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Sanja Hinic- Frlog

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Endocrine I January 7th The human contains roughly 30 chemical messengers known as hormones, which regulate activities such as sleep, body, temperature, hunger, and stress management. These hormones are products of the endocrine system, which along with the nervous system controls and coordinates our body processes. The endocrine system uses chemical messengers to relay information and instructions between cells. How do cells communicate? Direct communication Transmission – Through gap junctions; must be between two cells of the same type Mediators – Ions, small solutes, lipid soluble materials Distribution – usually limited to adjacent cells of the same type that are interconnected by connexons Paracrine communication – use of chemical messengers to transfer information from cell to cell within a single tissue. Transmission – Through extracellular fluid Mediators – Paracrine Factors Distribution – Primarily limited to a local area where paracrine factor concentrations are relatively high; target cells must have appropriate receptors Endocrine communication Transmission – Through the blood stream Mediators – hormones Distribution – Target Cells are primarily in other tissues and organs must have appropriate receptors Synaptic Communication Transmission – Across synaptic clefts Mediators – Neurotransmitters Distribution – Limited to very specific area; target cells must have appropriate receptors What are hormones? Chemical messengers Travel through bloodstream From one tissue to specific cells in another type of tissue What are three main groups of hormones? Amino Acid Derivatives – small molecules that are structurally related to amino acids, the building blocks of proteins. Derivatives of Tyrosine: Thyroid Hormones (T4) / Catecholamines (Epinephrine) Peptide Hormones – chain of amino acids. Most peptide hormones are synthesized as prohormones – inactive molecules that are converted to active hormones before or after they are secreted. Glycoproteins – These proteins are more than 200 amino acids long and have carbohydrate side chains. The glycoproteins include thyroid-stimulating hormone (TSH), Luteinizing Hormone (LH), and follicle stimulating hormone (FSH) from the anterior lobe of the pituitary gland as well as several hormones produced in other organs. Short Polypeptides/Small Proteins - This group of peptide hormones is large and diverse. It includes hormones that range from short chain polypeptides such as antidiuretic hormone (ADH) and oxytocin (OXT) (each 9 amino acids long), to small proteins such as growth hormone (GH; 191 amino acids) and prolactin (PRL; 198 amino acids). This group includes all the hormones secreted by the hypothalamus, heart, thymus, digestive tract, pancreas, and posterior lobe of the pituitary gland, as well as several hormones produced in other organs. Lipid Derivatives – There are two classes of lipid derivatives: elcosanoids, derived from arachidonic acid, a 20 carbon fatty acid; and steroid horm
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