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Cell Communication
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Regulation & Communication
Animals rely on 2 systems for regulation endocrine system system of ductless glands secrete chemical signals directly into blood chemical travels to target tissue target cells have receptor proteins slow, long-lasting response nervous system system of neurons transmits “electrical” signal & release neurotransmitters to target tissue fast, short-lasting response Hormones coordinate slower but longer–acting responses to stimuli such as stress, dehydration, and low blood glucose levels. Hormones also regulate long–term developmental processes by informing different parts of the body how fast to grow or when to develop the characteristics that distinguish male from female or juvenile from adult. Hormone–secreting organs, called endocrine glands, are referred to as ductless glands because they secrete their chemical messengers directly into extracellular fluid. From there, the chemicals diffuse into the circulation.
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Local and Long-Distance Signaling
Cells in a multicellular organisms communicate by chemical messengers Animal and plant cells have cell junctions that directly contact the cytoplasm of adjacent cells Paracrine: In local signaling, animal cells may communicate by direct contact In many other cases, animal cells communicate using local regulators, messenger molecules that travel only short distances (Synaptic) Endocrine: In long-distance signaling, plants and animals use chemicals called hormones
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Local Direct contact Plasma membranes Gap junctions
between animal cells Plasmodesmata between plant cells Local Cell junctions Direct contact Cell-cell recognition
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Long Distance Local Paracrine Synaptic Endocrine Local signaling
Long-distance signaling Target cell Electrical signal along nerve cell triggers release of neurotransmitter Endocrine cell Blood vessel Neurotransmitter diffuses across synapse Secreting cell Secretory vesicle Hormone travels in bloodstream to target cells Local regulator diffuses through extracellular fluid Target cell is stimulated Target cell Paracrine Paracrine signaling Synaptic Synaptic signaling Hormonal signaling Endocrine
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Regulation by chemical messengers
Neurotransmitters released by neurons Hormones release by endocrine glands endocrine gland neurotransmitter axon hormone carried by blood receptor proteins receptor proteins Lock & Key system target cell
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Ligand A signaling molecule Binds to a Receptor Protein Can be a…
Individual Amino acid Nucleotide Steroid or another lipid Dissolved Gasses Binds to a Receptor Protein DO NOT make this harder than it needs to be!
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How do hormones act on target cells
Lipid-based hormones hydrophobic & lipid-soluble diffuse across cell membrane & enter cells bind to receptor proteins in cytoplasm & nucleus bind to DNA as transcription factors turn on genes Protein-based hormones hydrophilic & not lipid soluble can’t diffuse across cell membrane bind to receptor proteins in cell membrane trigger secondary messenger pathway activate internal cellular response enzyme action, uptake or secretion of molecules…
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Action of lipid (steroid) hormones
target cell blood S 1 S cross cell membrane protein carrier S 2 cytoplasm binds to receptor protein becomes transcription factor 5 mRNA read by ribosome 3 S plasma membrane 4 DNA mRNA 6 7 nucleus protein protein secreted ex: secreted protein = growth factor (hair, bone, muscle, gametes)
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Action of protein hormones
signal-transduction pathway Action of protein hormones 1 signal protein hormone P plasma membrane binds to receptor protein activates G-protein activates enzyme cAMP receptor protein acts as 2°messenger ATP transduction GTP transduction: the action or process of converting something and especially energy or a message into another form activates cytoplasmic signal ATP activates enzyme 2 secondary messenger system cytoplasm activates enzyme 3 response target cell produces an action
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Relay molecules in a signal transduction
Protein-based Hormones EXTRACELLULAR FLUID CYTOPLASM Plasma membrane Reception Transduction Response Receptor Activation of cellular response Relay molecules in a signal transduction pathway Signal molecule
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Benefits of a 2°messenger system
1 signal Activated adenylyl cyclase receptor protein 2 Not yet activated amplification 4 amplification 3 cAMP amplification 5 GTP G protein protein kinase 6 amplification Amplification! enzyme Cascade multiplier! 7 amplification FAST response! product
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Regulation Why are hormones needed?
chemical messages from one body part to another communication needed to coordinate whole body daily homeostasis & regulation of large scale changes solute levels in blood glucose, Ca++, salts, etc. metabolism growth development maturation reproduction growth hormones
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Nervous & Endocrine systems linked
Hypothalamus = “master nerve control center” nervous system receives information from nerves around body about internal conditions releasing hormones: regulates release of hormones from pituitary Pituitary gland = “master gland” endocrine system secretes broad range of “tropic” hormones regulating other glands in body hypothalamus posterior pituitary anterior
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Any Questions?? Robert Wadlow 8' 11"
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