Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Yr 1 - Nerves & Muscle > Molecular Mechanisms of Muscle Contraction > Flashcards

Molecular Mechanisms of Muscle Contraction Flashcards

1
Q

What is a fascicle?

A

A bundle of structures, such as nerve or muscle fibres (contain numerous muscle cells or muscle fibres, contain 100s to 1000s of myofibrils)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a myofilament?

A

A filament composed of either multiple myosin or actin proteins that slide over each other to generate tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a myofibril?

A

A fibre made up of several myofilaments that facilitates the generation of tension in a myocyte, found in striated muscle cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is myosin?

A

A motor protein which forms myofilaments that interact with actin filaments to generate tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is actin?

A

A protein which forms myofilaments that interact with myosin filaments to generate tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is striated?

A

The striped appearance of certain muscle types in which myofibrils are aligned to produce a constant directional tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a myocyte?

A

A muscle cell (numerous make up muscle tissue)

Myocytes contain myofibrils comprised of actin and myosin filaments which slide past each other producing tension that changes the shape of the myocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe pennate muscles

A
  • Feather like in arrangement of their fascicles
    • Unipennate, bipennate, multipennate

Muscle with fascicles that attach obliquely (in a slanting position) to its tendon. When a muscle contracts and shortens, the pennation angle increases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What can pennate muscle generate?

A

These types of muscles generally allow higher force production but smaller range of motion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe fusiform muscles

A

Spindle-shaped (wider in middle, narrower both ends) e.g. biceps

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe parallel muscles

A

Fascicles lie parallel to long axis of muscle (flat muscles with parallel fibres often have aponeuroses)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is aponeurosis?

A

A sheet of pearly white fibrous tissue that takes the place of a tendon in flat muscles having a wide area of attachment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe convergent muscles

A

Have a broad attachment from which the fascicles converge to a single tendon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe circular muscle

A

Surround a body opening or orifice, constricting it when contracted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe skeletal muscle

A

striated, multinucleated, voluntary, non-branching, attached to skeleton

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe cardiac muscle

A

striated, single nucleus, involuntary, branched, heart muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe smooth muscle

A

non-striated, single nucleus, involuntary, tapered, forms walls of organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe order of myocytes to sarcomeres

A
  • Myocytes composed of myofibrils

- Myofibrils composed of myofilaments (actin and myosin) and numerous adjacent sacromeres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How are myocytes bound together?

A

By perimysium (a sheath of connective tissue) into fascicles which are bundled to form muscle tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Where are sarcomeres?

A

Segment between 2 Z lines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

In electron micrographs of cross-striated muscle, what does the Z-line appear as?

A

A series of dark lines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the Z line?

A

The disc in between the I-bands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What surrounds the Z-line?

A

The region of the I-band

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the I-band?

A

the zone of thin filaments that is not superimposed by thick filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What follows the I-band?

A

A-band

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How are the bands named?

A

For the properties under a polarising microscope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What does an A band contain?

A

The entire length of a single thick filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is within the A-band?

A

H-zone –> a paler region (lighter appearance under polarising microscope)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the H-zone?

A

H-band is the zone of the thick filaments that is not superimposed by the thin filaments

30
Q

What is inside the H-zone?

A

A thin M-line

31
Q

What is the M-line?

A

The disc in the middle of the sarcomere formed of cross-connecting elements of the cytoskeleton

32
Q

What are actin (thin) filaments a major component of?

A

I-band and extend into A-band

33
Q

Where are myosin (thick) filaments found?

A
  • Are bipolar and extend throughout the A-band

* They are cross-linked at the centre by the M-band

34
Q

What is Titin? Where is it found?

A

A giant protein

• Extends from the Z-line of the sarcomere, where it binds to the thick filament (myosin) system, to the M-band, where it is thought to interact with the thick filaments

35
Q

What is Nebulin? Where is it found?

A

A giant protein

• Hypothesised to extend along the thin filaments and the entire I-band

36
Q

What is sarcolemma?

A

The fine transparent tubular sheath which envelops the fibres of skeletal muscles.

37
Q

Describe processes that leads to muscle contraction

A
  1. AP arrives at NMJ
  2. ACh released (binds to receptors and opens sodium ion channels leading to an action potential in sarcolemma)
  3. AP travels along T-tubules
  4. Ca++ released from sarcoplasmic reticulum
  5. Ca++ binds to TnC region of Troponin
  6. Troponin changes shape, moving Tropomyosin, exposing binding site on actin filament
  7. Myosin head binds with ADP + Pi binds actin
  8. Myosin head bends, pulling along actin filament, ADP and Pi are released
38
Q

What is formed when myosin head attaches to actin?

A

A cross bridge forms

39
Q

What is the ‘power stroke’?

A

Myosin head bends, pulling along the actin filament. ADP is then released

40
Q

What initiates power stroke?

A

Inorganic phosphate generated in the previous contraction cycle is released

41
Q

What happens as the new ATP attaches to myosin?

A

The link weakens and the cross bridge detaches

As ATP splits into ADP and phosphate, the myosin head is energised

42
Q

During contraction, what happens to the:

  1. A-band
  2. H-zone
  3. Distance between 2 Z-lines (sarcomere)
A
  1. A-band –> Stays constant
  2. H-zone –> Gets shorter
  3. Z-lines –> sarcomere shortens
43
Q

What are isotonic contractions?

A

Isotonic contractions are those which cause the muscle to change length as it contracts and causes movement of a body part

44
Q

What are the 2 types of isotonic contractions?

A
  1. Concentric

2. Eccentric

45
Q

What are concentric contractions?

A
  • Cause the muscle to shorten as it contracts
  • An example is bending the elbow from straight to fully flexed, causing a concentric contraction of the Biceps Brachii muscle
  • Most common type of muscle contraction
46
Q

What are eccentric contractions?

A
  • Opposite of concentric
  • Occur when the muscle lengthens as it contracts
  • Less common and usually involves the control or deceleration of a movement being initiated by the eccentric muscles agonist
  • For example, when kicking a football, the Quadriceps muscle contracts concentrically to straighten the knee and the Hamstrings contract eccentrically to decelerate the motion of the lower limbs
47
Q

Which type of contraction is normally involved in injuries and why?

A

Eccentric contractions –> puts a lot of strain through muscle

48
Q

What are isometric contractions?

A

Occur when there is no change in the length of the contracting muscle

49
Q

Give an example of isometric contraction

A

• This occurs when carrying an object in front of you
o The weight of the object is pulling your arms down, but your muscles are contracting to hold the object at the same level
• Another example is when you grip something, such as a tennis racket
o There is no movement in the joints of the hand, but the muscles are contracting to provide a force sufficient enough to keep a steady hold on the racket

50
Q

What does the amount of force a muscle is able to produce during an isometric contraction depend on?

A

The length of the muscle at the point of contraction (each muscle has an optimum length at which the maximum isometric force can be produced)

51
Q

What are the stages of a twitch?

A
  1. Latent period
  2. Contraction period
  3. Relaxation period
52
Q

What is the latent period?

A

The delay of a few milliseconds between an action potential and the start of a contraction and reflects the time for excitation-contraction coupling

53
Q

When is the contraction phase?

A

Starts at the end of the latent period and ends when the muscle tension peaks

54
Q

What occurs during the contraction phase in regards to calcium?

A

cytosolic calcium levels are increasing as released calcium exceeds uptake

55
Q

When is the relaxation phase?

A

the time between peak tension and the end of the contraction when the tension returns to zero

56
Q

What occurs during the relaxation phase in regards to calcium?

A

cytosolic calcium is decreasing as reuptake exceeds release

57
Q

What is a twitch?

A

A twitch is the mechanical response of an individual muscle fibre, an individual motor unit, or a whole muscle to a single action potential

58
Q

Are muscle reproducible?

A

Yes - Repetitive stimulation produces twitches of the same magnitude and shape

59
Q

What fibres are involved in a slow twitch?

A

Type 1 fibres (red in colour)

60
Q

Why are type 1 fibres red in colour?

A

Due to high concentrations of myoglobin

61
Q

Describe type 1 fibres

A
  • Very resistant to fatigue
  • Dense capillaries & myoglobin
  • Contract slowly
  • Produce low amount of power when contracted
  • Contains large amounts of mitochondria
62
Q

When are type 1 fibres used?

A

Used in aerobic activities e.g. long-distance running

63
Q

What fibres are involved in a fast twitch?

A
  1. Type IIa fibres (red in colour) (also called fast twitch A fibres)
  2. Type IIb fibres (white in colour) (also called fast twitch B fibres)
64
Q

Why are type IIa fibres red in colour?

A

Due to high concentrations of myoglobin

65
Q

Describe type IIa fibres

A
  • Resistant to fatigue (not as much as Type I fibres)
  • Contains large amounts of mitochondria
  • Contracts relatively quickly
  • Produces moderate amount of power when contracted
66
Q

When are type IIa fibres used?

A

Used in long-term anaerobic activities such as swimming (activities lasting less than 30 mins)

67
Q

Why are type IIb fibres white in colour?

A

Due to low myoglobin concentrations

68
Q

Describe type IIb fibres

A
  • Fatigue very easily
  • Contains low amounts of mitochondria
  • Contracts very quickly
  • Produces a high amount of power when contracted
69
Q

When are type IIb fibres used?

A

Used in short-term anaerobic activities such as sprinting and lifting heavy weights (activities lasting less than a minute)

70
Q

What does the force of muscle contraction depend on?

A
  1. The amount of overlap between thin and thick filaments
  2. Number of APs per second
  3. Number of motor units recruited

Yr 1 - Nerves & Muscle (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions