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Human Physiology 2 > Muscles I > Flashcards

Muscles I Flashcards

1
Q

What type of muscle is not striated?

A

Smooth

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2
Q

What types of muscle are striated?

A

Skeletal and Cardiac

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3
Q

What are some characteristic of Skeletal muscles?

A
  • Large fibres
  • Multinucleate
  • Repeating sarcomeres
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4
Q

What are some characteristic of Cardiac muscles?

A
  • Medium-sized fibers
  • Single nucleus
  • Repeating sarcomeres
  • Intercalated disks
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5
Q

What are some characteristic of Smooth muscles?

A
  • Small spindle-shaped fibres
  • Single nucleus
  • Contractile fibres not arranged as repeating sarcomeres
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6
Q

What is the only muscle type that is NOT directly influenced by endocrine system?

A

Skeletal

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7
Q

What is the cell in muscles?

A

Muscle fiber

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8
Q

Is a myofibril a cell?

A

No

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9
Q

What is the myofibril made out of ?

A

Bundles of contractile proteins

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10
Q

What is the plasma membrane of muscle fibres?

A

Sarcolemma

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11
Q

What are t-tubules?

A

They are extensions of pm that help spreading action potential by regulating concentration of calcium ions

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12
Q

What are the components of a sarcomere?

A

Myosin thick filament
actin thin filament
Z disk
M line

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13
Q

What are the different areas in a sarcomere?

A

A band = area of the myosin filaments

H zone = are between actin filaments and m-line

I band = area between a group of myosin filaments of one sarcomere and the other

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14
Q

What does the sarcoplasmic reticulum do?

A

It wraps around myofibril. Similar to ER. Stores calcium ions

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15
Q

What is the role of nebulin?

A

It helps to align actin

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16
Q

What does titin do ?

A

functions as a molecular spring which is responsible for the passive elasticity of muscle in addition to keeping myosin molecules in place.

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17
Q

What is myosin composed of?

A

2 heavy chains

4 light chains (regulatory LC, essential LC)

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18
Q

Where does Calcium bind on actin filament?

A

To the troponin complex

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19
Q

What wraps around actin ?

A

Tropomyosin

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20
Q

What is the troponin complex made out of?

A

Troponin T: binds tropomyosin

Troponin I : binds actin

Troponin C : binds Ca++

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21
Q

What is the role of tropomyosin?

A

To cover actin filament and prevent binding. of myosin heads to it (and therefore muscle contraction)

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22
Q

Is sarcoplasmic reticulum Smoot or rough?

A

Smooth (no ribosomes)

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23
Q

What happens to the bands during muscle contraction?

A

Z disks get closer
H zone and I band shorten
A band remains constant

24
Q

What is the receptor that is affected by action potential?

A

DHR

25
Q

What happens to DHR upon action potential?

A

It changes conformation and it opens RyR Ca2+ release channels in sarcoplasmic reticulum

26
Q

How does ACh cause action potential in muscle fibre?

A

It opens up ACh receptor channel that allow exchange of ions, especially entry of Na+ that depolarises the cell creating END PLATE POTENTIAL (EPP)

27
Q

What happens after released calcium causes muscle contraction?

A

Calcium ions are pumped back in the sarcoplasmic reticulum by Ca2+-ATPase

28
Q

In what position is myosin usually found in living muscles?

A

In the cocked position.

29
Q

What is cocked position?

A

Myosins have just finished hydrolysing ATP, so they have ADP and Pi still bound to them and are ready to do the power stroke. This cross bridge is quite weak since tropomyosin covers most of binding site, however it helps in creating potential energy.

30
Q

What happens during power stroke?

A

Calcium binds to troponin, leading to movement of tropomyosin.
The myosins cross bridges transform into strong bonds.
Myosin releases Pi.
This allows myosin to swivel, swinging the actin filament towards M line.

31
Q

What happens at the end of a power stroke’

A

Myosins release ADP

32
Q

What is the rigor state?

A

When myosins don’t have ATP nor ADP bound to them so they bind really strongly to myosin heads. Does not happen often in living muscles because plenty of ATP can bind to the heads. Happens in dead muscles as no more ATP is produced (rigor mortis); however stops after a few days when enzymes released start the decay of the muscle

33
Q

What happens when ATP binds to myosin head?

A

Myosin releases actin, however the ATP is quickly hydrolysed so the myosin head can rotate and locks itself in the cocked position

34
Q

What is phospocreatine

A

A quick source of ATP

35
Q

What enzyme makes Atp from Adp and phosphocreatine?

A

Creatine kinase

36
Q

Where is ATP needed in the ec cycle?

A

1) Myosin ATPase (contraction)
2) Ca2+-ATPase (relaxation)
3) Na+-K+-ATPase (restores ions that cross cell membrane during action potential)

37
Q

What is tension?

A

Force generated by contraction

38
Q

What is a twitch?

A

A single contraction/relaxation cycle in a muscle fibre

39
Q

What does force generation depend upon?

A 
#sarcomeres
#myofibrils
#muscle fibres
40
Q

What is a motor unit?

A

A unit made up of the motor neuron and its corresponding muscle fibre(s).

41
Q

Can a single motor neuron innervate more than one muscle fibres?

A

Yes

42
Q

What does maximum tension depend on?

A
  1. Sarcomere length at beginning of contraction

2. Frequency of action potentials

43
Q

Duration of contraction depends on:

A
  1. resistance to fatigue

2. Speed of Calcium pumping back into the SR

44
Q

Speed of contraction activation depends on:

A

Myosin isoform present in the muscle

45
Q

How many isoforms of myosins?

A

12

46
Q

What are the three types of muscle fibres?

A

Type I : slow-twitch red
Type IIa: fast-twitch red
Type IIb: fast-twitch white

47
Q

What type of muscle fibre is the most fatigue resistant?

A

Type I : slow-twitch red

48
Q

Are slow-twitch fibres smaller or bigger in diameter?

A

Smaller

49
Q

What is kinesthesia?

A

The awareness of how the body is moving in space

50
Q

What is proprioreception?

A

The awareness of where the different parts of the body are in space

51
Q

What are the three types of proprioreceptors?

A

1) Muscle spindles (stretch)
2) Golgi tendon organs (tension)
3) Joint capsule receptors ( position)

52
Q

Which proprioreceptor responds to stretch?

A

Muscle spindle

53
Q

Which proprioreceptor responds to tension?

A

Golgi tendon

54
Q

Where do the sensory neurons lie in skeletal muscle ?

A

In the intrafusal fibres

55
Q

Where do motorneurons end in the skeletal muscle?

A

Alpha- extrafusal fibres

Gamma- intrafusal fibres

56
Q

Does the sensory neuron coming from muscle spindle synapse directly with motor neuron in spinal chord?

A

Yes

57
Q

Does the sensory neuron coming from gold tendon synapse directly with motor neuron in spinal chord?

A

No

Human Physiology 2 (5 decks)

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