In Module 2, we will discuss three models of abnormal behavior to include the biological, psychological, and sociocultural models. Each is unique in its own right and no single model can account for all aspects of abnormality. Hence, we advocate for a multi-dimensional and not a uni-dimensional model.

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Module Outline

2.1. Uni- vs. Multi-Dimensional Models of Abnormality2.2. The Biological Model2.3. Psychological Perspectives2.4. The Sociocultural Model

Module Learning Outcomes

Differentiate uni- and multi-dimensional models of abnormality.Describe how the biological model explains mental illness.Describe how psychological perspectives explain mental illness.Describe how the sociocultural model explains mental illness.

2.1. Uni- vs. Multi-Dimensional Models of Abnormality

Section Learning Objectives

Define the uni-dimensional model.Explain the need for a multi-dimensional model of abnormality.Define model.List and describe the models of abnormality.

2.1.1. Uni-Dimensional

To effectively treat a mental disorder, we have to understand its cause. This could be a single factor such as a chemical imbalance in the brain, relationship with a parent, socioeconomic status (SES), a fearful event encountered during middle childhood, or the way in which the individual copes with life’s stressors. This single factor explanation is called a uni-dimensional model. The problem with this approach is that mental disorders are not typically caused by a solitary factor, but multiple causes. Admittedly, single factors do emerge during a person’s life, but as they arise, the factors become part of the individual. In time, the cause of the person’s psychopathology is due to all of these individual factors.


2.1.2. Multi-Dimensional

So, it is better to subscribe to a multi-dimensional model that integrates multiple causes of psychopathology and affirms that each cause comes to affect other causes over time. Uni-dimensional models alone are too simplistic to explain the etiology of mental disorders fully.

Before introducing the current main models, it is crucial to understand what a model is. In a general sense, a model is defined as a representation or imitation of an object ( For mental health professionals, models help us to understand mental illness since diseases such as depression cannot be touched or experienced firsthand. To be considered distinct from other conditions, a mental illness must have its own set of symptoms. But as you will see, the individual does not have to present with the entire range of symptoms. For example, five out of nine symptoms may be enough to be diagnosed as having dysthymia, paranoid schizophrenia, avoidant personality disorder, or illness anxiety disorder. There will be some variability in terms of what symptoms are displayed, but in general, all people with a specific psychopathology have symptoms from that group.

We can also ask the patient probing questions, seek information from family members, examine medical records, and in time, organize and process all of this information to better understand the person’s condition and potential causes. Models aid us with doing all of this. Still, we must remember that the model is a starting point for the researcher, and due to this, it determines what causes might be investigated at the exclusion of other causes. Often, proponents of a given model find themselves in disagreement with proponents of other models. All forget that there is no individual model that completely explains human behavior, or in this case, abnormal behavior, and so each model contributes in its own way. Here are the models we will examine in this module:

Biological – includes genetics, chemical imbalances in the brain, the functioning of the nervous system, etc.Psychological – includes learning, personality, stress, cognition, self-efficacy, and early life experiences. We will examine several perspectives that make up the psychological model to include psychodynamic, behavioral, cognitive, and humanistic-existential.Sociocultural – includes factors such as one’s gender, religious orientation, race, ethnicity, and culture.

Key Takeaways

You should have learned the following in this section:

The uni-dimensional model proposes a single factor as the cause of psychopathology while the multi-dimensional model integrates multiple causes of psychopathology and affirms that each cause comes to affect other causes over time.There is no individual model that completely explains human behavior and so each model contributes in its own way.

Section 2.1 Review Questions

What is the problem with a uni-dimensional model of psychopathology?Discuss the concept of a model and identify those important to understanding psychopathology.

2.2. The Biological Model

Section Learning Objectives

Describe how communication in the nervous system occurs.List the parts of the nervous system.Describe the structure of the neuron and all key parts.Outline how neural transmission occurs.Identify and define important neurotransmitters.List the major structures of the brain.Clarify how specific areas of the brain are involved in mental illness.Describe the role of genes in mental illness.Describe the role of hormonal imbalances in mental illness.Describe the role of viral infections in mental illness.Describe commonly used treatments for mental illness.Evaluate the usefulness of the biological model.

Proponents of the biological model view mental illness as being a result of a malfunction in the body to include issues with brain anatomy or chemistry. As such, we will need to establish a foundation for how communication in the nervous system occurs, what the parts of the nervous system are, what a neuron is and its structure, how neural transmission occurs, and what the parts of the brain are. All while doing this, we will identify areas of concern for psychologists focused on the treatment of mental disorders.

2.2.1. Brain Structure and Chemistry Communication in the nervous system. To truly understand brain structure and chemistry, it is a good idea to understand how communication occurs within the nervous system. See Figure 2.1 below. Simply:

Receptor cells in each of the five sensory systems detect energy.This information is passed to the nervous system due to the process of transduction and through sensory or afferent neurons, which are part of the peripheral nervous system.The information is received by brain structures (central nervous system) and perception occurs.Once the information has been interpreted, commands are sent out, telling the body how to respond (Step E), also via the peripheral nervous system.

Figure 2.1. Communication in the Nervous System


Please note that we will not cover this process in full, but just the parts relevant to our topic of psychopathology. The nervous system. The nervous system consists of two main parts – the central and peripheral nervous systems. The central nervous system (CNS) is the control center for the nervous system, which receives, processes, interprets, and stores incoming sensory information. It consists of the brain and spinal cord. The peripheral nervous system consists of everything outside the brain and spinal cord. It handles the CNS’s input and output and divides into the somatic and autonomic nervous systems. The somatic nervous system allows for voluntary movement by controlling the skeletal muscles and carries sensory information to the CNS. The autonomic nervous system regulates the functioning of blood vessels, glands, and internal organs such as the bladder, stomach, and heart. It consists of sympathetic and parasympathetic nervous systems. The sympathetic nervous system is involved when a person is intensely aroused. It provides the strength to fight back or to flee (fight-or-flight instinct). Eventually, the response brought about by the sympathetic nervous system must end. The parasympathetic nervous system calms the body.


Figure 2.2. The Structure of the Nervous System

* The neuron. The fundamental unit of the nervous system is the neuron, or nerve cell (See Figure 2.3). It has several structures in common with all cells in the body. The nucleus is the control center of the body and the soma is the cell body. In terms of distinctive structures, these focus on the ability of a neuron to send and receive information. The axon sends signals/information to neighboring neurons while the dendrites, which resemble little trees, receive information from neighboring neurons. Note the plural form of dendrite and the singular form of axon; there are many dendrites but only one axon. Also of importance to the neuron is the myelin sheath or the white, fatty covering which: 1) provides insulation so that signals from adjacent neurons do not affect one another and, 2) increases the speed at which signals are transmitted. The axon terminals are the end of the axon where the electrical impulse becomes a chemical message and passes to an adjacent neuron.

Though not neurons, glial cells play an important part in helping the nervous system to be the efficient machine that it is. Glial cells are support cells in the nervous system that serve five main functions:

They act as a glue and hold the neuron in place.They form the myelin sheath.They provide nourishment for the cell.They remove waste products.They protect the neuron from harmful substances.

Finally, nerves are a group of axons bundled together like wires in an electrical cable.


Figure 2.3. The Structure of the Neuron

* Neural transmission. Transducers or receptor cells in the major organs of our five sensory systems – vision (the eyes), hearing (the ears), smell (the nose), touch (the skin), and taste (the tongue) – convert the physical energy that they detect or sense, and send it to the brain via the neural impulse. How so? See Figure 2.4 below. We will cover this process in three parts.

Part 1. The Axon and Neural Impulse

The neural impulse follows the following steps:

Step 1 – Neurons waiting to fire are said to be in resting potential and polarized, or having a negative charge inside the neuron and a positive charge outside.Step 2 – If adequately stimulated, the neuron experiences an action potential and becomes depolarized. When this occurs, voltage-gated ion channels open, allowing positively charged sodium ions (Na+) to enter. This shifts the polarity to positive on the inside and negative outside. Note that ions are charged particles found both inside and outside the neuron.Step 3 – Once the action potential passes from one segment of the axon to the next, the previous segment begins to repolarize. This occurs because the Na channels close and potassium (K) channels open. K+ has a positive charge, so the neuron becomes negative again on the inside and positive on the outside.Step 4 – After the neuron fires, it will not fire again no matter how much stimulation it receives. This is called the absolute refractory period. Think of it as the neuron ABSOLUTELY will not fire, no matter what.Step 5 – After a short time, the neuron can fire again, but needs greater than normal levels of stimulation to do so. This is called the relative refractory period.Step 6 – Please note that this process is cyclical. We started at resting potential in Step 1 and end at resting potential in Step 6.

Part 2. The Action Potential

Let’s look at the electrical portion of the process in another way and add some detail.

Figure 2.4. The Action Potential


Recall that a neuron is usually at resting potential and polarized. The charge inside is -70mV at rest.If it receives sufficient stimulation, causing the polarity inside the neuron to rise from -70 mV to -55mV (threshold of excitation), the neuron will fire or send an electrical impulse down the length of the axon (the action potential or depolarization). It should be noted that it either hits -55mV and fires, or it does not fire at all. This is the all-or-nothing principle. The threshold must be reached.Once the electrical impulse has passed from one segment of the axon to the next, the neuron begins the process of resetting called repolarization.During repolarization the neuron will not fire no matter how much stimulation it receives. This is called the absolute refractory period.The neuron next moves into a relative refractory period, meaning it can fire but needs higher than normal levels of stimulation. Notice how the line has dropped below -70mV. Hence, to reach -55mV and fire, it will need more than the normal gain of +15mV (-70 to -55 mV).And then we return to resting potential, as you saw in Figure 2.4

Part 3. The Synapse

The electrical portion of the neural impulse is just the start. The actual code passes from one neuron to another in a chemical form called a neurotransmitter. The point where this occurs is called the synapse. The synapse consists of three parts – the axon of the sending neuron, the space in between called the synaptic space, gap, or cleft, and the dendrite of the receiving neuron. Once the electrical impulse reaches the end of the axon, called the axon terminal, it stimulates synaptic vesicles or neurotransmitter sacs to release the neurotransmitter. Neurotransmitters will only bind to their specific receptor sites, much like a key will only fit into the lock it was designed for. You might say neurotransmitters are part of a lock-and-key system. What happens to the neurotransmitters that do not bind to a receptor site? They might go through reuptake, which is the process of the presynaptic neuron taking up excess neurotransmitters in the synaptic space for future use or enzymatic degradation when enzymes destroy excess neurotransmitters in the synaptic space. Neurotransmitters. What exactly are some of the neurotransmitters which are so critical for neural transmission, and are essential to our discussion of psychopathology?

Dopamine – controls voluntary movements and is associated with the reward mechanism in the brainSerotonin – regulates pain, sleep cycle, and digestion; leads to a stable mood, so low levels leads to depressionEndorphins – involved in reducing pain and making the person calm and happyNorepinephrine – increases the heart rate and blood pressure and regulates moodGABA – blocks the signals of excitatory neurotransmitters responsible for anxiety and panicGlutamate – associated with learning and memory

The critical thing to understand here is that there is a belief in the realm of mental health that chemical imbalances are responsible for many mental disorders. Chief among these are neurotransmitter imbalances. For instance, people with Seasonal Affective Disorder (SAD) have difficulty regulating serotonin. More on this throughout the book as we discuss each disorder. The brain. The central nervous system consists of the brain and spinal cord; the former we will discuss briefly and in terms of key structures which include:

Medulla – regulates breathing, heart rate, and blood pressurePons – acts as a bridge connecting the cerebellum and medulla and helps to transfer messages between different parts of the brain and spinal cordReticular formation – responsible for alertness and attentionCerebellum – involved in our sense of balance and for coordinating the body’s muscles so that movement is smooth and precise. Involved in the learning of certain kinds of simple responses and acquired reflexes.Thalamus – the major sensory relay center for all senses except smellHypothalamus – involved in drives associated with the survival of both the individual and the species. It regulates temperature by triggering sweating or shivering and controls the complex operations of the autonomic nervous systemAmygdala – responsible for evaluating sensory information and quickly determining its emotional importanceHippocampus – our “gateway” to memory. Allows us to form spatial memories so that we can accurately navigate through our environment and helps us to form new memories about facts and eventsThe cerebrum has four distinct regions in each cerebral hemisphere. First, the frontal lobe contains the motor cortex, which issues orders to the muscles of the body that produce voluntary movement. The frontal lobe is also involved in emotion and in the ability to make plans, think creatively, and take initiative. The parietal lobe contains the somatosensory cortex and receives information about pressure, pain, touch, and temperature from sense receptors in the skin, muscles, joints, internal organs, and taste buds. The occipital lobe contains the visual cortex for receiving and processing visual information. Finally, the temporal lobe is involved in memory, perception, and emotion. It contains the auditory cortex which processes sound.

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Of course, this is not an exhaustive list of structures found in the brain but gives you a pretty good idea of function and which structure is responsible for it. What is important to mental health professionals is some disorders involve specific areas of the brain. For instance, Parkinson’s disease is a brain disorder that results in a gradual loss of muscle control and arises when cells in the substantia nigra, a long nucleus considered to be part of the basal ganglia, stop making dopamine. As these cells die, the brain fails to receive messages about when and how to move. In the case of depression, low levels of serotonin are responsible, at least partially. New evidence suggests “nerve cell connections, nerve cell growth, and the functioning of nerve circuits have a major impact on depression… and areas that play a significant role in depression are the amygdala, the thalamus, and the hippocampus.” Also, individuals with borderline personality disorder have been shown to have structural and functional changes in brain areas associated with impulse control and emotional regulation, while imaging studies reveal differences in the frontal cortex and subcortical structures for those suffering from OCD.