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The endocrine system
Chapter 18
| Question | Answer |
|---|---|
| What processes do the Endocrine System? | Regulates long-term processes: Growth, Development, and Reproduction |
| What the Endocrine system uses? | Uses chemical messengers to relay information and instruction between cells. |
| Direct comunication | Exchange of ions and molecules between adjacent cells across gap junctions Occurs between two cells of same type Highly specialized and relatively rare |
| Paracrine Comunication | Uses chemical signals to transfer information from cell to cell within single tissue. Most common form of intercellular communication |
| Endocrine Comunication | Endocrine cells release chemicals (hormones into bloodstream Alters metabolic activities of many tissues and organs simultaneously. |
| Homeostasis and intercellular communications??? | Direct, Paracrine, Endocrine, and Synaptic |
| Target Cells | Area specific cells that possess receptors needed to bind and "read" hormonal messages. |
| Hormones | Stimule synthesis of enzymes or structural proteins Increase or descrease rate of synthesis. Increase or decrease rate of synthesis. Turn existing enzyme or membrane channel " on or "off." |
| Endocrine communication has? | Target Cells and hormones |
| Synaptic comunication | Ideal for crisis management Occurs across synaptic clefts Chemical message is neurotransmitter Limited to a very specific area. |
| Transmission Direct communication | Through gap junction |
| Paracrine communication(Transmission) | Through extracellular fluid |
| Endocrine comunication (Transmission) | Through bloodstream |
| Synaptic comunication(Transmission) | Across synapses |
| Direct comunication (Chemical /Mediators) | Ions, small solutes, lip-soluble materials |
| Paracrine comunication(Chemical /Mediators ) | Paracrine factors |
| Endocrine comunication (Chemical /Mediators ) | Hormones |
| Synaptic comunication(Chemical /Mediators ) | Neurotransmitters |
| Direct Communication(Distribution of Effects ) | Usually limited to adjacent cells of the same type that are interconnected by connexons. |
| Paracrine communication (Distribution of Effects ) | Primarily limited to a local area, where paracrine factor concentrations are relatively high Target cells must have appropiate receptors. |
| Synaptic communication(Distribution of Effects ) | Limited very specific area: target cells must have appropriate receptors. |
| Hormones can be divided into three groups. | Amino acid derivatives,Peptide hormones, and Lipid derivatives |
| Secretion and Distribution of Hormones | Hormones circulate freely or travel bound to special carrier proteins. |
| Amino Acid Derivatives | Are small molecules structurally related to amino acids. |
| Two Amino Acid Derivatives | Derivatives of tyrosine Thyroid hormones Catecholamines Epinephrine, Norepinephrine Derivatives of tryptophan Dopamine, serotinin, melatonin |
| Peptide Hormones | are chains of amino aid Most are synthesized as prohormones Inactive molecules converted to active hormones before or after they are secreted |
| Glycoproteins | Proteins are more than 200 animo acids long have carbohydrate side chains |
| Thyroid-stimulation hormone | (TSH) |
| Luteinizing hormones | LH |
| Follicle -stimulation hormone | FSH |
| Peptide Hormones divide | Short chain Polypeptides and small proteins |
| Short chain Polypeptides | Antidiuretic hormone (ADH) and oxytocin (OX) (each 9 amino acids long) |
| Small proteins | Growth hormone (GH;191 amino acids) and prolactin (PRL; 198 amino acids) In |
| Hormones secreted by: | Hypothalamus, heart, thymus digestive tract, pancreas, and posterior lobe of the pituitary gland, as well as several hormones produced in other orga |
| Lip Derivatives divide | Eicosanoids, and Steroid hormones, |
| Eicosanoids | derived from arachidonic acid, a 20-carbon fatty acid. |
| Which is the factor of Eicosanoids | Paracrine factors that coordinate cellular activities affect enzymatic processes (such as blood clotting in extracellular. |
| Leukotrienes | some eicosanoids have secondary roles as hormones. |
| Second group of eicosanoids | prostaglandins involved primally in coordination local cellular activities. |
| Which have strong paracrine effects? In some prostaglandins | Thromboxanes and prostacyclins |
| Steroid hormones | derived from cholesterol. |
| Steroid hormones released by | The reproductive organs (testes in male, estrogens and progestin by the ovaries females The cortex of the adrenal gland (corticosteroids) The kidney (calcitriol) |
| Circulation steroid hormones | Are bound to specific transport proteins in the plasma. Peptide hormones |
| In the Secretion and distribution of hormones; Free hormones | Remain functional for less the 1 hour. Diffuse out of bloodstream and bind to receptor on target cells Are broken down and absorbed. by cells of liver or kidneys Are broken down by enzymes in plasma or interstitial fluid |
| Secretion and distribution of hormones are divided into: | Free Hormones and Thyroid and Steroid Hormones |
| In the Secretion and distribution of Hormones: Thyroid and Steroid Hormones | Remain in circulation much loger because most are " bound." Enter bloodstream. |
| Enter bloodstream | More than 99 percent become attached to special transport proteins. |
| bloodstream contains. | Substantial reserve of bound hormones |
| Mechanisms of Hormone Action | Hormone Receptor Hormones and Plasma Membrane Receptor |
| Hormones Receptor | Is a protein molecule to which a particular molecule binds strongly. Responds to several different hormones Different tissues have different combination of receptors Presence or absence of specific rector determines hormonal sensitivity |
| Hormones and Plasma Membrane Receptor | Catecholamines and Peptide Hormones Eicosanoids First and Secondo Messengers |
| Catecholamines and Peptide Hormones ( Hormones and Plasma Membrane Receptor) | Are no lipid soluble. Unable to penetrate plasma membranes. Bind to receptor proteins a outer surface of plasma membrane (extracellular receptors) |
| Eicosanoids in the Hormones and plasma membranes receptor | Are lipid soluble. Diffuse across plasma membranes to reach receptors proteins on inner surface of plasma membrane (intracellular receptors) |
| First and Second Messenger in the Hormones and plasma membranes receptor | Bind to receptors in plasma membrane. Cannot have direct effect on activities inside target cell. Use intracellular intermediary to exert effects. |
| First Messenger | Leads to second messenger. May act as enzyme activator, inhibitor or cofactor. Results in change in rates of metabolic reactions. |
| Second Messenger | Cycli-AMP (cAMP) Derivative of ATP Cyclic-GMP (cGMP) Derivate of GTP Calcium ions |
| The process of Amplification | Is the binding of small numbers of hormone molecules to membrane receptors. Leas to thousands of second messsenger in Magnifies efect of hormone on targe cell. |
| Down-regulation | Presence of a hormone triggers decrease in number of hormone receptors. |
| up -regulation | Absence of a hormone triggers increase in number of hormones receptors. When levels of particular hormone are low, cells become more sensitive to it. |
| G Protein | Enzyme complex coupled to membrane receptor. Involved in link between first messenger and second messenger. |
| Proteins and cAMP | Adenylate cyclase is activated when hormone binds to receptor at membrane surface and changes concentration of second messenger cyclic-AMP (cAMP) within cell Increased cAMP level accelerates metabolic activity within cell. |
| Adenylate cyclase (G Proteins and cAMP) | is activated when hormone blind to receptor at membrane surface and changes concentration of second messenger , cyclic-cAMP(cAMP) within cell. Increase cAMP level accelerates metabolic activity within cell. |
| G Proteins an Calcium Ions | Activated G proteins trigger: Opening of calcium ion channels in membrane. Release of calcium ions from intracellular stores. G protein active enzymes phospholipase C(PLC). Enzyme trigger receptor cascade. |
| Enzyme trigger receptor cascade. | Production OF Diacyglycerol (DAG) and inositol triphosphate (IP) from membranes phospholipids. May further activate calcium ion channels though protein kinase C (PKC). Calcium ions may activate calmodulin, which causes further cellular changes. |
| Hormones and intracellular Receptors | After rate of DNA transcription in nucleus. Change patterns of protein synthesis. Directly affect metabolic activity an structure of target cell. include steriords and thyroid hormones. |
| Endocrine Reflexes | Functional counterparts of neural reflexes. most cases, controlled by negative feedback mechanisms. Stimulus tiggers production of hormone , the direct or indirect effects of the hormone reduce intensity of the stimule. |
| Endocrine Reflexes can be triggers by | 1. Humoral stimuli (changed in composition of extracellular fluid), 2. Hormonal stimuli (arrival or removal specific hormone) 3.Neural sitmuli (arrival of neurotransmitter at neuroglandular junctions) |
| Simple Endocrine Reflex | involves only one hormones, controls hormone secretion by the heart, pancreas, parathyroid gland and digestive tract. |
| Complex Endocrine Reflex | one or more intermediary steps. Two or more hormones. The hypothalamus provides highest level of endocrine control. |
| Neuroendocrine Reflex | Pathways include both neural and endocrine. |
| Complex Commands | Issued by changing. amount of hormone secreted. Patterm of hormone release. Hypothalamic and pituitary hormones released in sudden bursts. Frequency changes response of target cells. |
| Pituitary Gland | Called Hypophysis. Lies within sella turcica. Sellar diaphragm. Hangs inferior to hypothalamus, connected by infundibulum. Release nine important peptide hormones. Hormones bind to membrane receptors (use cAMPas second messenger. |
| Sellar diaphragm | a dural sheet that lick pituitary in position, Isoletes it from cranial cavity) |
| Anterior lobe | Pituitary gland. called adenohypophysis. Hormones "turn on" endocrine glands or support other organs. |
| Anterior robe three regions | Para distalia, Para tuberlis, and Para intermedia. |
| Two Classes of hypothalamic regulatory hormones (anterior lobe) | 1.Releasing hormones (RH) -stimulate synthesis and secretion of one or more hormones at anterior lobe. 2. Inhibiting hormones (H) Prevent synthesis and secretion of hormones from the anterior lobe. Rate of secretion is controlled by negative feedback. |
| Posterior lobe | Pituitary gland. Neurohypohysis. contains unmyelinated axons of hypothalamic neurons. Supraoptic and paraventricular nucleis manefacture. Antidiurectic hormones (ADH) Oxycotin (OXT) |
| Thyroid Gland | Lies inferior to thyroid cartilage of larynx. Tow lobes connected by narrow isthumus |
| Thryroid follicies | Hollow spheres lined by cuboidal epithelium. Cells surround follicie cavity that contains viscous colloid. |
| Thyroglobulin | Globular Protein. Synthesized by follicie cells. Secreted into colloid of thyroid follicies. Molecules contatins the amino acid tyrosine |
| Thyroxine | T4- Tetraiodothyronime. contains four iodide ions. |
| Triiodothyronine | T3 contains thrree iodide ions. |
| Thryroid-stimulatiing Hormone | (TSH) absence cause tyroid follicies to become inactive. Neither synthesis nor secretion occurs. Binds to membrana receptors. Activities key enzymes in thyroid hormone. |
| Functions of Thyroid Hormones | 1.Enter target cells by transport system. 2. affect most cells in body. 3.Bind to receptor in: Cytoplasm, Surface of mitochondria, Nucleus. 4 Children essential to normal development (Skeletal, muscular and nervous system. |
| Calorigenic Effect | Cells consumes more energy resulting in increase heat generation. Is responsible to strong immediate and short-lived increase in rte of cellular metabolism. |
| Effects of Thyroid Hormones on Peripheral Tissues | 1. Elevate rates of oxygen. 2. Increase heart rate . 3. Increase sensitivity of sympathetic 4. Maintains normal sensitivity of respiratory. 5. Stimulates red blood cell formation. 6. Stimulates activity in other endocrine tissues. 7. Accelerate turnover o |
| C cells of the TG and Calcitonin | Produce Calcitonin (CT). Helps regulate concentrations o fCA in body fluids. (Inhibits osteoclasts. which slow the rate of Ca release from bone. Stimulate CA excretion by the Kidneys.) |
| Parathyroid Hormone PTH | parathyroid (chief) cells in response to low concentrations of Ca2 . Antagonist for calcitonin. |
| Three effects of PTH | 1. stimulates osteoclasts and inhibits osteoblasts. 2. enhances reabsorption of Ca1 at kidneys (reducing urinary losses. 3. Stimulates formation ad secretion of calcitriol by the kidneys. |
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Maguirre1537
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