Neuroendocinology Flashcards
Effect of hormone on a tissue is determined by?
the plasma conc
number of active receptors
Hormone-receptor interactions
Hormones only affect tissues that contain specific hormone receptors
Magnitude of effect dependent on:
conc of hormone
number of target receptors on the cell
affinity of the receptor for the hormone
Downregulation
decrease in receptor number in response to high conc of hormone (e.g., age and B-receptors)
Upregulation
increase in receptor number in response to low conc of hormone
conc of hormone so high that all receptors bound to it = any additional increase in plasma hormone has no additional effect = saturation
Mechanisms of hormone action
- activation of genes to alter protein synthesis - steroid hormones
- activating ‘second messengers’ in the cell via G protein - cyclic AMP, Ca++, inositol triphosphate, diacylglycerol
- altering membrane transport - insulin via tyrosine kinase
Change in plasma ADH conc during exercise
increased during exercise >60% VO2 max
to maintain plasma volume
secreted via posterior pituitary gland
Mechanisms of steroid hormone action
estrogen, cortisol and testosterone
slow acting but effects are long lasting
Cyclic AMP “second messenger” mechaism
PK phosporylates other proteins –> amplified response
examples
1. glycogen to glucose (by activating phosphorylase)
2. triglyceride molecules to free fatty acids (by activating hormone-sensitive lipase)
Membrane transport mechaism
insulin receptor - insulin binds to tyrosine kinase receptor’s alpha (a) subunits
glucose transporters (GLUT4) translocate from the cytoplasm to the cell membrane so glucose can enter the cell
net effect = glucose diffuses to inside membrane for use in cell - glycogen synthesized from glucose
What 3 hormones increase with increasing exercise intensity?
renin
angiotensin II
aldosterone
What is plasma conc determined by?
rate of secretion of hormones from endocrine gland
change plasma volume
quantity transport proteins
rate metabolism or excretion of hormone
