18. Excitation Contraction Coupling Flashcards

1
Q

Where is the myosin when the ATP is hydrolyzed?

A

Cocked and ready to interact with actin and contract

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2
Q

What happens after the myosin head attaches to the actin?

A

Pi dissociates and the power stroke contracts the sarcomere.

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3
Q

What enzyme breaks down acetylcholine in the synaptic gap?

A

Acetylcholine Esterase

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4
Q

What small structures are made in the sarcolemma of the neuromuscular junction to increase the action potential going into the muscle?

A

Subneural Clefts

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5
Q

What receptors have to change confirmation to allow calcium to release into the sarcoplasm?

Which one is located in the membrane of the T Tubule?

A

DHP and RYR

DHP

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6
Q

Where is the myosin head after ATP binds, but before ATP is hydrolyzed?

A

Released from the actin, but not yet cocked.

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7
Q

What are the three members of the troponin complex, and what do they bind to?

A

Troponin I: Actin

Troponin C: Calcium

Troponin T: Tropomyosin

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8
Q

Besides the muscle cell hypertrophy, what changes in the muscles of a trained athelete vs someone like me (a nerd)?

A

More mitochondrial enzymes

More glycogen

More phosphocreatine

More stored fat

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9
Q

Which type of muscle fibers are larger?

A

Type II

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10
Q

When we strength train, do we get more muscle fibers, or just bigger muscle fibers?

A

Just bigger muscle fibers

(more myofibrils per muscle fibers)

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11
Q

How do we induce a smooth, continuous muscle movement within a single motor unit when our neurons can only produce all or nothing responses?

A

Summation and tetanization

Increasing frequencies of stimulation increases the rate of contraction

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12
Q

What receptors are responsible for initiating a local potential at the neuromuscular junction?

A

Ligand gated acetylcholine receptors

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13
Q

How do we make a muscle contract with more or less force?

A

Recruitment - activate more or fewer muscle units

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14
Q

How long can we use phosphocreatine for muscle contraction?

A

8-10 seconds

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15
Q

How long does Rigor Mortis last?

A

15-25 hours

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16
Q

Where are the two hinges in a myosin molecule?

A

Hinge 1: Separating the two heads

Hinge 2: One on each of the myosin heads, allowing independent movement

17
Q

What allows the sarcoplasmic reticulum to hold up to 40x more calcium than it otherwise would?

A

Calsequestrin

18
Q

What enzyme is used to shuttle calcium from the sarcoplasm into the sarcoplasmic reticulum after a contraction occurs?

A

Calcium ATPase

19
Q

When is a sarcomere able to produce the maximum amount of force?

A

When there is no overlap in actin, and every myosin head is able to access a binding site.

20
Q

Which type of muscle fiber has more glycogen?

A

Type II

21
Q

Which type of muscle fibers have more phosphocreatine?

A

Type II

22
Q

Would smaller, more precise muscles have more or less muscle fibers?

A

More muscle fibers

This allows them to regulate the force of their contraction more precisely.

23
Q

Which type of muscle fiber has more mitochondria and myoglobin?

A

Type I

24
Q

How long can we use stored ATP for a muscle contraction?

A

Two seconds

25
Q

How long can we use Glycolysis for a muscle contraction?

A

1.3 - 1.6 minutes

26
Q

Where is the myosin head after a contraction, but before it binds a new ATP?

A

Still stuck to its binding site on the actin.

27
Q

What is a motor unit?

A

All the muscle fibers innervated by a single nerve fiber.

28
Q

How long can we use oxidative phosphorylation to sustain a muscle contraction?

A

Until the muscle runs out of things to throw into the TCA cycle.