Hockenbury Discovering Psychology 5th txtbk

The Nervous System and the Endocrine System55muscle spasms. Drugs may also affect the lengthof time the neurotransmitter remains in the synapticgap, either increasing or decreasing theamount available to the postsynaptic receptor.One way in which drugs can prolong the effectsof the neurotransmitter is by blocking the reuptakeof the neurotransmitter by the sendingneuron. For example, there is aNeurotransmittersDrugs can mimicneurotransmitters,producing thesame effect.Synaptic gapcategory of antidepressant medi -cations that are referred to asSSRIs, which stands for selectiveseroatonin reuptake inhibitors. SSRIsinclude such trade name medicationsas Prozac, Zoloft, and Paxil.Each of these medications inhibitsthe reuptake of serotonin in certainneurons, increasing the availabilityof serotonin in the brain. Similarly, theillegal drug cocaine produces its exhilarating rushby interfering with the reuptake of dopamine(Volkow & others, 2007).Drugs can also mimic specific neurotransmitters. When adrug is chemically similar to a specific neurotransmitter, itmay produce the same effect as that neurotransmitter. It isSynaptic vesiclesDrugs can block receptor siteson the receiving neuron, preventingthe neurotransmitter’s effect.partly through this mechanism that nicotine works as a stimulant. Nicotine is chemicallysimilar to acetylcholine and can occupy acetylcholine receptor sites, stimulatingskeletal muscles and causing the heart to beat more rapidly.Alternatively, a drug can block the effect of a neurotransmitter by fitting intoreceptor sites and preventing the neurotransmitter from acting. For example, thedrug curare blocks acetylcholine receptor sites, causing almost instantaneous paralysis.The brain sends signals to the motor neurons, but the muscles can’t respondbecause the motor neuron receptor sites are blocked by the curare. Similarly, a drugcalled naloxone eliminates the effects of both endorphins and opiates by blockingopiate receptor sites.Axon terminalof sending neuronDendrite of receiving neuronDrugs can blockreuptake of theneurotransmitter,increasing theneurotransmitter’seffect.Figure 2.6 How Drugs AffectSynaptic Transmission Drugs affectbrain activity by interfering withneurotransmitter functioning in thesynapse. Drugs may also affect synaptictransmission by increasing or decreasingthe amount of a particular neurotransmitterthat is produced.The Nervous System and the Endocrine SystemCommunication Throughout the BodyKey Theme• Two major communication systems in the body are the nervous system andthe endocrine system.Key Questions• What are the divisions of the nervous system and their functions?• How is information transmitted in the endocrine system, and what are itsmajor structures?• How do the nervous and endocrine systems interact to produce the fightor-flightresponse?Specialized for communication, up to 1 trillion neurons are linked throughout yourbody in a complex, organized communication network called the nervous system.The human nervous system is divided into two main divisions: the central nervousnervous systemThe primary internal communication networkof the body; divided into the central nervoussystem and the peripheral nervous system.