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Human Physiology > Human Phys 2.4 > Flashcards

Human Phys 2.4 Flashcards

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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?

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A

G-actin subunits polymerized together

21
Q

How does actin facilitate whole cell locomotion?

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A

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

22
Q

Fimbrin

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A

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

23
Q

Alpha actin

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A

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

24
Q

Tropomyosin

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A

Stabilizes filament

25
Capping protein
Prevents assembly and disassembly at plus end
26
What is myosin 2 a member of?
Larger superfamily of myosin proteins
27
What is the myosin superfamily a member of?
Larger family of motor proteins
28
What was the first motor protein identified?
Skeletal muscle myosin
29
How did myosin 2 get its name?
It has 2 heads
30
What is myosin composed of?
2 heavy chains and 4 light chains
31
How is the myosin head formed?
One end of each tail is folded
32
How does shortening of the sarcomere happen?
Myosin heads attach to filaments and pull z discs together
33
How many individual myosin molecules make up a myosin filament?
200 or more
34
What is another name for a myosin head?
Cross bridge
35
How does muscle contraction occur?
By sliding the myosin filament past the actin filament without any change in length of either filament
36
How many cycles does a myosin head have per contraction?
5x per second
37
What are accessory proteins responsible for?
Structural uniformity of the sarcomere
38
What is the actin filament anchored to the z disc by?
Cap Z and alpha actin on the plus end
39
What does the Z disc cap?
Actin filament and prevents depolymerization
40
Nebulin
Helps determine exact length of each actin filament
41
What are the minus ends capped by?
Tropomodulin
42
What do opposing pairs of titin molecules do?
Position thick filaments midway between z discs
43
What does titin do?
Acts like a molecular spring and allows the muscle fiber to recover after being overstretched
44
What is the function of the tropomyosin in skeletal muscle?
Acting as a “relaxed protein” at rest by covering up the sites where myosin binds to actin
45
Troponin complex I
Inhibits binding of myosin head
46
Troponin complex C
Binds to Calcium
47
Troponin complex T
Is what binds troponin to tropomyosin
48
What causes the tropomyosin to move revealing myosin binding sites on actin?
Calcium binding to troponin C

Human Physiology (41 decks)

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