Brainscape's Knowledge GenomeTM

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


See full index

KINESIOL 2C03 > Final Exam > Flashcards

Final Exam Flashcards

1
Q

A motor unit consists of …

A

A motoneuron and all the muscle fibres it innervates

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

Compare fibres per motor unit for gross movement and fine movement

A

Gross movement = many fibres per MU

Fine/Complex movement = few fibres per MU

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

Is a muscle limited to 1 fibre type?

A

No. Fibres of different MUs intermingle with each other

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

Why is MU territory spread over a larger area?

A
  1. Mus’ Force distributed over a larger area
    a. “smoother” contraction
    b. More equal force on tendon
    i. If not equal it might tear
    1. May help delay fatigue
      a. Active and inactive fibres sharing metabolites and capillaries
      By spreading out we can share load of metabolites and have more oxygen per muscle fibre
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

All fibers of one motor unit are the _____ fiber type

A

SAME

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

Neuron cell bodies are larger the more _______ the fiber type is

A

anaerobic

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

List the fibre types in order of decreasing fibre size in animals and humans

A

IIB > IIA > I (ANIMALS)

IIA > IIB > I (HUMANS)

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

List the fiber types in order of decreasing motoneuron soma size

A

IIb/x > IIA > I

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

List the fibre types in order of decreasing fibre number

A

IIB/X > IIA > I

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

List the fiber types in order of decreasing axon diameter

A

IIb/x > IIa > I

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

What is the limitation of fibre sizes across different fiber types?

A

Fibre size was based on animal studies (frog muscles)

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

What are the functional characteristics of MU types?

A 
Contraction force (strength)
Contraction speed (velocity) 
Speed of activation
Metabolic power
Fatigue resistance (endurance)
Recruitment threshold
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Compare MU Contraction Force (strength) between fiber types

A

Fiber type II MU’s have a greater absolute force (force of 1 MU; N) because they have more and larger muscle fibers

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

Why do fiber type II muscle fibers have greater specific (relative) force than fiber type I?

A

Because fiber type II fibers have greater force per unit muscle CSA and because they have more actin and myosin filaments (more Sarcomeres) because of that, more cross bridges = more force

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

Why is there greater specific force in type II fibers

A

Myosin heavy chains - fast twitch isoforms
- more force per CB
- more CB attached
(assumes maximal activation. saturating Ca)

BUT fast twitch have similar myofilament density and similar myofibrillar density

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

Compare MU contraction speed across fiber types

A

Type II fibers contract with a higher velocity than type I fibers. Type IIx are fastest.

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

Compare force produced at velocities in the fiber types

A

Type II fibers produce greater force at higher velocities ; type IIx produces most force at highest velocity

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

Which fiber type produces the greatest power ?

A

Type IIx produce the greatest amount of power as they produce the most amount of force at the highest velocity

so more fast twitch fibers = higher max power and higher velocity

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

Determinants of Contraction Speed

A
  1. Myosin ATPase Activity
  2. CB Power Stroke Speed
  3. Ca2+ release and reuptake
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does myosin ATPase activity impact contraction speed and which fiber type has greatest activity?

A

Myosin ATPase activity determines the cross-bridge cycle speed
Activity is greatest in type IIx fibers > IIa > I

21
Q

Compare CB power stroke speed between fibre types. Explain

A

CB power stroke in type II is faster because of myosin heavy chain in type II fibres are different from type I

22
Q

How does calcium release and reuptake determine contraction speed of fiber types?

A

Fiber type II have larger and more extensive sarcoplasmic reticulum. Thus, they have more rapid release and uptake of calcium, allowing for faster contraction and relaxation of type II fibers

23
Q

What is speed of activation and what factor does it depend on?

A

Speed of activation is how fast the action potential makes it down the neuron and across the muscle fibre
it depends on diameter of the axon: the larger the diameter, the faster the conduction velocity (due to less resistance)

24
Q

Do muscles fibres with a big diameter (100um) conduct faster than nerve axons (10um)? why or why not?

A

No because nerve axons are myelinated and specially designed for fast conduction, allowing for saltatory conduction

25
Q

Match the time to the process of energy production.
Time: 10 seconds, 1-2 seconds, indefinite, 1 minute
Process: Oxidative phosphorylation, PCr, Stored ATP, glycolysis

A

Stored ATP = 1-2 seconds
PCr = 10 seconds
Glycolysis = 1 minute
Ox. Phosphorylation = indefinite

26
Q

Fast twitch muscle fibres (type II) have more…?

A 
Myosin ATPase Activity 
Storage of PCr
CK Activity
Glycogen Storage
Glycolytic Enzyme Activity
27
Q

Why are slow oxidative fibers the most fatigue resistant ?

A

Because SO have an enhanced ability to perform oxidative phosphorylation

28
Q

What are the determinants of fatigue resistance?

A

Mitochondrial size and number
Myoglobin concentration
Muscle fiber diameter
Capillarization

29
Q

What does myoglobin do and which fiber type is it found most in?

A

Myoglobin facilitates diffusion of oxygen from the capillary to the mitochondria. It stores oxygen.
Type I fibers have more myoglobin.

30
Q

How does muscle fiber diameter make type I fibers more fatigue resistant?

A

Type I fibers have a smaller muscle fiber diameter so there is a smaller diffusion distance and more capillary/area of fiber

31
Q

How does Capillarization affect fatigue resistance?

A

MU activity affects the number of capillaries arount its fibres, therefore fatigue resistance

Type I has more capillary per muscle fibre so its more fatigue resistant

32
Q

What are recruitment thresholds?

A

% of maximum force at which a MU is recruited
Low Threshold = recruited at low % of max force
High Threshold = recruited at high % of max force

33
Q

What is the size principle?

A

Motor units are recruited in order according to the size of the motoneuron’s cell body

Larger size = larger threshold

34
Q

Why does the size principle work?

A

Larger cell bodies are more difficult to excite, so theyre more difficult to recruit
Thus they need a higher activation from the nervous system to reach threshold

35
Q

What is Motor Unit Activation?

A

Motor unit activation is the number of motor units activated and their firing rates
so 100% MUA means all motor units are firing and at their maximal firing rates

36
Q

How do we measure Motor Unit Activation?

A

Using EMG:
Surface EMG & Indwelling EMG

Indwelling:
To measure for 1 specific muscle : indwelling EMG (just 5-6 muscle fibers) (can stick it into belly of muscle)

Surface:
Surface EMG : measuring for all the muscles in that nearby area (but they can do more movement and stuff while having them attached) (only picks up surface signals)

37
Q

What Does EMG Measure?

A

It records Wave of Depolarization from Motor Unit AP

38
Q

What are the factors that impact the magnitude of EMG?

A
  • number of fibres active (MUs recruited)
  • MAPs per fibre (firing rate)
  • size of fibre
39
Q

EMG shows absolute or relative motor unit activation?

A

relative

40
Q

Why does an eccentric contraction have less MUA than a concentric contraction?

A

because an eccentric contraction produces more absolute force than a concentric contraction at the same relative force, so it requires less MUA to produce the same amount of force

41
Q

Why is MUA less for eccentric contractions at the same absolute load/force?

A

Because in an eccentric contraction, for the same absolute force, there is more force per CB. Thus less CBs are needed, so less muscle fibers are needed, so there is less MUA (smaller EMG signal).

42
Q

Why is there a dip in Eccentric Contraction EMG

A
  1. Fear of Max Eccentric Contraction?
  2. Unfamiliar with max Eccentric Contraction
  3. Reflex inhibition by Golgi Tendon Organ?
43
Q

At the same relative force, why is there same MUA in eccentric and concentric contractions?

A

Because the same number of CBs are active, so the same number of muscle fibers are active, so same number of motor units are active, and same motor unit activation occurs (same EMG amplitude)

44
Q

How does the GTO contribute to the maximal eccentric EMG being lower than the maximal concentric EMG (at the same relative force)?

A

The GTO senses high force in the tendon and is stimulated. It inhibits motor output (reflex inhibition) to prevent too much tendon force and thus injury.

And the GTO is more active at higher eccentric velocities.

45
Q

How do higher firing rates result in greater rate of force development?

A

At a higher firing rate, more MAPs are sent per second, so there’s a faster release of Calcium from the SR, so more rapid onset of CB cycling
as a result there is greater rate of force development

46
Q

What is fatigue?

A

A decrease in force/power generating capacity

47
Q

What does fatigue look like during a concentric and eccentric contraction?

A

Concentric: reduced force and velocity, so reduced power
Eccentric: reduced force and reduced velocity? so reduced power (but also more likely to cause ultrastructural damage)
- we may or may not be able to reduce velocity but we’ll be able to produce less force at a given velocity and therefore be able to produce less eccentric power
- eccentric contraction when there is fatigue, is more likely to cause structural damage to muscle (sarcolemma tearing)

48
Q

What Does Fatigue Look like in an Isometric Contraction?

A

Reduced Force
Reduced Rate of Force Development (RFD): takes Longer for force to increase w/ Fatigue
Reduced Rate of Force Relaxation (RFR): takes Longer for force to be fully gone after relaxation

49
Q

describe neuromuscular junction failure

A

There is only a finite amount of Ach and if APs are sent for too long or there are too many of them, eventually Ach will be depleted.
The axon terminal cannot resynthesize APs fast enough so the AP will not be transmitted across to the motor end plate to cause a motor AP
Additionally, there may be reduced excitability of the motor end plate and if AP’s occur too frequently across the motor endplates then the concentration gradients of potassium and sodium might be messed up a bit and cause them to not be as easily excited

The nerve axon itself is not fatiguable, it can transmit APs indefinitely

KINESIOL 2C03 (2 decks)

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