W10 - Central fatigue

Question 1

what is the central governor model?

Answer 1

• predicts that neural control systems in the brain and spinal cord establish the number of motor units that are activated(knock on effect on contraction) in the exercising muscles, specifically to ensure that homeostasis is maintained

Question 2

What is central fatigue caused by?

How can this effect the force of a muscle contraction?

Answer 2

Force decline caused by a reduction in the motoneuron firing frequency, caused by reduced excitatory drive from the brain
- If the brain sends less signals = less motor units stimulated = less contraction

Question 3

What is the role of serotonin?

What is the role of dopamine?

Answer 3

• feelings of tiredness, mood, sleep, pain and appetite regulation
  Serotonin can have an adverse effect on performance, not wanted in large amounts
• important for motivation, attention
• involved in memory, coordination
• preferrable in large quantities for exercise performance

Question 4

why is the presence of large amounts of adenosine not favourable for exercise performance?

Answer 4

Adenosine also governs dopamine release - can have an inhibitory affect

Question 5

What are the effects of increased brain serotonin during exercise

Answer 5

• Decreased arousal and motivation
  
  • Decreased tolerance to pain/discomfort
  • Increased lethargy & tiredness

Question 6

describe Newholme’s fatigue hypothesis:

What is the effect of increasing the number of BCAA in the blood?

Answer 6

• Blood brain barrier separates the brain from the blood
  
  • Serotonin is built from tryptophan, so important for free Trp(bound to albumin, cannot cross) to enter the brain
  • Lots of Trp BCAA in blood = more of these in the brain
    (Trp BCAA is competitive with free Trp to cross blood-brain barrier)
  • The more Trp shuttled to the brain, the more serotonin built
  • FFA binding to albumin releases Trp into the blood circulation, our body can also metabolise BCAA

Increasing number of BCAA = balance between Trp and BCAA
- Competitive transport leads to less Trp being transported to the brain (less serotonin production)
- Better performance

Question 7

Why is amphetamine an illegal supplement?

Answer 7

Amphetamine works to improve performance
- Amphetamines can override the danger signals in the body (lead to death)

Question 8

How is dopamine synthesised in the brain during exercise?

Answer 8

Food supplementation:
TYR(tyrosine) - is essential to build dopamine
- Ingesting TYR can increase concentration in blood, more transported across blood-brain barrier = more dopamine produced
- Low dopamine synthesis in the brain is associated with central fatigue

Question 9

What affects does ingesting caffeine have on performance?

Answer 9

• Caffeine inhibits the effects of adenosine
  
  • Adenosine can have an inhibitory effect on dopamine, as it inhibits the release of most excitatory neurotransmitters e.g.: dopamine
  • Therefore taking caffeine stops the inhibitory effects on adenosine on dopamine
  • Caffeine can also facilitate Calcium release leading to better contraction of muscles

Question 10

What happens when there is low availability of glucose during exercise?

Answer 10

• brain is dependent on glucose
• Glucose from bloodstream is predominant energy source for the brain
• Voluntary muscle activation ↓ during hypoglycaemia

Question 11

Describe the effects of glucose solution mouth rinse:

What impact did the mouth rinse have on performance?

Answer 11

Increased brain activity in the hypothalamus immediately after glucose ingestion
- Ingesting glucose increases neural activity in the brain(1st peak) in neural activity - pre-warning must be because of carb receptors in the mouth
- Second peak in neural activity is because blood glucose concentration increased

- Just rinsing mouth with glucose increases exercise performance 3%, significant