Hormones Flashcards
Where are hormones secreted?
from endocrine glands
How is plasma glucose during exercise maintained?
- mobilization of glucose from liver glycogen stores
- mobilization of FFA from adipose tissue
- glucogenesis from AA, lactic acid and glycerol
- blocking entry of glucose into cells
Permissive/slow acting hormones
exert full effect
thyroxine
cortisol
growth hormone
Fast-acting hormones
epinephrine
norepinephrine
insulin
glucagon
Thyroid hormones
influences the number of receptors on the surface of a cell for other hormones to interact with
affinity of receptor for hormone
no change during exercise
T3
enhances effect of epinephrine to mobilize free fatty acids from adipose tissue
Growth hormone
essential for growth of all tissues
- increase AA uptake and protein synthesis
- reduces use of plasma glucose
- increases gluconeogenesis
- mobilizes fatty acids from adipose tissue
Changes in GH during exercise
Net effect of GH is to preserve plasma glucose concentrations
Increases gluconeogenesis in liver
Blocks glucose entry to adipose cell tofavourfatmobliization
Increase in plasma GH with increasing intensity
Cortisol
steroid hormone derived from cholestrol
secreated from adrenal cortex
Cortisol stimulated by
stress via ACTH
exercise
When does cortisol peak?
AM
drops throughout the day
Cortisol pattern
increase proportional to increase exercise intensity
What is the direct effect of cortisol mediated through?
slow process of DNA transcription and translation to protein synthesis
What are changes in cortisol related to?
repair of exercise-induced tissue damage rather tham mobilization of fuel
Hormonal response to exercise
mobilize fat and CHO
preserve glucose
What hormones are elevated with exercise?
GH
glucagon
cortisol
(nor)epinepherine
=favour mobilization FFA
not insulin
During heavy exercise
FFA oxidation decreases despite hormonal stimulation
increase glucose use
Decrease in FFA oxidation due to
high levels of lactic acid
elevated H+ conc inhibit HSL
inadequate blood flow to adipose tissue
insufficient albium to transport FFA in plasma
Impact of endurance training
decrease lactate conc at any fixed work rate = reduce inhibition to FFA mobilization
= use more fat as a fuel, spare limited CHO stores = improve performance
Where is catecholamine secreated from?
adrenal medulla
Epinephrine/nor
bind to adrenergic response (alpha and beta cells)
fight or flight
Effects of epinephrine/nor
increase glycogenolysis
increase lipolysis
Plasma E and NE during exercise
fast-acting hormone
increase HR and BP (sympathetic activation)
Catecholamine response to exercise
trained individuals = greater capacity to increase C
endurance training = rapid decrease to fixed intensity exercise bout
Glycogen depletion during exercise
high-intensity = greater/rapid depletion
Plasma epinephrine
powerful simulator of glycogenolysis (via B receptor)
greater increase during high intensity exercise
Why is there no difference in glycogen depletion plasma E?
Ca++ released (from sarcoplasmic reticulum with muscle contraction)
Ca++ ions bind to Calmodulin = activates protein kinase
phosphorylase –> glucose –> glycolysis
Exocrine
secreted via ducts
Endocrine
secreted directly into bloodstream
Pancreas
secretes counter-regulatory hormones from islts of Langerhans
Insulin
from B cells
promotes storage of glucose, AA and fats
drives uptake and storage of substrate to lower their levels in plasma
Glucagon
from A cells
promotes the mobilization of fatty acids and glucose
stimulates gluconeogenesis in liver
Ratio of glucagon to insulin
control over mobilization of glucose and FFA
Changes in insulin during exercise
conc drop by ~50%
favour mobilization of glucose from liver and FFA from adipose tissue
Changes in glucagon during exercise
endurance training programme = glucagon diminished = no increase during exercise
Effect of catecholamine on insulin and glucagon
when glucose constant = SNS can modify hormone secretion
endurance training decrease SNS response to a fixed exercise bout
Hormone-substrate interaction due to
high levels lactic acid
elevated H+ conc inhibits HSL
inadequate blood flow to adipose tissue
insufficient albium to trasport FFA in plasma
= decrease FFA
increase glucose use
