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Flashcards in Factors affecting muscle force Deck (34)
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1
Q

What is the definition of tension?

A

The force that a muscle exerts on an object when it is contracting

2
Q

What is the definition of load?

A

The force that is exerted on a muscle by an object

3
Q

What must be the relationship between muscle tension and load in order for concentric contraction to occur?

A

The muscle tension generated must be greater than the load in order for muscle fibres to shorten and object responsible for the load to move

4
Q

What must be the relationship between muscle tension and load in order for eccentric or isometric contraction to occur?

A

The muscle tension must not exceed the load, such that the muscle fibres or remain the same length

5
Q

What is concentric contraction?

A

Aka isotonic contraction, where the muscle shortens under a constant load

6
Q

What is eccentric contraction?

A

Where the muscle length increases, and load is greater than tension

7
Q

What is isometric contraction?

A

Where the muscle length remains constant. When the object is free, load is equal to tension; when the object is fixed, load can be greater than or equal to tension

8
Q

Why is the latent period of isometric contraction much shorter than in isotonic contraction?

A

Because isotonic contraction needs to generate enough tension to overcome load; isometric latent period is related to tension, whilst isotonic latent period is related to distance shortened by

9
Q

With increasing load, what occurs to the single fibre contraction?

A

The latent period increases; velocity of shortening slows down; total duration of twitch became shorter; distance fibre is shortened by becomes less

10
Q

What is the relationship between load and velocity of isotonic contraction?

A

Increased load decreases shortening velocity until load is increased to point where muscle is unable to move, becoming isometric. When load increases above peak tension that muscle can produce, becomes eccentric contraction

11
Q

At what load point is isotonic contraction near maximum shortening velocity?

A

When there is no load

12
Q

What must the stimuli be like in order to create separate small tensions?

A

Stimuli must be separated by more time than total contraction time

13
Q

What occurs if a second stimulus is introduced halfway through contraction time, before muscle can fully relax?

A

Muscle tension rises further as more Ca2+ is in cell, meaning more tropomyosin is moved and more binding sites are available for actin and myosin to form cross-bridges and generate a stronger contraction

14
Q

What occurs if two stimuli happen very close together?

A

Higher tension is created, forming a smooth curve indicating summation

15
Q

What is summation?

A

Increase of muscle tension from successive action potentials

16
Q

What occurs if successive stimulation results in a sustained contraction?

A

A tetanus is formed

17
Q

What happens in an unfused tetanus?

A

Muscle fibre has time to partially relax before the next stimulation; development of tension oscillates

18
Q

What happens in a fused tetanus?

A

Muscle fibre has no time to relax; development of tension is continuous and smooth

19
Q

What is the length-tension relationship?

A

As the muscle length deviates higher or lower than optimal, force generation is low

20
Q

Why is force generation low when initial muscle length is less than optimal?

A

Actin filaments overlap with one another, so removes the potential of cross-bridges forming with one of the actin filaments (interfere with cross-bridges); Z-lines meet the ends of the myosin filament

21
Q

Why is force generation low when initial muscle length is more than optimal?

A

Fewer cross-bridges overlap actin molecules

22
Q

What are the three main sources of energy?

A

Creatine phosphate, oxidative phosphorylation, glycolysis

23
Q

What does creatine phosphate do?

A

Provides P very quickly to form ATP from ADP; lasts only for a short time

24
Q

Why is an oxygen debt?

A

The oxygen required to produce energy after exercise has finished in order to replenish stores of glycogen and CP, and remove lactate

25
Q

What are causes of muscle fatigue?

A

Conduction failure; lactic acid buildup; inhibition of cross-bridge cycling; fuel substrates; central command fatigue

26
Q

What is conduction failure?

A

Accumulation of K+ in t-tubules. Has a fast recovery

27
Q

Why does lactic acid buildup cause fatigue?

A

Acidic environment means proteins are not at optimum, and Ca2+ release and re-uptake mechanisms are interfered with

28
Q

Why does inhibition of cross-bridge cycling cause fatigue?

A

Accumlation of ADP and Pi in muscle fibres slows down cross-bridge cycling by preventing release of cross-bridges from actin molecules

29
Q

What fuel substrates can cause fatigue?

A

Muscle glycogen deficit, blood glucose deficit, dehydration

30
Q

What is central command fatigue?

A

Failure to propagate signals from the brain to motor neurons

31
Q

What are the three muscle fibre types?

A

Slow oxidative, fast oxidative, and fast glycolytic

32
Q

What are features of slow oxidative fibres?

A

Low ATPase activity, and highly oxidative

33
Q

What are features of fast oxidative fibres?

A

High ATPase activity, and highly oxidative/ moderately glycolytic

34
Q

What are features of fast glycolytic fibres?

A

High ATPase activity, and highly glycolytic