Metabolic and Endocrine Control during Special Circumstances Flashcards
What are the anti-insulin hormones and why are they known by this term
Glucagon, adrenaline, growth hormone, cortisol
Their actions oppose that of insulins
What is the normal glucose range in a healthy individual
4.0-6.0mmol/L
What is hypoglycaemia
A reduction in blood glucose to 3.0mmol/L or lower
What are the acute effects of hypoglycaemia
Weakness/tiredness
Palpitations
Changes in mood
Sweating
Headache
Sickness
Slurred speech
Can lead to unconsciousness and dead if untreated
What is hyperglycaemia
Elevation of the fasting blood glucose above 7.0mmol/L
What hormones are important in starvation and how do they act
Cortisol - stimulates gluconeogenesis, lipolysis and use of fatty acids instread of glucose by cells
Glucagon - stimulates gluconeogenesis and lipolysis
Anti-insulin hormones - stimulate ketone body production
Why does maternal metabolism change during pregnancy
Ensure foetus is supplied with range of nutrients it requires
Ensure nutrients are supplied at appropriate rate for each stage of development
Ensure there is minimal disturbance to materal nutrient homeostasis
Ensure foetus is buffered from any major disturbances in materal nutrient supply
What hormones are produced/involved in pregnancy
Maternal insulin
Oestrogens
Progesterone
Placental lactogen
What is the role of materal insulin
Promotes uptake and storage of nutrients, largely as fat in maternal adipose tissue
What are the foetal-placental hormones and what effect do they have
Human placental lactogen, progesterone, corticotropin releasing hormone
Have an anti-insulin effect
What metabolic changes occur during the first half of pregnancy
Increase in maternal nutrient stores - increased insulin level to promote anabolic state
This is for the more rapid growth of foetus, birth and subsequent lactation
What metabolic changes occur during the second half of pregnancy
Second half of pregnancy marked by increase in growth of placenta and foetus
Maternal metabolism adapts to meet increasing demands of foetal-placental unit by keeping nutrient concentration in maternal circulation relatively high
There is an increase in production of anti-insulin hormones
How is nutrient concentration in materal circulation kept high during second half of pregnancy
Reduced maternal utilisation of glucose by switching tissues to use of fatty acids
Delayed disposal of maternal nutrients after meals
Release of fatty acids from stores built up during first half of pregnancy
Due to the increased availability of fatty acids, what process is switched on during pregnancy
Maternal ketogenesis - ketone body production is switched on
Where are the ketone bodies produced by maternal ketogenesis used
Used as a fuel by the developing foetal brain
How is the increased insulin produced achieved by the cells of the pancreas during pregnancy
B-cell hyperplasia and hypertrophy
Insulin synthesis in B-cells increases
What is gestational diabetes
Where the endocrine pancreas is unable to respond to metabolic demands of pregnancy and pancreas fails to release increased amounts of insulin required
There is a loss of control of metabolism, blood glucose increases and diabetes mellitus results
After birth, metabolic demands of pregnancy are removed and diabetes disappears as endocrine pancreas can respond normal demands
What does the metabolic response to exercise ensure
Increased energy demands are met by mobilisation of fuel molecules from energy stores
Minimal disturbances to homeostasis by keeping rate of mobilisation equal to rate of utilisation
Glucose supply to brain is maintained
End products of metabolism are removed as quickly as possible
What does the energy requirement of exercise reflect
The increased activity of skeletal and cardiac muscle, increased activity of respiratory muscle is less significant
Why is liver glycogen not used by muscles during exercise
It is used to prevent hypoglycaemia and associated impairment of CNS function
What are the advantages of using muscle glycogen over circulating glucose
Availability not affected by blood supply
No need for membrane transport into muscle cells
Produces G-6-P without using ATP
Mobilisation can be very rapid - branched molecule
What limits anaerobic metabolism of glucose in muscles
Accumulation of H+ and lactate
How do H+ ions impair muscle function
H+ inhibits glycolysis
H+ interferes with actin/myosin interaction
H+ causes sarcoplasmic reticulum to bind calcium, inhibiting contraction
What factors limit the use of fatty acids by muscles
Rate of lipolysis - rate of release from adipose tissue
Limited capacity of blood to transport fatty acids
Rate of fatty acids uptake into muscle cells and into muscle mitochondria
Fatty acid oxidation requires more oxygen/mole of ATP produced than glucose
Fatty acids only metabolised under aerobic conditions
What is the metabolic response to short-duration, high intensity exercise and what controls this response
Metabolic response is rapid and largely confined to skeletal muscle that works anaerobically
Controlled by nervous system (NA) and some endocrine input (adrenaline)
Describe the metabolic response to short-duration, high intensity exercise
Muscle ATP and C~P are used initially
Muscle glycogen is rapidly mobilised to provide ATP
G-6-P is metabolised by substrate level phosphorylation
Glycolysis is carried out under anaerobic conditions
Dramatic increase in rate of anaerobic glycolysis produced lactate and H+
H+ ions build up, producing fatigue
What is the metabolic response to medium duration, medium intensity exercise
Initial spint uses muscle ATP, C~P and anaerobic glycogen metabolism
Long middle phase where ATP is produced aerobically from glycogen in muscle
Finial burst relying on anaerobic metabolism of glycogen
What control the changes in metabolism that occur during long duration, low intensity exercise
Hormonal - insulin, adrenaline, growth hormone, glucagon, cortisol
Nervous system - noradrenaline
What are the major features of the metabolic response that occur during long duration, low intensity exercise
Muscles work aerobically
Muscles can use all types of fuel molecules
Origin and type of fuel changes as exercise proceeds
What fuel molecules are used during a marathon and during what points are they used
Initially muscle glycogen is used as major fuel
As marathon proceeds, there is increased utilisation of circulating blood glucose - replaced by glucose release from liver
Fatty acids can be used by muscle due to aerobic conditions
There are limited substrates for gluconeogenesis though so blood glucose level may fall
How is the metabolic response during a marathon controlled - what is secreted and what is inhibited
Insulin secretion inhibited by adrenaline and noradrenaline
Noradrenaline, adrenaline and growth hormone levels increase rapidly
Glucagon and cortisol levels increase gradually
What are the effects caused by changes in the endocrine system during a marathon
Fall in insulin/anti-insulin ratio causing:
Increased glycogenolysis in liver
Increased gluconeogenesis in liver - lactate and glycerol
Increased lipolysis in adipose
No effect on ketogenesis
What is fatigue
Inability to maintain a given power output affecting the intensity and/or duration of exercise
Give some biochemical causes of fatigue
Depletion of muscle glycogen
Accumulation of H+ in muscle
Dehydration
What are the whole body reponses to prolonged exercise
Increased fuel consumption by muscles
Increased ATP production and utilisation by muscles
Increased heat production
Increased oxygen delivery - arteriole vasodilation
Increased removal of CO2, H+ and lactate
Increased cardiac output - beat faster, larger stroke volume
Redistribution of blood from to muscles, away from kidneys and gut
Changes in breathing - increased rate and depth
What is training and what body systems does it primarly affect
Long term adaptations to improve capacity for physical work
Cardiovascular and musculoskeletal systems
What are the cardiovascular changes due to training
More 2,3-bisphosphoglycerate
Heart beats slower for same cardiac output
What are the musculoskeletal changes as a result of training
GLUT4 in cell membrane
Glycogen storage
Potential for oxidation metabolism - especially fatty acids
Number and size of muscle fibres
Vascularisation of muscles
Myoglobin content of muscle
What are the benefits of exercise
Body composition changes - increased muscle, decreased adipose
Glucose tolerance improves - increased muscle glycogenesis
Insulin sensitivity increases
Blood TAGs decrease - increased HDL, decreased VLDL and LDL
BP falls
Feeling of well-being - psychological effect
What are the two types of muscle and what exercise are they good for
Type 1 (red) - low intensity, high endurance
Type 2 (white) - high intensity, low endurance
