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30 Cards in this Set
- Front
- Back
describe hemocrine hormonal communication (the main endocrine form of communication)
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chemical messenger produced by cell, secreted into blood stream, and has effect at a distance
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juxtacrine
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things on the cell membranes of 2 cells come into contact and effect one another
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solocrine
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cell releases hormone into lumen (such as in GI)
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autocrine
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cell releases hormone that effects self
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neurocrine
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cell to blood
or cell to nerve |
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paracrine
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one cell releases hormone that effects the neighboring cell
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intercrine
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gap junctions allow for hormonal communication btw 2 cells
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intacrine
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cell takes up precursor of hormone, gets activated hormone, hits intracellular receptor
(example: androgens) |
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Regulation of Anterior Pituitary Hormone Secretion? (axis for activation/regulation; general)
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Hypothalamus--->Pituitary-->Target Gland
Target gland then sends info back to pituitary and hypothalamus to shut off |
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the pancreatic beta cell is an example of what type of feedback loop?
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feedback loop regulating ‘free standing’ endocrine organ
glucose activates pancreatic beta cell-->insulin release-->reduces glucose-->turns off pancreatic beta cell |
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3 chemical classes of hormones?
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Peptide/polypeptide/protein
Insulin, growth hormone, calcitonin….. Range from 3 AAs (TRH) to 198 AAs ( Prolactin) Lipid derivatives Steroid (cortisol, estradiol, aldosterone…..) Eicosanoid (prostaglandins, thromboxanes…) Amino acid derivatives Epinephrine, norepinephrine, dopamine, T3, T4 |
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what is glycosylation with respect to peptide hormone synthesis?
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makes proteins more stable, less likely to be broken down
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Steroid hormones are synthesized from ....? are they stored?
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Cholesterol
not stored (peptides are made from cleavage of protein, and are stored) |
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common first step in steroid hormone synthesis?
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cholesterol to pregnenolone
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sources of cholesterol for steroid synthesis
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de novo
LDL/HDL |
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what step will prevent steroid synthesis?
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deficiency in StaR
required for transport into the mitochondria |
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Eicosanoids are synthesized from what?
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fatty acids
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key step in formation of Eicosanoids? enzyme responsible?
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release of arachidonic acid (done by Phospholipase A2 or Phospholipase C)
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Thyroid hormone is a derivative of what?
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tyrosine
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• Discuss the impact of half-life, protein binding, metabolism and excretion of peptide hormones
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Short half lives:
Those that are glycosylated are more stable Are not protein bound: Exceptions include GH, vasopressin, oxytocin Eliminated through multiple mechanisms: Serum proteases Receptor mediated endocytosis followed by lysosomal degradation Kidney/liver excretion |
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• Discuss the impact of half-life, protein binding, metabolism and excretion of thyroid hormones
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Bound to plasma proteins:
Thyroid hormone binding globulin Transthyretin Albumin Long half lives (days, T4 longer than T3): Peripheral metabolism through deiodination: Metabolized to active or inactive forms |
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Several different methods can be used to measure hormone levels, what is the key one?
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Immunoassays
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Binding to receptor tyrosine kinases stimulates a cascade of
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phosphorylation events
that starts the whole cascade |
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in general, what are important regulators of tyrosine kinases?
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phosphatases
cleave phosphate and thus regulate the cascade |
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What is desensitzation?
a few examples of how it occurs? |
same amount of hormone, but diminished response
can occur through: Uncoupling of the G-protein (can be triggered by modification of the receptor) endocytosis (ex: insulin receptor) Modification by other proteins resulting in decreased signaling activity (without changing receptor #) Altered expression level of receptors One hormone may regulate expression, internalization, etc of the receptor for a different hormone |
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what kind of receptors do thyroid and steroid hormones utilize?
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internal receptors that are transcription factors
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describe Endocrine organ hypofunction
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Primary endocrine organ failure – genetic; acquired
agenesis genetic defect in hormone biosynthetic pathway (CAH) destruction (autoimmune; infection) deficiency in precursor (iodine) Production of abnormal hormone Secondary organ failure (hypogonadal due to hypopituitarism) |
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describe Endocrine organ hyperfunction (primary/secondary)
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Primary (tumor – parathyroid adenoma; autoimmune – Grave’s)
Secondary (ACTH pituitary adenoma; ectopic production - cancer) |
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what is dynamic assesment of endocrine function?
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stimulation: to confirm hypofunction
inhibition: to confirm hyperfunction |
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when assessing endocrine disease, which is assessed first (structure/function
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Function assessed 1st
Structure assessed 2nd |