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Endocrinology -- Freedman > Exam 1 --Pt1 Intro to Endocrinology > Flashcards

Exam 1 --Pt1 Intro to Endocrinology Flashcards

1
Q

What is the endocrine system?

A

the system of ductless glands that synthesize and secrete chemical messengers (hormones) carried to target tissue by the blood

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2
Q

The endocrine system is tightly coupled to what other system? And what are the both sometimes called together?

A

the nervous system

called the “neuroendocrine system”

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3
Q

What are some of the chemical messengers that interact with one another and coordinate cells, tissues, and organs, to maintain homeostasis?

A
  • NT (neuropeptides)
  • endocrine hormones
  • neuroendocrine hormones
  • paracrines
  • autocrines
  • cytokines
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4
Q

What two glands secrete their hormones primarily in response to neural stimuli?

A

the adrenal medulla (primarily NE) and pituitary gland

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5
Q

Where are the three places that hormonal receptors are located?

A
  • in the cell membrane (for peptide hormones)
  • in the cell cytoplasm (for steroid hormones)
  • in the cell nucleus
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6
Q

What body functions do hormonal systems play a key role in regulating?

A
  • metabolism
  • growth and development
  • H2O and electrolyte balance
  • reproduction
  • behavior
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7
Q

What are the three levels that hormones act at?

A
  1. Whole body level
  2. Molecular level
  3. cellular level
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8
Q

At the Whole body level, what do hormones regulate and integrate?

A
  • ionic and fluid balance
  • E balance (metabolism)
  • coping with env.
  • growth and development
  • reproduction
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9
Q

At the molecular level, what do hormones regulate?

A
  • gene transcription
  • protein synthesis and degradation
  • enzyme activity
  • protein conformation
  • protein-protein interaction
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10
Q

At the cellular level, what do hormones regulate?

A
  • cell division
  • differentiation
  • apoptosis
  • motility
  • secretion
  • nutrient uptake
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11
Q

What is a classical hormone?

A

one secreted by tissue, picked up by blood, and transported to other tissue

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12
Q

What are three general classes of hormones?

A
  1. Proteins and polypeptides
  2. Steroids
  3. Tyrosine derivatives (biogenic amines)
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13
Q

Anterior and posterior pituitary hormones, insulin and glucagon, parathyroid hormone, and many others are examples of what class of hormones? Where are they stored in the cell?

A

proteins and polypeptides; stored in secretory vesicles until needed

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14
Q

What is the precursor for all steroid hormones? Where are they stored? What are two examples?

A

cholesterol; they are NOT stored; Ex: cortisol and aldosterone

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15
Q

What are three examples of Tyrosine derivatives?

A
  • dopamine
  • thyroxine (T4)/ triiodothyronine (T3)
  • Norepinephrine/ epinephrine
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16
Q

T/F. Onset of hormone secretion after stimulus is the same for all locations.

A

False

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17
Q

What does the Adrenal medulla secrete (and it what ratio) and is it fast or slow?

A

epinephrine/NE in a 80:20 ratio; and it is rapid, w/in seconds

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18
Q

How long does the effect take for Pituitary and Thyroid hormones?

A

it is slower, and may take months for full effect

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19
Q

T/F. The concentration of hormones required for most functions is very large.

A

False–the conc. needed is usually very small; therefore rates of secretion are extremely small

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20
Q

What type of feedback prevents over-activity of hormonal systems? What are the two variables that could be used to control this?

A

negative feedback; controlled via secretory rate or degree of activity of target tissue

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21
Q

What levels can Negative feedback occur at?

A
  • gene transcription
  • gene translation
  • steps in processing hormones
  • steps in releasing stored hormones
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22
Q

What is positive feedback control of hormones and give an example?

A

ass. with surges of hormone; Ex: Luteinizing hormone ass. with ovulation

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23
Q

What is an example of a hormone ass. with a Diural cyclical variation ?

A

(diurnal = daily or circadian)

Growth hormone

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24
Q

What is a gland and hormone involved in a seasonal cyclical variation?

A

(seasonal = circannual)

Pineal gland–> melatonin effect on reproduction in seasonal breeders (shuts down reproduction)

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25
Q

What type of activity usually governs hormonal release and cyclical variation in hormone secretion?

A

due to changes in neural activity

26
Q

What type of hormones are water soluble and how are they transported?

A

Peptides and catecholamines; dissolve in plasma and transported from sites of synthesis to target tissue where diffuse out of capillaries–> ISF–> cells

27
Q

What hormones circulate through blood by being primarily bound to plasma proteins? Example?

A

Steroid and thyroid hormones; (<10% exists free in solution)

Ex: 99% of T4 in blood is bound to plasma protein

28
Q

How is the clearance of steroid and thyroid hormones affected due to being bound to plasma proteins? How do they get across capillaries?

A

greatly slows clearance of these hormones; serves as reservoirs; have to dissociate to diffuse across capillaries

29
Q

What two things will affect the hormonal concentration?

A

hormonal secretion and hormonal removal

30
Q

What is the “equation” for hormonal concentration?

A

= rate of secretion - rate of clearance

if rate of secretion > rate of clearance = conc. increases

if rate of secretion < rate of clearance = conc. decreases

31
Q

What is the “equation” for the Metabolic clearance rate (MCR)?

A

= rate of disappearance of hormone from plasma/ conc. of hormone

32
Q

What are four ways in which hormones are “cleared” from plasma?

A
  1. metabolic/enzymatic degradation by the tissue
  2. binding with the tissues
  3. excretion by the liver into the bile
  4. urinary excretion by the kidneys
33
Q

Clinical Note: What disease can cause abnormally high levels of steroid hormones and why?

A

liver disease; b/c these hormones are conjugated mainly by the liver and excreted in the bile

34
Q

Where are the 3 locations where hormonal receptors are located?

A
  1. in/on the surface of the cell membrane
  2. in the cell cytoplasm
  3. in the cell nucleus

~# and sensitivity of hormone receptors are regulated

35
Q

What are four intracellular signaling pathways, after receptor activation?

A
  1. ion channel-linked receptors
  2. G protein-linked receptors
  3. enzyme-linked receptors
  4. intracellular receptors and activation of genes (for steroids)

~1-3 are primarily protein receptors

36
Q

What are second messengers?

A
  • they are mechanisms for mediating intracellular hormonal function
  • allow hormones that can’t cross the cell membrane (proteins/peptides) to affect intracellular fxns/processes
  • create signal amplification
37
Q

What are four cell membrane receptors ass. with second messengers?

A
  1. Adenylyl Cyclase- cAMP
  2. Phospholipase C mechanism (IP3/Ca++)
  3. Calcium-Calmodulin
  4. Enzyme linked receptor
38
Q

Describe the way the Ca++ - calmodulin pathway works in smooth muscle.

A

Ca++ and calmodulin can combine and active MLCK–> will phosphorylate stuff and muscle contracts

Myosin phosphatase will dephosphorylate stuff and muscle relaxes

39
Q

What is the most common 2nd messenger pathway for mechanism of action of protein/peptide hormones?

What is second most common?

A

Adenylyl Cyclase (cAMP)

Phospholipase C (IP3/Ca++)

40
Q

What are the general steps for the Adenylyl Cyclase-cAMP pathway? (MC second messenger pathway)

A

Hormone binds to receptor on cell surface that is coupled with G protein –> alpha subunit binds and activated adenylyl cyclase–> which converts ATP into cAMP–> cAMP activates PKA–> which phosphorylates proteins and causes physiologic actions

41
Q

What inactivates cAMP (adenylyl cyclase)?

A

phosphodieesterase (which would stop the phosphorylation rxn and therefore the effect of the hormone)

42
Q

What are the general steps for the Phopholipase C (IP3/Ca++) pathway? (2nd MC second messenger pathway)

A

Hormone binds to receptor on cell surface–> HR complex coupled to Gq protein–> alpha-q–GTP complex migates w/in cell membrane and binds to and activates phospholipase C –> which frees IP3 and IP3 cuases release of Ca++ from ER–> Ca++ and diacylglycerol activate PKC–> which phsophorylates proteins and causes physiologic effects

43
Q

What do the Adenylyl cyclase (cAMP) and Phospholipase C pathways have in common? In other words, what is important for hormonal response?

A

they both require phosphorylation in order for the hormone to exert their effect

44
Q

What do 2nd messenger systems allow for that is significantly important?

A

signal amplification

45
Q

What are two hormones that can cross the membrane and act directly on genes? And what do they do?

A
  1. Steroid hormones – increase protein synthesis

2. Thyroid hormones – increase gene transcription in nucleus

46
Q

What is the pathway for Steroid hormones acting directly on genes?

A
  1. Steroid hormone binds to receptor in cytoplasm
  2. H-R complex diffuses OR is transported into nucleus
  3. binds to DNA–> transcription–> mRNA
  4. mRNA diffuses into cytoplasm where translation occurs at ribosomes to form protein
47
Q

What is the pathway for Thyroid hormones acting directly on genes?

A
  1. T3 and T4 bind directly to receptor proteins in nucleus
    - form many intracellular proteins (many are enzymes)
  2. once bound to intranuclear receptors, can express control for days-weeks
48
Q

Glucocorticoids, estrogen, progesterone, testosterone, aldosterone, 1,25-Dihydroxycholecalciferol, and T3 and T4, are all what type of homrones?

A

steroid hormones

~recall: precursor = cholesterol

49
Q

GH, insulin, leptin, prolactin, vascular endothelial growth factor, hepatocyte growth factor, and fibroblast growth factor, are all what type of hormone?

A

require Tyrosine kinase

50
Q

What two hormones fall under the category of using Guanylyl Cyclase (cGMP)?

A
  • Atrial natriuretic peptide

- Nitric oxide

51
Q

What three things influence the magnitude of hormonal responses?

A
  1. Conc. of hormone at target cell membrane
  2. Sensitivity of target cell to hormone
  3. Number of functional target cells
52
Q

What 3 things does the conc. of hormone at target cell membrane depend on?

A
  1. rate of secretion
  2. rate of delivery via circulation
  3. rate of degradation
53
Q

What 4 things does sensitivity of target cell to hormone depend on?

A
  1. number of functional receptors
  2. receptor affinity for the hormone
  3. post receptor amplification
  4. abundance of available effector molecules
54
Q

What three things influence the Duration of hormonal responses?

A
  1. Duration of hormonal availability
  2. Mode of production of cellular response
  3. Rapidity of onset of compensatory changes
55
Q

When it comes to duration of hormonal availability what three things are taken into consideration?

A
  • duration of secretion
  • amount secreted
  • half-life in the blood
56
Q

What are two ways the rapidity of onset of compensatory changes are influenced?

A
  • counteracting responses (insulin vs glucagon)

- receptor desensitization or down regulation (turn down # receptors)

57
Q

What are two way to measure Hormones in blood?

A
  1. Radioiummoassay (RIA)

2. Enzyme-linked immunosorbent assay (ELISAs)

58
Q

How is Radioimmunoassay (RIA) done?

A
  • specific antibody to the hormone is produced
  • radioactive labeled hormones
  • hormone to be measured competes with labeled hormone for binding sites on antibody
  • standard curve
59
Q

What is the relationship between % of antibody bound with radioactive antibody to hormone in test sample of the RIA standard curve?

A

increase the amount of hormone, then decrease the amount of radioactive hormone

60
Q

What are the advantages of ELISA?

A
  • NO radioactive isotopes required
  • easily automated
  • cost effective
  • accurate for assessing hormone levels
  • method of choice for clinical labs
61
Q

What can ELISA be used to measure and how is it done?

A
  • can be made to measure any protein
  • combines specificity of antibodies with sensitivity of simple enzyme assays
  • Quantified with colorimetric or fluorescent optical methods

Endocrinology -- Freedman (14 decks)

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