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Science for Medicine > Muscle 1 > Flashcards

Muscle 1 Flashcards

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1
Q

What are the 2 subclasses of muscle?

A
  • Striated

- Smooth

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2
Q

What kind of muscles are striated?

A
  • Skeletal (involuntary muscles)

- Cardiac

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3
Q

Where would you find smooth muscle?

A
  • Blood vessels
  • Vas deferens
  • Airways
  • Uterus
  • GI tract
  • Bladder
  • etc..
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4
Q

What is a skeletal muscle cell?

A
  • Muscle fibre

- Multinucleate

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5
Q

Describe the growth and repair of skeletal muscle.

A
  • Form in utero from mononucleate myoblasts
  • Increase fibre size during growth
  • Myoblasts do not replace cells if damaged
  • Satellite cells replace cells after injuryWhat do sate
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6
Q

What are muscles?

A

Bundles of fibres encased in connective tissue sheaths

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7
Q

What do tendons do?

A

Attach muscle to bone

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8
Q

What do satellite cells do?

A

Differentiate to from new muscle fibres

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9
Q

What do other fibres do to compensate when muscle fibres are injured?

A

Undergo hypertrophy

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10
Q

What is the A band?

A

Stretch of myosin filament

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11
Q

What is the H zone?

A

Space between ends of actin filaments

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12
Q

What happens during muscle contraction?

A
  • Muscle shortens
  • Myosin stays same length
  • Space between actin filaments decrease
  • Space between myosin filaments decrease
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13
Q

What is the I band?

A

Space between ends of myosin filaments

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14
Q

What is a cross bridge?

A

ATP binding site on myosin filament

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15
Q

How does tension develop?

A

Through contraction of muscle

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16
Q

What are the stages in the cross-bridge cycle?

A
  • Cross bridge binds to actin
  • It drags actin along the myosin filament
  • ATP binds to Myosin
  • Myosin detaches and cross bridge returns to original position
17
Q

Describe the role of troponin, tropomyosin and calcium ions in muscle contraction.

A

-Tropomyosin partially covers the myosin binding sites on actin.
Tropomyosin is held in this position by troponin which acts as a cooperative block.
-When calcium binds to troponin it causes a conformational change which pulls tropomyosin away and allows myosin to bind to actin.

18
Q

What is a motor unit

A

Motor neurons
+
muscle fibres

19
Q

Tension

A

Force exerted by muscle

20
Q

Load

A

Force exerted on muscle

21
Q

Isometric

A

Contraction with constant length

22
Q

Isotonic

A

Contraction with shortening length

23
Q

Lengthening

A

Contraction with increasing length

24
Q

What causes a twitch?

A

A single action potential sent to a muscle fibre

25
Q

What is the latent period?

A

The time before the excitation contraction starts

26
Q

When does the contraction time occur?

A

Between start of tension and time when we have peak tension

27
Q

What is contraction time dependent on?

A

Calcium ion concentration

28
Q

Describe the latent period and contraction event of isometric contraction?

A
  • Shorter latent period

- Longer contraction event

29
Q

What happens as load increases?

A

-Contraction velocity and distance shortened decreases

30
Q

Summation

A

Addition of AP to give waves with greater amplitude

31
Q

Describe the AP of tetanus.

A

AP is 1-2 ms long but twitch can last up to 100ms

32
Q

Tetanus

A

Sustained level of tension in a given period of time

33
Q

Unfused tetanus

A

AP continue to rise and fall when recorded on graph

34
Q

Fused tetanus

A

APs are so frequent there is no repolarisation

35
Q

Why is tetanic tension greater than twitch tension?

A

[Ca] never gets low enough to allow troponin/ tropomyosin to re-block myosin binding sites

36
Q

What are the length tension relationships/

A
  • Less overlap of filaments= less tension
  • Too much overlap of filaments=filaments interfere with each other
  • Muscle length for greatest isometric tension=optimal length
37
Q

What does movement around a limb require?

A

2 antagonistic groups of muscles (1 flexes, the other straightens)

38
Q

What does the lever system of muscles do?

A

Amplifies muscle shortening velocity producing increased manoeuvrability

Science for Medicine (50 decks)

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