Central Fatigue

Question 1

What is central fatigue related to?

Answer 1

Reduced neural output of central structures (brain)

Question 2

The central governor model (CGM)

Answer 2

predicts that neural control systems in the brain and spinal cord establish the number of motor units that are activated in the exercising muscles, specifically to ensure homeostasis is maintained.
Without the CGM you would keep exercising until you collapsed

Question 3

Central fatigue

Answer 3

Force decline caused by a reduction in the motoneuron firing frequency, caused by reduced excitatory drive from the brain.
Loss of brain output reduces the use of peripheral neurons therefore reduces the activation of muscles

Question 4

3 brain neurotransmitters

Answer 4

Serotonin
Dopamine
Noradrenaline

Question 5

Serotonin

Answer 5

Involved in feelings of tiredness and lethargy, mood, sleep, sensory perception, thermoregulation.
Implicated in many psychiatric disorders.
With anxiety and depression serotonin can be an issue - have medication to balance levels again
In sport, too much serotonin can make you tired and impact your mood

Question 6

Dopamine

Answer 6

Important in motivation, reward and attention.
Involved in memory, motor control and coordination
Want dopamine in your system for sport - more feeling of reward and it is involved in motor control

Question 7

Noradrenaline

Answer 7

Implicated in the regulation of attention, arousal and sleep-wake cycles. Learning and memory, anxiety, pain, mood and brain metabolism
Stress increases noradrenaline levels

Question 8

Effects of increased brain serotonin during exercise:

Answer 8

Decreased arousal and motivation
Decreased tolerance and motivation
Increased lethargy and tiredness

Question 9

Blood brain barrier

Answer 9

Separates the brain and spinal cord from the rest of the body
Tightly controlled
Has transporters to exchange molecules across the membrane

Question 10

Albumin

Answer 10

Protein in the blood that helps carry molecules around

Question 11

Newsholme’s Central Fatigue Hypothesis at rest

Answer 11

There are free Tryptophan (essential to building serotonin) but quantity is low
Less Tryptophan than branch chain amino acids

Question 12

Newsholme’s central fatigue hypothesis during exercise

Answer 12

Free fatty acids bind to Albumin which unloads Tryptophan - lots more Trp in blood
Lots more Trp transported across the blood brain barrier so more serotonin produced

Question 13

Exercise and BCAA Supplementation

Answer 13

BCAA supplementation creates equilibrium in the blood between BCAA and Trp
So less Trp across the BBB (same transporter protein as BCAA) - less serotonin produced than no supplementation

Question 14

Aim of BCAA supplementation

Answer 14

To reduce the shuttling of Tryptophan across the blood brain barrier

Question 15

Amphetamines

Answer 15

Increases brain dopamine activity
Up to a certain dose there is a steady increase in running endurance to exhaustion. Past this dose it reduces endurance time (IN RATS!!!)

Question 16

Brain dopamine plays an important role in:

Answer 16

Motivation and reward
Pleasure
Motor control and coordination

Question 17

Brain dopamine and central fatigue

Answer 17

Dopamine synthesis and metabolism increases during exercise
Fatigue coincides with decreased synthesis and metabolism
Maintaining brain dopamine synthesis and metabolism delays fatigue

Question 18

Tyrosine and dopamine synthesis

Answer 18

Tyr goes across the BBB by the transporters and helps synthesis dopamine (it is an essential building block for dopamine)

Question 19

Hypoglycaemia and central fatigue

Answer 19

Increased brain activity in the hypothalamus immediately after glucose ingestion.
At the moment glucose is taken in there is increased brain activity - after 10 mins there’s another spike