Neuroscience & Psychology

Neurons: Relation of neurons and human behavior

Neurotransmitters have been studied quite a bit in relation to psychology and human behavior. What we have found is that several neurotransmitters play a role in the way we behave, learn, the way we feel, and sleep. And, some play a role in mental illnesses. The following are those neurotransmitters which play a significant role in our mental health.

Acetylcholine – involved in voluntary movement, learning, memory, and sleep
1. Too much acetylcholine is associated with depression, and too little in the hippocampus has been associated with dementia.
Dopamine – correlated with movement, attention, and learning
2. Too much dopamine has been associated with schizophrenia, and too little is associated with some forms of depression as well as the muscular rigidity and tremors found in Parkinson’s disease.
Norepinephrine – associated with eating, alertness
1. Too little norepinephrine has been associated with depression, while an excess has been associated with schizophrenia.
Epinephrine – involved in energy, and glucose metabolism
2. Too little epinephrine has been associated with depression.
Serotonin – plays a role in mood, sleep, appetite, and impulsive and aggressive behavior
1. Too little serotonin is associated with depression and some anxiety disorders, especially obsessive-compulsive disorder. Some antidepressant medications increase the availability of serotonin at the receptor sites.
GABA (Gamma-Amino Butyric Acid) – inhibits excitation and anxiety
2. Too little GABA is associated with anxiety and anxiety disorders. Some antianxiety medication increases GABA at the receptor sites.
Endorphins – involved in pain relief and feelings of pleasure and contentedness
Please note that these associations are merely correlations, and do not necessarily demonstrate any cause and effect relationship. We don’t know what other variables may be affecting both the neurotransmitter and the mental illness, and we don’t know if the change in the neurotransmitter causes the illness, or the illness causes the change in the neurotransmitter.

Endocrine system & behavior:

The classical endocrine system has an important regulatory action on body metabolism generally and, like the nervous system, is concerned with the integrated functioning of the organism. It differs from the nervous system in this role in that its chemically coded messages are less specific than those of the nervous system, influencing many body tissues simultaneously. Also, the body's response to the hormonal message is slower to occur and longer in duration. The two systems interact with each other, however, at many levels. The dependence of behavior on hormonal factors will be briefly illustrated with thyroid hormones, sex steroids, and adrenocorticoids.

Thyroid. The hormones of the thyroid gland have a general stimulating effect on metabolic rate. Underfunctioning of the thyroid (hypothyroidism) is associated with a general sluggishness, lethargy, and lack of spontaneity. Hyperthyroidism is associated with restlessness, irritability, and often an abnormally elevated mood (euphoria).

Sex Hormones. Profound changes occur in complex patterns of behavior when gonadal hormones are manipulated. Although complex human behavior seems less immediately dependent upon gonadal hormones than in the case of lower animals, alterations in endocrine function in humans is accompanied by changes in behavior. Castration of human males has been practiced since antiquity as a means of altering behavior and personality. Systematic psychologic assessment of human male castrates reveals changes in attitude and other aspects of personality functioning.

Adrenocorticoids and ACTH. For many years various steroids of the adrenal cortex, and their synthetically produced analogues, have been used in the treatment of a variety of medical disorders. The prolonged administration of these drugs, or of ACTH, the pituitary hormone which stimulates the release of corticoids from the adrenal glands, is sometimes accompanied by restlessness, euphoria, or anxiety. Withdrawal of the steroids is sometimes followed by lethargy and depression. These clinical observations suggest a relationship between adrenocorticoids and anxiety.