Hormonal Response to Exercise Flashcards
What are the 4 processes that maintain plasma glucose when fasting or during exercise?
- Mobilization of glucose from liver glycogen stores.
- Mobilization of FFA from adipose tissue.
- Spares blood glucose. - Gluconeogenesis from amino acids, lactic acid, and glycerol.
- Blocking the entry of glucose into cells.
- Forces use of FFA as a fuel.
What are the 2 types of hormones?
- Permissive/slow-acting (thyroxine, cortisol, GH)
- Fast-acting (Epinephrine, norepinephrine, insulin and glucagon)
How do permissive hormones act?
Act in a permissive manner to allow other hormones to exert their
full effect.
How is GH essential for growth of al tissues?
Increases amino acid
uptake and protein
synthesis.
How does GH spare plasma glucose?
- Reduces the use of
plasma glucose - Increases
gluconeogenesis - Mobilizes fatty acids
from adipose tissue
How does GH preserve plasma
glucose concentrations?
- Increases gluconeogenesis in liver
- Blocks glucose entry to adipose cell to favour fat mobilization
What happens to plasma GH with increased intensity?
Increase
What is cortisol derived from and where is it secreted?
Cholesterol, secreted from adrenal cortex.
What is cortisol stimulated by?
- Stress, via Adrenocorticotropic hormone
(ACTH) - Exercise
When do cortisol levels peak?
First thing when you wake up.
What are considerations with cortisol levels?
- Diurnal variation:
Concentrations peak in
the am & drop
throughout the day. - Events other than
exercise, e.g.,
emotional arousal
How does cortisol change in response to exercise intensity?
↑ proportional to ↑ in exercise intensity.
Where are catecholamines secreted from?
Adrenal medulla
- Epinephrine (E) (80%)
and norepinephrine(NE)
How does Epinephrine and Norepinephrine increase during exercise?
In a linear fashion.
What does endurance training cause in relation to catecholamines?
A very rapid decrease in catecholamine responses to a
fixed intensity exercise bout.
Do trained individuals have higher or lower capacity to increase catecholamines?
Trained individuals have a greater capacity (~35% higher) to increase catecholamines compared to untrained individuals
What effect does plasma epinephrine have on glycogenolysis?
Plasma epinephrine is a powerful simulator of glycogenolysis (via
beta1 receptor)
- High-intensity exercise results in greater increases in plasma epinephrine.
Why does reduced effects of epinephrine not cause a major difference in glycogen depletion?
Breakdown of muscle glycogen is under dual
(redundant) control.
1. Intact sympathoadrenal
system not necessary to
initiate glycogenolysis
2. Does not mean that
epinephrine cannot, or
does not, cause
glycogenolysis
How does plasma glucagon change 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 primary stimulus for the secretion of insulin and glucagon?
Plasma glucose
Despite glucagon (and other hormones favouring mobilization of FFA) being elevated with increasing exercise intensity, FFA oxidation decreases during heavy exercise. Why could this be?
May be due to:
1. High levels of lactic acid.
2. Elevated H+ concentration inhibits
HSL.
3. Inadequate blood flow to adipose
tissue.
4. Insufficient albumin to transport FFA
in plasma.
Endurance training decreases lactate concentration at any fixed work rate causing..?
Reduced inhibition of FFA mobilization from adipose tissue.
- When this is combined with the training induced increase in mitochondria, the trained person can use more fat as a fuel, spare the limited CHO stores and improve performance.
