LECTURE 6: Endocrine system & exercise Flashcards
list four factors affecting blood hormone concentration
- rate of secretion (regulated by rate magnitude of input, inhib. vs stim. input)
- rate of metabolism & excretion (at kidneys/liver/target cell)
- availability of transport hormones
- plasma volume (higher concentration when dehydrated)
list three mechanisms of actions of hormones
- altering cell membrane (allow more/less mvmt of substrates across)
- altering activity of cell DNA
- activating 2nd messengers within cells
list the three categories of hormones
- amino acid derivatives
- peptides & proteins
- steroids
list 6 hormones released by the anterior pituitary
thyroid stimulating hormone/TSH, growth hormone/GH, adrenocorticotropic hormones/ACTH, prolactin, follicle stimulating hormone/FSH, leutenising hormone/LH,
list 2 hormones released by the posterior pituitary gland
oxytocin, ADH
t/f: ADH levels drop linearly during exercise
false: ADH levels rise exponentially as intensity increases
what dietary sources can tryptophan be obtained from?
eggs, fish, poultry, nuts, seeds, dairy etc
what hormone is tryptophan a precursor for?
melatonin (via serotonin)
what hormones does the thyroid secrete? what are their effects?
T3 & T4 - metabolic & permissive hormones (raise metabolic rate of most cells & facilitate effectiveness of other hormones), calcitonin - lowers plasma Ca2+ content
what hormone does the parathyroid secrete and what is it’s effect?
Parathyroid hormone - increases plasma Ca2+ levels
why is calcium supplementation sometimes recommended for low-impact sports?
when calcium is lost in sweat, plasma Ca2+ levels lower triggering a rise in PTH and breakdown of bones. chronically, this can lead to lower BMD
what hormones does the adrenal medulla secrete?
adrenaline, noradrenaline
does adrenaline dilate or constrict skeletal muscle blood vessels and intestinal blood vessels?
dilates skeletal muscle blood vessels (acts on beta cells), constricts intestinal blood vessels (acts on alpha cells)
what categories of hormones does adrenal cortex secrete?
mineralocorticoids, glucocorticoids, sex steroids
provide an example of a mineralocorticoid, glucocorticoid and sex steroid secreted by the adrenal cortex
aldosterone, cortisol, androgens & oestrogens
does aldosterone secretion rise or fall with exercise?
rises - to counteract fluid loss
list three factors stimulating secretion of cortisol
circadian rhythm, exercise, stress
list three hormones and their functions released by the pancreas
insulin - lowers blood glucose (promotes uptake of glucose and AA in cells)
glucagon - raises blood glucose (promotes glucose and FFA mobilisation)
somatostatin - controls nutrient absorption in GI tract
does oestrogen & progesterone plasma concentration rise or fall in exercise? explain
rises, dependent on phase of menstrual cycle but likely due to fluid loss increasing plasma concentration.
levels rise as intensity of exercise rise
what are the androgenic and anabolic effects of testosterone in men
androgenic –> develops secondary sex characteristics
anabolic –> promotes tissue building
list the two causes of relative energy deficit syndrome (RED-S)
inadequate energy intake
excessive training
t/f: plasma adrenaline is a powerful stimulator of glyconeogenesis
true: high intensity exercise increases plasma adrenaline levels and allows for greater glucose use
what kind of control is muscle glycogen breakdown under? describe it’s components
dual control - two systems control the use of muscle glucose.
1. adrenaline-cAMP: breakdown of muscle glycogen stimulated by adrenaline via beta-adrenergic receptors
2. Ca2+-calmodulin: most Ca2+ (that which isn’t used for contraction) released from SR in exercise binds to calmodulin, activating protein kinases that initiate glycogen breakdown
t/f: glucose is not the main fuel source for exercise at near-max intensities
false
can muscles still contract when the beta-receptors are inhibited?
yes - the calcium-calmodulin system allows muscles to contract without adrenaline
list 4 ways blood glucose is maintained by hormones
- mobilisation of glucose from liver glycogen stores
- mobilisation of FFA from adipose tissue
- gluconeogenesis from AA, lactic acid & glycerol
- blocking entry of glucose into cells
list the four fast-acting hormones that control blood glucose
adrenaline, noradrenaline, insulin, glucagon
list the three slow-acting hormones that control blood glucose
thyroxine, cortisol, growth hormone
do plasma levels of catecholamines in exercise increase, stay the same or decrease following weeks of training?
decrease - indicate body’s ability to adapt to repeated stressful events
do plasma levels of catecholamines in exercise increase, stay the same or decrease following weeks of training?
decrease
does the secretion of insulin & glucagon depend on catecholamine action?
yes - catecholamine binding to alpha cells stimulates secretion of glucagon, binding to beta cells inhibits insulin secretion
list four ways catecholamines quickly restore blood glucose levels
- muscle glycogen mobilisation
- increased liver glycogenolysis
- mobilisation of FFA from adipose tissue
- opposing glucose uptake by tissue
as exercise intensity increases, do plasma insulin and glucagon levels fall or rise?
insulin falls, glucagon rises
how does a glucose pressure gradient develop between tissue and blood in exercise?
higher blood glucose levels (due to higher glucagon/lower insulin) creating high blood glucose concentration & high rate of muscle glucose use creating a low intracellular glucose concentration creates a pressure gradient, allowing glucose to more readily pass into the cell
do glucagon/insulin levels increase in endurance trained athletes?
not much, due to greater sensitivity of cells to insulin/glucagon, greater FFA metabolism with training (especially with increase in duration/intensity) & reduced SNS response to exercise (lower catecholamine levels to stimulate pancreas)
how do T3 & T4 contribute to blood glucose homeostasis?
act in permissive manner - allow other hormones to exert their full effect
to T3/T4 levels change in exercise?
no - metabolism increases in exercise but secretion increases to restore plasma levels
list four ways cortisol contributes to blood glucose homeostasis
- MOSTLY permissive hormone (allows fast acting hormones to work more efficiently)
- stimulates FFA mobilisation from adipose tissue
- stimulates gluconeogenesis in live
- blocks entry of glucose into tissue
do cortisol levels increase or decrease in low intensity exercise (less than 60%VO2max)? what about high intensity (greater than 60%VO2max)
low: decrease (rate of use is greater than rate of secretion)
high: increase (stress of exercise stimulates more secretion)
list four ways growth hormone contributes to blood glucose homeostasis
- supports action of cortisol
- blocks glucose uptake in cell
- increases FFA mobilisation
- increases gluconeogenesis in liver
does plasma GH concentration increase or decrease as exercise intensity rises?
increases - at high concentrations at near-VO2max GH can start its slow effect
does plasma GH concentration increase or decrease with training
likely increase (especially earlier in exercise).
why is it uncertain whether GH levels in exercise increase or decrease with training?
GH is hard to isolate, many factors affect it’s release
do concentrations of fast and slow acting hormones respectively increase or decrease as exercise intensity increases?
FAST: increase
SLOW: decrease + small bounce up close to VO2max to provide more glucose
do concentrations of fast and slow acting hormones respectively increase or decrease as exercise duration increases?
FAST: increase, but mostly due to fluid loss
SLOW: decrease, no bounce up due to lower intensity
what enzyme is FFA mobilisation dependent on?
hormone sensitive lipase (HSL)
why does FFA mobilisation decrease in heavy exercise despite increased hormonal stimulation for FFA mobilisation?
high lactic acid levels trap FFA in adipose cell (force FFA back into triglyceride form)
high H+ levels inhibit HSL
lower blood flow to adipose tissue lowers FFA release
what two adipokines does adipose tissue secrete (as endocrine action of adipose)?
leptin
adiponectin
are leptin and adiponectin pro- or anti-inflammatory?
leptin - pro-inflammatory
adiponectin -anti-inflammatory
do both adiponectin and leptin enhance insulin sensitivity & fatty acid oxidation in muscle cells?
yes, both
what endocrine effects of adipose tissue change when fat mass increases to obese levels?
higher leptin secretion - lower appetite suppression due to lower hypothalamic sensitivity, more pro-inflammatory effect of leptin
lower adiponectin secretion - lower anti-inflammtory effects, lower insulin sensitivity of muscle cells
what is the primary myokine secreted by muscles (as an endocrine function)
interleukin 6 (IL-6)
does exercise-induced release of IL-6 have a pro- or anti-inflammatory effect?
anti-inflammatory effect - IL-6 can have both effects but when released with exercise is anti
what effects does the autocrine effect of myokine release have on local cells
higher glucose uptake, higher FFA oxidation
what paracrine/endocrine effects does myokine release have on the body?
promotes blood vessel growth in muscle
promotes liver gluconeogenesis and TAG breakdown
what stimulates increased erythropoietin (EPO) release?
hypoxia
what does erythropoietin to do the blood?
increases RBC content
what organ secretes EPO?
kidneys
what does ESA stand for?
erythropoietin stimulating agent
what does rhEPO stand for?
recombinant erythropoietin
what is the difference between rhEPO & ESAs?
rhEPO is an exogenous form of EPO that directly increases RBC levels, ESAs are exogenous stimulators of EPO release in the body.
does altitude increase or decrease EPO secretion?
increases
what is the form of classic altitude training?
LHTH - Live high train high
what is the form of contemporary altitude training?
LHTHL - live high train high & low
what does altitude do to stimulate EPO secretion?
hypoxia
does growth hormones (as a PED) affect contractile proteins or collagen?
collagen
does testosterone affect collagen or contractile protein growth?
Contractile protein
