What is the sarcomere between?

A

Z discs

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13
Q

What type of fiber is a skeletal muscle fiber?

A

Multi nucleated fiber

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14
Q

What is the sarcomere?

A

Portion of the myofibril that lies between 2 Z discs

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15
Q

What do light bands indicate on a sarcomere?

A

Only actin

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16
Q

What do dark bands indicate on a sarcomere?

A

Actin overlapping myosin

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17
Q

What is the length of the sarcomere at contraction?

A

2 microns (gets shorter with contraction)

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18
Q

What are actin important for?

A

Component of a cells cytoskeleton

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19
Q

What does actin do?

A

Determines the shape of the cells surface and are necessary for whole cell locomotion

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20
Q

What makes up an actin filament?

A

G-actin subunits polymerized together

21
Q

How does actin facilitate whole cell locomotion?

A

It can break down into subunits to move and then re polymerize when its location is reached

22
Q

Fimbrin

A

Accessory protein that causes tight packing (contractions are not possible)

23
Q

Alpha actin

A

Accessory protein that helps keep actin filaments apart (allows contraction)

24
Q

Tropomyosin

A

Stabilizes filament

25
Q

Capping protein

A

Prevents assembly and disassembly at plus end

26
Q

What is myosin 2 a member of?

A

Larger superfamily of myosin proteins

27
Q

What is the myosin superfamily a member of?

A

Larger family of motor proteins

28
Q

What was the first motor protein identified?

A

Skeletal muscle myosin

29
Q

How did myosin 2 get its name?

A

It has 2 heads

30
Q

What is myosin composed of?

A

2 heavy chains and 4 light chains

31
Q

How is the myosin head formed?

A

One end of each tail is folded

32
Q

How does shortening of the sarcomere happen?

A

Myosin heads attach to filaments and pull z discs together

33
Q

How many individual myosin molecules make up a myosin filament?

A

200 or more

34
Q

What is another name for a myosin head?

A

Cross bridge

35
Q

How does muscle contraction occur?

A

By sliding the myosin filament past the actin filament without any change in length of either filament

36
Q

How many cycles does a myosin head have per contraction?

A

5x per second

37
Q

What are accessory proteins responsible for?

A

Structural uniformity of the sarcomere

38
Q

What is the actin filament anchored to the z disc by?

A

Cap Z and alpha actin on the plus end

39
Q

What does the Z disc cap?

A

Actin filament and prevents depolymerization

40
Q

Nebulin

A

Helps determine exact length of each actin filament

41
Q

What are the minus ends capped by?

A

Tropomodulin

42
Q

What do opposing pairs of titin molecules do?

A

Position thick filaments midway between z discs

43
Q

What does titin do?

A

Acts like a molecular spring and allows the muscle fiber to recover after being overstretched

44
Q

What is the function of the tropomyosin in skeletal muscle?

A

Acting as a “relaxed protein” at rest by covering up the sites where myosin binds to actin

45
Q

Troponin complex I

A

Inhibits binding of myosin head

46
Q

Troponin complex C

A

Binds to Calcium

47
Q

Troponin complex T

A

Is what binds troponin to tropomyosin

48
Q

What causes the tropomyosin to move revealing myosin binding sites on actin?

A

Calcium binding to troponin C

Human Physiology (41 decks)

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