Theories in Biological Model

Thees are famous Theories in biological model.

Biochemical Theory

Very small amounts of certain chemicals in the body can cause profound changes in behavior as proved by researches.


Diathesis Stress Theory

Predisposition i.e., diathesis (including genes) and stressful environment combine together to cause abnormal behavior Traits are influenced by genes and by environment



The synapse of the neuron releases special chemicals

• Existence of neurotransmitters has been known

since 1920’s; but the evidence of their relationship

with psychological disorders has been found and known since 1950s

• More than 50 neurotransmitters exist in human body


Neurotransmitters and Their Role

• Acetylcholine: Learning, Memory and Muscle control

• Dopamine: Motor activity, Coordination, Emotion and Memory

• Epinephrine: Emotion, Stress

• GABA (Gamma-Amino Butyric Acid): Anxiety, Arousal, Learning

• Serotonin: Sensory Processing, Sleep, Arousal

• Glutamate: Anxiety, Mood


Endocrine Glands

These glands form the body’s “slow” chemical communication system; a set of ductless glands that secrete hormones (special chemicals) into the bloodstream”


Endocrine Glands and Abnormality

• Low secretions of the thyroid produce anxiety like symptoms such as irritability and tension

• Low level of pituitary secretions produces depression like symptoms—Fatigue, apathy etc.

• Abnormal secretions of hormones may cause major depression

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