Muscle recruitment/contraction

Question 1

Types of Fibre type

Answer 1

1. Type I- Slow Twitch
2. Type IIa- Fast Twitch: Fatigue Resistant
3. Type IIx (IIb rat)- Fast Twitch: Fast Fatiguing

Question 2

Type I- Slow Twitch

Answer 2

• slower contracting

- fatigue resistance

Question 3

Type IIa- Fast Twitch: Fatigue Resistant

Answer 3

• faster contracting

- moderate resistance to fatigue

Question 4

Type IIx (IIb rat)- Fast Twitch: Fast Fatiguing

Answer 4

• fastest contracting

- easily fatigued

Question 5

Slow Twitch (I)

Answer 5

• Red
• Slow oxidative (SO)
• Heavy reliance on mitochondria
• Fatigue resistant
• ⬆️ Max Tension

Question 6

Fast Twitch (IIa)

Answer 6

• Red
• Fast oxidative glycolytic (FOG)
• Heavy reliance on mitochondria, also high glycolytic capacity
• ⬆️ Fatigue
• ⬆️⬆️ Max Tension

Question 7

Fast Twitch (IIx)

Answer 7

• White
• Fast glycolytic (FG)
• Heavy reliance on glycolysis
• ⬆️⬆️⬆️ Fatigue resistant
• ⬆️⬆️⬆️ Max Tension

Question 8

Force-velocity

Answer 8

As load increase, the velocity of shortening decreases

Question 9

Contraction Time (CT)

Answer 9

Depends on the type of myosin present

Question 10

Relaxation Time (RT)

Answer 10

• Dissociation of Ca2+ from troponin
• Uptake of Ca2+ into SR
• Speed of relaxation tends to match speed of contraction

Question 11

What determines the force generated by muscle?

Answer 11

1. Optimal length of contracting muscle fibre
2. Action potential frequency/Frequency Summation
3. Number of fibres per motor unit and cross-sectional area

Question 12

1. Optimal length of contracting muscle fibre

Answer 12

1. ) Compressed:
   - Actin-myosin filaments
   - Less tension produced
2. ) Optimal:
   - Optimal tension when stimulated optimal actin-myosin interaction
3. ) Stretched:
   - Actin-myosin filaments barley touch
   - Decreased amount of tension

Question 13

2. Action potential frequency/Frequency Summation

Answer 13

• When there is a single action potential there is a single contraction that is followed by a relaxation
• If there is a second action potential that occurs prior to the complete relaxation, the force that is generated by the 2 action potentials is summed up

Question 14

3. Number of fibres per motor unit and cross-sectional

Answer 14

1. ) The amount of tension developed by each fibre
2. ) The number of fibres contracting at a given time
   i. ) the number of fibres in each motor unit (motor unit size)
   ii. ) the number of active motor units

Question 15

Factors determining muscle tension

Answer 15

1. Tension developed by each fibre
   a. ) Action potential frequency (frequency-tension relation)
   b. ) Fibre length (length-tension relation)
   c. ) Fibre diameter
   d. ) Fatigue
2. Number of active fibres
   a. ) Number of fibres per motor unit
   b. ) Number of active motor unit

Question 16

Requirements for Actin-Myosin Interaction

Answer 16

• ATP
• Ca2+
• Structural integrity/ alignment