Human Physiology/The Nervous System

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Wernicke's area is part of the auditory and visual associations cortex. This region is responsible for the analysis and

formation of language content. For example, patients with lesions in this area:

1. Are unable to name objects

2. Are unable to understand the meaning of words

3. Articulate speech readily but usually nonsensically

Diseases of the Limbic System

There are several well known diseases that are disorders of the limbic system. Several are discussed here.

Schizophrenia

An increased dopamine (DA) response in the limbic system results in schizophrenia. DA may be synthesized or

secreted in excess, DA receptors may be supersensitive, and DA regulatory mechanism may be defective. Symptoms

are decreased by drugs which block DA receptors. Symptoms of schizophrenia are:

1. Loss of touch with reality

2. Decreased ability to think and reason

3. Decreased ability to concentrate

4. Decreased memory

5. Regress in child-like behavior

6. Altered mood and impulsive behavior

7. Auditory hallucinations

Symptoms may be so severe that the individual cannot function.

Depression

Depression is the most common major mental illness and is characterized by both emotional and physical symptoms.

Symptoms of depression are:

1. Intense sadness and despair

2. Anxiety

3. Loss of ability to concentrate

4. Pessimism

5. Feelings of low self esteem

6. Insomnia or hypersomnia

7. Increased or decreased appetite

8. Changes in body temperature and endocrine gland function

10 to 15% of depressed individuals display suicidal behavior during their lifetime.

The cause of depression and its symptoms are a mystery but we do understand that it is an illness associated with

biochemical changes in the brain. A lot of research goes on to explain that it is associated with a lack of amines

serotonin and norephinephrine. Therefore pharmacological treatment strategies often try to increase amine

concentrations in the brain.

One class of antidepressants is monoamine oxidase inhibitors. Mono amine oxidase is a enzyme that breaks down

your amines like norephinephrine and serotonin. Because the antidepressants inhibit their degradation they will

remain in the synaptic cleft for a longer period of time making the effect just as if you had increased theses types of

neurotransmitters.

A newer class of antidepressants is selective serotonin reuptake inhibitors (SSRI's). With SSRI's decreasing the

uptake of serotonin back into the cell that will increase the amount of serotonin present in the synaptic cleft. SSRI's

are more specific than the monoamine oxidase inhibitors because they only affect serotonergic synapses. You might

recognize these SSRI's by name as Prozac and Paxil.