Caffeine nerve cells

Caffeine acts in the brain by blocking receptors for the neurotransmitter adenosine. Normally, adenosine helps to calm nerve cells and promote sleep, but when the receptors... 

Caffeine acts as a stimulant of the central nervous system (CNS) through several proposed mechanisms. The most important seems to be its interference with the ability of the neurotransmitter adenosine to bind to its nerve cell receptor. Also, caffeine inhibits the enzyme cyclic nucleotide phosphodiesterase, which breaks down intracellular cyclic adenosine monophosphate (cAMP), another messenger involved in the transmission of nerve signals from hormones originating outside the central nervous system... 

Opiates snch as morphine and codeine are thonght to enhance the release by nenrons of the nenrotransmitter dopamine the release of dopamine leads to a sense of enphoria. These drugs are addictive and are often abused. In general, all antipsychotic medications work by blocking dopamine receptors in the forebrain. Nicotine mimics the action of the nenrotransmitter acetylcholine at receptors having to do with the transmission of signals between antonomic nerve cells and skeletal muscle, see also Caffeine Epinephrine Methylphenidate Neurochemistry Neurotransmitters Norepinephrine. 

Caffeine, once in the bloodstream, interacts with nerve cells to block adenosine receptors. The result is an increase of dopamine and norepinephrine neurotransmitters. The effects of increased levels of these neurotransmitters are a feeUng of alertness, competence, and wakefulness. 

The methylxanthine molecule is built on a foundation common to many biologic compounds, the xanthine double ring of carbons. The three methylxanthines, caffeine, theophylline, and theobromine, all block the action of the body s adenosine molecule, sending a signal that helps slow the chemical buildup inside cells. Because the methylxanthines closely resemble adenosine at the molecular level, they can occupy the molecular sites on cells that normally recognize, and react to, adenosine. Caffeine prevents the normal slowing action of adenosine at the cellular level, in both nerves and muscle. 

A functional magnetic resonance imaging (fMRI) study of the brain can actually determine between the regular and the occasional coffee drinker. Caffeine consistently slows blood flow by 25% to the gray matter of the brain, which contains the cells, and by 20% to the white matter, which contains the connecting nerve fibers. Heavy users of caffeine show more blood flow in the gray matter in the front of the brain when they had abstained for 30 hours, compared to those who infrequently ingest caffeine. With fMRI, the doctor can look inside the brain and observe the phenomenon of caffeine withdrawal in action. 

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