Lecture 21- Endocrine 1 Flashcards
What is a hormone?
-Chemical messengers secreted into blood or extracellular fluid by one cell that affect functioning of other cells -Specific hormones usually affect only a limited number of cells -i.e. they bind to specific receptors on or in target cells to elicit a response -chemical in blood stream that have an effect on tissues further away from where they are made =usually hormone secretion is at a distance from the target cells
What is an agonist and antagonist?
-An agonist is a chemical that binds to some receptor of a cell and triggers a response by that cell. Agonists often mimic the action of a naturally occurring substance. Whereas an agonist causes an action, an antagonist blocks the action of the agonist agonist=chemicals competing for the target cells antagonist=block or prevent the action of the hormone
What is a paracrine?
-secreting cells and target cells close together, goes into interstitial fluid and finds target cell
What is an autocrine?
-group of cells when stimulated release a chemical that stimulates the neighbouring cells or the same cells
What is a neurohormone?
-can have the neurons send a signal, release neurohormone that goes to distant target cell (noradrenalin)
What are the endocrine glands?
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What are the hormone categories based on?
-chemical classification 1. Peptides and proteins=small proteins= peptides produced in cells in the normal production of proteins 2.Steroids=chemically and biochemically linked, one can be converted to other -fat soluble -gives them access to the cell easily by diffusion 3.Amino acid derivates=(amino acids can be used as neurotransmitters as well) 4.(Fatty acid derivatives and Eicosanoids) - Eg prostaglandins(=prostaglandins= also effect on bleeding and blood pressure) - Major precursor is Arachadonic acid)
How are peptide hormones synthesised?
- Pre-hormone (RER) 2.Prohormone (RER+ Golgi) 3. Hormone (Golgi) 4 storage vesicles 5. exocytosis
What is an advantage of the peptide hormones?
-major advantage: can be produced in such a package so a snot to be active (eg. trypsin) so first produced as pre prohormone -also can be active right away=once secreted by exocytosis (insulin) is active whereas other hormones are delivered to their target sites before changing to the active form
What are the two groups of hormones derived from the amino acid tyrosine?
- Thyroid hormones=basically a “double” tyrosine with the critical incorporation of 3 or 4 iodine atoms & half-life of a few days -one form more active than the other depending on the structure and the number of iodine atoms also varies in how long are they active for -typically thyroid hormones are active for a long time (days) 2.Catecholamines=include epinephrine and norepinephrine, which are used as both hormones and neurotransmitters= half-life a few minutes(active only for a few minutes)
How are steroids synthesised and secreted?
-Lipid-soluble: diffuse out of cell as they are secreted -structure based on cholesterol but changes to the structure vary a lot aldesterone= important in regulation of body fluids cortisol= stress response also important (fairly linked with aldesterone= some agonist response) -aldesterone and cortisol= similar sort of function just opposite -cortisol also have effect on water balance -only look at aldosterone and cortisol
How are hormones transported (general picture only)?
-have to be secreted from a cell, enter the circulation and then have to get into the target cell/s
Which of the classes have long term and which have short term action?
-short term action= peptides and catecholamines -long term action= thyroid hormones and steroids
How are peptide hormones transported?
-Water soluble, circulate in free form -Some exceptions eg Insulin-like Growth Factor 1 -once created they can just be secereted into the plasma as they are except for Growth Factor 1= needs binding for it to work
How are amine derivates transported?
–the amine der. can be in much higher levels as they can be bound to plasma proteins than if they were in water (as only a bit soluble) -CATECHOLAMINES=Water soluble, 50% circulate in free form, 50% loosely bound to plasma proteins -plasma proteins= albumin and globulins= needed to transport these -buffering effect as 50/50 in different condition when goes through kidney, not all cleared as some bound= gives dynamic as to how long the hormone stays in the circulation -THYROID HORMONE=Lipid soluble, mostly bound to plasma proteins -not water soluble -long term effects (days, weeks) thanks to being bound to the plasma proteins