MCAT Psychological, Social, and Biological Foundations of Behavior: Passage 11 — Flashcards

Use the following passage to answer questions:

The term mental illness clearly indicates that there is a problem with the mind. But is it just the mind in an abstract sense, or is there a physical basis to mental illness? As scientists continue to investigate mental illnesses and their causes, they learn more and more about how the biological processes that make the brain work are changed when a person has a mental illness.
How does the brain take in all of this information, process it, and cause a response? The basic functional unit of the brain is the neuron. A neuron is a specialized cell that can produce different actions because of its precise connections with other neurons, sensory receptors, and muscle cells. A typical neuron has four structurally and functionally defined regions: the cell body, dendrites, axons, and axon terminals.
When the electrical signal reaches the presynaptic axon terminal, it cannot cross the synaptic space, or synaptic cleft. Instead, the electrical signal triggers chemical changes that can cross the synapse to affect the postsynaptic cell. When the electrical impulse reaches the presynaptic axon terminal, membranous sacs called vesicles move toward the membrane of the axon terminal. When the vesicles reach the membrane, they fuse with the membrane and release their contents into the synaptic space. The molecules contained in the vesicles are chemical compounds called neurotransmitters.
The nervous system uses a variety of neurotransmitter molecules, but each neuron specializes in the synthesis and secretion of a single type of neurotransmitter. Some of the predominant neurotransmitters in the brain include glutamate, GABA, serotonin, dopamine, and norepinephrine. Each of these neurotransmitters has a specific distribution and function in the brain.
Research scientists want to learn about the chemical or structural changes that occur in the brain when someone has a mental illness. If scientists can determine what happens in the brain, they can use that knowledge to develop better treatments or find a cure. At this time, scientists do not have a complete understanding of what causes mental illnesses. If you think about the structural and organizational complexity of the brain, together with the complex effects that mental illnesses have on thoughts, feelings, and behaviors, it is hardly surprising that figuring out the causes of mental illnesses is a daunting task.
Most scientists believe that mental illnesses result from problems with the communication between neurons in the brain. For example, the level of the neurotransmitter serotonin is lower in individuals who have depression. This finding led to the development of certain medications for the illness. Selective serotonin reuptake inhibitors (SSRIs) work by reducing the amount of serotonin that is taken back into the presynaptic neuron. This leads to an increase in the amount of serotonin available in the synaptic space for binding to the receptor on the postsynaptic neuron. Changes in other neurotransmitters (in addition to serotonin) may occur in depression, thus adding to the complexity of the cause underlying the disease.
Scientists believe that there may be disruptions in the neurotransmitters dopamine, glutamate, and norepinephrine in individuals who have schizophrenia. One indication that dopamine might be an important neurotransmitter in schizophrenia comes from the observation that cocaine addicts sometimes show symptoms similar to schizophrenia. Cocaine acts on dopamine-containing neurons in the brain to increase the amount of dopamine in the synapse.