11. Metabolism in Exercise Flashcards
What are the benefits of exercise?
- Body composition changes ( less adipose, more muscle)
- Insulin sensitivity increases (diabetics!)
- Blood TAG decrease
- BP falls
- Psychological “well-being”
- Glucose tolerance improves (muscle glycogenesis increases)
How do insulin levels change in response to a marathon?
Insulin levels fall slowly due to inhibition of secretion by adrenaline
How do glucagon levels change when running a marathon?
Increase
Stimulates glycogenolysis
Stimulates gluconeogenesis
Stimulates lipolysis
Which enzymes does glucagon stimulate to exert those effects?
PEPCK and fructose-1,6-BP - gluconeogenesis
Glycogen phosphorylase - glycogenolysis
Hormone sensitive lipase - Lipolysis
Which hormone levels rise rapidly when undergoing exercise such as a marathon?
Adrenaline and growth hormone
What does adrenaline stimulate?
Glycogenolysis and lipolysis
What effect does growth hormone?
Mobilises fatty acids (lipolysis)
What happens to cortisol levels over long, marathon-like exercise?
Slowly rise
Stimulates gluconeogenesis and lipolysis
Which energy stores are the first to be used up during exercise?
ATP and creatine phosphate
After ATP and creatine phosphate is used up, how does the muscle tissue release energy?
Anaerobic glycolysis of muscle glycogen (no increased delivery of oxygen yet)
If longer duration of exercise, what happens after glycogen stores are used up?
Increased oxygen supply allows for aerobic oxidation of muscle glycogen, glucose and liver glycogen.
In a marathon, what happens after glucose from liver glycogen is declining steadily (1 hour)?
Utilisation of fatty acids rises steadily after 30 minutes
What 3 things are used during low intensity, long duration exercise?
Muscle glycogen
Liver glycogen
Fatty acids
Which exercise type has the most aerobic activity?
Low intensity, long duration - marathon
Increased delivery of oxygen to tissues, whereas in a sprint this doesn’t happen in time.
What happens to oxygen supply during moderate intensity exercise, e.g. 1500m?
Some extra oxygen can be delivered to tissues, but still 40% anaerobic metabolism.
What are the 3 phases of moderate intensity exercise?
- Initial start - creatine phosphate and ATP
- Long middle - aerobic ATP production from muscle glycogen
- Finishing sprint - anaerobic metabolism of glycogen, lactate producing
What is the main energy supply in a 100m sprint (short, high intensity exercise)?
- ATP and creatine phosphate
Cannot deliver oxygen and nutrients in time… - Anaerobic ATP production of muscle glycogen
Lactate build up leading to fatigue
How long do creatine phosophate stores provide energy for?
5 seconds during a sprint
Muscle glycogen can supply energy for how long during intensive exercise?
2 minutes
What happens if exercise is low intensity?
Enough oxygen can be supplied for complete oxidation of glucose and glycogen stores (from muscle and liver) to last for around 60 minutes.
When can fatty acids be used as a fuel during exercise?
Only in aerobic conditions
- slow release from adipose tissue
- Low rate of ATP production but high capacity for sustained production
What is the cori cycle?
Liver recycles lactate:
Lactate produced from muscle cells is carried to the liver in the blood, where it is converted back to glucose and released into the circulation for uptake.
How does exercise increase blood glucose concentration?
Increased gluconeogenesis
Increased glycogenolysis
Which glucose transporters are present in muscle cells?
GLUT 4 (insulin dependent) GLUT 1 - constitutively active
What other glucose uptake process can muscle use during exercise?
Insulin independent uptake - increase in AMP stimulates AMPK which signals to increase GLUT4 translocation.
