Control Of Metabolism - Pregnancy And Exercise Flashcards
How are nutrients transported from the maternal to fetal blood?
- ACROSS PLACENTA
- Most substances DIFFUSE DOWN A CONCENTRATION GRADIENT
- Glucose is transported across GLUT1 receptor
What is the principal fuel for fetal growth?
Glucose
What is meant by the ‘fetoplacental unit’?
Placenta, fetal adrenal glands and fetal liver form a NEW ENDROCRINE ENTITY
Name 2 steroid hormones produced by the placenta
- Progesterone
- Oestriol
How do insulin levels change in the first half of pregnancy?
- Increased insulin secretion to promote ANABOLIC processes
- Increased LIPOGENESIS helps with building maternal nutrient stores
Why must maternal nutrient stores be built up during the first half of pregnancy?
Nutrients in preparation for:
- Rapid growth of fetus
- Birth
- Subsequent lactaction
Why does increased lipolysis occur during the second half of pregnancy?
- Breakdown of maternal fat stores from first half of pregnancy
- REDUCES MATERNAL GLUCOSE UTILISATION by metabolism of fatty acids rather than glucose
- Glucose is spared for rapid growth of fetus
Explain how the insulin/anti-insulin ratio falls during the second half of pregnancy
- Fetoplacental unit secretes anti-insulin hormones into maternal blood AT A FASTER RATE than maternal insulin secretion
- Overall anti-insulin concentration is greater than insulin concentration
What is the main anti insulin hormone secreted by the placenta?
Corticotropin releasing hormone CRH
What is the effect of anti insulin hormones on maternal blood glucose?
- IMPAIRED GLUCOSE UPTAKE
- Transient HYPERGLYCAEMIA due to increased insulin resistance
Why does hypoglycaemia occur during meals and fasting in the second half of pregnancy?
Continuous draw of glucose to fetus from maternal blood
How does insulin secretion during pregnancy affect maternal pancreatic β cells?
- INCREASED APPETITE leads to increased consumption of glucose
- Oestrogen and progesterone increase sensitivity of pancreatic β cells to glucose
- Causes HYPERTROPHY and HYPERPLASIA of β cells which leads to increased insulin secretion
What is gestational diabetes?
Pancreatic β cells do not produce sufficient insulin to meet requirements in late pregnancy
What are the causes of gestational diabetes?
- β CELL DYSFUNCTION due to obesity and chronic INSULIN RESISTANCE
- Destruction of β cells by AUTOANTIBODIES
- Genetic predisposition
What are the clinical complications associated with gestational diabetes?
- Increased risk of miscarriage
- Increased risk of congential malformation
- FETAL MACROSOMIA
- Hypertensive disorders such as GESTATIONAL HYPERTENSION and PREECLAMPSIA
What is preeclampsia?
High blood pressure during pregnancy leads to INCREASED LOSS OF PROTEIN IN URINE
How is gestational diabetes managed?
- DIETARY MODIFICATIONS
- Insulin injections
- Regular ultrasound scans to assess fetal growth
What does the rate of metabolism during exercise depend on?
- Type of exercise
- Intensity
- Duration
- Physical and nutritional state of individual
Why must ATP be rapidly resynthesised during a sprint?
- Only enough ATP in muscles to last ~2secs
- NEED TO MATCH RESYNTHESIS RATE WITH HYDROLYSIS RATE to meet metabolic demands
Where does the ATP for replenishing muscle stores during exercise come from?
- CREATINE PHOSPHATE
- Glycolysis
- Oxidative phosphorylation
Describe how muscle glycogen is metabolised during high and low intensity exercise
High intensity (no O2):
- Sustained breakdown of muscle glycogen by MUSCLE GLYCOGEN PHOSPHORYLASE which is activated by adrenaline and AMP
- Produces glucose-6-P which can enter glycolysis to produce ATP
Low intensity (some O2):
- Complete oxidation of glucose and glycogen stores from liver and muscle
- Produce more ATP through oxidative phosphorylation so can last longer
Explain how the liver recycles lactate that is produced by muscle cells during exercise
- CORI CYCLE
- Lactate produced by muscle cells from glucose is transported to liver
- Liver converts Lactate to pyruvate (via lactate dehydrogenase) which then enters gluconeogenesis to produce glucose
- Glucose is transported back to muscle
Which glucose transporters are present in muscle cells?
GLUT1 and GLUT4
Why is it essential that blood glucose levels are maintained during exercise?
Some tissues have an absolute requirement for glucose e.g. BRAIN, RBC, cornea and lens of eye
Why is the use of fat stores limited during exercise?
- REQUIRES OXYGEN
- Slow release from adipose tissue
- Limited carrying capacity in blood
- Limited uptake across mitochondrial membrane
Explain how hormone concentrations change during a marathon
- INSULIN levels fall slowly
- GLUCAGON levels rise (stimulates catabolism of carbs and fat stores)
- ADRENALINE and GH rise rapidly (stimulates glycogenolysis, lipolysis and mobilisation of fatty acids)
- CORTISOL rises slowly (stimulates gluconeogenesis and lipolysis)
What are the benefits of exercise?
- DECREASES ADIPOSE and increases muscle
- Improves GLUCOSE TOLERANCE
- Improves INSULIN SENSITIVITY of tissues
- Decreases TAGs in blood and stores
- Decreases BLOOD PRESSURE
- Psychological effects
Explain the metabolic changes that occur during a 100m sprint
- 0-5secs MUSCLE ATP STORES AND CREATINE PHOSPHATE STORES ARE USED UP
- 5+secs PRODUCE ATP ANAEROBICALLY
- Production of LACTATE
- Breakdown of MUSCLE GLYCOGEN stores via gluconeogenesis to MAINTAIN GLUCOSE FOR BRAIN
Explain the metabolic changes that occur during a 1500m race
- Initially use CREATINE PHOSPHATE and ANAEROBIC GLYCOGEN METABOLISM
- Middle phase AEROBIC PRODUCTION OF ATP from MUSCLE GLYCOGEN
- Final sprint is ANAEROBIC metabolism of glycogen and produces LACTATE
Explain the metabolic changes that occur during a marathon
- 95% AEROBIC
- 0-5mins uses MUSCLE GLYCOGEN STORES
- 5-60mins uses LIVER GLYCOGEN STORES
- Utilisation of FATTY ACIDS after 30mins
Describe the metabolic changes that occur during pregnancy
- Early pregnancy metabolism of mother is ANABOLIC
- Nutrients are stored to meet future demands of rapid fetal growth, gestation and lactation after birth
- Late pregnancy metabolism is CATABOLIC
- Decreased insulin sensitivity so blood glucose increases and lipolysis of TAGs meaning there is more available for fetal growth
