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Lecture 4

Lecture 4.docx

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Chris Garside

Lecture 4  Cell signaling o Communication between cells o Produce messenger -> releases messenger -> activates response  Types of cell signaling o Direct signaling: cytoplasm connecting: used for small molecules  Gap junctions  Aqueous pore between cells  Moves ions  Chemical messengers  Ex. cAMP  Moves through a hemi channel: 6 connexins  Dynamic can open or close  Increase in Ca2+ o Autocrine and paracrine signaling: (Indirect) short, rapid distance: involves receptors o Endocrine signaling: (Indirect) gland releases directly to circulatory system o Neural signaling: (Indirect) long distance across the cell, through the synapse then is passed to a receptor  Indirect Signaling o Signaling cell releases chemical messenger o Messenger is carried through ECF o Communication of signal to target cell  Messenger binds to receptor  Activates signal transduction pathway  Response in target cell  Indirect signaling: short and long distance o Short  Paracrine  Chemical messenger diffuses in cell  Soluble messenger  Autocrine  Chemical messenger diffuses back to the signalling  Soluble messenger  Juxtacrine  Cell surface: signaling between juxtaposed cells  Membrane attached o Long  Endocrine system  Chemical messenger (hormone) transported by circulatory system  Nervous system  Electrical signal travels along a neuro and chemical messenger (neurotransmitter) is released  Across a synapse  Glands o Exocrine: released to external environment (digestive tract); secreted through acinus o Endocrine: released to internal environment; ductless gland  Chemical messengers o Peptide o Steroids o Amines o Lipids o Purines o Gases o Bold KNOWN hormones o Structure of chemical messenger (hydrophilic vs. hydrophobic)  Peptide/ Protein hormones o 2-200 a.a long o Hydrophilic can travel in ECF o Bind to receptors o Rapid effects on cells o Protein-protein phosphorylation  Protein hormone: synthesis and secretion o Synthesis on RER (usually prprohormones) o Stured in vesicls (often as prohormone o Secreted by exocytosis o Hydrophilic o Travel to target cell and dissolved in ECF  Secretory pathways o Regulated by signals stored in vesicles: released  Synthesis of AVP o Posterior pituitary: o Maturation of peptide  Peptides/Proteins bind transmembrane receptor o Hydrophilic, soluble travel to target cell o Bind to transmembrane receptors  Steroid hormones o Derived from cholesterol o Synthesisized by sER and mitochondria o Mineralocorticoids  Electrolyte balance o Glucocortoids  Stress hormone o Reproductive hormone  Sex specific characteristics  Sites of steroid hormone biosynthesis o Liver: cholesterol (from diet); modified steroids o Adrenal gland (cortex: glucocorticoids, mineralocortides, reproductive hormones o Gonads/placenta: reproductive steroid hormones o Brain: neurosteroids o Vitamin D:
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