Muscles Flashcards

1
Q

What is another word for cell?

A

Myocytes

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2
Q

Did muscles evolve before or after the sponge? And why?

A

Muscles probably developed after the sponges since sponges do not have muscles, and they are the only animals that lack muscles.

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3
Q

What animal did muscles evolve from?

A

Cnidarians, which include hydra and corals.

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4
Q

What can the initial invention of muscles be described as?

A

the ability to organize basic cytoskeletal machinery into arrangements that permitted the cells to change shape.

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5
Q

How can cells move? And how does this connect with the initial evolution of muscles from Cnidarians?

A

Cells can be moved by changing how cytoskeletal proteins interact with each other.

Cnidarians probably first was arrange these proteins into a complex matrix.

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6
Q

What are the 3 main filaments in the cytoskeleton?

A

Microtubules: are made of tubulin

Intermediate Filaments: made up of lots of different things

Actin filaments:

*each of these filaments have a role in structure.

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7
Q

What are stress fibers?

A

collections of actin into more rigid structures that are importsnt for changing the shape of the cell.

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8
Q

What do we focus on when talking about cellular movement?

A

Microtubules and actin, as they serve as tracks over which motor proteins walk.

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9
Q

What does it mean when a structure has polarity?

A

the polymer is arranged in a way that has two distinct ends, which we call positive or negative.

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10
Q

What is the main function of microtubules?

A

maintenance of cell shape (compression resisting), cell motility (as cilia or flagella), chromosome movements in cell division, organelle movements. Made up of tubulin.

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11
Q

What is the main function of microfilaments (Actin filaments)?

A

maintenance of cell shape (tension bearing elements), changes in cell shape, muscle contractions, cytoplasmic streaming in plant cells, cell motility, division of animal cells. Made up of actin.

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11
Q

What is the main function of microfilaments (Actin filaments)?

A

maintenance of cell shape (tension bearing elements), changes in cell shape, muscle contractions, cytoplasmic streaming in plant cells, cell motility, division of animal cells. Made up of actin.

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12
Q

What is the main function of intermediate filaments?

A

maintenance of cell shape (tension bearing elements), anchorage of nucleus and certain other organelles, formation of nuclear lamina. They are made up of several different proteins (such as keratins).

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13
Q

How do motor proteins change their shape?

A

motor proteins use the energy of ATP hydrolysis to change their three dimensional shape.

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14
Q

What are 3 main motor proteins? What makes them relevant?

A

Kinesin, dynein, and myosin.

Each of them has a head that id the part that walks on the track, and a tail that binds something to be moved. Kinesin and dynein are motor proteins that walk along their microtubule tracks. This is as they recognize the polarity of a microtubule, one walks toward the positive end and one on the negative end. Myosin walks over actin, and they are in all eukaryotic cells and all animal cells as part of the cytoskeleton.

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15
Q

What back and forth process do kinesin and dynein mediate?

A

Underneath axons are microtubules. the vesicles of neurotransmitters are constructed in the cell body, then carried to the axon termini. When emptied they are carried back to the cell body to get remade. The back and forth of this process if when Kinesin and dynein mediate.

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16
Q

What is a homodimer? And what is an example of one?

A

it is a protein composed of two polypeptide chains that are identical in the order, number, and kind of their amino acid residues. It has two subunits of the same protein.

Myosin can be an example of one (the type II one).

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17
Q

What do proteins along the neck of myosin II do?

A

The proteins on the neck between the head and long tail of the myosin motor helps to regulate the catalytic properties of this myosin.

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18
Q

Why might there be confusion with the myosin II motor?

A

the single subunit is called myosin, the homodimer is called myosin, and the heterohexamer is also called myosin. Therefore, you have to know context to be able to talk about its structure and function.

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19
Q

How individual myosins exist within cells?

A

They often exist with their tails attached to the other proteins, and through those connections, the cell membrane. The myosin head binds the microfilament and when it hydrolyzes ATP, it bends at the neck and pulls the actin toward its own tail. As well, within muscle actin does the same sort of movement, and the bending triggers a different kind of more complicated movement.

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20
Q

What happens with myosin that are used to make muscle?

A

the myosin molecules assemble themselves into a thick filament. On the end of the filament it looks like a bouquet of flowers, with the tails being the stems at one end and the heads sticking in diff directions as the flowers.

21
Q

How is a thick myosin filament formed in muscle?

A

when one bouquet binds to another bouquet of myosin, tail to tail. each myosin head is sticking out in this form, looking for actin to bind.

22
Q

What happens when a myosin head binds to actin?

A

if it is able to bind, then it uses the energy of ATP hydrolysis to bed its neck, pulling the actin toward its tail.

23
Q

What are thin filaments?

A

thick filaments are arranged in a muscle so that it is surrounded by actin filaments, where are called think filaments.

24
Q

What do thin filaments have them? What type of binding proteins are they?

A

These are decorated with actin binding proteins, troponin and tropomyosin. These proteins occur at regular intervals (1 per 7 actin monomers) and control actin-myosin interactions. In a muslce, these proteins essentially block the place on actin where myosin binds.

25
Q

How do tropomyosin and troponin work together to control the actin-myosin interactions?

A

tropomyosin is a long thing protein that blocks a series of 7 myosin binding sites. Troponin is what ensures that the tropomyosin is in the right position.

26
Q

What happens when calcium enters the actin-myosin interaction?

A

When calcium comes in, it binds to troponin (which is trying to stop this interaction) and that structural change triggers the troponin-tropomyosin complex to roll out of the way, letting myosin to bind to actin.

27
Q

Does the arrangement of thick and thin filaments change in different muscle cell types?

A

Yes, the thin and thick filaments are found everywhere in muscle cells, but arrangements differ depending on cell type. This would be present in the differences between smooth and striated muscle.

28
Q

How do thick and thin filaments arrange themselves in smooth muscle? How do they arrange themselves in striated muscle?

A

Smooth: thick and thin filaments are distributed throughout the cell and go in every directions, this allows it to contract in all dimensions

Striated: thick and thin filaments are arranged into a three dimensional array of repeating units.

29
Q

What is a sarcomere? What is the organization of it?

A

z-disc to z-disc is the place where the ends of the actin filaments are embedded into an array. the thick filaments are arranged to fit between z-discs, interacting with actins emerging from the z-disc. When actin and myosin interact, myosin pulls the actin to bring the Z discs closer together. This is the repeating contractile unit called the sarcomere. This gives the striated appearance.

30
Q

What are myofibrils?

A

long strings of sarcomeres make this structure. bundles of myofibrils are arranged side by side in a myocyte. They are the working bits.

31
Q

What is the sarcomere length?

A

the distance between Z discs.

32
Q

What happens when z discs are activated?

A

the muscle cell starts to contract, and the z-discs become closer together and then at some point it is reduced by 1/2 or 1/3 of its length.

33
Q

Can the cell get shorter if the z-discs are bumping into the filament?

A

No. Every muscle has a natural range.

34
Q

What happens when myosin binds?

A

It generates force. If the sarcomere is free to move, that force shortens the sarcomere length. As force is translated into shortening.

35
Q

Why are there situations why Z discs can’t move?

A

It has already shortened its maximum length. In these situations, the myosin binding causes the same force, but the muscles can’t shorten. Therefore, there isn’t always a shortening in an activated muscle.

36
Q

What is myosin often called?

A

a mechano enzyme, since it is an enzyme that breaks down ATP, and when this happens it experiences a major change in structure.

37
Q

Does myosin always have ATP floating around?

A

Yes.

38
Q

How is myosin ATPase activated?

A

when calcium appears.

39
Q

What is the interaction between motor nerve and muscles?

A

an axon from a motor neuron comes in and one axon terminus interacts with one muscle cell. Each single cell has one neuron controlling it?

40
Q

What are T tubules?

A

to enhance the penetration oft he depolatization into the depthhs of the cell, all over the cell membrane there are invaginationa that push cell membranes into the cell, which creates T tubules.

these are juxtapositioned to the muscle enviplasmic reticulum, known as the SR (sarcoplasmic reticulum)

41
Q

What happens when the T Tubules depolarize?

A

it triggers the opening of the calcium channels in the SR, which causes the calcium to rush into the muscle cytoplasm, known as sacroplasm.

42
Q

How can you modulate how much force you generate?

A

by changing the number of cells that are stimulated.

43
Q

How does cicada make its buzzing noise?

A

it has a muscle that bends a piece of exoskeltan and when it snaps back it clicks and it does this hundreds of times a second.

44
Q

How are muscles integrated into a locomotor system?

A

this interaction translates a cell shortening into a productive movement of a limb.

45
Q

How are muscle inserted into bones?

A

by tendons, a type of connective tissue.

46
Q

What happens when a muscle contracts?

A

it pulls onto the bone, causing it to pivot around a joint (called a fulcrum).

47
Q

How is it determined whether a limb will swing forcefully or quickly?

A

It depends on how close the insertion point is to the fulcrum

48
Q

What are locomotor modules?

A

when individual muscles are combined with each other and the skeleton

49
Q

What do many locomotor activities include?

A

antagonistic muscle arrangements

50
Q

Describe antagonistic groups of muscles and an example.

A

they are controlled to manage productive movement. Butterflies have two muscles, one that pulls up the wing and one that pulls the wing down.

51
Q

Are all muscles arranged into antagonistic controls?

A

No, they can have other ways to cause the limb to return to position following a contraction.

Flea: since fleas jump a meter high, it uses a muscle to slowly load up part of its leg into what amounts to a catapult, and when it wants to jump it releases the loaded leg and it springs back faster than any muscle could possibly contract.