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Histology > Skeletal Muscle Contraction > Flashcards

Skeletal Muscle Contraction Flashcards

1
Q

What is the epimysium?

A

connective tissue surrounding the entire muscle

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2
Q

What is the muscle made up of?

A

multiple fascicles.

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3
Q

What is the perimysium?

A

tissue surrounding multiple fascicles.

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4
Q

what is the endomysium?

A

tissue surrounding each myofiber

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5
Q

what is the sarcolemma?

A

cell membrane of muscle fiber

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6
Q

what is a myofiber?

A

muscle cell; an indivudali multinucleated muscle cell

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7
Q

what is the myofibril?

A

a chain of sarcomeres within a myofiber; it contains actin and myosin necessary for a muscle contraction.

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8
Q

What is a myofilament?

A

actin and myosin filaments that make up a sarcomere.

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9
Q

What are T-tubues

A

invaginations of the sarcolemma that lie close to cisternae of the sarcolasmic reticulum.

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10
Q

What does the sarcoplasmic reticulum do?

A

regulates calcium storage and reuptake; important for muscle contraction.

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11
Q

What does the sarcomere lie inbetween?

A

two Z-disks.

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12
Q

Where are the Z discs, and what do they do?

A

at the end of the sarcomere; they anchor the actin filaments.

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13
Q

What are I bands composed of?

A

actin; their width changes during contraction.

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14
Q

What are A bands composed of?

A

myosin and actin; they do not change during contraction

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15
Q

What are H bands composed of?

A

myosin; the width changes during contaction.

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16
Q

What does Titin do?

A

holds actin and myosin in place and acts as a framework. It is springy and allows for contraction of the sarcomere.

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17
Q

What enters a nerve fiber’s terminal buttons after an action potential has been fired?

A

calcium

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18
Q

What neurotransmitter does the nerve fiber release?

A

acetylcholine

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19
Q

What kind of sodium channels are opened when Ach binds?

A

ligand-gated

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20
Q

What kind of channels are open once sodium enters through the ligand-gated channel?

A

voltage-gated

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21
Q

What do DHP channels on T-tubules interact with once an action potential has been initiated on the sarcolemma?

A

ryanodine receptors

22
Q

What are ryanodine receptors sensitive to?

A

calcium

23
Q

Where are ryanodine receptors located?

A

sarcoplasmic reticulum membrane

24
Q

What is released after the opening of ryanodine receptors on the SR membrane?

A

calcium

25
Q

What do calcium ions from the SR bind to?

A

troponin

26
Q

What is deactivated (and allows binding of actin to myosin) once calcium binds to troponin?

A

tropomyosin

27
Q

What molecule do the ATPase heads of myosin use before binding to actin?

A

ATP

28
Q

What does myosin have to use to break away from actin?

A

ATP

29
Q

When does contraction stop?

A

When ATP-dependent calcium pumps moves calcium ions back into the sarcoplasmic reticulum.

30
Q

What is DHP?

A

Dihydropyridine receptor; it is on the membrane of the sarcolemma (T-tubules) and changes conformation of ryanopyridine if an action potential is initiated.

31
Q

What is SERCA?

A

ATP dependent pump that moves calcium back into the SR

32
Q

What is calsequestrin?

A

molecule in the SR that maintains optimum calcium concentration gradients.

33
Q

When does a sarcomere have the least tension?

A

When the actin filaments do not overlap.

34
Q

When does a sarcomere have the most tension?

A

When the actin filaments either touch or overlap all of the cross bridges.

35
Q

Does velocity increase or decrease with the amount of contraction?

A

decrease

36
Q

When is ATP required for muscle contraction?

A

pumping calcium ions into SR, maintaining Na/K concentration after action potentials, binding/release of myosin heads from actin filaments.

37
Q

What is phosphocreatine?

A

a molecule that contains a high-energy phosphate; it releases it to make ATP for 5 - 8 seconds of contraction.

38
Q

How long can glycolysis sustain muscle contractions?

A

1 minute

39
Q

What metabolic pathway provides the most energy needed for long-term contraction?

A

oxidative metabolism

40
Q

What are isometric contractions?

A

Increase in tension, but not length

41
Q

What are isotonic contractions?

A

Change in muscle length. Is either eccentric or concentric.

42
Q

What is an eccentric contraction?

A

isotonic contraction in which the muscle length lengthens

43
Q

What is an concentric contraction?

A

isotonic contraction in which the muscle length shortens

44
Q

What are characteristics of fast, white fibers?

A

are muscles that react rapidly; they have fast twitch fibers, few mitocondria, high levels of ATPase, and use anaerobic respiration

45
Q

What are characteristics of slow, red fibers?

A

are muscles that contract slowly, but have endurance. They have high mitochondria and myoglobin and small ATPase; they use aerobic respiration.

46
Q

What muscle component can be increased after birth?

A

myofibrils; lost muscle tissue is replaced by scar tissue.

47
Q

Which muscle is composed predominantly of dark fibers?

A

soleus

48
Q

Which muscle is composed predominantly of light fibers?

A

gastrocnemius

49
Q

What is a motor unit?

A

a single nerve cell (neuron) that innervates myofibers. When a neuron fires, all the myofibers in the motor unit contract.

50
Q

What is summation?

A

Addition of individual twitch contractions to the increase the overall intensity of a muscle contraction. It increases muscle tension and adds to the effects of the previous spikes.

51
Q

How is summation caused?

A

When electrical event soccur before the previous calcium ions enter the SER again; the amount of Ca ions ourside the SER increases.

52
Q

What is tetany?

A

When a muscle rmains at maximal contraction from summation; little ability to use the muscle for a perio dof time.

Histology (17 decks)

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