Hormonal Responses to Exercise W2 Flashcards
Where are hormones secreted from?
Endocrine glands
What are the 4 process which maintain plasma glucose during fasting or exercise?
1) Mobilisation of glucose from liver glycogen stores
2) Mobilisation of FFA from adipose tissue
3) Gluconeogenesis from amino acids, lactic acid and glycerol
4) Blocking the entry of glucose into cells
What are the “permissive” or slow-acting hormones?
Thyroxine
Cortisol
Growth hormone
What are the fast-acting hormones?
Epinephrine
Norepinephrine
Insulin
Glucagon
What do thyroid hormones do?
1) Influences the number of receptor on the surface of a cell for other hormones to interact with
2) Influences the affinity of the receptor for the hormone
What does Triiodothyronine (T3) do?
It enhances effects of epinephrine to mobilise free fatty acids from adipose tissue
What interferes with the ability of other hormones to mobilise fuel for exercise?
Hypothyroid state
What are growth hormones 2 primary functions?
1) Essential for growth of all tissues
2)Spares plasma glucose
How does the growth hormone promote tissue growth?
Increases amino acid uptake and protein synthesis
How does the growth hormone spare plasma glucose?
Reduces the use of plasma glucose
Increases gluconeogenesis
Mobilises fatty acids from adipose tissue
What causes an increase in plasma growth hormone?
Increase in exercise intensity
What is cortisol?
Steroid hormone derived from cholesterol and secreted from the adrenal cortex
What is cortisol stimulated by?
Stress (ACTH)
Exercise
What does cortisol do?
Contributes to the maintenance of plasma glucose by a variety of mechanisms
What are the 2 major considerations when looking at cortisol?
Diurnal variation
Events other than exercise
What is diurnal variation?
Concentrations peak in the am and drop throughout the day
What is the direct effect of cortisol mediated by?
Mediated through the slow process of DNA transcription and translation to protein synthesis
What are the 2 different catecholamines?
Adrenaline
Noradrenaline
Where are catecholamines secreted from?
Adrenal medulla
What are effects of catecholamines dependent on?
Hormone used
Receptor type
What do catecholamines bind too?
Adrenergic receptors
What are adrenergic receptors?
Alpha receptors
Beta receptors
What are catecholamines?
Fast-acting hormones
What happens to plasma epinephrine and norepinephrine during exercise?
Increases
Why does plasma epinephrine and norepinephrine increase during exercise?
As there is an increase in heart rate and blood pressure (due to sympathetic activation)
How do catecholamines react to endurance training during a fixed intensity exercise bout?
It causes a very rapid decrease in response
How much higher capacity does a trained individual have compared to an untrained to increase there catecholamine capacity?
35%
How does supramaximal exercise influence catecholamines?
Increases them due to regular stimulation of the sympathetic nervous system= increases capacity to respond to extreme challenges
What causes greater and more rapid glycogen depletion?
High-intensity exercise
What is glycogenolysis related to?
Exercise intensity
What is the power simulator of glycogenolysis?
Plasma epinephrine via the beta-1 receptor
What results in greater increases of plasma epinephrine?
High-intensity exercise
What type of control is the breakdown of muscle glycogen under?
Dual control (redundant)
What activates protein kinase?
Ca++ ions binding to calmodulin
What is the relationship between an intact sympathoadrenal system and glycogenolysis like?
It does not necessarily initiate glycogenolysis
What functions are in the pancreas?
Exocrine (secreted via ducts)
Endocrine functions (directly into the blood)
What does the pancreas do?
Secretes counter-regulatory hormone from the islets of Langerhans
What are the 2 counter-regulatory hormones secreted from the islets of Langerhans?
Glucagon
Insulin
What does glucagon do (from alpha cells)?
Promotes mobilisation of fatty acids and glucose
Stimulates gluconeogenesis in the liver
What does insulin do (from beta cells)?
Promotes the storage of glucose, amino acids and fats
drives uptake and storage of substrates to lower their levels in plasma
What provides control of mobilisation of glucose and FFA?
The ratio of glucagon to insulin
What is the primary stimulus for secretion of insulin and glucagon?
Plasma glucose
What can cause insulin concentrations to drop by 50%?
Moderate-intensity exercise
What does moderate-intensity exercise favour which causes the drop in insulin concentrations?
Favours the mobilisation of glucose from the liver and FFA from adipose tissue
When can the SNS modify hormone secretion?
When plasma glucose is relatively constant (trained individuals)
How does endurance training effect SNS response?
Decreases the response to a fixed bout of exercise
What hormones mobilise fat and CHO and preserve blood glucose?
Epinephrine
Norepinephrine
Growth hormone
Cortisol
Glucagon
What hormone does not mobilise fat and CHO and preserve blood glucose?
Insulin
Why does FFA oxidation decrease during exercise?
1) High levels of lactic acid
2) Elevated H+ concentration which inhibits HSL
3) Inadequate blood flow to adipose tissue
4) Insufficient albumin to transport FFA in plasma
What is the impact of endurance training on hormone-substrate interaction?
Decreases the lactate concentration at any fixed work rate, which reduces the inhibition to FFA mobilisation from adipose tissue
When combined with an training-induced increase in mitochondria, the trained person can use more fat as fuel, spare the limited CHO stores and improve performance
