Term
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Definition
| Membrane proteins link the cytoplasm adjacent cells |
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Term
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Definition
| Messenger travels through the extracellular fluid to target cell |
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Term
| Paracrine chemical messenger |
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Definition
Chemical that signals a nearby cell
–Example: Histamine, responsible for an inflammation response |
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Term
| Autocrine chemical messenger |
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Definition
A subclass of paracrines
–Chemical that signals the same cell that secreted it
–Source and target are the same |
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Term
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Definition
Messenger produced by neurons
–Released into the ECF of the synaptic cleft
–Examples: Acetylcholine, GABA, serotonin |
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Term
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Definition
Messenger produced by endocrine cells
–Secreted into the blood via the interstitial fluid
–Examples: Insulin, estrogen, thyroxin |
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Term
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Definition
A special class of hormone
–Messenger produced by neurons
–Secreted into the blood
–Examples: Antidiuretic hormone (ADH), oxytocin
Hormone
Secretory cell (endocrine cell)
Blood
vessel
Receptor
Target cell
Non- target cell (no recep- tors)
Classified by Function
Chemical Classification
•Lipophobic ligand
–Water soluble; not lipid soluble
–Does not cross the cell membrane
–Receptors on the cell membrane
–General action of target response
•Enzyme activation
•Membrane permeability changes
•Lipophilic ligand
–Lipid soluble; not water soluble
–Easily crosses the cell membrane
–Usually intracellular location of receptors
–General action of target response |
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Term
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Definition
Water soluble; not lipid soluble
–Does not cross the cell membrane
–Receptors on the cell membrane
–General action of target response
•Enzyme activation
•Membrane permeability changes |
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Term
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Definition
–Lipid soluble; not water soluble
–Easily crosses the cell membrane
–Usually intracellular location of receptors
–General action of target response is via gene activation |
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Term
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Definition
Time for a chemical to decrease its concentration by half
–Concentration of the messenger could be in blood or interstitial fluid |
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Term
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Definition
| Process of producing a response in the target |
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Term
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Definition
–Receptor number increases on the target
–May result from too little messenger
–Sensitivity to the messenger increases |
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Term
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Definition
–Receptor number decreases on the target
–May result from excess messenger
–Sensitivity to the messenger decreases
–Tolerance to the messenger develops |
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Term
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Definition
–Chemical that binds to a receptor
–Its action mimics the normal response |
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Term
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Definition
–Chemical that binds to a receptor
–Binding does not result in a response
–Competes with the normal ligand
–Response is the opposite of that to an agonist |
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