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62 Cards in this Set
- Front
- Back
Cells not in direct contact communicate w/ each other by?
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Chemical messengers
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What is endocrine signaling?
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Hormones secreted into ECF & carried by circulatory system to distant targe cells
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What is paracrine signaling?
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Hormones secreted into ECF & carried by diffusion to nearby cells
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What is autocrine signaling?
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Target cells of the same type act as secreting cells
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What are the classical endocrine glands? (8)
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1. Hypothalamus
2. Pituitary gland 3. Adrenal gland 4. Pancreas 5. Testes 6. Ovaries 7. Thyroid gland 8. Parathyroid glands |
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What is sensitivity?
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How a tissue responds to the hormone
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What is availability?
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Concentration of hormone in target tissue
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WHat are the factors that determine how a tissue is influenced by a hormone? (5)
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1. Quantity secreted
2. Transport in plasma 3. Activation of prohormone 4. Inactivation 5. Removal from system |
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How are hormones classsified? (3)
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1. Peptide & protein hormones
2. Amino acid-derived hormones 3. Steroid-derived hormones |
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Examples of peptide & protein hormones? (2)
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1. Thyrotropin releasing hormone TRH
2. Glucagon |
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What factors are important in regulation? (2)
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1. Inactivation
2. Removal |
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Examples of amino-acid derived hormones? (2)
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1. Epinephrine
2. Thyroxine (T4) |
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Examples of steroid hormones? (2)
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1. Progesterone
2. Vitamin D |
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Two general mechanisms of hormones?
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1. Cell membrane receptors
2. Intracellular receptors in cytoplasm or nucleus |
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Which types of hormones act by membrane receptors? (3)
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1. Polypeptide hormones
2. Protein hormones 3. Catecholamine hormones |
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Which types of hormones act by intracellular receptors? (3)
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1. Thyroid hormones
2. Steroid hormones 3. Steroid-derived hormones |
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Protein kinase A phosphorylates which residues on proteins?
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Serine or threonine
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What are C-response element binding proteins? (CREB)
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Transcription factors which influence gene expression
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What enzyme hydrolyzes cAMP to AMP to turn response off?
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Phosphodiesterase
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What do tyrosine kinase receptors do when hormone binds?
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Autophosphorylation of tyrosine-OH
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What puts the mitogen activated protein kinase MAPK phosphorylation cascade in action?
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Tyrosine kinase activity
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Growth factors often work through what type of receptors?
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Tyrosine kinase receptors
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Growth hormone acts through what type of receptors?
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Receptors associated w/ tyrosine kinases
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Binding of GH to receptors associated w/ tyrosine kinases activates?
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JAK kinases
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JAK kinases phosphorylate each other, the receptor and?
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STAT
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What happens once STAT is phosphorylated?
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STAT protein forms dimers & pass into nucleus where they act on gene expression
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Heat shock proteins act as?
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Chaperone proteins
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Hormone binds cytosolic receptor, heat shock proteins dissociate, and what happens to hormone-receptors?
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Hormone-receptor complex & form dimers that can bind DNA
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How does thyroid hormone, VItamin D & PPRAR act on gene expression?
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Hormone binds heterodimer on DNA
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Thyroid gland is made up of?
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Follicles
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What cell type lines follicles? What fills lumen of follicles?
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Follicular cells line follicle
Colloid fills lumen |
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Follicular cells secrete? (2)
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1. Thryoxin (T4)
2. Triiodothyronine (T3) |
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What is located between follicles? (2)
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1. Capillaries
2. Parafollicular or C cells |
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What do C cells secrete?
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Calcitonin
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Which is the active form of thyroid hormone?
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T3
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What does the thyroid gland actually secrete?
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T4 (thyroxine)
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Iodide is transported into follicle cell from blood by?
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Active transport
Na/ I symporter |
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What happens iodide enters follicle?
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Iodide coupled to tyrosine residues in thyroglobulin
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Iodide coupled to thyroglobulin produces? (2)
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1. Monoiodotyrosine (MIT)
2. Diiodotyrosine (DIT) |
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In healthy thryoid, which form is made more? MIT or DIT?
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DIT
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MIT & DIT residues couple to form?
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T3 & T4 residues linked to thyroglobulin
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Colloid is?
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Storage of thyroglobuiln bound to T3 & T4 in follicle
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How is thyroglobulin taken back into follicular cells?
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Endocytosis
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Hydrolysis of thyroglobulin produces amino acids including?
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T3 & T4
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Enlarged thyroid gland is due to?
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Diet deficiency of iodine
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TRH is secreted by?
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Hypothalamus
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TRH stimulates secretion of?
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TSH by anterior pituitary
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TSH stimulates?
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Growth & metabolism of thyroid follicle cells--> secretion of T3 & T4
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TSH acts via what type of signaling pathway?
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AC --> cAMP --> PKA
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Secretion of TSH is regulated by?
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Negative feedback of T3 & T4 on TSH (thyrophrons not able to respond to TRH)
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T4 is carried through blood bound to which proteins? (3)
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1. Thyroid-binding globulin (TBG--mostly)
2. Transthyretin (TTR or TBPA) 3. Albumin |
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T3 is carried through blood bound to which proteins? (2)
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1. TBG (mostly)
2. Albumin |
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What percentage of T4 is bound in healthy adults?
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99.98%
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Free T4 in blood corresponds to?q
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Concentration that correlates w/ physiologic responses to thyroid hormones
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How are thyroid hormones activated or inactivated?
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Deiodination
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What converts T4 --> T3?
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5'-deiodinases
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What is the prohormone of thyroid hormones?
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Circulating T4
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5-deiodinase can convert T4 into? (2)
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1. Active T3
2. Reverse T3 (inactive) |
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Thyroid hormones & their metabolites may be converted to water-soluble products by coupling them to?
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Glucuuronic acid & cleared into urine
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Actions of thyroid hormones? (8)
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1. Increase tissue respiration (O2 consumption & heat production)
2. Stimulate body growth & CNS development 3. Stimulate nervous system activity 4. Increase carbohydrate absorption 5. Increase carb & lipid metabolism 6. Lower blood cholesterol 7. Increase beta-adrenergic receptors (sensitve to epinephrine) 8. Stimulate bone turnover |
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Where is T3 receptor located?
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TR located in nucleus bound to DNA
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What happens when T3 binds TR?
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Activity of polymerase II is altered changing gene expression
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