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Phase 2 Limbs and Back > Week 3: Skeletal Muscle > Flashcards

Week 3: Skeletal Muscle Flashcards

1
Q

What percentage of your body weight is make up of skeletal muscle, for males?

A

40% of body weight

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2
Q

What are the three major causes of changes to skeletal muscle?

A

Use
Age
Disease

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3
Q

What type of muscle has a major effect on metabolic rate?

A

Skeletal muscle

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4
Q

What percentage of body weight is skeletal muscle for women?

A

30%

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5
Q

What is the function of skeletal muscles?

A

Moves bones attached to it by tendons

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6
Q

When a muscle contracts what effect does it have on the insertion and origin?

A

Muscle shortens and pulls its insertion TOWARDS its origin

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7
Q

What are the 3 mechanisms used to gain more skeletal muscle force?

A
  1. More complete activation of one muscle
  2. More activation of muscles with similar function
  3. Inactivation of muscles with opposite action
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8
Q

When you feel muscle pain what is it you are feeling?

A

Skeletal muscles themselves dont get much sensory innervation usually its the connective tissue (fascicles) that surround the muscle fibres

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9
Q

Define fascicles?

A

Connective tissue that surrounds a bundle of muscle fibres

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10
Q

Define motor unit?

A

Group of individual muscle fibres innervated by a single motor neurone.

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11
Q

What is defined as the functional units of motor control?

A

Motor units

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12
Q

How many neurones can innervate one muscle?

A

Hundreds of motor neurones.

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13
Q

What muscle units are associated with high precision control and why?

A

Small muscle units as they are associated with low forces.

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14
Q

At what point does the muscle neurone branch to innervate its many muscle fibres?

A

Close to the muscle

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15
Q

What type of muscle unit is associated with lower precision control?

A

Large muscle units

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16
Q

What muscle is the slowest contracting muscle in humans?

A

Soleus

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17
Q

What muscle is the fastest contracting muscle in humans?

A

Gastrocnemius

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18
Q

Will a slow muscle only contain solely slow motor units?

A

No will have some fast ones too

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19
Q

Name the different types of motor units?

A
  1. Type 1
  2. Type 2a
  3. Type 2x
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20
Q

Describe type 1 motor units?

A

Low peak force and slow fatiguing

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21
Q

Why is type 1 motor units good at resisting fatigue?

A

Nourished with an extensive blood supply which maintains aerobic metabolism

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22
Q

Which muscle unit is the first recruited by the central nervous system when a muscle is activated?

A

Slow fatigue (type 1)

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23
Q

Describe type 2a motor units?

A

Intermediate peak force in an intermediate time.

Known as fast fatigue resistant- between type 1 and 2x.

24
Q

Which muscle unit will be recruited by the central nervous system after type 1, when a muscle is activated?

A

2a

25
Q

Describe type 2x motor units?

A

High peak force in a short period of time.
Known as fast fatigue
Most force when stimulated by very prone to fatigue.

26
Q

What is the first muscle unit to stop being used by the central nervous system when the force from a muscle is no longer required?

A

Type 2x

27
Q

Which muscle unit is the last to be recruited by the CNS when a muscle is activated?

A

Type 2x

28
Q

How many motor units will an individual muscle have? why?

A

Multiple of all 3.

Provides the muscle the ability to produce increased force (from long to high)

29
Q

If a muscle contains more type 1 motor units what type of capability does it have?

A

Endurance capability

30
Q

If a muscle contains more type 2x motor units what type of capability does it have?

A

Strength capability

31
Q

When you train what happens in the muscle units?

A

Selective hypertrophy in the specific motor units e.g. type 1.
Does not cause type conversion i.e. type 1->type 2x

32
Q

Define fatigue?

A

Inability to maintain power output, reversible by rest. Distinct from injury!

33
Q

When fatigue occurs which factors decline as a result

A

Force
Shortening velocity
Relaxation rate
Power (drops quickest as it P-FxV)

34
Q

Name the two different types of fatigue?

A

Central fatigue

Peripheral fatigue

35
Q

Where does central fatigue occur?

A

Within the nervous system

36
Q

Describe central fatigue?

A

Loss of excitability of motor cortex
Failure of transmission anywhere up stream of the neuromuscular junction
Rare

37
Q

Where does peripheral fatigue occur?

A

Within the muscle fibres

38
Q

Describe peripheral fatigue?

A

Failure of ATP generation by depletion of energy stores

CNS can still signal the muscle to contract but the muscle is unable to

39
Q

Define the 3 techniques used to distinguish between central and peripheral fatigue?

A
  1. Stimulate muscle nerves
  2. Stimulate motor paths at cervical cord
  3. Stimulate motor cortex
40
Q

What happens to potassium concentration when there is a high intensity?

A

Extracellular accumulation of potassium.

Leading to T-tubules becoming inexcitable.

41
Q

If ATP stores ran out what state would the muscles go into?

A

Rigor

NOT fatigue

42
Q

What accumulations during muscle contraction which causes fatigue?

A
  1. ADP
  2. Phosphate ions
  3. Hydrogen ions
43
Q

How does ADP stimulate fatigue?

A

Interferes with the actin and myosin binding

44
Q

How does hydrogen ions effect fatigue?

A

Reduces calcium flux and competes with calcium for troponin binding

45
Q

What does creatine phosphate do?

A

Creatine Phosphate + ADP -> ATP + Creatine

Removes the excess ADP

46
Q

What energy source do you need to short duration high power exercise?

A

Mostly creatine + carbohydrate

47
Q

What energy source is used during moderate duration and low power work?

A

Carbohydrate with a small use of lipids (to extend the carbohydrate metabolism)

48
Q

What energy source is used during long duration work?

A

Lipids

49
Q

When do you go on to use lipid metabolism?

A

Only when carbohydrate stores are low (but not exhausted as you need a background level)

50
Q

Describe strength training?

A

Small number of repetitions high force contractions

51
Q

Describe endurance training|?

A

Large number of repetitions low force contractions

52
Q

What happens to the different muscle unit types during strength training?

A

Initially you get neural changes and then you get muscles and connective tissue getting stronger
Type 2a and 2x hypertrophy

53
Q

What happens to the different muscle unit types during endurance training?

A

Type 1 hypertrophy
2a variable
2x may reduce

54
Q

What are the two phases called of the strength training?

A

Neural phase

Hypertrophy phase

55
Q

Describe what molecular changes occur during the hypertrophy phase?

A

New contractile filaments are added to existing myofibrils.

Fibril splitting- long myofibrils split to increase force

Phase 2 Limbs and Back (31 decks)

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