Introduction to endocronology Flashcards
What are the different types of cell to cell communication?
Endocrine signalling
Autocrine signalling
Paracrine signalling
Neural signalling
What are the 3 categories of chemical structure of hormones?
Protein or small peptides = ADH
Steroids = cholesterol derivatives
Amines = derivatives of amino acids
What are examples of steroid hormones?
Mineralocorticoids - aldosterone
Glucocorticoids - cortisol
Androgens - oestrogen
Is cholesterol a hormone?
No - it is a common precursor for many steroid hormones
What are examples of amines?
Epinephrine - adrenaline
Thyroxin
What do epinephrine and thyroxin have in common?
Both derive from the amino acid tyrosine
What determines the way hormones are transported in the blood?
Chemical structure
How do peptide hormones and amines travel?
They are hydrophilic
Travel free in solution
How do steroid and thyroid hormones travel?
They are hydrophobic
Carried bound to plasma proteins
Are protein bound hormones filtered easier at the kidney glomerulus than free floating hormones?
No
What types of bonds hold the proteins and the hormones together?
Van der Waals forces
Names of proteins that bind to hormones
Sex hormone-binding proteins
Thyroxin-binding protein
Albumin
Where are the hormones receptors found?
Some are on the CSM and Some are on nucleus
What types of hormones have receptors on CSM?
Hydrophylic hormones
What happens when hydrophilic hormones bind to their receptor on CSM?
They relay the information outside the cell into an intracellular response
Interaction of receptor and hormone results in a conformational change in the protein shape
This activates intracellular proteins and releases second messengers that bring about cell responses
Second messengers affect targets inside the cell
What are common second messengers?
cAMP
CGMP
Ca2+
IP3
What happens when hydrophobic hormones enter cells?
Can cross the nuclear membrane
Interact with genetic material to enhance or decrease gene expression
How does oestrogen bring about changes in the cell?
Activates receptors in the cell nucleus
Activated receptors dimerise
These receptors directly affect gene expression - no need for second messengers
What are the two types of cell membrane receptors?
Tyrosine kinase receptors
G-protein coupled receptors
How does activation of the G-protein coupled receptors bring about cellular changes?
Interaction of hormone with the receptor brings about a change in shape
There is separation of the subunits of the G-proteins - alpha, beta and gamma
G - protein alpha targets the protein adenynyl cyclase which catalyses formation of cAMP
cAMP carries out different funcitons
What are the structural features of G-protein coupled receptors
They cross the membrane 7 times
Linked to G-proteins via GDP
G-protein is made of 3 sub-untis: alpha, beta and gamma
What effect does cAMP have in different tissues?
In cardiac cells - increases heart rate and contractility
In lung cells - causes bronchodilation via relaxation of bronchial smooth muscle
In liver - enhances glycogenolysis to increase blood glucose
What happens upon activation of tyrosine kinase receptors?
Two subunits form the receptor - dimerise when hormone activates it
Dimerised receptors catalyse phosphorylation of proteins
When proteins become phosphorylated = become active and activates other proteins inside the cell
What is a kinase?
Enzyme that catalyses the transfer of phosphate group s from high energy molecules to proteins
