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Physiology > Phys.II Test One: Skeletal Muscle > Flashcards

Phys.II Test One: Skeletal Muscle Flashcards

1
Q

What is the sarcolemma?

A

Plasma membrane of skeletal muscle fiber

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2
Q

What is the subunit of muscle composed of?

A

Fascicle

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3
Q

What makes up a fascicle?

A

Muscle fibers

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4
Q

What makes up a muscle fiber?

A

Myofibrils

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5
Q

What is a sarcomere?

A

Functional unit of muscle, portion of myiofibril between two adjacent Z discs

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6
Q

Thin filament?

A

Actin

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7
Q

Thick filament?

A

Myosin

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8
Q

Tropomyosin?

A

Protein on top of F-actin that covers up the binding site for myosin.

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9
Q

Troponin?

A

On actin attached intermittently along tropomyosin. T troponin binds tropomyosin I troponin binds Actin C troponin binds calcium

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10
Q

What makes up a sarcomere?

A

Complete A band and two halves of the I bands next to it

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11
Q

What is titin?

A

Protein that maintains alignment between actin and myosin and acts like a spring between Z discs and end of myosin.

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12
Q

What transmitter is released at a Neuromuscular Junction?

A

ACh

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13
Q

Describe the steps to muscle contracting.

A
  1. AP gets to the axon terminal and calcium voltage gates open allowing calcium in the synaptic bulb.
  2. Calcium entering causes ACh to be released exocytosis
  3. ACh diffuses across synaptic cleft and binds to ACh receptors on sarcolemma. Remaining is broken down by acetylcholinesterase.
  4. In the muscle fiber cation channels open and they enter producing an EPP followed by an AP.
  5. Action potential travels to the T tubules and causes calcium to be released from the SR.
  6. Calcium binds to tropoin and removes tropomyosins inhibition of actin myosin binding site.
  7. Myosin pulls on actin shortening the sarcomere producing the contraction.
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14
Q

How many molecules of ACh does one synaptic vesicle contain, and how many vescicles are relased during one AP?

A

5,000 molecues of ACh and 300 are released

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15
Q

How does Botuline Toxin impact skeletal muscle?

A

It blocks the releases of ACh leading to muscle weakness and paralysis

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16
Q

How does Curare impact skeletal muscle?

A

It is a competitive inhibitor of ACh. It competes with ACh for binding sites on Sarcolemma, but when it binds it does not result in anything so no electrical signal is mproduced in the muslce fiber when an AP arrives at the axon terminal.

17
Q
A
18
Q

What causes an mEPP?

A

spontaneous discharge of one synaptic vesicle

19
Q

In the T-tubule and SR what two proteins interact to release the calcium?

A

Dihydropyridine receptor in the t tubule senses the voltage change from the AP and interacts with Ryanodine receptor/Ca release channel in the SR.

20
Q

What causes the cocking of the myosin head in the sliding filament theory?

A

Hydrolysis of ATP to ADP and Pi causes the conformation change

21
Q

What does a cross bridge represent?

A

When the myosin head binds to actin

22
Q

What causes the springing of the myosin head?

A

Release of the phosphate group from the myosin head

23
Q

Does myosin shorten with contraction?

A

No, the sarcomere shortens and Z discs move towards each other but myosin does not shorten.

24
Q

How many motor neurons innervate one muscle fiber?

A

one motor neuron

* a motor neuron can innervate several muscle fibers but muscle fibers can only be innervated by one motor neuron*

25
Q

What is a motor unit?

A

One motor neuron plus all of the fibers it innervates

26
Q

What is multiple fiber summation?

A

Increased muscle tension caused by an increasing number of motor units contracting simultaneously

27
Q

What is tension?

A

Force exerted on an object by muscle

28
Q

What is load?

A

Force exerted on a muscle by the weight of an object

29
Q

For a fiber to shorten __ needs to exceed __.

A

tension, load

30
Q

Isotonic contraction?

A

Muscle shortens while the load is constant

31
Q

Isometric contraction?

A

Muscle develops tension but it doesn’t shorten

32
Q

What is a muscle twitch?

A

Contraction of a single muscle fiber in response to a single AP

33
Q

What is frequency summation?

A

Increase in muscle tension when successive AP occur rapidly enough that the fiber did not have time to completely relax from the prior twitch.

34
Q

What is Treppe?

A

Period of summation in which the strength of contraction rapidly increases as rate of stimulation rises

35
Q

What is unfused tetanus?

A

Maintained contraction at high rates of stimulation in which muscle tension oscillates due to slight relaxations between stimuli

36
Q

What is fused tetanus?

A

Maintained cotarction at even higher stimulation rates where no oscillations occur

37
Q

What can cause buckeling of myosin filaments?

A

When muscles are over contracted with very short sarcomere lengths. The Z lines can collide with the ends of myosin causing it to crumple.

38
Q
A

Physiology (12 decks)

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