hormonal control of metabolism Flashcards
which parameters can change to allow adaptation to energy demands?
HR, substrate levels, respiratory rate, ventilatory rate, temperature regulation, fluid homeostasis
how does the endocrine system respond to exercise?
slower onset but longer lasting response, can be global
what can the targets of hormone release be?
a organ or specific cells in tissues
what determines the cellular mechanism of action for a hormone?
chemical structure
how is secretion and plasma control of hormones dynamic?
responds to requirements, not constant secretion. may be time limited, over different periods of time or in cycles. often uses a negative feedback loop
why do plasma hormone levels not always reflect the activity?
receptor desensitisation
what do steroidal hormones do?
alter protein synthesis in the long-term via alteration of gene transcription
which glands secrete steroidal hormones?
adrenal cortex - cortisol, aldosterone
ovaries - oestrogen, progesterone
testes - testosterone
placenta - oestrogen, progesterone
what are non-steroidal hormones?
large, non-lipid soluble, polar
what can non-steroidal hormones be?
peptide or protein hormones - insulin or glucagon
amino acid derived hormones - thyroxine, noradrenaline
what are prostaglandins?
a type of hormone/pseudohormone derived from arachidonic acid
give an example of a prostaglandin hormone?
thromoxane, which is released from platelets and causes vasoconstriction
what is the role of endocrine glands during exercise?
metabolic regulation and metabolism of carbohydrates and fat
what hormones increase circulating glucose?
glucagon, adrenaline, noradrenaline, cortisol
what occurs as exercise intensity increases?
catecholamine release increases, glyconeogenolysis rate increases in the liver and muscles. muscle glycogen is used before liver glycogen
what occurs as exercise duration increases?
more liver glycogen is utilised, there is increased muscle glucose uptake, which causes increased liver glucose release. as glycogen stores decrease, glucagon levels increase
how do pancreatic beta cells control release of insulin?
when glucose is high, ATP synthesis is stimulated, this blocks the ATP-sensitive potassium channel, leading to depolarisation and activation of calcium channels. insulin is released via calcium dependent vesicular release
how does insulin promote influx of glucose in exercise?
insulin receptor activity stimulates Akt, which causes translocation of vesicles containing GLUT4 to the membrane. greater cell surface expression permits greater influx of glucose.
why is GLUT4 preferred in exercise?
GLUT1 is always present at the cell surface, but is not efficient
what is the role of pancreatic a-cells?
modulate glucagon release
how do pancreatic a-cells respond to low glucose?
Na+ and Ca2+ channels contribute to depolarisation, action potentials stimulate release of glucagon
how do pancreatic a-cells respond high glucose?
the Katp is blocked by the presence of increased ATP, Na channels cannot recover from inactivation. there is reduced Ca2+ entry and reduced glucagon release.
what process does glucagon stimulate?
glycogenolysis via the Gs/cAMP/PKA mediated pathway
what is the functional effect of sympathetic drive in exercise?
adrenaline release -> decreased blood flow to the gut, increased flow to vascular smooth muscle in skeletal muscle. via increase in b-adrenoceptor stimulation, and decrease in a-adrenoceptor stimulation cause vasodilation in skeletal muscle and vasoconstriction in the gut
how is the difference in response to the same ligand potentiated between the mesenteric vascular smooth muscle and the skeletal vascular smooth muscle?
in the mesentery, a-adrenoceptors predominate, whereas in the skeletal muscle, B-adrenoceptors predominate.
what is the effect of exercise on fat metabolism?
lipolysis, stimulated by decreased insulin, and increased adrenaline, noradrenaline, cortisol and growth hormone
where are antidiuretic hormone and aldosterone secreted from?
adh- posterior pituitary gland
aldosterone - adrenal cortex
how are ADH and aldosterone utilised to regulate fluid and electrolyte balance?
aldosterone increases water re-absorption
what part of the brain is responsible for satiety control?
ventromedial nucleus
what part of the brain is responsible for appetite control?
lateral hypothalamus
what does cholecystokinin do?
decrease appetite in response to secretion when the stomach is full
what does leptin do?
decrease appetite, secreted by the adipose tissue
what do Glucagon-like peptide 1 and peptide YY do?
decrease appetite in response to exercise
what does ghrelin do?
increase appetite, secreted by intestine
