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226 Cards in this Set
- Front
- Back
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What 2nd messenger systems does ACTH use?
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cAMP and Calcium
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Lack of thyroid hormones early in life produces which condition?
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Cretinism
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How do follicular cells accumulate iodine for production of thyroid hormones?
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Na/I symporter
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How much of the body's iodine does the thyroid use?
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Nearly the entire daily requirement is used by the thyroid
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Thyroid peroxidase
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oxidizes iodine to a reactive form that can covalently link tyrosine residues within thyroglobulin
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Stimulus for thyroid hormone production leads to uptake of what by the membrane villi?
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Colloid
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Where is thyroglobulin digested to its consituent amino acids?
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Lysosomes
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What is organification?
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Oxidation of iodine and its subsequent binding to Tyrosine residues within Thyroglobulin
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Where is thyroglobulin stored? What is it called?
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Stored as colloid in the lumen of the follicle
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What Thyroid hormones are secreted? Which are stored/recycled and deiodinated?
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T3, T4 and reverse T3 are secreted. monoiodotyrosine (MIT) and Diiodotyrosine (DIT) are secreted
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T/F: Most circulating T3 is produced from T4
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YES. This occurs in peripheral tissues like skeletal muscle, liver and kidney
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What happens to the T3/rT3 ratio during starvation?
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It declines
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Which has a higher half life T4 or T3? Which is more biologically active.
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T4, T3 has a 10 fold higher affinity to TH receptor.
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In the circulation, T3/T4 are bound to? Are these active?
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thyroxine binding globulin produced by liver
-No, only unbound form is active. |
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Iodine deficiency can lead to what condition?
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Goiter
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T/F: Slight iodine deficiency can lead to hypothyroidism
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False. The iodine transporter can result in a 250 fold increase in Iodine concentration over plasma
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Brain, PIT,and brown adipose tissue all use significant amounts of T3. Where does the majority come from?
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Endogenous production within the tissue converts T4 to T3 (iodinase activity)
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Where is the biological activity of TSH located?
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Beta subunit
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What activity is stimulated by TSH?
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adenylate cyclase-cAMP-PKA, intercellular calcium
-ALL aspects of thyroid hormone synthesis and secretion are stimulated |
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Division and enlargement of follicular cells, amino acid and sugar transport, synthetic rate of thyroglobulin, iodine active transport, coupling to tyrosines and increased endocytosis and digestion of colloid are stimulated by?
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TSH
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What is the negative inhibitor of TSH release (aside from hormones it produces)?
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Somatostatin
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What do T3/T4 negatively inhibit? What is this called?
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TSH and TRH- Long loop negative feedback inhibition
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T3 acts like what type of hormone? How is it different?
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Steroid. Not derived from cholesterol though. Also, too hydrophilic to pass through membrane on its own, uses diffusion.
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Increased thyroxine content will NOT affect metabolic rate of what tissues?
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BRAIN, SPLEEN, TESTES
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Which is more significantly affected by hyperthyroidism: Protein degradation or synthesis?
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Both are stimulated but degradation occurs at a higher rate
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What are a few mechanisms by which T3 increases metabolic rate?
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Increased oxidative phosphorylation (due to increased transcription of these genes)
-Turnover of cellular constituents -Activation of Na/K pump |
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How does hyperthyroidism lead to muscular wasting?
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Increased protein degradation vs. synthesis
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Thryoid hormone has what affect on Beta adrenergic receptors? Where is this particularly evident?
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Increases transcription of genes encoding Beta adrenergic receptors. Heart liver and adipose are particularly sensitive.
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What are some effects of increased beta adrenergic receptors due to hyperthyroidism?
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bradycardia, gluconeogenesis, lipolysis, glycogenolysis
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Is T3 important in development?
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Yes! Myosin, growth of axons/dendrites and myelination all rely on T3
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What is the pathogenesis of Graves disease?
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Autoantibody to TSH receptor acts as an agonist and leads to hyperthyroidism.
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What do beta cells in the islet of Langerhans secrete?
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Insulin
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What is C-peptide? How is it clinically significant?
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It is the connecting peptide secreted in equal amounts with insulin.
*Circulating levels are indicative of endogenous insulin production |
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A patient shows up in a diabetic coma and we find a lack of C-peptide. What type of diabetes? How might this have happened?
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Type 1. Probably overdose insulin injection.
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What is the biphasic response for glucose?
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Rapid burst within the first minute followed by a sustained release as long as glucose is present
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What occurs in the rapid burst phase of insulin response to glucose?
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Fusion and release of previously formed vesicles
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What happens in the sustained release phase of insulin response to glucose?
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Synthesis, packaging and secretion of insulin
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What binds to the receptor on beta cells?
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Glucose!
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What is HbA1C and how is it useful?
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occurs via directly glycosylation of Hb. Levels >6.5= diabetic
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HbA1C greater than 6.5?
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Diabetes
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What is stimulated by GLP-1, GIP, vagus nerve and dietary aa?
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Insulin release
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How does insulin affect GLUT-4?
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Brings vesicles to plasma membrane, glucose enters by facilitated diffusion
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What are the effects of insulin on the liver?
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Increased glycogenosis, inhibition of gluconeogenesis, triglyceride production.
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What type of receptor is the insulin receptor? How is it phosphorylated?
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Receptor Tyrosine Kinase. Autophosphorylation
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What do the alpha and beta subunit of the insulin receptor do?
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Insulin binds to the alpha receptor and the beta receptor autophosphorylates stimulating the Tyrosine Kinase activity
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In what pathway are IRS-1 and IRS-2 recruited? What do these further stimulate?
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Insulin binding to its receptor stimulates these molecules which stimulate PIP3 and a phosphorylation cascade
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What does Pkb/Akt do in response to insulin binding to its receptor?
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It is a downstream target that phosphorylates GLUT-4 bringing it to the plasma membrane
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What happens to insulin receptors in response to elevated insulin?
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Down-regulated. Endocytosis and lysosomal degradation occur
**Insulin is endocytosed with the receptor and degraded! |
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Where is glucagon produced?
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alpha cells of the pancreas
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After a high protein meal, which is elevated: Glucagon or Insulin?
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BOTH are elevated
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Insulin release is promoted by? Inhibited by?
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Epinephrine promotes release, somatostatin inhibits
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What is the main target of glucagon?
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LIVER
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Which has a more significant genetic component: Type 1 or Type 2 diabetes?
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Type 2!
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What is respiratory quotient?
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CO2 produced divided by O2 consumed?
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What has the highest respiratory quotient: Carbs, fat, protein?
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Carbs has the highest at 1.0.
Protein and fat are lower due to lower starting oxidation state |
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Which nutrient is the most efficient source of energy (cal/gram)??
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Fats- nearly double carbs and protein (ethanol is in between)
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In times of starvation how much muscle can we use at a maximum?
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1/3: More than this is deadly
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Where is the major source of energy during severe starvation?
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Adipose triglycerides
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T/F: The blood contains 80-110 mg/dL of blood, enough to maintain blood glucose for 4 hours.
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NO. False. Just one hour
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Can you use glycogen in muscle for glucose?
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No. Only the tissue that stores it can use it.
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Early fasting: Levels of what will be increased? Decreased?
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Glucagon, catecholamines, growth hormone, glucocorticoids = increased
Decreased= insulin |
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Late fasting: What increases above levels seen in early fasting? decreased?
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Growth hormone, glucocorticoids and rT3
-T3 is decreased |
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During exercise, blood flow to which organs decreases??
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Liver and Kidney
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Decreased protein degradation late in fasting is partially mediated by?
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Falling levels of T3
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In exercise what fuel is primarily used in: Anaerobic? Transition? Aerobic?
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Anaerobic: ATP
Transition: Creatine Aerobic: Glycogen and Fat |
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Which fiber type is used in aerobic metabolism? Characteristics?
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Type 1: Red fibers. Slower, increased mitochondria, increased myoglobin, increased capillaries, decreased glycogen
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T/F: In terms of fuel utilization aerobic exercise resembles starvation
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True. Muscle/liver glycogen and triglycerides
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Sprinting or weight lifting will increase what muscle fiber types?
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Type 2!!
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What can the liver convert to glucose: Ketone bodies, triglycerides, glycerol or free fatty acids.
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GLYCEROL
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What sort of transport is used in maintaining Calcium gradient? Higher intracellularly or extracellularly?
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ATP, active transport. Concentration is higher outside of the cell
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How much of the body's total calcium store is regulated? Where is most calcium found?
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about .5%
-Most calcium is found in the bones |
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Net absorption of calcium per day?
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20%. about 175 mg of 1000mg taken in
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Most of the body's phosphorous is found where? How much is circulating?
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Skeleton (85-90%)
-About 10-12 mg/dL is circulating |
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What is the outer layer of bone called? What percentage of bone does this layer represent?
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Cortex. 80%
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What is the major site of bone remodeling and what percentage of bone does it represent?
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Trabecular bone. 20%
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What is Osteoid? What is it made up of?
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Matrix of proteins secreted by Osteoblasts.
-Type 1 collagen, osteonectin and osteocalcin |
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What factors stimulate osteoclasts? WHy is this sort of ironic?
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Vitamin D, MCSF and Rank-L
-MCSF and Rank-L are produced by osteoBLASTS |
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What stimulates Osteoblasts to secrete M-CSF and RANK-L
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PTH
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What % of bone is turned over each year?
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about 20% in adults, 100 % in infants
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How does PTH act to increase serum calcium
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Increases reabsorption in the kidney, conversion of Vitamin D-3 to the 1,25-OH form, reabsorption from bone
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How does calcium binding to CaSR inhibit PTH release?
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Activates Protein Kinase C which inhibits the release of PTH
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T/F: Removal of the leader sequence leaving a 90 residue ProPTH (from 115) produces the active form of the hormone
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FALSE. Another cleavage of 6 AA from the N terminus produces the active enzyme
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Binding of PTH to its 1R receptor activates which pathways? What type of receptor.
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G protein receptor. Stimulates adenylate cyclase-cAMP pathway and PLC to produce DAG and IP3- Ca dependent
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Where does PTH act in kidney to increase Calcium absorption?
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Thick ascending limb and DCT
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How does PTH affect Phosphorous absorption? Where does it act?
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Decreases absorption in PCT and DCT
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1,25- Vitamin D, the most active form is produced by hydroxylations in the _________ and _________ respectively
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Liver and Kidney
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How does PTH increase active Vitamin D levels?
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Facilitates hydroxylation of the 1-OH group in the PCT
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T/F: PTH also acts to increase the synthesis of bone (albeit to a lesser degree than breakdown)
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True. Osteocytic osteolysis is the process by which this occurs.
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N-terminal truncation of PTH is used to what extent clinically?
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Antagonists!
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Unlke PTH, Active Vitamin D plays an important role in this organ. How?
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The Intestine! Stimulates uptake of calcium by enterocytes
Increases calcium pumps, channels and calbindin |
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What is the role of Vitamin D on the Na/Pi transporter?
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INCREASES phosphate transport into the cell
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How does Vitamin D affect uptake of calcium and phosphorous in the GI tract?
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Increases both!
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What are the roles of Vitamin D in the kidney?
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Increase reabsorption of Calcium (helps PTH) and Phosphorous and decreases C1 hydroxylation of vitamin D
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What is the paradoxical effect of Vitamin D?
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It is necessary for uptake of calcium and increase in serum calcium used in bone production but it also acts synergistically with PTH and stimulates osteoCLAST activty
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Calcitonin targets what molecules? What are its roles in the kidney?
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Osteoclasts!
-Inhibits phosphate transport in the PCT |
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A child presents with weakness, bowing of the legs, dental defects and hypocalcemia. What disease?
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Rickets
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What is osteopetrosis? Major defect?
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Osteoclasts cannot function properly! Results in increase bone density and neuro and hematologic problems
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Why does estrogen prevent bone loss?
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Stimulates secretion of OPG which outcompetes RANK-L for binding sites on osteoclasts
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A patient develops laryngospasm and full blown hypocalcemic tetany following thyroid surgery. WHY?
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parathyroids were likely removed inadvertantly! Leads to Hypocalcemia/
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What do ovaries develop from on the indifferent gonad? Testes?
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Ovaries develop from the cortex, testes from the medulla
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What is the significance of the SRY gene?
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On Y chromosome, transcribes gene products necessary for male characteristics. TDF (Testicular Differentiation Factor) is an important product
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T/F: y chromosome contains mostly information that is only common to males
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False. A vast majority is also common to females. SRY gene is a key difference
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Which cells produce MIF? Testosterone?
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MIF is produced by Sertoli Cells, Testosterone by Leydig cells
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What are the roles of MIF and Testosterone in male development?
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MIF inhibits growth of female features, while Testosterone PROMOTES male genitalia
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What is the difference between gonadal and somatic sex?
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Somatic sex is the way we appear on the outside
-Gonadal sex refers to the internal/genetic development of male or female characteristics |
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T/F: Until 7 weeks the embryo has both Wolffian and Mullerian structures
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True
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Inguinal testicles would indicate what level of development of the fetus?
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20-22 weeks, extremely premature
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Pre-scrotal testicles: What level of development?
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20 weeks- term. Pre-mature
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Gonadal Dysgenesis/Turners
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XO phenotype
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Seminiferous Tubule Dysgenesis
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Klinefelters (XXY)
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What is the result of defects in the aldosterone synthesizing branch of Pregnenolone?
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Significant shift towards the production of Androgens
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What is the normal age of puberty for males/females? When to begin an abnormal workup?
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Males-9, females-7 in AA, 8 in caucasians.
Begin workup at 13 for female and 14 for males |
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As puberty approaches in the male, what hormone is increased in production?
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GnRH
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What are the tanner stages (5) of male puberty?
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1: pre-pubescent
2:testicular enlargement, pubic hair begins to grow 3: Penile enlargement 4: Growth of Glans penis 5: Completion of adult genitalia |
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H-P-G Axis in the male: What is its purpose?
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To maintain homeostasis vs. menstrual cycle in females
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Why is it important for teens to get a good amount of sleep?
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GnRH is released in a pulsatile fashion while we sleep
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Do FSH and LH both rise during male puberty? Which rises more steeply?
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Yes indeed. FSH rises more steeply (more for sertoli?)
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T/F: Androgens are produced only by the testis
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False. Primarily but also produced by adrenals, adipose, skin
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Put these androgens in order of potency: DHEA, Testosterone, DHT, Andrestenedione
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DHT > T > Andro > DHEA
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What is a major medical consequence of using anabolic steroids?
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Testicular atrophy
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Tanner stages of female puberty
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1: Pre
2: Early thelarche (breast swelling) and pubic hair 3: Early breast development 4:Expansion of breasts 5: done |
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What is the target of FSH in females?
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Granuloma cells
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What is the target of LH in females?
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Theca cells
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What is the major difference between regulation of male and female Gonadotropins??
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Female hormones feedback in both Positive and Negative manners (activins and inhibins)
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What is precocious psuedopuberty? How this this occur?
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Development of secondary sexual characteristics without corresponding gonadal development. Early exposure to androgens
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Fertilization normally takes place in?
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The ampulla
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What erodes the endometrium, allowing implantation by the blastocyst?
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Synctitiotrophoblast
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What important hormone is secreted by the placenta? What type of signaling does it display?
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hCG, autocrine signaling!
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What is hCS (human chorionic sommatomamotropin)? Why is it important
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Synthesized by the placenta and is thought to be a maternal growth hormone produced during pregnancy
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Can insulin, IGF and T3 cross the placenta?
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NOPE
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LDL is endocytosed/transcytosed from the mother into the placenta. Why is this so important?
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Needed to make steroid hormones!
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Where are 16 and 17 alpha hydroxylase found? Why are they important?
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In the fetus. They are responsible for estriol and estradiol, respectively
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What is the importance of androgen binding protein?
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Keeps testosterone levels in the lumen high- essential for developing sperm
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Conversion of Testosterone into estradiol is accomplished by which enzyme? What releases it?
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P-450 aromatase in Sertoli cells
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T/F: Sertoli cells make Leydig cells more responsive to LH
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Yes, increase # of LH receptors
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Is there a pulsative release of GnRH in males or just females?
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Males too. Prevents receptor densitization probably
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Where are Leydig cells located? Sertoli cells?
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Leydig cells are located in the extracellular space, sertoli cells are in the lumen
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What cells are responsible for formation of the blood-testes barrier?
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Sertoli cells
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What is spermiogenesis and where does it take place?
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Maturity of sperm in the epididymus. Differentiation of tail and cytoplasmic reduction
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Stage 1 of spermatogenesis?
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Several rounds of mitosis and 2 rounds of meiosis to create spermatids
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Stage 2 of spermatogenesis
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Sperm moves towards lumen and tail begins to develop
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Stage 3 of spermatogenesis
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Tail continues to develop. Cluster in center of sem. tub
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Stage 4 of spermatogenesis
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head becomes more streamlined
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Stage 5 of spermatogenesis
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Sperm are swept in fluid flow towards the epididymis where maturation commences (tail develops, etc.)
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What is the importance of the acrosome?
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Allows sperm to invade the zona pellucida
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Where is DNA material found in the sperm?
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The head of the sperm
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T/F: Cell cytoplasm increases during the maturation of a sperm in epididymis
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False cytoplasm decreases during maturation
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What are the majority components of seminal fluid?
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Fructose and Prostaglandins (60%)
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Where is the most mitochondria rich region of the sperm?
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Proximal tail
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What protein regulates the motility of sperm?
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CatSper protein which activates cAMP dependent calcium influx
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Which stage of sperm development is androgen dependent? Independent?
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Late maturation is androgen dependent but early is not
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How do you define sterility in terms of sperm count?
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Less than 20 million/ml
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Epinephrine, norepinephrine and T3 are examples of what type of hormone?
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Amino acid derivatives
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PTH, insulin, glucagon: What type of hormone?
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Polypeptides
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Leukotrienes and Prostaglandins are what types of hormones?
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Lipid
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What is the half-life of epi and norepi?
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15 seconds
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In general, what has the shortest half life?
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Polypeptide hormones, although epi and norepi have VERY short half lives. Steroids are usually longer and T3 and T4 can last for days
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Where does the production of pregnenolone from cholesterol take place?
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Mitochondria
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T/F: Hormone receptor interactions are irreversible
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FALSE. They are in equilibrium and reversible
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1/Kass= ???
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Concentration of hormone that half saturates the receptor
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Steroid hormones often display striking similarities in DNA binding and modulator domains. Where do we see diferences though?
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HORMONE binding domain on C-terminus
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What type of receptor is the insulin receptor?
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RTK
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Which is the main signaling component of G proteins
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The alpha subunit. Disconnects from Beta and gamma subunits when bound to GTP.
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How does the GTP leave the alpha subunit of Gproteins allowing it to couple with the beta and gamma subunit once again?
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Intrinsic GTPase activity
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What is the effect of Cholera toxin? What G proteins does it affect? Symptoms?
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Keeps the GTP bound to alpha subunit/ constitutively active. Leads to loss of electrolytes/ water/ diarrhea
Affects Gs and Golf |
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cAMP is synthesized from _______ by ________ and rapidly degraded by _________
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ATP
Adenylate Cyclase Phosphodiesterases |
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What is CREB?
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Cyclic Amp Response Element Binding Protein - regulates gene expression in the nucleus
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What type of receptor does epinephrine bind to? What is the result of this activity?
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G protein! Results in ultimate phosphorylation of glycogen phosphorylase and glycogen synthase= glycogen breakdown
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How does receptor desensitization usually occur?
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Phosphorylation typically. Beta arrestin also ( can bind to phosphorylated domains)
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What type of signaling system used in vision? Mechanism?
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G protein. cGMP blocks neuron inhibition by reducing presence of a neurotransmitter that inhibits postsynaptic neurons.
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What are two mechanisms by which Cell maintains low calcium levels?
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Calcium ATPase and Ca/Na antiport in membrane and in ER
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If the cell is damaged, which organelle can actively pump in calcium?
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Mitochondria
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PIP2 is cleaved to what two products?
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IP3 and diacylglycerol
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What is the major role of IP3?
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Release of Calcium from ER
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What are 2 major roles of DAG?
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Activation of PKC and arachadonic acid synthesis
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Protein receptor with a single transmembrane sequence. What kind?
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Enzyme linked receptor- EGF, PDGF, etc
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Almost 1 % of our genes are for receptor tyrosine kinases. How are these receptors activated?
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Dimerization occurs after growth factor binds, tyrosine residues on proteins phosphorylated. Recruits signalling proteins
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Binding of what activates the Jak receptor?
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Erythropoetin
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What happens after the JAK proteins are phosphorylated?
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STAT proteins recruited and dimerize- enter nucleus to alter transcription
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In the case of epo, what is the end result of the Jak-stat pathway?
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Production of red blood cells
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These proteins, discovered in the dudes lab have properties of both singal transduction molecules and transcription factors
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STAT proteins
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Was Eeyro Montero a cheater? What mutation was in his Jak protein?
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Nope. mutation in C-terminus led to loss of response to phosphatase that decreases epo sensitivity
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Katherine Malcolm loves ____
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BOOBOO (what did you think it was gonna say>????)
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Graafian (dominant) follicle receives estrogen from which cells? How about Androgen?
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Estrogen from Granuloma cells
Androgen from Theca cells |
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What is the corpus luteum? When does it degenerate? Role in pregnancy?
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Ruptured follicle filled with blood/lipid. Degenerates after 10 days if fertilization doesn't occur. Prevents further periods after fertilization
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Mature follicles become mature because they have more of what kind of receptor? This leads to increase in what?
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More FSH receptors leads to increased estrogen production by granulosa cells
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What causes atresia in non-dominant follicles?
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Build-up of androgens from Theca cells due to lack of stimulation from FSH
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What important enzyme is missing in Theca cells that converts progesterone into Androstenedione
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17-alpha-hydroxylase. This is present in theca cells though
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Can Theca cells make estrogen? Why the hell not?
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Nope, they lack an aromatase that converts Testosterone into estradiol. This aromatase is present in the Granulosa cells though.
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What is the layer shed off of the endometrium called?
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Stratum functionale
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Days 5-14 of the menstrual cycle are known as? What happens?
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Proliferative phase- endometrium grows
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Where do you find spiral arteries? Straight arteries?
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Spiral arteries in stratum functionale, straight in basale
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How long after the LH surge does ovulation usually occur?
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9 hours
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Rise of what molecule is important during the secretory phase to suppress FSH and LH levels?
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Inhibin
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Most variability in the length of menstrual cycle between different women is which phase?
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Secretory phase, follicular phase is relatively constant
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Vascularization and edema occur during which phase of the menstrual cycle? What hormones are responsible?
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Secretory phase
-Estrogen and progesterone |
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A ferning pattern in the cervical mucus is caused by?
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Estrogen
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Does progesterone cause a ferning pattern? What is typical of the mucus layer when progesterone is present?
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NO just estrogen. Thicker mucus is seen with progesterone
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Does the breast change during the menstrual cycle?
A) What changes attributable to estrogen B) Progesterone? |
Yes
A)Mammary duct proliferation B)Growth of lobules and alveoli |
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What 2 disorders can benefit from treatment with a CONSTANT pulse of GnRH??
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Endometriosis and Leiomyomas. In both cases lack of estrogen caused by persistent GnRH leads to involution
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What is Kallman syndrome? Major symptom?
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Lack of GnRH due to disorganization of cells during development. Loss of sense of smell, no menses.
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What therapy would you use to treat a patient with Kallman syndrome?
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Pulsatile GnRH
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Burst in LH secretion is caused by a rise in secretion of what from the maturing follicle?
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Estrogen enhances responsiveness of the pituitary to GnRH!
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What cells facilitate production and release of anterior pituitary hormones
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Parvicellular neurosecretory cells
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How does GH act to inhibit insulin action?
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Reduced insulin receptors and signaling
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Most of the effects seen by GH are actually due to this enzyme? where is it released from?
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IGF-1 released from Liver
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What hormone is closely related to GH?
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Prolactin (also placental lactogen)
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T/F: TSH, LH, FSH share a common beta subunit
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False. Alpha subunits are the same but the beta subunit confers the activity of the enzyme
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Why is frequent tanning thought to be addictive?
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Release of Beta endorphins along with MSH and ACTH on the POMC molecule
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What molecules does TRH release?
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PROLACTIN and TSH
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Somatostatin inhibits?
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GH AND TSH
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What are the glycoprotein hormones in the AP?
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FSH, LH and TSH
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Name two negative regulators of TSH
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Somatostatin and T3
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Role of BDNF in decreased food intake??
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asdf
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What disease is associated with elevated steroid hormones?
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Liver disease
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Is the majority of cortisol in the plasma in free-form or bound to a carrier? If carrier, what is it called?
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Bound to a carrier, transcortin
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What is the effect of cortisol on the liver?
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Gluconeogenesis and aa degradation
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What effect does cortisol have on GLUT4 receptors?
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Decreased expression
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What hormone counters the proteolytic actions of cortisol?
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INSULIN
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What is an important role of cortisol on cellular signaling? Inflammation?
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Increases the catecholamine and glucagon signaling pathways
-Inhibits phospholipase A which leads to prostaglandin/ inflammation pathway |
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Annexin A1
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Secreted upon stimulation by corticoids- Inhibits phospholipase A
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I'm stressed as fuck right now so I probably have high levels of __________
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Glucocorticoids (cortisol)
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Surfactant and lipogenic enzymes are dependant on what for their production?
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Cortisol
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What pathways are activated by ACTH/ Cortisol binding to their receptors??
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cAMP/PKA, Calcium!
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Cortisol has a concentration 1000 times higher in the blood than does Aldosterone so why doesn't it bind to the receptor?
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11-beta-hydroxysteroid dehydrogenase. Converts Cortisol to cortisone
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11b-HSD
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Prevents cortisol from binding to aldosterone receptor. Mutations can lead to Hyperaldosteroneism
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