Brainscape's Knowledge GenomeTM

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


See full index

+ BIOL 325 > Lecture 4-5: Muscles > Flashcards

Lecture 4-5: Muscles Flashcards

1
Q

What are muscles?

A

biological actuators that drive the stiff levers of the musculoskeletal system

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

Why do muscles attach so close to the fulcrum?

A

because they are good at generating force, but not very good at getting shorter – it also keeps them out of the way

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

What is the pattern of contraction of a muscle at the end of a limb? What does this require?

A

contract a short distance, but produce long movement – requires small dE and large dL

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

What is the structure of a muscle? (4)

A
  • myofibril – basic unit of the muscle that contracts to shorten the muscle and generate force
  • muscle fibre – formed by many myofibrils
  • muscle fascicle – formed by many muscle fibres
  • muscle – formed by many muscle fascicles
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What type of muscle is skeletal muscle?

A

striated muscle

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

What is a sarcomere?

A

functional unit of the muscle

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

What causes muscle contractions?

A

myosin thick filament heads form cross bridges with actin filaments, then pull on them to cause contractions

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

In what direction do striated muscle fibres shorten?

A

in the direction of the contracting muscle

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

By how much do striated muscles shorten?

A

by only 20-25% of their relaxed length

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

What determines the (absolute) contraction distance of a muscle?

A

all muscle sarcomeres shorten by approximately 20% when they contract, therefore absolute distance a muscle can contract is due to its length – proportional to the number of sarcomeres in series

ie. 1 m muscle can shorten by 20 cm (20% of 1 m)
ie. 10 cm muscle can only shorten by 2 cm (20% of 10 cm)

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

Do shorter or longer muscles have a higher contraction speed?

A

longer muscles are faster – because the sarcomeres in series are shortening simultaneously

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

What determines contraction force?

A

force produced by a muscle is proportional to the number of sarcomeres in parallel

more sarcomeres in parallel = more force generated

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

What is the cross-sectional area of muscle proportional to?

A

number of fibres

therefore, also proportional to the force it can exert

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

What is displacement (contraction distance) of a muscle proportional to?

A

muscle length

therefore, the work a muscle can do is proportional to its volume (W = F x d)

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

What is muscle volume?

A

cross-sectional area (force) x length (muscle shortening or displacement)

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

Do shorter or longer muscles have longer maximum displacement?

A

longer

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

How much can sarcomeres contract?

A

by around 20% of its relaxed length

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

What is contraction speed determined by?

A

number of sarcomeres in series

important metric: length

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

What is contraction force determined by

A

number of sarcomeres in parallel

important metric: cross-sectional area

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

How do vertebrate fibres types differ?

A
  • different mechanical properties
  • different composition and activity of myosin heavy chain (myosin head has many isoforms)
  • different myofibrillar ATPase activity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How are vertebrate fibre types similar?

A

sarcomere lengths are invariant

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

Type I Muscle

  • Motor Unit Type
  • Contraction Force (High/Low)
  • Contraction Speed (High/Low)
  • Time to Fatigue (Long/Short)
  • ATPase Activity (High/Low)
A
  • motor unit type: slow twitch oxidative (SO)
  • contraction force: low
  • contraction speed: low
  • time to fatigue: long
  • ATPase activity: low
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Type II Muscle

  • Motor Unit Type
  • Contraction Force (High/Low)
  • Contraction Speed (High/Low)
  • Time to Fatigue (Long/Short)
  • ATPase Activity (High/Low)
A
  • motor unit type: fast twitch oxidative (IIA), glycolytic (IIB)
  • contraction force: medium
  • contraction speed: high
  • time to fatigue: short
  • ATPase activity: high
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How do invertebrate muscles differ?

A
  • different ATPase activity
  • different sarcomere lengths
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the force (high/low) and speed (high/low) of invertebrate long sarcomeres?

A

high force, low speed

  • more myosin/actin cross-bridges pulling directly on the load
  • can only pull the load as fast as each myosin head can move
  • each myosin head generates 1 unit of force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the force (high/low) and speed (high/low) of invertebrate short sarcomeres?

A

low force, high speed

  • myosin/actin cross-bridges pull on each other, as well as on the load
  • each sarcomere will pull on adjacent sarcomeres and their speed will add up
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is specific force production?

A

force / cross-sectional area of muscle

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

What is the unit for tension?

A

Pa

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

When is tension measured?

A

during isometric (non-moving) contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How is force related to shortening velocity (speed)?

A

force decreases as shortening velocity increases

  • cross-bridges are being made and broken more quickly as speed increases – at any given moment, there are fewer actin/myosin cross-bridges and therefore less force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is isometric contraction?

A

all force, no speed

32
Q

What is unloaded contraction?

A

all speed, no force

33
Q

Describe the relationship between muscle force and power?

A

maximum power is reached at 15-40% of the maximum force (depending on the muscle), then it begins to decline

34
Q

When is there no work being done?

A

no displacement of weight = no work done and no energy expended

35
Q

Does a rope need to expend any energy generating a tension opposing the weight?

A

no

36
Q

Does a muscle need to expend energy to maintain a tension to support the weight?

A

no

  • myosin heads continually make and break contact with actin filaments, consuming ATP
  • can think of it like a motor running against a slipping rope – if the motor turns, it keeps tension on the rope (which consumes energy), and if the motor stops, the rope will slide through and the weight will drop
37
Q

What has a big effect on a muscle’s functional properties?

A

arrangement of fascicles (and therefore fibres)

38
Q

What is the shape of pennate muscle fibres?

A

parallelogram-shaped (area = width x length)

this does not change as fibres contract, therefore volume is approximately constant

39
Q

Do pennate muscle fibres bulge when contracting?

A

no, due to their shape

40
Q

Parallel vs. Pennate Muscle Fibres

Length

A

parallel: long fibres – can contract further

pennate: short fibres – short contraction distance

41
Q

Parallel vs. Pennate Muscle Fibres

Number of Fibres in a Given Muscle Volume

A

parallel: few fibres – produce lower forces

pennate: more fibres – produce higher forces

42
Q

Parallel vs. Pennate Muscle Fibres

Force Orientation

A

parallel: oriented along muscles’ line of action – ie. both muscle and fibres contract along the same direction

pennate: oblique to the muscles’ line of action (pennation angle θ)

43
Q

Parallel vs. Pennate Muscle Fibres

Bulge

A

parallel: outward

pennate: (mostly) do not bulge, therefore occur where space is an issue and/or there is a requirement for generating large forces

44
Q

What are the 3 types of pennate muscle?

A
  • unipennate
  • bipennate
  • multipennate
45
Q

What are unipennate muscles?

A

all fascicles of the pennate muscle are on the same side of the tendon

46
Q

What are bipennate muscles?

A

fascicles lie to either side of the tendon

47
Q

What are multipennate muscles?

A

central tendon branches within a pennate muscle

48
Q

What are the 3 components of the force generated by the fibre?

A
  • F fibre – force in line with the fibre
  • F muscle – force in line with the muscle
  • F perpendicular to muscle – force perpendicular to the muscle

F muscle = cos(θ) x F fibre

49
Q

Pennate Pump Muscles – Calculations

A

see slides

50
Q

What is gearing?

A

trading force for distance (same as how levers conserve work)

51
Q

The skeletal system can alter what part of a force?

A

how the force generated by a muscle translates into high force/short distance (MA) OR low force/long distance (DA)

52
Q

What can muscle fibre arrangement within a muscle alter?

A
  • velocity of contraction
  • force generated by the muscle
53
Q

What is the architectural gear ratio (AGR)?

A

ratio of whole muscle contraction velocity to fibre contraction velocity

54
Q

What is AGR in parallel muscle?

A

AGR = 1

individual muscle fibres are oriented in the same direction as the whole muscle, therefore muscle contraction velocity is equal to fibre contraction velocity, and therefore AGR = 1

55
Q

What is AGR in pennate muscle?

A

AGR ≠ 1

rate at which pennate muscle contracts depends on pennation angle θ of the fibres, therefore muscle contraction velocity is NOT equal to fibre coontraction velocity

56
Q

What happens to muscle contraction speed when pennation angle θ increases?

A

speed increases

57
Q

What part of a right-angle triangle is a muscle fibre in a pennate muscle equivalent to?

A

hypotenuse

58
Q

What part of a right-angle triangle is muscle length equivalent to?

A

adjacent side

59
Q

How is muscle fibre (hypotenuse) and muscle length (adjacent side) related?

A

if the muscle fibre (hypotenuse) contracts at a constant rate, muscle length (adjacent side) grows shorter faster

60
Q

Does muscle contraction velocity exceed fibre contraction velocity, or vice versa?

A

muscle contraction velocity exceeds fibre contraction velocity – it increases as pennation angle increases

61
Q

Which muscle fibre type generates more force?

A

type II

62
Q

What length of invertebrate sarcomeres generate more force?

A

longer sarcomeres

63
Q

Does more or less muscle cross-sectional area generate more force?

A

more cross-sectional area (more sarcomeres in parallel)

64
Q

Do parallel or pennate muscle fibres generate more force?

A

pennate muscle fibres – force is highest at low pennation angle θ < 30º

65
Q

In a lever system, does MA or DA generate more force?

A

MA as large as possible

66
Q

What type of muscle fibre is faster?

A

type II

67
Q

What length of sarcomeres are faster?

A

short sarcomeres

  • speed increases as more sarcomeres in series contract simultaneously
  • short sarcomeres = more units contracting per fibre length = faster
  • long sarcomeres = fewer units contracting per fibre length = slower
68
Q

Are parallel or pennate muscle fibres faster?

A

parallel – speed increases as more sarcomeres in series add up

69
Q

In a lever system, does MA or DA generate faster speed?

A

DA as large as possible

70
Q

Muscle fibres of identical resting length, but different sarcomere length.

A
  • fibre with longer sarcomeres generates more force – sarcomere length determines force
  • fibre with shorter sarcomeres contracts faster – contraction velocities of more (shorter) sarcomeres in series add up
71
Q

Muscle fibres of different resting length, but identical sarcomere length.

A
  • both generate the same amount of force – only sarcomere length determines force, therefore same sarcomere lengths results in same force generated
  • fibre of longer resting length contracts faster – more sarcomeres in series, therefore faster contraction
72
Q

Muscle Speed and Force Variation

A
  • muscles with short sarcomeres: fast, but less forceful
  • pennate muscles: slow, but more forceful
  • type II fibres: more forceful than type I fibres (but still limited)
73
Q

Can a lever system increase a muscle’s power?

A

NO

levers conserve work (W = F x d)
- F and d are inversely related and occur during the same time, for the same duration
- can never increase power in a lever system because work and time are the same

74
Q

What can the work a muscle does be stored as?

A

can be stored by an elastic mechanism as potential energy, which can then be released very rapidly to move a lever system, without the force/velocity contrasting that afflict molecular motors

75
Q

Catapult Example – Calculations

A

see slides

76
Q

Describe elastic energy storage.

A

rather than using gravitational potential energy to store the work done by slow, forceful muscles, animals can use elastic potential energy – invertebrates store this in specially modified parts of their exoskeleton

77
Q

How does a power amplifier work?

A

take the slow, low power contraction and turn it into a rapid, high power release

+ BIOL 325 (14 decks)

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