Muscles

Question 1

What is another word for cell?

Answer 1

Myocytes

Question 2

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

Answer 2

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

Question 3

What animal did muscles evolve from?

Answer 3

Cnidarians, which include hydra and corals.

Question 4

What can the initial invention of muscles be described as?

Answer 4

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

Question 5

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

Answer 5

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

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

Question 6

What are the 3 main filaments in the cytoskeleton?

Answer 6

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.

Question 7

What are stress fibers?

Answer 7

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

Question 8

What do we focus on when talking about cellular movement?

Answer 8

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

Question 9

What does it mean when a structure has polarity?

Answer 9

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

Question 10

What is the main function of microtubules?

Answer 10

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

Question 11

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

Answer 11

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.

Question 11

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

Answer 11

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.

Question 12

What is the main function of intermediate filaments?

Answer 12

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).

Question 13

How do motor proteins change their shape?

Answer 13

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

Question 14

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

Answer 14

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.

Question 15

What back and forth process do kinesin and dynein mediate?

Answer 15

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.

Question 16

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

Answer 16

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).

Question 17

What do proteins along the neck of myosin II do?

Answer 17

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

Question 18

Why might there be confusion with the myosin II motor?

Answer 18

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.

Question 19

How individual myosins exist within cells?

Answer 19

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.

Question 20

What happens with myosin that are used to make muscle?

Answer 20

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.

Question 21

How is a thick myosin filament formed in muscle?

Answer 21

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.

Question 22

What happens when a myosin head binds to actin?

Answer 22

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

Question 23

What are thin filaments?

Answer 23

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

Question 24

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

Answer 24

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.

Question 25

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

Answer 25

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.

Question 26

What happens when calcium enters the actin-myosin interaction?

Answer 26

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.

Question 27

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

Answer 27

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.

Question 28

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

Answer 28

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.

Question 29

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

Answer 29

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.

Question 30

What are myofibrils?

Answer 30

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

Question 31

What is the sarcomere length?

Answer 31

the distance between Z discs.

Question 32

What happens when z discs are activated?

Answer 32

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.

Question 33

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

Answer 33

No. Every muscle has a natural range.

Question 34

What happens when myosin binds?

Answer 34

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

Question 35

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

Answer 35

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.

Question 36

What is myosin often called?

Answer 36

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

Question 37

Does myosin always have ATP floating around?

Answer 37

Yes.

Question 38

How is myosin ATPase activated?

Answer 38

when calcium appears.

Question 39

What is the interaction between motor nerve and muscles?

Answer 39

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?

Question 40

What are T tubules?

Answer 40

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)

Question 41

What happens when the T Tubules depolarize?

Answer 41

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

Question 42

How can you modulate how much force you generate?

Answer 42

by changing the number of cells that are stimulated.

Question 43

How does cicada make its buzzing noise?

Answer 43

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.

Question 44

How are muscles integrated into a locomotor system?

Answer 44

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

Question 45

How are muscle inserted into bones?

Answer 45

by tendons, a type of connective tissue.

Question 46

What happens when a muscle contracts?

Answer 46

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

Question 47

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

Answer 47

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

Question 48

What are locomotor modules?

Answer 48

when individual muscles are combined with each other and the skeleton

Question 49

What do many locomotor activities include?

Answer 49

antagonistic muscle arrangements

Question 50

Describe antagonistic groups of muscles and an example.

Answer 50

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

Question 51

Are all muscles arranged into antagonistic controls?

Answer 51

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.