Test 2- Muscle Physiology/ Fatigue

Question 1

3 biochemical properties of muscle fibre types

Answer 1

1. Oxidative capacity (# of capillaries, mitochondria, myoglobin)
2. Type of myosin atpase isoform
3. Abundance of contractile protein in muscle fibres

Question 2

4 contractile properties of muscle fibres

Answer 2

1. Max force production
2. speed of contraction
3. max power output
4. muscle fibre efficiency

Question 3

Force production and power output between type 11 and type 11x ( which has bigger jump)

Answer 3

bigger jump for max power between type 11 and type 11x

Question 4

what is muscle fibre distribution influenced by

Answer 4

1. Genetics
2. Hormones
3. exercise habits

Question 5

Steps of EC coupling- #1 Exitation

Answer 5

• Nerve signal arrives
• Ach releases into cleft, binds to receptors on end plate and opens ion channels to allow Na to enter muscle
• Depolarizes muscle

Question 6

Steps of EC coupling- #2 Contraction

Answer 6

• depolarization causes release of Ca from SR
• Ca binds to troponin, causing tropomyosin to uncover binding sites on actin
• myosin binds to actin
• Pi releases and causes power stroke
• New ATP attaches which energizes myosin again

Question 7

Steps of EC coupling- #3 Relaxation

Answer 7

• Stim ends , muscle repolarizes

- Ca is pumped back in SR, tropomyosin goes back to position

Question 8

What is the Size Principle

Answer 8

Recruitment is dependent on size of MN (small-> large)

- 1st recruited is last drecruited

Question 9

Two types of causes of Fatigue during exercise

Answer 9

Central- Includes CNS, Motivation, Psychology

Peripheral- PNS to muscle

Question 10

How to know if decreased force is because of central fatigue

Answer 10

if an external stimuli restores force then it is because of central fatigue

Question 11

What is Central Governor Theory

Answer 11

• Is an anticipator mechanism that regulates intensity of effort w/ intent on conserving homeostasis

Question 12

What is the Stechnov Phenomenon

Answer 12

Fast recovery of strength with a distraction or active pauses during recovery from exhaustion

Question 13

what is some evidence of the central governor

Answer 13

• fatigue by reduced neural command by brain
• Fluctuations in power output/ HR not linear
• Presece of homeostasis in all organ functions

Question 14

what are criticisms of central fatigue

Answer 14

• lack of evidence

- Argues against some fundamentals( ex. No plateu in VO2)

Question 15

Evidence of peripheral fatigue

Answer 15

• Stimulation is constant, but force goes down

- Large increase in EMG, but no increase in force.

Question 16

2 hypothesis for peripheral fatigue

Answer 16

1. Depletion

2. Accumulation hypothesis

Question 17

What is the depletion theory of peripheral fatigue

Answer 17

• Depletion of ACh
• Depletion of energy substrates (glycogen, Pi)
• Is rapid then slows

Question 18

What is the Accumulation hypothesis of peripheral fatigue

Answer 18

Build up of metabolic byproducts

a) muscle acidosis- ATP breakdown produces H+
- May inhibit Pfk, slowing glycolysis and interfere with CA

b)Phosphate- Inhibits PFK , cross bridges

Question 19

H+ role in Fatigue

Answer 19

• interferes with Ca+ release from SR
• Interferes with actin-myosin affinity
• interferes with ATP hydrolysis/ Production

Question 20

Reasons for muscle cramps

Answer 20

1. Electrolyte depletion

2. Abnormal spinal reflex activity