Flashcards in Chapter 5 Deck (24):
What is indirect communication?
Indirect communication does not have cells physically touching each other instead involves a chemical messenger, binding a receptor on a cell. Its binding to whatever it can bind to. Communication via chemial signals
What is direct communication
Direct communiction is very fast; allows for synchronized activation of cells, not good for long distance.
What is paracrine messages?
Paracrine's are side by side messages. Involves a paracrine message being relased binding a receptor to a cell next door.
What is neurotransmitter?
Neurotransmitter – cell that releases the messenger is a neuron; target cell is a gland, muscles, or another neuron; needs to be fast for survival purposes.
what is endocrine signaling?
Endocrine signaling utilize hormones. When hormones enter the blood stream have the ability to reach any cell in the body
Pro: can effect cells long away from the secretory glands
Con: slow, but not really slow just compared to neurotransmitter signaling
When ever a endocrine cell secretes a hormone it will be either hydrophilic or hydrophobic. What is a hydrophilic messanger>
Hydrophilic messenger dissolve in the blood with no problem. Cannot dissolve throughout membrane because membrane is hydrophobic, so the receptor of the Hydrophilic messenger has to be located on the outside of the cell because it can not cross the membrane.
What are hydrophobic messangers?
Hydrophobic messenger will not dissolve in water. Can cross the membrane so the receptor for the hydrophobic messanger are gonna be located on the inside of the cell, can have an affect on the inside of the cell, almost always a steroid hormone.
What are ligands examples?
Paracrines, Neurotransmitters, and Hormones are ligands that bind receptors
What are receptor proteins?
A target cell receives a signal because it has receptor proteins specific to it on the plasma membrane or inside the cell. Nonpolar signal molecules such as steroid hormones can penetrate the plasma membrane and interact with receptors inside the cell.
What are reseptor properties?
Specificity: Each type of receptor only binds one type of ligand/molecule
Affinity: Strength of binding between a ligand and its receptor
What is receptor affinity?
Receptor affinity are more attracted to the binding sites based on charges.
What does receptor activation depend on?
Receptor activation depends on Concentration of ligand, Expression level of receptor, Affinity of receptor for ligand.
What is the relationship between ligand concentration and receptor activation?
In general more ligand more receptor activated, but there are a number of receptors that can be activated. Once all receptors are bound by a ligand, it will not change anything by adding more.
How can the number of receptors change?
Upregulation: Increase in receptor synthesis.
Downregulation: Decrease in receptor synthesis
Describe drug interaction?
Every addictive drug available today takes advantage of pre-existing receptors in the human body. Binding of the drug to these receptors often activates a network of dopaminergic cells in the mesolimbic region of the brain that are involved in emotional reward. Every drug binds to a receptor. Mesolimbic region of brain deal with addiction, compulsive behavior, and reward using the hormone dopamine.
Overactive Mesolimibic regions equal scyhaphrania.
Not enough dopamine equal Parkinsons.
Describe drug addiction?
Opiates: painkillers such as codeine, morphine, oxycodone, oxycontin, heroin, etc, activate natural G-protein coupled receptors for endorphins in the brain. Endorphin concentration is usually extremely low.Triggers receptor downregulation, as well as de-sensitization resulting from functional un-coupling of G-protein receptors to their effector molecule. Most addictive
Without endorphins any pain you feel would be way worse. Opiates release enormous quantities of endorphins and take down receptors for dopamine.
What happens in nicotine addiction?
Nicotine has an extremely high affinity for acetylcholine receptors in the brain. It essentially out-competes acetylcholine for these receptors.
Cells that require acetylcholine for signaling respond by making more acetylcholine receptors, and releasing much more acetylcholine.
Now everything can bind to the receptors
Now it takes more nicotine to out compete the aetylcholine and metabolize it more quickly. There is also evidence that increased use of nicotine results in increased ability of an individual to metabolize nicotine. Results in a shorter half-life of the drug. It has also been suggested that nicotine up regulates extracellular mechanisms for degrading the drug.
Body becomes better at breaking down the drug (Tolerance- body’s ability to detoxify)
What are the two mechanism for drug tolerance?
Mechanism for drug tolerance are; Pharmacokinetic tolerance: the result of lower concentrations of a drug actually reaching the receptor. Could be caused by degradation, or increased metabolism of the drug. (nicotine)
Pharmacodynamic tolerance: cellular mechanism that results in receptor down regulation (opiates), or upregulation (nicotine).
What are agonist?
Agonist are ligands that bind to receptors and cause biological response.
What are antagonist?
Antagonist are ligands that bind to receptors and DO NOT cause biological response.
What are G proteins?
G Proteins (molecular switches) are the most complex. Receptors could be coupled with G Proteins that are physically attached to proteins that will break off and bind with an effector protein (ion channel or enzyme). G proteins can open and close ion channels. When a G protein is bout to GTP; it is on. When GDP is bound, it is dead or inactive.
What are lipophilic ligands?
Lipophilic ligands usually causes a change in gene expression (protein synthesis). They need a second messenger, the first is the ligand, but it cant cross the non polar membrane. Is hydrophobic.
What are lipophobic ligands
Lipophobic ligands are hydrophillic ligands.