3.4 - Mechanics of Muscle Contraction & Body Movement Flashcards

1
Q

Compared to slow twitch fibres, fast twitch fibers can generate more or less tension?

A

More tension

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

What factors influence tension exerted by a muscle during a single twitch?

A
  • muscle type (slow twitch vs. fast twitch)

- sarcomere length at the start of contraction

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

What is the sarcomere length determined by?

A

the degree of overlap between thick and thin filaments

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

What happens if there is too little overlap?

A
  • few cross-bridges

- little force can be generated

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

What happens if there is too much overlap?

A
  • actin filaments interfere with each other

- less force generated

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

What happens if there is way too much overlap?

A
  • thick filaments collide with Z disk

- force rapidly decreases

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

TRUE OR FALSE:

A single twitch represents the maximum force a muscle fibre can produce

A

FALSE

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

The force of a muscle fibre can be increased by ___

A

increasing the rate of action potentials firing to stimulate the fibre

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

What is summation? When does it happen?

A
  • increase in force generated by a muscle

- Due to repeated stimulation from action potentials before muscle has fully relaxed

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

What is tetanus?

A

state of a muscle when it reaches maximum force of contraction

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

Define incomplete/unfused tetanus

A
  • slow stimulation rate

- muscle fibre relaxes slightly b/w stimuli

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

Define complete/fused tetanus

A
  • fast stimulation rate

- muscle fibre does not have time to relax b/w stimuli

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

What is a motor unit?

A

basic unit of contraction in an intact skeletal muscle

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

A motor unit is composed of:

A
  • group of muscle fibres

- the somatic motor neuron that controls them

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

TRUE OR FALSE:

In a single motor unit, muscle fibres can be of both fast-twitch and slow-twitch muscle fibre types.

A

FALSE

All muscle fibres of a single motor unit are of the same muscle fibre type; either fast-twitch or slow-twitch

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

An action potential in the somatic motor neuron leads to what?

A

contraction of all muscle fibres in each motor unit

17
Q

TRUE OR FALSE:

Muscle units contract in an all-or-none fashion

A

TRUE

18
Q

Contraction of the muscle can be varied by?

A
  • changing the type of motor unit that is activated

- changing the # of active motor units (# of motor units firing)

19
Q

Explain recruitment as it relates to contraction

A
  • force of contraction is increased by using more motor units
  • different muscle fibres are recruited at different times
  • slow oxidative fibres = low threshold for stimulation
  • fast glycolytic fibres = high threshold for stimulation
20
Q

Which will have more muscle fibres per motor unit, those involved in fine or coarse movement?

A

Coarse movements = 1 single motor neuron controls a lot more muscle fibres in a single motor unit

21
Q

What are the 2 main types of muscle contraction?

A
  • isotonic

- isometric

22
Q

______ contraction creates force and movement while ______ contraction creates force without movement

A
isotonic = force + movement
isometric = force only
23
Q

During _____ contraction, muscle length changes while muscle length is constant during _____ contraction

A
  • isotonic

- isometric

24
Q

Why can’t movement be produced during isometric contractions?

A

because the load is larger than the force applied by the muscle

25
Q

How can an isometric contraction create force if there is no change in muscle length?

A
  • sarcomeres still shorten

- elastic components stretch to take up force until fully stretched