Skeletons, Muscles and Movement

29 important questions on Skeletons, Muscles and Movement

What do animals do in order to move?

Exert force against the environment

What are hydrostatic skeltons?

FLuid under pressure in closed compartments, animals can move by contracting muscles in one part of the body to push fluid into another part. These provide no protection

What is an example of an animal that has a hydrostatic skeleton?

The earthworm
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What kind of skeleton do arthropods have?

A jointed exoskeleton

What secretes the exoskeleton

the epidermis

How is the exoskeleton hardened?

With added quinones and then furthered hardened with calcium carbonate

What do chordates use for their endoskeleton?

Bone, which is made of living cells and an extracellular matrix of collagen fibers in which are embedded crystals of calcium phosphate

How are skeletons attached?

Antagonistically, each works to move the skeleton in a direction opposite to the other

What are the two kinds of myofilaments?

Thick and thin

What are thin filaments made of?

Of two strands of actin and one strand of regulatory proteins

What is a myofibril made of?

A series of sarcomere joined end to end

What are thick filaments made of?

Protein myosin

Why do contractions occur in muscles and what is this called?

Contractions occur because filaments slide past one another; it is

Do all cross bridges detach at once?

No, when one detaches, others are still attached

What is the name of the cycle that describes how thin filaments get energy?

The Cross-Bridge Cycle

When does the cross-bridge detach?

When a molecule of ATP binds

What happens after ATP binds?

ATP is hydrolyzed, mysoin in its high-energy form. ADP and Pi are NOT released and the energized myosin attaches to actin

What happens after the energized mysoin head attaches to actin?

ADP and Pi are released, the myosin head returns to its original form and changes shape

What is the power stroke?

When the cross bridge is attached, it moves the thin filament toward the center of the sarcomere

What does calcium do in excitation-contraction coupling?

It binds to troponin and alters the way that troponin binds tropomyosin, freeing myosin and allowing cross bridges to occur

What is the sarcoplasmic reticulum?

A special type of endoplasmic reticulum that stores calcium inside it, away from the sarcomere

What happens when the sarcoplasmic reticulum is signaled?

It releases calcium because calcium channels in its membrane open to let calcium flow out down its concentration gradient

What is the area where the neuron and muscle interact?

The neuromuscular junction

What does the neurotransmitter bind to and what does it do?

The receptor proteins that are found on the outer surface of the muscle fiber, it opens the ion channels

What protein complex, where the binding site and ion channel are together, is found in the muscle?

Acetylcholine receptor-channel

What causes an action potential in acetylcholine receptor-channels?

The inward flow of positive sodium ions down the concentration gradient due to the channel opening

What are the membranous structures that the action potential moves along on?

The transverse (t-tubules). Since these connect to the SR, the action potential moves to the SR as well

How do we get varying degrees of contractions?

By only firing a few motor neurons, rather than all of them

What is the strongest contraction a muscle can make?

Tetanus, all cross bridges bind and develop full force

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