Flashcards in Metabolism - Adaptations Deck (19)
What does growth of the foetus require in pregnancy, and how does the body respond to these needs?
Growth requires energy and raw materials from the maternal circulation via the placenta. As this often relies on diffusion, the nutrients need to be in higher in the maternal circulation.
Body responds by:
- adjusting maternal blood conc of nutrients
- modifying nutrient stores (mostly fat) to cope with demand (which is highest in late pregnancy and lactation).
How do the reproductive hormones influence the build up of maternal fat stores?
1). Stimulate appetite so more glucose is taken in.
2). Store more fat and glycogen
3). Increase the action of insulin on storage tissues and decrease the action of insulin on energy using tissues.
= storage tissues take up more glucose, energy using tissues take up less.
4). Increase beta cell sensitivity to blood glucose
How do beta cells respond to reproductive hormones in pregnancy?
Their sensitivity to look glucose levels is increased
= increase insulin synthesis
= increase insulin secretion
What secretes anti-insulins in pregnancy?
The ovaries and later the placenta.
How do anti insulins work?
By making the muscle resistant to insulin = use less glucose.
Name 3 anti insulins.
In basic terms, what does having a higher blood glucose in maternal blood achieve?
Glucose can diffuse down the conc gradient to the foetus via the placenta. More glucose is also driven into storage tissue for later in the pregnancy.
What is gestational diabetes and its consequences?
If the beta cells don't respond properly and produce insulin, anti-insulins will dominate = glucose can't be taken into tissues properly.
Results in hyperglycaemia and excess foetal growth (macrosomia with liver and muscle glycogen).
How must the body respond during exercise?
Meet acute O2 and fuel molecule needs
Dispose of CO2 and metabolic waste products
Minimise disturbance of other systems
Mobilise fuel stores
Preserve blood glucose levels for the brain.
What does the magnitude if the body's response to exercise depend on?
Type of exercise
Intensity of exercise
Physical and nutritional condition of the individual
Where is energy derived from in exercise in terms of ATP?
1). Short term stores
- ATP, CrP
2). Recreation of ATP
- oxidative phosphorylation
- anaerobic glycolysis
How does the body adapt to exercise when running 100m and what is O2 delivery like?
O2 can't be delivered to the muscle in time.
1). Uses up ATP and CrP
2). Generates ATP anaerobically (glycolysis/LDH)
3). Uses muscle glycogen
Why is muscle glycogen a good store?
It is available when blood flow is limited
It produces G6P without requiring ATP = fed into glycolysis
No need to cross any cell membranes = metabolised faster
How does the body adapt to exercise when running 1500m and what is O2 delivery like?
Some O2 is delivered but this is limited as when the muscle contracts, it temporarily limits blood flow.
1). Anaerobic respiration/a little aerobic
2). Mobilisation of fatty acids
- slowly released from adipose (but this is limited by amount of protein carriers available in blood)
- uptaken by mitochondria (limited by capacity if carnitine shuttle which transfers it across mitochondrial membrane)
- requires more O2 per ATP produced.
How do insulin and glucagon aid in mobilisation of reserves?
Insulin increases GLUT4 expression = glucose enters muscle
Glucagon and adrenaline stimulate glycogenolysis
How does the body adapt to exercise when running a marathon and what is O2 delivery like?
O2 is delivered mostly aerobically
1). Mobilises muscle glycogen (~5 mins)
2). Mobilises fatty acids (~20mins)
3). Mobilises liver glycogen (~1 hour peak)
Hormones help this process...
1). Insulin levels fall while glucagon rise (conserves glucose for brain and mobilises glycogen)
2). Adrenaline and GH rise rapidly (glycogen and lipolysis respectively)
3). Cortisol begins to rise (fat mobilisation and stimulates gluconeogenesis)
How does cortisol stimulate gluconeogenesis?
Increases transcription of PEPCK and fructose-1,6-bisphosphate
What are the benefits of exercise?
Better balance of lean tissue and fat
Lower blood pressure
Lower blood lipids
Improved glucose tolerance
Improved muscle sensitivity to insulin