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bkheath
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Type of cell-to-cell communication which is common in smooth and cardiac muscle
Gap junctions
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Substance that has a signaling function
Chemical messenger
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Molec that binds to a biomolec
Ligand
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Chemical that signals & triggers a cellular response by binding to receptor on the cell
Agonist
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Chemical which binds to cell receptor, basically blocking it from other chemicals binding, resulting in no cellular signal/response
Antagonist
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Chemical that serves to signal nearby cell (ex: histamine responsible for inflammation response)
Paracrine chemical msngrs
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Chemical that signals the same cell that secreted it (source cell & target cell are the same)
Autocrine chem msgnrs
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Chem msgnr produced by neurons & released into the ECF of synaptic cleft (short distance)
Neurotransmitters
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Chem msgnr produced by endocrine cells & secreted into blood via interstitial fluid
Hormones
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Chem msngr produced by neurons and secreted into blood via interstitial fluid (ex: antidiuretic hormone (ADH), oxytocin)
Neurohormones
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Chem msgnr which cannot easily pass cell membranes so may need pump or channel; often on cell mem
Lipophobic Ligands
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General action of lipophobic ligands (2)
- Enzyme activation
- Membrane permeability chgs
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Chem msngr which easily crosses cell mem; receptor located w/in cell
Lipophilic Ligands
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General action of lipophilic ligands
Gene activation
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Ligands move to their target cells by:
- Diffusion through interstitial fluid
- Blood-borne transport
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In blood-borne transport, lipophobic ligands ________ and lipophilic ligands ________
- Dissolve in plasma
- Bind to carrier protein
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Messenger Half-life
time for a chem to decrease concentration in half (half of msngrs are still signaling)
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How a chemical signal is translated into a cell action:
Msngr binds to receptor
Binding results in cell response
Signal transduction
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Strength of binding
affinity
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Location of binding:
Lipophobic ligands:
Lipophilic ligands:
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When receptor number decreases on target cell; may result from excess msngr
Results in lower sensitivity to msngr b/c of tolerance
Down-regulation
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When receptor number increases on target cell, causing increase of sensitivity to msngr; may result from too little msngr
Up-regulation
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2 mechanisms of signal transduction
- 1. Intracellular-mediated responses: responses w/in the cell
- 2. Membrane-bound receptor-mediated responses
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3 types membrane-bound receptors
- Channel-linked receptors
- Enzyme-linked receptors
- G protein-linked receptors
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What kind of ligands are involved in intracellular-mediated response & why
Lipophilic ligands, b/c they can easily pass thru cell mem, to receptors inside (in cytosol or nucleus)
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How does cell respond to a lipophilic ligand coming in and binding to a receptor?
Gene activation: gene is made via transcription to make whatever specific protein is needed
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How do the membrane-bound receptors of the target cell respond to ligand binding? (2 general ways)
- Mvmt of ions
- Phosphorylation of enzymes (activation or inactivation of cell signaling pathways)
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Type of receptor in which the receptor and channel are the same protein; binding of ligand causes channel to open or close; chg in transport of ions thru channel causes response
(Binding on outside causes chg on inside)
Channel-linked receptor
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Type of receptor in which the receptor and enzyme are the same protein; the ligand binding activates the enzyme which causes response
(enzyme is "w/in" protein)
(picture cell mem protein w/ receptor end on outside, enzyme end on opposite side inside gets chgd at the "active site")
Enzyme-linked receptor
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Type of receptor which involves a regulatory protein that links a receptor to other mem proteins, including ion channels and amplifier enzymes
G protein-linked receptor
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Why are G protein-linked channels called slow ligand-gated channels?
The receptor and channel are diff proteins (which are linked by G protein)
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Type of receptor which is activated by binding of ligand, and then goes on to activate a channel protein, causing target response b/c of chg in transport of ions thru channel (this chgs cell mem permeability b/c ions can now enter or not)
G protein-linked channel
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How do G proteins-linked receptors activate second messengers?
When ligand binds to G protein-linked receptor, the G protein activates an amplifier enzyme, which activates second msgnr production, which amplifies the ligand's signal
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cAMP is a type of _____ that signals that the cell is out of energy
second msngr
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A second msngr is a type of ____
enzyme
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