Lecture 21- Endocrine 1 Flashcards

1
Q

What is a hormone?

A

-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

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2
Q

What is an agonist and antagonist?

A

-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

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3
Q

What is a paracrine?

A

-secreting cells and target cells close together, goes into interstitial fluid and finds target cell

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4
Q

What is an autocrine?

A

-group of cells when stimulated release a chemical that stimulates the neighbouring cells or the same cells

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5
Q

What is a neurohormone?

A

-can have the neurons send a signal, release neurohormone that goes to distant target cell (noradrenalin)

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6
Q

What are the endocrine glands?

A

-

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7
Q

What are the hormone categories based on?

A

-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)

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8
Q

How are peptide hormones synthesised?

A
  1. Pre-hormone (RER) 2.Prohormone (RER+ Golgi) 3. Hormone (Golgi) 4 storage vesicles 5. exocytosis
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9
Q

What is an advantage of the peptide hormones?

A

-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

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10
Q

What are the two groups of hormones derived from the amino acid tyrosine?

A
  1. 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)
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11
Q

How are steroids synthesised and secreted?

A

-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

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12
Q

How are hormones transported (general picture only)?

A

-have to be secreted from a cell, enter the circulation and then have to get into the target cell/s

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13
Q

Which of the classes have long term and which have short term action?

A

-short term action= peptides and catecholamines -long term action= thyroid hormones and steroids

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14
Q

How are peptide hormones transported?

A

-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

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15
Q

How are amine derivates transported?

A

–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

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16
Q

How are steroid hormones transported in the body?

A

-Lipid soluble, 1% circulate in free form, 99% bound to plasma proteins -Only the free form is biologically active -1% are water soluble and active 99% like a reservoir (like cortisol= measuring have to look at bound and unbound)

17
Q

How is endocrine activity controlled?

A

-endocrine gland produces the hormone (in one of the two forms) and is in the plasma, then activation occuring: (fluid balance) then going to the target cells doing what it’s supposed to -have negative feedback to the gland so it stops producing more -can have excretion in the kidney= inactivation -many hormones=excretion in kidney= inactivation of many hormones -epinephrine

18
Q

What is desensitization (in control of endocrine activity)?

A

-Down regulation of receptors -hormone produced, then a number of receptors -the number can change= down regulation of receptors, continuous stimulation of receptors= like eating lot of glucose= lot of insulin= the receptors will be desenthysised

19
Q

How do hormonal interactions control endocrine activity?

A

-permissivness:can trigger responses in the target cells, some cells may cause stimulation in tissues = more responsivness = permissiveness -synergism= when different hormones act even on different tissues but have similar effects -antagonistisc=when one hormone is balancing the activity of another

20
Q

How do diurnal rhythms control endocrine activity?

A

-Light/dark -Sleep/awake -cortisol= have different level in the morning and evening = nocturnal will have it the opposite -connection with metabolism= when awake have to get it going! (cortisol= stress hormone, but also important in day to day life getting the metabolism going)

21
Q

How does it happen that abnormal endocrine activity: Too low?

A

-hyposecretion -increase in clearance from blood -decrease in tissue responsivness =for example:Lack of receptors -thyroid is important for regulating metabolism expecially long-term regulation hypo= less being produces or higher clearance from blood -or decrease in tissue responsiveness due to lack of receptors dog: not as active, lethargic, different distribution of fat and skin problems= also connected to the lack of the thyroid hormone, and decrease in tissue responsiveness

22
Q

How does it happen that abnormal endocrine activity: Too high?

A

-Hypersecretion (too much produced) -decerase in clearance from blood(slowing down of clearance in blood (kidney related issues possibly) -increase in free (biologically active hormone) =for example=Lack of plasma binding proteins -or not enough plasma proteins= liver makes them so maybe liver problem -we can be loosing them = can be parasite= worms -bleeding problem= loosing the plasma proteins that way

23
Q

What is Cushing’s syndrome (hyperadrenocorticism)?

A

-higher than normal secretion of cortisol -become sensitive to high levels of starch (can’t cope with starch in diet= have to be low glycemic so it’s released slowly= the glucose)=disturbance to metabolism -disturbance to the reproductive system -skin can change due to the cortisol -long hair as it hasn’t molted(loss of hair in spring) =HORSE

24
Q

How can endocrine activity be affected by genetic modification?

A

-abnormal activity can be due to genetic issues= can be naturally occuring but also transgenics -eg. extra growth hormone

25
Q

How do water soluble hormones change their target cells?

A
  1. some=Alters channel permeability of pre-existing channel-forming proteins 2.Acts via second-messenger system to alter activity of pre-existing proteins
26
Q

How do lipid soluble hormones change their target cells?

A

-Activates specific genes to cause formation of new proteins

27
Q

What is cyclic AMP?

A

-used for intracellular signal transduction -messenger important in many biological processe

28
Q

What hormones act via the cyclic AMP?

A

-when bind to the surface of the target cell=cyclic AMP is produced -Epinephrine and norepinephrine, glucagon, thyroid-stimulating hormone, calcitonin, antidiuretic hormone

29
Q

What is protein kinase?

A
  • kinase enzyme that modifies other proteins by chemically adding phosphate groups to them (phosphorylation). Phosphorylation usually results in a functional change of the target protein (substrate) by changing enzyme activity, cellular location, or association with other proteins.
30
Q

Which hormones act via protein kinase?

A

-Insulin, growth hormone, oxytocin, erythropoietin

31
Q

Which hormones act via calcium and/or phosphoinositides?

A

-Epinephrine and norepinephrine, angiotensin II, antidiuretic hormone, thyroid-releasing hormone

32
Q

What is cyclic GMP?

A

-acts as a second messenger much like cyclic AMP. Its most likely mechanism of action is activation of intracellular protein kinases in response to the binding of membrane-impermeable peptide hormones to the external cell surface

33
Q

What hormones act via cyclic GMP?

A

-Atrial naturetic hormone, nitric oxide -saw before NO= often in the circulatory regulation

34
Q

How will the activation pathway of a fat soluble hormone look like?

A

-the lipid soluble hormone will not be looking for a receptor on the surface of the membrane but inside the cell