Week 2 - Hormonal responses to exercise Flashcards
How is plasma glucose during exercise maintained
Mobilisation of glucose from liver glycogen stores
Mobilisation of FFA from adipose tissue
Gluconeogenesis from amino acids, lactic acid and glycerol
Blocking the entry of glucose into cells
How is blood glucose homeostasis controlled by hormones during exercise
Permissive or flow acting (Thyroxine, cortisol and growth hormone)
Gast acting (Epinephrine, norepinephrine, insulin and glucagon)
What is the role of thyroid hormones (ON SHEET)
Influences rhe number of receptors on the surface of a cell for other hormones to interact with
The affinity of the receptor for the hormone
Whats the role of Triiodothyronine (ON SHEET)
Enhance the effect of epinephrine to mobilise free fatty acids from adipose tissue
No real change in thyroid hormones during exercise
Hypothyroid state interferes with the ability of other hormones to mobilise fuel for exercise
Whats the main roles of growth hormone (ON SHEET)
Essential for growth of all tissues
Spares plasma glucose
How does growth hormone help growth of all tissue (ON SHEET)
Increases amino acid uptake and protein synthesis
How does growth hormone spare plasma glucose (ON SHEET)
Reduce the use of plasma glucose
Increase gluconeogenesis
Mobilise fatty acids from adipose tissue
How does growth hormone effect performance
GH increases protein synthesis - used to treat childhood dwarfism
High does have more adverse effects than benefits
No evidence that GH promotes strength gains
Difficult to detect usage by athletes
Questionable benefits as anti aging therapy
How does exercise intensity effect GH
Increase in plasma GH with increased intensity
What is cortisol
Steroid hormone derived from cholesterol
and secreted from the adrenal cortex
What stimulates cortisol
Stress via adrenocoricotropic hormone
Exercise
What are some considerations for cortisol
Diurnal variation - concentrations peak in the am and drop throughout the day
Events other than exercise e.g emotional arousal
How does cortisol percentage change in relation to exercise intensity
Linear relationship
What are catecholamines
Secreted from the adrenal medulla
Epinephrine 80% norepinephrine - fast acting hormones
Bind to adrenergic receptors
Also known as adrenaline and noradrenaline
What are the effects of epinephrine and norepinephrine on various tissues
Increased glycogenolysis
Increased lipolysis
Increased vasoconstriction
Whats the effect of endurance training on catecholamines
Endruance training casues a very rapid decrease in catecholamine responses to fixed intensity exercise bout
What are the catecholamine responses to supramaximal exercise
Trained individuals have a greater capacity to increase catecholamines compared to untrained individuals
Regular stimulation of the SNS increases capacity to respond to extreme challenges
How does high intensity exercise impact glycogen availability
High-intensity exercise results in greater and more rapid glycogen depletion
How does high intensity exercise impact plasma epinephrine
Results in greater increases in plasma epinephrine.
What is the role of the pancreas
Secretes counter-regulatory hormones fro the islets of Langerhans
Insulin - promotes glucose storage, amino acids and fat
Glucagon - promotes the mobilisation of fatty acids and glucose
Stimulates gluconeogenesis in the liver
Whats the relationship between glucaogn and insulin
The ratio of glucagon and insulin provides control over the mobilisation of glucose and FFA
How is plasma insulin effected during exercise
During moderate-intensity exercise insulin concentrations can drop by 50%
Decreased plasma insulin concentrations during moderate intensity long term exercise
How is plasma glycagon effected during exercise
Following an endurance training program the glucagon response is diminished to the point that there is little to no increase during exercise
What is the hormone-substrate interaction
Hormones that are elevated with exercise favor the mobilisation of FFA
However in spite of this persisting hormonal stimulation FFA oxidation decreases during heavy exercise
Why does FFA oxidation decrease during heavy exercise
May be due to:
High levels of lactic acid
Elevated h+ concentrations inhibits HSL
Inadequate blood flow to adipose tissue
Inadequate blood flow to adipose tissue
Insufficient albumin to transport FFA in plasma
Therefore decreased FFA and increased glucose use
What is the impact of endurance training on lactate
Decreases the lactate concentration at any fixed work rate, which reduces this inhibition to FFA mobilization from adipose tissue
combined with the training- induced increase in mitochondria, the trained person can use more fat as a fuel, spare the limited CHO stores
