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69 Cards in this Set
- Front
- Back
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What does the Endocrine System do?
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regulates long-term processes such as growth, development, and reproduction
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What does the Endocrine System use to communicate between cells?
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chemical messengers
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There are 4 types of communcation involved with the Endocrine System, what are they?
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Direct, Paracrine, Endocrine, and Synaptic
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What is Direct Communication?
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The exchange of ions and molecules between 2 cells of the same type across gap junctions; it is highly specialized
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What is Paracrine Communication?
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It is the most common form of intercellular communication.
It uses chemical signals to transfer information from cell to cell within single TISSUE |
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What happens in Endocrine Communicaton?
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Endocrine cells release chemicals (hormones) into bloodstream and alters metabolic activities of many tissues and organs simultaneously
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What are Target Cells?
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specific cells that possess receptors needed to bind and “read” hormonal messages
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What do Hormones stimulate?
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synthesis of enzymes or structural proteins
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How do Hormones increase or decrease the rate of synthesis?
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By turning existing enzyme or membrane channels “on” or “off”
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What system is unable to handle split-second responses?
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the endocrine system
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What system handles crises?
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the nervous system
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What type of communcation is ideal for crises?
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Synaptic Communication
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What happens in Synaptic Communication?
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neurotransmitter is released at a synapse that is very close to target cells
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How are the Endocrine and the Nervous systems organized similarly?
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- they rely on release of chemicals
- they share many chemical messengers - they are regulated primarily by negative feedback - they share a common goal: to preserve homeostasis |
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What makes up the Endocrine system?
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all endocrine cells and body tissues that produce hormones or paracrine factors
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What are Endocrine Cells?
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Glandular secretory cells that release their secretions into extracellular fluid
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Where do Exocrine Cells secrete their products?
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onto epithelial surfaces
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What are the 3 groups that Hormones can be divided into?
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1. amino acid derivatives
2. peptide hormones 3. lipid derivatives |
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What are Amino Acid Derivatives?
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Small molecules structurally related to amino acids
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What are Amino Acid Derivatives synthesized from?
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from the amino acids tyrosine and tryptophan
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What are Tyrosine Derivatives?
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Thyroid hormones: epinephrine (E)
norepinephrine (NE) dopamine |
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What is another name for dopamine?
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catecholamines
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What is a Tryptophan Derivative?
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Melatonin
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What produces Melatonin?
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pineal gland
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What are Peptide Hormones?
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Chains of Amino Acids
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What are the 2 groups of Peptide Hormones?
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glycoproteins and all hormones secreted by:
hypothalamus, heart, thymus, digestive tract, pancreas, and pituitary gland |
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What are glycoproteins?
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they are more than 200 amino acids long, with carbohydrate side chains
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What are the carbohydrate side chains on glycoproteins?
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- thyroid-stimulating hormone (TSH)
- luteinizing hormone (LH) - follicle-stimulating hormone (FSH) |
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What are the 2 Classes of Lipid Derivatives and where are they derived from?
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1. Eicosanoids: derived from arachidonic acid
2. Steroid hormones: derived from cholesterol |
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Describe the structure of Eicosanoids.
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small molecules with five-carbon ring at one end
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What do Eicosanoids do?
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Coordinate cellular activities & affect enzymatic processes in extracellular fluids
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What are Leukotrienes?
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They are eicosanoids released from activated white blood cells
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What are Leukotrienes important in?
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coordinating tissue responses to injury or disease
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What are Prostaglandins?
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eicosanoids produced in most tissues of body involved in coordinating local cellular activities
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Steroid Hormones are what?
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lipids structurally similar to cholesterol
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What releases Steroid Hormones?
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- reproductive organs (androgens by testes, estrogens and progestins by ovaries)
- adrenal glands (corticosteroids) - kidneys (calcitriol) |
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Steroid Hormones remain in circulation longer than peptide hormones, true or false?
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True
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How does the body get rid of steroid hormones?
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Steroid hormones are absorbed gradually by liver, converted to soluble form, and excreted in bile or urine
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What circulate freely or bound to transport proteins?
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Hormones
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How long do Free Hormones remain functional?
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Less than an hour
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How do hormones reach target cells?
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They diffuse out of the bloodstream and bind to receptors on target cells.
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What organs absorb and break down hormones?
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liver or kidneys
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Hormones can also be broken down by:
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enzymes
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More than 99% of what become attached to special transport proteins in the bloodstream?
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Thyroid and Steroid Hormones
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What is a Hormone Receptor?
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a protein molecule to which a particular molecule binds strongly; it can respond to several hormones
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Different tissues have different combinations of receptors, True or False?
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True
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Catecholamines and Peptide Hormones are not lipid soluble meaning:
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They are unable to penetrate cell membrane
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What do catecholamines and peptide hormones do instead of going through cell membranes?
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They bind to receptor proteins at outer surface of cell membrane (extracellular receptors
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Since Eicosanoids ARE lipid soluble, what do they do?
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They diffuse across membrane to reach receptor proteins on inner surface of membrane (intracellular receptors)
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Hormones bind to what?
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Receptors inside membrane
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Since hormones cannot have direct effect on activities inside target cell, they use what?
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intracellular intermediary
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With Intracellular Intermediaries, a First Messenger is used first. What does it do?
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It leads to a second messenger; it may act as enzyme activator or inhibitor; and it results in change in rates of metabolic reactions
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What are 3 Important Second Messengers?
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- Cyclic-AMP (cAMP): derivative of ATP
- Cyclic-GMP (cGMP): derivative of GTP - Calcium ions |
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What is Amplification?
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the binding of a small number of hormone molecules to membrane receptors
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What does Amplification lead to?
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it leads to thousands of second messengers in cell
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What does Amplification magnify?
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it magnifies the effect of the hormone on the target cell
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What is Receptor Cascade?
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A single hormone promotes release of more than 1 type of second messenger
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What is Down-regulation?
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Presence of a hormone triggers decrease in number of hormone receptors, resulting in less cell sensitivity due
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What is Up-regulation?
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Absence of a hormone triggers increase in number of hormone receptors; cells become more sensitive
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What is a G Protein?
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An enzyme complex coupled to membrane receptor
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What does a G Protein do?
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It links the First Messenger to the Second Messenger
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When is a G Protein activated?
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When a hormone binds to a receptor at membrane surface
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What does a G Protein do to a Second Messenger?
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It changes amount of second messenger cyclic-AMP (cAMP) within cell
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What does an increased cAMP level within a cell do?
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accelerates metabolic activity
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How do Steroid Hormones reach receptors? And where are these receptors?
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They cross cell membrane to bind to receptors in cytoplasm or nucleus
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What do Steroid Hormones do?
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They alter rate of DNA transcription in nucleus by changing patterns of protein synthesis and directly affect metabolic activity and structure of target cell
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What do Thyroid Hormones bind to?
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They bind to receptors in nucleus and on mitochondria
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How do Thyroid Hormones get to their receptors?
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They cross cell membrane, primarily by transport mechanism
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What do Thyroid Hormones do?
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activate specific genes and change rate of transcription
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