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Section 2: Introductory Overview of Physical Systems

The subject matter involved in this training will necessarily require that the trainee have some knowledge of certain of the physical mechanisms in the brain that are responsible for mental and emotional symptomatology. This course will therefore need to present at least some rudimentary information concerning relevant physiological and neuro-chemical components of healthy and unhealthy emotional and mental functioning.

It is not necessary for the mental health clinician to have the same degree of information in this area as a neurosurgeon or neurologist. However, head injuries and trauma, medical disorders of the brain, and medication effects are very common occurrences. It is likely that every mental health clinician will be presented with a least a handful of cases where knowledge of this subject matter is relevant to the accurate assessment of these problems. Some knowledge of brain anatomy, therefore, is a part of the core foundation knowledge each mental health clinician should have.

We will attempt to strike the right balance by presenting key information that should be known by all clinicians - while not attempting to cover what a pharmacist, neurologist or physician would need to know in order to practice in their field.

Brief Physiology and Anatomy of the Brain

A brief description of brain functioning and structure will be helpful in understanding the dynamic interaction of the many factors that may affect mood and may present clinically as depression and/or anxiety. By understanding the physical/mental factors, drugs and medications, as well as the co-morbid states of medical and mental illnesses, one can assess more accurately, and direct the client/patient to appropriate resources for healing.

A Brief Overview of Brain Physiology

Brain cells (neurons) communicate with each other through the action of neurotransmitters that are manufactured in these cells and released into a small space between cells. (10) This much should clearly be known by mental health clinicians. There is an extensive communication system between brain cells along what are known as neurotransmitter pathways.

Neurotransmitter pathways are essential to a healthy brain. They affect everything from moods to sleeping patterns to our ability to put thought into action. Although there are many chemicals that serve as neurotransmitters, there are four main chemicals related to mood change. Three of these should be familiar to most clinicians, while one is less likely to be known. They are dopamine, serotonin, norepinephrine and gamma aminobutyric acid (GABA). (10)

As you review these neurotransmitters, it will be helpful to note what areas of the brain are significant to which neurotransmitter and what behaviors they affect or control. This will help to understand the impact on brain cells and tissue due to disease or damage.

- Dopamine - whose pathway is concentrated in the front of the brain - is involved in regulating awareness of the environment and other higher information processing tasks. Abnormal dopamine functioning may lead to difficulties in relating to others, social isolation and distorted perceptions of the world.

- Serotonin is widespread throughout the brain, with its pathways covering all major areas of the brain. It is important in regulating mood and aggressive, impulsive and suicidal behaviors. Abnormal serotonin levels appear to be related to a diminished ability to control one’s impulses, to depressed moods and to heightened risk of suicide.

- Norepinephrine pathways travel to many areas of the brain, including the cerebral cortex and spinal cord. This is the chemical transmitter for the autonomic nervous system. (10) Norepinephrine is considered to be a chemical that is excitatory. In other words, it is associated with enhancing the responsiveness of nerve cells and plays a major role in creating and maintaining mood states. Low levels are associated with depression while excessive amounts may play a role in mania and anxiety. (24)

- Gamma aminobutyric acid (GABA) is an amino acid whose function is to be an inhibitor - blocking impulses from one cell to another. It functions in the central nervous system to prevent the excessive firing of neurons. Its effect in brain metabolism is calming, and it helps to block anxiety and stress related impulses. A shortage is likely linked with panic attacks, since the intake of tranquilizers increases the body’s GABA levels. (23)

For the sake of this training, the Central Nervous System (CNS), the brain, brainstem, and spinal cord will be the primary focus. However, to better understand the medical and mental implications of illness, one important part of the Peripheral Nervous System (PNS) will also be explored.

The PNS is part of the nervous system expressing away from the brain center and traveling throughout the body. It is critical in connecting the CNS with muscles, organs and other body systems. The part we will be examining is the Autonomic Nervous System.

The Autonomic Nervous System (ANS) is important in the understanding of physical illnesses in relation to the brain. It is closely associated with the spinal cord, but does not lie entirely within its column.

The ANS is responsible for moving sensory and conduct information from the brain to muscles and organs, and for linking communications from these locations back to the brain. It is involved in the body’s response to real or perceived emergencies, through the body's “fight or flight” reaction, as well as in the peripheral actions of many medications. (24)

This system is further divided into the sympathetic and parasympathetic nervous systems. The sympathetic system is responsible for the release of adrenaline - also called epinephrine - in the face of a threatening situation in order to create additional sources of energy for fighting or running.

The parasympathetic system serves as a regulator to reverse the effects of stress on the individual through the release of norepinephrine. (27)

The actions of this system are believed to operate independent of conscious thought, hence the name autonomic or automatic. (However, given the fact that thoughts produce chemical reactions and that these, in turn, create cellular responses, it is difficult to consider any of the body’s systems as purely automatic.)

Below are some peripheral organ responses to the Autonomic Nervous System. These physical body reactions are dependent on the activation of sympathetic (S) or parasympathetic (P) responses respectively:

- EYE –dilates (S) or iris constricts (P), ciliary muscle relaxes (S) or accommodates to near vision (P)
- HEART – heart rate increases (S) or decreases (P), chambers have more (S) or less (P) contractility or conduction velocity
- BLOOD VESSELS – constrict (S) or dilate (P)
- LUNGS – bronchial muscles relax (S) or constrict (P), bronchial glands secrete
- GASTROINTESTINAL TRACT – relaxed (S) or increased (P) motility and tone, sphincters contract (S) or relax (P), secretion is stimulated
- URINARY BLADDER – muscle relaxation (S) or contraction (P), sphincter contraction (S) or relaxation (P)
- SKIN – pilomotor muscles contract (S) (goose bumps), increased gland secretion (S)
- GLANDS – salivary and sweat glands increase secretion with parasympathetic stimulation (24)

A Brief Overview of Selected Brain Anatomy

As noted, the Central Nervous System is made up of the brain, brain stem and spinal cord. Because the most frequent physical contributors to depression, anxiety and other mental health problems will be head injuries / trauma, and chemical effects on the CNS due to a variety of medical ailments, it will be helpful to the understanding of this training to do a very brief review of the anatomy of this system.

Each part of the CNS has a vital role in the healthy functioning of the whole human system. Physical or chemical damage – through trauma or illness - to any area can produce symptoms of mental illness. Certain medications affecting these areas can produce consequences as well.

A thorough assessment for problems related to CNS functioning should particularly look for any history of prior physical trauma, toxic chemical ingestion (including medication or vitamin overdosing), and viral or bacterial diseases that have crossed into the brain, especially viral or bacterial encephalitis or meningitis.


CEREBRUM – This is the largest part of the human brain and fills the entire upper portion of the skull. The cerebral cortex is the outer surface and accounts for 80% of the brain itself. The cerebrum is divided into two halves called hemispheres. Each hemisphere, right and left, has functions that it controls.

Right hemisphere: input into reception of nonverbal communication, spatial orientation, recognition, speech intonation and aspects of music, facial recognition and expression of emotion and nonverbal learning and memory

Head injury or trauma to the right hemisphere will more likely show up in deterioration in these mental faculties. If there are clear indicators of demonstrable losses in these abilities in conjunction with depression, anxiety or other mental health difficulties, it will be important to do a thorough check of the patient's history of head injury or trauma. It may also be important to consider the possibility of a tumor or a stroke. In either instance, a referral to a neurologist may be indicated.

Left hemisphere: verbal language functioning, both receptive and expressive speech control, time order and sequencing, numeric symbols, verbal learning and memory (24)

Head injury or trauma to the left hemisphere will present with slightly different symptoms than damage to the right hemisphere. Demonstrable changes in the ability to speak, or in the ability to transfer short-term memory to medium and long-term memory are key indicators that suggest trauma or damage from stroke, or possibly a tumor on the left hemisphere. Again, should there be such indicators in conjunction with anxiety, depression or other mental health problems, a referral to a neurologist is indicated.

Because the left hemisphere controls motor functioning on the right side of the body, and the right hemisphere controls motor functioning on the left side of the body, it is also important to note if there has been any recent change in the ability of the client in terms of equal functioning of both sides of the body. A demonstrable weakness in one side or the other is often a clear indicator that something has occurred in the physical functioning of the brain.

The two halves of the brain are connected by a bridge of nerve tissue known as the corpus collosum. Although each half has it own function, it is necessary for there to be quick communication of information between the two hemispheres for the system to respond in a smooth and coordinated manner. (24)

Trauma, illness or injury affecting this area of the brain will have fairly profound consequences, and these consequences should be readily visible. Multiple sclerosis - an illness with serious consequences for mental health functioning - often attacks the corpus callosum, stripping away the myelin sheath that allows for rapid communication between the two hemispheres of the brain. (20)

Damage to the front part of the corpus callosum can produce impaired judgment and memory problems. Damage to the rear part of the corpus callosum results in noticeable and sometimes profound changes in behavior.

Because multiple sclerosis has a number of physical manifestations from damage to other areas of the brain, it is more likely to be diagnosed by a physician. However, the mental health clinician should be aware that early psychological symptoms of multiple sclerosis may also lead the client to seek counseling help, and this must be considered when assessment is being undertaken. One of these symptoms, however, can be a sense of euphoria, which may lead the client to underestimate the impact of the disease. (45)

LOBES OF THE BRAIN – Each hemisphere is further divided into four lobes, each of which has its specific functions while maintaining coordination with each other.

Frontal Lobes –Right and Left: These lobes represent about a quarter of the cerebral cortex. They are responsible for the highest and most complex aspects of cortical functioning which include the motor function of speech, working memory, the ability to plan and initiate activity, insight, judgment, reasoning, concept formation, problem-solving, abstraction and self-evaluation. (24)

These high level skills are also known as executive functions. When this area of the brain is damaged, these executive functions - designed to prevent primitive impulsive behaviors - are impaired. The individual may not be able to control or modulate responses to impulses. There may be changes in mood and personality such as a lack of spontaneity or drive, and emergence of impulsive, inappropriate and often violent behavior.

Damage to this area of the brain can come from a number of sources. Many mind altering substances with neurotoxic effects – such as methamphetamine and PCP – target this area of the brain. Damage to the frontal lobes – and the pre-frontal cortex – can take months or even years to heal following periods of heavy drug use.

The behavioral problems, therefore, can be evident even if the client denies current drug use. For this reason, a thorough assessment will always include a history of prior substance use. Where behavioral problems are part of the diagnostic picture, this assessment should specifically address prior use of methamphetamine, cocaine, PCP, alcohol, as well as inhalants and certain of the club drugs, including Ketamine.

Parietal Lobes: These lobes consist of the area top middle behind the central sulcus, the shallow groove from left to right dividing the brain front to rear. This is the primary area for perceiving and discriminating visual and somatosensory (other bodily senses, like touch and taste) input. These lobes support the ability to recognize objects by touch, calculate, write, draw, and organize spatial directions - such as finding one's way around familiar places. (24)

Damage to these lobes leads to problems in discriminating sensory input, difficulty with spatial relationships and inability to detect stimuli from the opposite sides of the body. Sudden changes in any of these abilities should be indicators of the need for thorough assessment and possible referral to a neurologist.

Temporal Lobes: These are on each side of and below the cerebral cortex. These lobes contain areas of olfactory (smell) and auditory (hearing) functioning. It is the area of the brain where integration occurs for combining the sensory and visual information involved in written and verbal language skills. Memory as well as modulation of mood and emotion are influenced by these lobes. (24)

Damage in these areas will result in difficulties with verbal and written communication, and will also cause disruptions in the sense of smell and hearing. A tumor in this part of the brain may be responsible for the development of distortions in smell and hearing that may be difficult to discriminate from the beginning of a psychosis.

It is always important to ask a client who presents with problems in these areas whether he or she has a recent history of headaches. Tumors will not always produce headaches, particularly early in their development. However, the development of frequent or persistent headaches in conjunction with noticeable changes in mood, behavior, or affect should always trigger some concern about whether the client may have a tumor.

Occipital Lobes: Lying in the most posterior portion of the brain, this area is responsible for vision. It is here that the visual integration of information takes place. These lobes allow the individual to perceive moving objects and color and to recognize objects and faces. (24)

Damage here leads to what is called cortical blindness: the optic nerve is intact, but the person cannot see. Loss of any portion of vision should always be a clue to advocate for further medical assessment.

Statistic: A McGill University study found that more than 60 percent of college level soccer players reported symptoms of a concussion in the course of a soccer season.

Source: Neurosurgery Today


Beneath the cortex are structures essential to regulation of emotions and behavior. Several of them will be described in this training. They are the Hypothalamus, Thalamus, Hippocampus, Amygdala, and Limbic System.

The Hypothalamus is a gland that appears to be the master regulator of the autonomic nervous system. It controls body temperature, blood pressure, water levels, sex, appetite/food intake and hormone levels. It is part of the pleasure and pain system.

Depending on which part of the hypothalamus is stimulated, rage or pleasure reactions will be generated. It functions as the central control for the limbic system and is the liaison between the limbic system and the cerebral cortex. (25)

Any serious damage to the hypothalamus is usually fatal, since the normal homeostasis of the body is thrown out of regulation, and body temperature, blood chemistry, and other homeostatic functions are no longer mediated in a way that allows the body to survive.

Less serious damage to the hypothalamus, however, can show up as homeostatic problems, such as problems regulating body temperature, or problems with appetite and food intake -since an individual with damage in certain areas of the hypothalamus may refuse food and water.

On the other side of the continuum, are problems associated with Prada-Willi syndrome. This is a non-hereditary genetic disorder in which, among other things, the hypothalamus does not function properly. Due to this damage, patients with Prada-Willi are unable to experience a sensation of being sated when they eat. This dysfunction leads to problems with severe overeating and a high mortality rate. (35)

For clients who may not seem to fit the typical profile for anorexia, it may be useful to consider the possibility of hypothalamus problems if under-eating is a problem. Sudden problems with severe over-eating may also indicate problems in this area. Other hypothalamus problems can result in sleep difficulties that can resemble narcolepsy.

The Thalamus is centrally located and surrounded by cortical tissue. It is the relay station of the brain where information from all of the senses, except smell, is routed from the body to the CNS, mainly the cerebral cortex. It acts as a filter for incoming information, determining what to pass on to the areas of higher thinking and processing. This filtering helps to keep the brain from being overloaded with sensory stimulus. (24)

Damage to the left side of the thalamus can lead to speech and language problems, including decreases in verbal fluency, and memory and learning difficulties. Damage to the right side of the thalamus can cause problems with cognitive skills in pattern recognition, which may cause problems with directions and facial recognition.

Damage to both sides of the thalamus can lead to severe apathy. Thalamic damage will also create problems with overall intellectual abilities, severe memory loss, and selective mutism.

This constellation of symptoms may closely resemble problems seen with major depression. Hopefully, most mental health clinicians would make a psychiatric referral when such a profound set of symptoms appear. The psychiatrist will usually, although not inevitably, consider the possibility of thalamic damage when presented with this set of problems.

The Hippocampus lies tucked in the temporal lobes of the cerebrum. It appears to be responsible for adjusting moods and emotions to incoming environmental information and plays a critical role in memory formation. (28)

Damage to the hippocampus appears to result in serious problems with new memory formation, and also appears to affect the ability to access old memories. Because more serious depression will often interfere with memory formation and retrieval, it may be difficult to distinguish hippocampal damage from memory problems associated with the neurochemistry of depression. When in doubt, refer the client to a psychiatrist to look for the finer features that may help with this kind of differential diagnosis.

The Amygdala is one of the main nuclei of the limbic system. It is involved with associative memory, long-term memory and retrieval. It is part of the system involved in the production of sensations of pleasure and pain, with the pain component being more significant.

Aggression, rage and fear reactions are produced when the amygdala is stimulated The amygdala is involved in the experience of post-traumatic stress disorder and plays a role in regulating the changes in heart rate as a result of emotional stimulation. (28)

The amygdala also appears to have some role in interpreting the emotional states of others, since damage to the amygdala in childhood seems to be associated with autism, and damage in adults results in alterations in social behavior and in lessened understanding of complex social situations, as well as reduced social memory.

If there are radical changes in social behavior or in the understanding of social situations, the clinician may be inclined to look for the presence of a psychosis or schizophrenia, and less inclined to think of the possibility of damage to this area of the brain through trauma or tumor. In such cases, a referral to psychiatric care will be indicated, but it may also be wise to discuss with the patient the need to address the possibility of a physical problem with the psychiatrist to whom the patient is referred.

The Limbic System is part of the middle brain believed to be involved with the emotions, body temperature and sex as well as with memory storage and retrieval. This area of the brain is sometimes referred to as the “emotional brain” since its integrity is essential for emotional well-being.

This area of the brain is actually an interrelated group of structures that work together in the regulation of emotions and their accompanying behavior, as well as physiological and psychological responses. (28) The hypothalamus, hippocampus and amygdala are all part of this larger integrated structure, as well as some other structures in the center of the brain near these main three components of the limbic system.

Damage to the limbic system from a larger structural perspective can result in any number of difficulties in managing emotions, responding appropriately to sensations of pleasure and pain, and learning from rewards and consequences tied to life experiences. This constellation of problems may appear in a variety of forms that mimic psychological problems, appearing at first glance to present as depression, attention deficit disorder, or even psychopathic disorders.

Differential diagnosis would need to take into consideration the patient's life history, family history and other factors that would offer other plausible explanations for the symptoms. A relatively sudden onset of this symptoms, when those symptoms are very different from the whole arc of a client's life, would be a trigger to consider the possibility of physical or medical explanations for the problems.


The Brain Stem is located beneath the thalamus. It is comprised of the midbrain, pons and medulla. The brain stem structures are composed of numerous pathways to the cerebral cortex and have important life sustaining functions, such as breathing, heart function, etc.. It is possible that they have a significant effect in mediating emotional dysfunction - since this area is a primary source of neuro-chemicals such as serotonin. (24)

Because the brain stem is so important as the regulator of body functions, damage to the brain stem is usually results in very serious and unmistakably physical problems, such as paralysis or loss of sensation.


The Spinal Cord runs inside the vertebrae from the base of the skull to the tail bone. As noted previously, the Autonomic Nervous System is closely associated with the nerves of the Spinal Cord. Up and down the spine are nerves that constrict or dilate, contract or relax vital organs of the body. These in turn send messages up the Spinal Cord, through the Thalamus to centers of the Brain that are important in the determination of mood and emotion.

With this understanding of basic anatomy and physiology, we will explore a variety of conditions in which physical illness or trauma may present itself as depression/anxiety.