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A&P. I > (Lesson 21) Lesson 10: The Muscular System: Muscle Contraction > Flashcards

(Lesson 21) Lesson 10: The Muscular System: Muscle Contraction Flashcards

1
Q

How many neuromuscular junctions does each muscle fiber have?

A

1 NMJ (neuromuscular junction)

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2
Q

What does a single axon do in order to control more than 1 muscle fiber?

A

It branches out to more skeletal fibers

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3
Q

If a single axon branches out to more skeletal fibers, does this mean it has more than one NMJ?

A

No this does not mean it has more than one NMJ. There is only 1 NMJ in each axon.

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4
Q

What can the myosin head bind to?

A
  1. The active site of F-actin
  2. Active site for ATP
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5
Q

When the myosin binds to the active site of ATP, what can the myosin act as?

A

It can act as ATPase

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6
Q

What purpose does ATPase serve during the contraction cycle?

A

It assists in breaking down the ATP and ADP.

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7
Q

What is excitation-contraction coupling?

A

AP reaches triad
coupling refers to the series of events that link the action potential (excitation) of the muscle cell membrane (the sarcolemma) to muscular contraction.

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8
Q

What is a triad?

A

Triad is the T tubercle & terminal cisternae of the S.R.
RESPONSIBLE?= skeletal muscle substructure responsible for the regulation of excitation-contraction coupling.

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9
Q

What is the first step in excitation-contraction coupling?

A

The release of Ca+ from the S.R.

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10
Q

The sarcoplasmic reticulum is similar to which organelle?

A

The smooth E.R.

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11
Q

When does a skeletal muscle contract

A

When stimulated by a motor fiber @ the neuromuscular junction

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12
Q

Which area of the axon needs to be stimulated in order to produce a muscle contraction?

A

The neuromuscular junction

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13
Q

How does the stimulus arrive at the terminal?

A

As an action potential

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14
Q

What does the action potential cause?

A

It triggers the release of ACh into the synaptic cleft.

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15
Q

After AP causes the release of ACh into the synaptic cleft, what occurs next?

A

Leads to excitation

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16
Q

What is excitation and where does it occur?

A

The production of action potential
and it comes from the sarcolemma

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17
Q

List the steps to excitation-contraction coupling.

A

(Pre) 1. Neural control
(Pre) 2. Excitation
3. Release of Ca+
4. Concentration cycle begins
5. Sacromere shortens
6. Muscle is generated

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18
Q

What occurs during neural control?

A
  1. Skeletal muscle contracts by stimulus (motor neuron @ neuromuscular junction)
  2. Stimulus enters as action potential to the axon terminal.
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19
Q

What occurs during excitation?

A

Action potential releases ACh into the synaptic cleft, which triggers excitation.

20
Q

(1st official step of concentration cycle)
Release of Ca+ refers to the?

A
  1. Action potentials traveling down the sarcolemma & down the tubules to the triad.
    This muscle triggers the release of Ca+ from the terminal cisternae of the SR
21
Q

When does the contraction cycle begin?

A
  1. Ca+ ions initiate a contraction cycle when they bind w/ troponin
  2. Troponin results in exposure of active sites on the thin filaments
  3. Exposure allows cross-bridge form & will continue to form as long as there’s enough action potential.
22
Q

The sarcomere shortens as __________.

A

Thick and thin filaments get together and pull the muscle fibers together via the sarcomere.

23
Q

When does the generation of muscle tension occur?

A
  1. During the contraction, the entire skeletal muscle shortens.
    Shortening = production of a pull, tension, on tendons @ either end.
24
Q

List what makes up the concentration cycle.

A
  1. Concentration cycle BEGINS
  2. Active-site exposure
  3. Cross-bridge formation
  4. Myosin head pivoting
  5. Cross-bridge deattachment
  6. Myosin reactivation
25
Q

Explain what occurs during the beginning of the contraction cycle.

A

The arrival of Ca+ to the zone of overlap in the sarcomere.

26
Q

What occurs during active site exposure?

A
  1. Ca+ binds to troponin
  2. Troponin shifts positions w/ tropomyosin
  3. Exposes active sits on F-actin strands.
27
Q

What is cross-bridge formation?

A
  1. Myosin heads (with ADP & P bounded to it) bind to the active site w/ F-action strands
    Forms cross bridges
28
Q

What occurs as myosin pivots?

A

F-actin is pulled along w/ it
(Move the F-actin strand closer to M-line)

29
Q

What is the pivot action myosin performs called?

A

Power stroke

30
Q

What does power stroke cause?

A

It causes ADP & P to bind on the myosin head and causes it to be released

31
Q

What occurs to ATPase as the power stoke bind ADP & P to the myosin head?

A

ATPase on the myosin head is now empty

32
Q

Cross-bridge attachment?

A
  1. ATP molecule binds onto myosin head.
    - Causes myosin head to detach from the active site on the F-actin.
33
Q

Explain how the myosin head changes during reactivation.

A

Myosin head primes back to the high-energy position

34
Q

What do myosin heads hydrolyze?

A

ATP - ADP & P

35
Q

How is the myosin head primed back to its original energy position?

A

By utilizing the energy that was produced by the ATP hydrolysis

36
Q

What happens when the myosin binding site on the adjacent F-actin is still unblocked?

A

The myosin can bind to it in order to continue the contraction cycle.

37
Q

What is the functional unit of contraction?

A

The sarcomere

38
Q

When does the sarcomere shorten?

A

When the myosin heads in thick filaments form cross-bridges w/ actin molecules in thin myofilaments.

39
Q

When does the cross-bridge cycling end?

A

When the Ca+ is actively transported in the S.R.

40
Q

When does fiber shortening occur?

A

When the sarcomere shortens, pulling the muscles together and causing tension.

41
Q

Where can muscle shortening occur?

A

Can occur on both ends of the muscles or @ only one end of the muscle.

42
Q

What determines where muscle shortening occurs?

A

Depends on the way the muscle is attached to the end

43
Q

Where is the muscle held fixed?

A

@ the origin w/ the insertion end moving towards the fixed end.

44
Q

How does the muscle fiber move when both ends are free to move?

A

The ends of a contacting muscle fiber move toward the center of the muscle fiber.

45
Q

How does the muscle fiber move when both ends are free to move?

A

The ends of a contracting muscle fiber move toward the center of the muscle fiber.

A&P. I (7 decks)

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