Brain from stimulants

Information transfer between two nerves in the brain occurs at synaptic junctions, across which chemical messengers (neurotransmitters) diffuse. The neurotransmitter binds to a receptor on the postsynaptic neurone, changing its membrane potential. If the membrane potential decreases, this either initiates an action potential or increases the likelihood that a further depolarisation, from stimulation by another nerve, will initiate an action potential. Such a neurotransmitter is described as excitatory. In contrast, if it increases the membrane potential, it reduces the likelihood of initiation of an action potential, such a... 

Nicotine binds to a type of receptor, now called a nicotinic receptor, and causes the same effects as a release of the neurotransmitter acetylcholine at nerve endings. In this it is similar to organophosphates, which lead to excess acetylcholine at nerve endings (see pp. loo-ioi). Nicotine first excites and then inhibits the central nervous system it first stimulates and then paralyses nerves. It reacts with receptors in muscle and nerves, and is able to enter the brain from the bloodstream and interact with nicotinic receptors. At first there is a stimulation, with the smoker experiencing alertness and decreased irritability, aggression, and anxiety. With higher doses there is depression of the brain as a result of saturation of the receptors. 

Cocaine is a very addictive drug. Cocaine is a stimulant—it directly affects your brain. Cocaine stimulates certain nerve cells in the brain, producing feelings of intense pleasure. Users talk about feeling carefree, or relaxed, or utterly in control. But this artificial stimulation comes with a price tag. The high from cocaine lasts only from five to 20 minutes, and you will need more and more cocaine each time you try to match the feelings of that first, initial experience. Cocaine causes severe mood swings and irritability. 

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