Hormones and Receptors Flashcards
Is the endocrine system ductless or does it contain ducts?
ductless
Are glands anatomically distinct?
Yes, but do form functional system
What does the anterior pituitary release to cause the adrenal cortex to make cortisol?
ACTH
By what three ways is specificity of signalling achieved?
- chemically distinct hormones
- specific receptors for each
- distinct distribution of receptors across target cells
Name the 3 main classes of hormones.
Glycoproteins and peptides
Steroids
Tyrosine and tryptophan derivatives
Which hormone class is most diverse?
glycoproteins and peptides
Give an example of the glycoproteins and peptides class
oxytocin or insulin
Give examples of steroids.
Cortisol, testosterone
Give examples of Tyrosine and tryptophan derivatives.
adrenaline, melatonin and thyroid hormones
Are amines, peptides and proteins hydrophilic or phobic, and are they transported freely or bound?
hydrophilic, freely
Are steroids hydrophilic or phobic, and are they transported freely or bound?
hydrophobic, bound to plasma proteins
Are steroids and thyroxine soluble or insoluble in plasma?
relatively insoluble
What is the function of carrier proteins?
- increase amount of hormone transported in blood
- prevent rapid excretion by preventing filtration at kidney
What act as a buffer and ensure free and bound hormones are in equilibrium?
carrier proteins
Is albumin a specific or general carrier protein?
general
What does albumin bind?
many steroids
thyroxine
What does transthyretin bind?
thyroxine
some steroids
Do peptides and proteins need carrier proteins and why?
no, are soluble in plasma
What type of hormones, free or bound, can cross the capillary wall?
only free
What does cortisol bind globulin bind to sometimes as well as cortisol?
aldosterone
What does thyroxine binding globulin bind to?
T4 (thyroxine) as well as some triiodothyronine (T3)
What does sex steroid binding globulin (SSBG) bind to mostly?
testosterone and estradiol
What buffer surges in hormone?
carrier proteins
What is the primary determinant of plasma secretion?
rate of secretion
What 3 things is rate of secretion subject to?
- negative feedback control
- neuroendocrine (sudden bursts of secretion in response to stimulus eg stress)
- diurnal rhythm
Does rate of elimination contribute to plasma concentration?
Yes
How does rate of elimination generally occur?
By liver metabolism and kidney excretion
How long does amine elimination take?
seconds
How long does protein/peptide elimination take?
minutes
How long does steroid elimination take?
hours - days
What are the 3 main types of hormone RECEPTOR?
- G protein coupled
- receptor kinases
- nuclear receptors
What is the receptor for insulin an example of?
receptor kinases
Which classes are cell surface receptors?
G protein coupled and receptor kinases (nuclear receptors are intracellular)
What are G protein coupled receptors activated by?
amines and some proteins/peptides
What are receptor kinase receptors activated by?
proteins/peptides
How many classes are there of nuclear receptors?
3 (1, 2 and hybrid)
What activates class 1 nuclear receptors?
steroid hormones
Where are class 1 nuclear receptors when activated and when not?
no activated - cytoplasm, bound to heat shock proteins
activated- nucleus
Where are class 2 nuclear receptors?
nucleus mostly
What activates class 2?
mainly lipids
What activates the hybrid class?
thyroid hormone
What class is the hybrid class similar to in function?
class 1
What must the ligands be to diffuse across the membrane in nuclear receptors?
lipophilic
