Glial Cells: The Support System of the Central Nervous System

The central nervous system is composed of two basic cell types: neurons and glial cells. Glial cells, also known as support cells, play a crucial role in maintaining the health and function of neurons. There are several types of glial cells, including macroglia (astrocytes and oligodendrocytes), ependymal cells, and microglia.

Astrocytes are the most abundant type of glial cell and have numerous functions, such as providing structural support, repairing nervous tissue, nourishing neurons, contributing to the blood-brain barrier, and regulating neurotransmission and blood flow. There are two main types of astrocytes: protoplasmic and fibrous.

Oligodendrocytes are responsible for the formation of myelin sheaths, which insulate and protect axons, allowing for faster and more efficient transmission of nerve impulses.

Ependymal cells line the ventricular system and are involved in the circulation of cerebrospinal fluid (CSF) and fluid homeostasis in the brain. Specialized ependymal cells called choroid plexus cells produce CSF.

Microglia are the immune cells of the CNS and play a crucial role in protecting the brain from infection and injury. They also contribute to the maintenance of neuronal health and function.

In summary, glial cells are essential for the proper functioning of the central nervous system. They provide structural support, nourishment, insulation, and immune defense to neurons, ensuring the health and well-being of the brain and spinal cord.

Kohlberg’s Six Stages of Moral Development

Kohlberg’s theory of moral development consists of six stages that can be categorized into three levels. The first level is the preconventional stage, which is characterized by obedience and punishment orientation, where the focus is on the direct consequences of actions and unquestioning deference to power. The second stage is the self-interest orientation, where right behavior is defined purely by what is in the individual’s own interest.

The second level is the conventional stage, which is characterized by interpersonal accord and conformity, where the focus is on how the individual will appear to others. The behavior should accord with a consensus view on what is good. The second stage is the authority and social order obedience driven, where what is lawful is judged to be morally right. Right behavior is dictated by societal rules, and there is a greater respect for social order and the need for laws.

The third level is the postconventional stage, which is characterized by the social contract orientation, where individual rights determine behavior. The individual views laws and rules as flexible tools for improving human purposes. The fourth stage is the universal ethical principles orientation, where the right action is the one that is consistent with abstract reasoning using universal ethical principles.

It is important to note that the age ranges for Kohlberg’s developmental stages are rough guides, and sources vary widely. Kohlberg developed his stage theory following an experiment he conducted on 72 boys aged 10-16. However, the theory is criticized as sexist as it only included boys.

While alpha (α) and beta (β) activity are typical in adults who are awake and at rest, delta activity (δ) may suggest the presence of a brain tumor. Mu (μ) activity is linked to movement, and theta activity (θ) is uncommon in the waking adult population, occurring briefly in only 15% of individuals.

Serotonin: Synthesis and Breakdown

Serotonin, also known as 5-Hydroxytryptamine (5-HT), is synthesized in the central nervous system (CNS) in the raphe nuclei located in the brainstem, as well as in the gastrointestinal (GI) tract in enterochromaffin cells. The amino acid L-tryptophan, obtained from the diet, is used to synthesize serotonin. L-tryptophan can cross the blood-brain barrier, but serotonin cannot.

The transformation of L-tryptophan into serotonin involves two steps. First, hydroxylation to 5-hydroxytryptophan is catalyzed by tryptophan hydroxylase. Second, decarboxylation of 5-hydroxytryptophan to serotonin (5-hydroxytryptamine) is catalyzed by L-aromatic amino acid decarboxylase.

Serotonin is taken up from the synapse by a monoamine transporter (SERT). Substances that block this transporter include MDMA, amphetamine, cocaine, TCAs, and SSRIs. Serotonin is broken down by monoamine oxidase (MAO) and then by aldehyde dehydrogenase to 5-Hydroxyindoleacetic acid (5-HIAA).

The synthesis of serotonin involves the conversion of tryptophan to 5-hydroxy-L-tryptophan (5-HTP) by tryptophan hydroxylase (TPH), followed by the conversion of 5-HTP to serotonin by pyridoxal phosphate and aromatic amino acid decarboxylase. Tryptophan, which is found in most protein-based foods, is the precursor for serotonin synthesis. While exogenous serotonin cannot cross the blood-brain barrier, tryptophan and 5-HTP can be taken as dietary supplements to increase serotonin levels.

Dopamine, on the other hand, is synthesized from phenylalanine and tyrosine. The major pathway involves the conversion of phenylalanine to tyrosine, then to L-Dopa, and finally to dopamine. Noradrenaline and adrenaline are derived from further metabolic modification of dopamine. Serine and alanine are other amino acids that are not directly involved in catecholamine synthesis.

Ethical theory and principles are important in medical ethics. There are three key ethical theories that have dominated medical ethics: utilitarianism, deontological, and virtue-based. Utilitarianism is based on the greatest good for the greatest number and is a consequentialist theory. Deontological ethics emphasize moral duties and rules, rather than consequences. Virtue ethics is based on the ethical characteristics of a person and is associated with the concept of a good, happy, flourishing life.

More recent frameworks have attempted to reconcile different theories and values. The ‘four principles’ of ‘principlism’ approach, developed in the United States, is based on four common, basic prima facie moral commitments: autonomy, beneficence, non-maleficence, and justice. Autonomy refers to a patient’s right to make their own decisions, beneficence refers to the expectation that a doctor will act in a way that will be helpful to the patient, non-maleficence refers to the fact that doctors should avoid harming their patients, and justice refers to the expectation that all people should be treated fairly and equally.

preconventional Stage of Moral Development

Kohlberg’s first stage of moral development is the preconventional stage. In this stage, children’s moral reasoning is based on avoiding punishment and seeking rewards. They follow rules to avoid getting in trouble and to gain approval from authority figures. Children in this stage are not yet able to understand the perspective of others of consider the consequences of their actions on others. They may also believe that what is right is what benefits them personally. As they grow and develop, children will move on to the next stages of moral development, which involve more complex reasoning and consideration of others’ perspectives.

Perseveration: The Clinical Symptoms in Chronic Schizophrenia and Organic Dementia

Perseveration is a common behavior observed in patients with organic brain involvement. It is characterized by the conscious continuation of an act of an idea. This behavior is frequently seen in patients with delirium, epilepsy, dementia, schizophrenia, and normal individuals under extreme fatigue of drug-induced states.

In chronic schizophrenia and organic dementia, perseveration is a prominent symptom. Patients with these conditions tend to repeat the same words, phrases, of actions over and over again, even when it is no longer appropriate of relevant to the situation. This behavior can be frustrating for caregivers and family members, and it can also interfere with the patient’s ability to communicate effectively.

In schizophrenia, perseveration is often associated with disorganized thinking and speech. Patients may jump from one topic to another without any logical connection, and they may repeat the same words of phrases in an attempt to express their thoughts. In organic dementia, perseveration is a sign of cognitive decline and memory impairment. Patients may repeat the same stories of questions, forgetting that they have already asked of answered them.

Overall, perseveration is a common symptom in patients with organic brain involvement, and it can have a significant impact on their daily functioning and quality of life. Understanding this behavior is essential for effective management and treatment of these conditions.

Managing Violent Behavior: Time Out vs Punishment vs Positive Reinforcement

When dealing with violent behavior, non-coercive methods such as time out are preferred. The goal is to help the patient calm down and learn to handle their anger of frustration in a non-violent manner. Time out involves the patient voluntarily removing themselves from the aggressive situation to a less stimulating environment. This technique is different from punishment, which is an aversive stimulus used to suppress an undesired response. Punishment reduces the likelihood of the response occurring again. Generalizing a learned behavior of stimulus generation is another method used to explain higher learning. This is related to classical conditioning and is not related to the time out technique. Positive reinforcement, such as praise, can be used to increase of learn new behaviors. For example, children may complete homework to earn a reward from a parent of teacher, of employees may finish projects to receive praise of promotions. Time out is not used to increase unwanted behavior of reduce desirable behavior.

Theories of aggression can be categorized into three main perspectives: psychodynamic, sociological/drive, and cognitive and learning. Psychodynamic theory, proposed by Freud, suggests that aggression arises from a primary instinct called thanatos, which aims for destruction and death. Sociobiological/drive theory, proposed by Lorenz, suggests that aggression is instinctual and necessary for survival, and that stronger genes are selected through aggression. Cognitive and learning theory, proposed by Berkowitz, Rotter, Bandura, and Anderson, suggests that aggression can be learned through observational learning and is influenced by environmental factors. Bandura’s work introduced the concept of reciprocal determinism, which suggests that behavior is influenced by both the environment and the individual’s behavior. Rotter’s social learning theory emphasizes the interaction between the individual and their environment, while Anderson and Bushman’s general aggression model considers the role of social, cognitive, developmental, and biological factors on aggression.

Genomic Imprinting and its Role in Psychiatric Disorders

Genomic imprinting is a phenomenon where a piece of DNA behaves differently depending on whether it is inherited from the mother of the father. This is because DNA sequences are marked of imprinted in the ovaries and testes, which affects their expression. In psychiatry, two classic examples of genomic imprinting disorders are Prader-Willi and Angelman syndrome.

Prader-Willi syndrome is caused by a deletion of chromosome 15q when inherited from the father. This disorder is characterized by hypotonia, short stature, polyphagia, obesity, small gonads, and mild mental retardation. On the other hand, Angelman syndrome, also known as Happy Puppet syndrome, is caused by a deletion of 15q when inherited from the mother. This disorder is characterized by an unusually happy demeanor, developmental delay, seizures, sleep disturbance, and jerky hand movements.

Overall, genomic imprinting plays a crucial role in the development of psychiatric disorders. Understanding the mechanisms behind genomic imprinting can help in the diagnosis and treatment of these disorders.

Side effects of sildenafil (viagra) that occur frequently (affecting more than 1 in 10 people) include:

Antidepressants can cause sexual dysfunction as a side-effect, although the rates vary. The impact on sexual desire, arousal, and orgasm can differ depending on the type of antidepressant. It is important to rule out other causes and consider non-pharmacological strategies such as reducing the dosage of taking drug holidays. If necessary, switching to a lower risk antidepressant of using pharmacological options such as phosphodiesterase inhibitors of mirtazapine augmentation can be considered. The Maudsley Guidelines 14th Edition provides a helpful table outlining the risk of sexual dysfunction for different antidepressants.

Selective attention involves filtering external stimuli and assigning meaning to things that should get our attention. Three main models have been proposed: Broadbent’s Filter model, Treisman’s Attenuation Theory, and Deutsch and Deutsch’s Late stage model. Broadbent’s model is an early selection model that filters input based on physical characteristics, while Treisman’s model is an intermediate selection model that uses a leaky filter to weaken some stimuli but allow them through. Deutsch and Deutsch’s model is a late selection model that analyzes input for meaning before filtering occurs. Treisman’s model includes a dictionary unit that emphasizes certain words have lower thresholds for getting our attention, such as our own name.

Studies have consistently shown that migrant populations have higher rates of schizophrenia, particularly among certain minority ethnic groups. The NICE guidelines on schizophrenia (CG178) have highlighted the importance of investigating social and environmental factors that may increase the risk of developing the illness, such as urban birth and rearing, social adversity and trauma, heavy cannabis use, migration, and stressful life events. Schizophrenia is the most common form of psychotic disorder, with a mean incidence of 0.11 per 1000 (range 0.07-0.17 per 1000) reported in epidemiological studies. The average rates for men and women are similar, but the age of onset is typically 5 years later in women, resulting in a lower female rate during adolescence and a second smaller peak after menopause. The lifetime prevalence of schizophrenia ranges from 0.4 to 1.4%, and a UK survey found a population prevalence of probable psychotic disorder of 5 per 1000 in the age group of 16 to 74 years.

Acute stress disorder is a brief yet intense condition triggered by a highly distressing event that can cause a range of symptoms. Although the symptoms can appear quickly, they typically subside within a few days. These symptoms may include psychological effects like feeling disconnected of confused, as well as physical symptoms such as sweating, trembling, heart palpitations, and difficulty sleeping. In some cases, individuals may progress to develop post-traumatic stress disorder.

Projective identification is a multifaceted mechanism that involves elements of transference, countertransference, and projection. It occurs when a patient’s mistaken belief leads them to behave in a manner that causes the other person in the interaction to adopt the attitudes that the patient wrongly attributed to them.

For instance, a person at an airport who is overly anxious about being perceived as a terrorist may draw the attention of security guards. In a similar vein, a patient’s assumption that a doctor holds them in contempt may prompt them to act in a manner that elicits disrespectful feelings from the doctor.

The blood retinal barrier refers to the membrane that separates the aqueous humour from the blood.

Understanding the Blood Brain Barrier

The blood brain barrier (BBB) is a crucial component of the brain’s defense system against harmful chemicals and ion imbalances. It is a semi-permeable membrane formed by tight junctions of endothelial cells in the brain’s capillaries, which separates the blood from the cerebrospinal fluid. However, certain areas of the BBB, known as circumventricular organs, are fenestrated to allow neurosecretory products to enter the blood.

When it comes to MRCPsych questions, the focus is on the following aspects of the BBB: the tight junctions between endothelial cells, the ease with which lipid-soluble molecules pass through compared to water-soluble ones, the difficulty large and highly charged molecules face in passing through, the increased permeability of the BBB during inflammation, and the theoretical ability of nasally administered drugs to bypass the BBB.

It is important to remember the specific circumventricular organs where the BBB is fenestrated, including the posterior pituitary and the area postrema. Understanding the BBB’s function and characteristics is essential for medical professionals to diagnose and treat neurological disorders effectively.

FGM is against the law in the UK, and arranging for a child to undergo the procedure abroad is also illegal. Those who are caught can face a prison sentence of up to 14 years and a hefty fine. Shockingly, it is estimated that 66,000 women in the UK have already undergone FGM, and over 20,000 girls under the age of 15 are at risk. Often, children are taken to have the procedure during the summer holidays so that they have time to heal before returning to school. There are four main types of FGM, including clitoridectomy, excision, infibulation, and other harmful procedures such as pricking, piercing, cutting, scraping, and burning the genital area. FGM is carried out for cultural, religious, and social reasons and is most prevalent in Africa, although it also occurs in Asia and the Middle East. The experience can be extremely traumatic, and those who have undergone FGM may require counseling in the future. Recently, medical professionals have faced criminal prosecution for allegedly performing the procedure, which is illegal in the UK.

Patients may feel that they have lost control over their thoughts, which can manifest as passivity of thought. This refers to the belief that an external agency is controlling one’s thoughts. Passivity can take different forms, such as thought withdrawal, thought insertion, and thought broadcasting.

Ego (Boundary) Disturbances

Ego (boundary) disturbances refer to experiences where there is a disturbance in the perception of self as distinct from the environment of the integrity of self. It also includes instances where bodily processes, personal thought processes, feelings, and actions are experienced as being externally directed. These phenomena are referred to as passivity phenomena, and some of the symptom characteristics are classified as bizarre delusional phenomena in the DSM.

Derealization is when a patient experiences their surroundings of time as if they are unreal and changed, losing all feelings of familiarity and trust in the environment. People, objects, and surroundings appear unreal, unfamiliar, of spatially altered. The sensations may be intense of weak in nature.

Depersonalization is when a patient perceives themselves as alien, unreal, changed, of as a stranger. The disturbances of depersonalization may be of a transient nature only of become more persistent over a longer period of time. It is generally felt to be both strange and unpleasant.

Thought broadcasting is when a patient’s personal thoughts are experienced as no longer belonging to the patient alone but accessible by others who will know what the patient is thinking (mind reading). Thought withdrawal is when a patient’s thoughts are being removed of stripped from them. Thought insertion is when patients experience their thoughts and ideas as being externally influenced, made externally, controlled, directed, entered/ of externally imposed.

Other feelings of alien influence refer to feelings, intentions, behavior, of bodily functions that are experienced as externally controlled of made by others (passivity phenomena). The patient feels externally compelled to say something specific, to scream, to act of behave in a particular way, to attack someone, to throw a tantrum, etc.

Visual Agnosia: Inability to Recognize Familiar Objects

Visual agnosia is a neurological condition that affects a person’s ability to recognize familiar objects, even though their sensory apparatus is functioning normally. This disorder can be further classified into different subtypes, with two of the most important being prosopagnosia and simultanagnosia.

Prosopagnosia is the inability to identify faces, which can make it difficult for individuals to recognize family members, friends, of even themselves in a mirror. Simultanagnosia, on the other hand, is the inability to recognize a whole image, even though individual details may be recognized. This can make it challenging for individuals to understand complex scenes of navigate their environment.

Visual agnosia can be caused by various factors, including brain damage from injury of disease. Treatment options for this condition are limited, but some individuals may benefit from visual aids of cognitive therapy to improve their ability to recognize objects.

The patient’s clinical presentation suggests a possible diagnosis of schizophrenia, but there is evidence of an organic cause that may be influencing his experiences. According to the hierarchical approach to diagnosis in both ICD-10 and DSM-5, diagnoses lower in the hierarchy are trumped by those above. Therefore, it may be appropriate to revise the diagnosis of schizophrenia to a provisional diagnosis of substance-related psychosis until a period of assessment in the absence of substance use.

Psychiatric diagnoses can be classified using different approaches. Categorical classification is based on symptomatology of phenomenology, while dimensional classification recognizes that some diagnoses lie on a continuum with normality. Dual diagnostic classification involves the recognition of two diagnoses, such as major depressive disorder with comorbid alcohol use disorder, and requires the presence of depressive episodes in the absence of alcohol use. Multi-axial diagnostic classification involves representing a diagnosis on a series of axes, although this approach has been dropped from DSM-5.

In 1951, Charpentier in France synthesised Chlorpromazine with the aim of creating a centrally acting antihistamine to assist with general anaesthesia. Later, studies conducted by Delay and Deniker provided evidence for its effectiveness in treating schizophrenia.

A Historical Note on the Development of Zimelidine, the First Selective Serotonin Reuptake Inhibitor

In 1960s, evidence began to emerge suggesting a significant role of serotonin in depression. This led to the development of zimelidine, the first selective serotonin reuptake inhibitor (SSRI). Zimelidine was derived from pheniramine and was marketed in Europe in 1982. However, it was removed from the market in 1983 due to severe side effects such as hypersensitivity reactions and Guillain-Barre syndrome.

Despite its short-lived availability, zimelidine paved the way for the development of other SSRIs such as fluoxetine, which was approved by the FDA in 1987 and launched in the US market in 1988 under the trade name Prozac. The development of SSRIs revolutionized the treatment of depression and other mood disorders, providing a safer and more effective alternative to earlier antidepressants such as the tricyclics and MAO inhibitors.

Verbal fluency can be demonstrated by listing as many animals as possible within a minute using a specific letter.

The mental state exam assesses various areas of cognition, including orientation, attention/concentration, short term memory, long term memory, and executive function. Standard tests for each area include asking about time, place, and person for orientation, serial 7’s for attention/concentration, digit span for short term memory, delayed recall of name and address for long term memory, and various tasks such as proverbs, similarities, differences, verbal fluency, and cognitive estimates for executive function.

During REM sleep, the EEG patterns resemble those observed during wakefulness, characterized by numerous beta-rhythms that are fast.

Sleep Stages

Sleep is divided into two distinct states called rapid eye movement (REM) and non-rapid eye movement (NREM). NREM is subdivided into four stages.

Sleep stage
Approx % of time spent in stage
EEG findings
Comment

I
5%
Theta waves (4-7 Hz)
The dozing off stage. Characterized by hypnic jerks: spontaneous myoclonic contractions associated with a sensation of twitching of falling.

II
45%
Theta waves, K complexes and sleep spindles (short bursts of 12-14 Hz activity)
Body enters a more subdued state including a drop in temperature, relaxed muscles, and slowed breathing and heart rate. At the same time, brain waves show a new pattern and eye movement stops.

III
15%
Delta waves (0-4 Hz)
Deepest stage of sleep (high waking threshold). The length of stage 3 decreases over the course of the night.

IV
15%
Mixed, predominantly beta
High dream activity.

The percentage of REM sleep decreases with age.

It takes the average person 15-20 minutes to fall asleep, this is called sleep latency (characterised by the onset of stage I sleep). Once asleep one descends through stages I-II and then III-IV (deep stages). After about 90 minutes of sleep one enters REM. The rest of the sleep comprises of cycles through the stages. As the sleep progresses the periods of REM become greater and the periods of NREM become less. During an average night’s sleep one spends 25% of the sleep in REM and 75% in NREM.

REM sleep has certain characteristics that separate it from NREM

Characteristics of REM sleep

– Autonomic instability (variability in heart rate, respiratory rate, and BP)
– Loss of muscle tone
– Dreaming
– Rapid eye movements
– Penile erection

Deafness:

(No information provided on deafness in relation to sleep stages)

Hyponatremia is commonly linked to the use of SSRIs (antidepressants) and typical antipsychotics.

Hyponatremia in Psychiatric Patients

Hyponatremia, of low serum sodium, can occur in psychiatric patients due to the disorder itself, its treatment, of other medical conditions. Symptoms include nausea, confusion, seizures, and muscular cramps. Drug-induced hyponatremia is known as the syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH), which results from excessive secretion of ADH and fluid overload. Diagnosis is based on clinically euvolemic state with low serum sodium and osmolality, raised urine sodium and osmolality. SSRIs, SNRIs, and tricyclics are the most common drugs that can cause SIADH. Risk factors for SIADH include starting a new drug, and treatment usually involves fluid restriction and sometimes demeclocycline.

ADHD medications can be classified into stimulant and non-stimulant drugs. The therapeutic effects of these drugs are believed to be mediated through the action of noradrenaline in the prefrontal cortex. Common side effects of these drugs include decreased appetite, insomnia, nervousness, headache, and nausea. Stimulant drugs like dexamphetamine, methylphenidate, and lisdexamfetamine inhibit the reuptake of dopamine and noradrenaline. Non-stimulant drugs like atomoxetine, guanfacine, and clonidine work by increasing noradrenaline levels in the synaptic cleft through different mechanisms. The most common side effects of these drugs are decreased appetite, somnolence, headache, and abdominal pain.

Tricyclic antidepressants are known to cause various side effects, which can be attributed to their mechanisms of action. These include antimuscarinic effects, which can lead to dry mouth and urinary retention, antihistaminergic effects, which can cause weight gain and drowsiness, antiadrenergic effects, which can result in postural hypotension, sexual dysfunction, and cognitive impairment, and antiserotonergic effects, which can lead to weight gain. Additionally, tricyclic antidepressants can cause cardiotoxicity and reduce the seizure threshold due to their membrane stabilizing effects. Other important side effects of these drugs include arrhythmias and ECG changes, black tongue, tremor, altered liver function tests, paralytic ileus, and neuroleptic malignant syndrome. Black hairy tongue, a harmless condition where the tongue appears black and hairy due to elongated filiform papillae, is also a possible side effect of tricyclic antidepressants.

The two main ethical approaches in philosophy are teleological ethics, which focuses on the end result, and deontological ethics, which focuses on an individual’s actions being morally right regardless of the end result. In medicine, deontology is patient-centered, while utilitarianism is society-centered. Deontological ethics judges the moral status of actions according to rules of principles, such as the duty not to harm the patient versus the duty to help them. Kantian ethics is a strict form of deontological ethics that emphasizes behaving as though one’s behavior is creating a universal ethical rule. Utilitarianism is a teleological approach that prioritizes the action that leads to the greatest happiness of the greatest number, regardless of how it is brought about. In medicine, autonomy is one of four ethical principles, along with beneficence, non-maleficence, and justice, that enable patients to choose their own treatment and ensure fairness and equality.

Brain Structures and Their Etymologies

The hippocampus, with its swirling shape, was named after the seahorse, combining the Greek words ‘hippos’ (horse) and ‘kampos’ (sea-monster). Meanwhile, the cerebellum, which resembles a smaller version of the brain, was named after the Latin word for ‘little brain’. The corpus callosum, a bundle of nerve fibers connecting the two hemispheres of the brain, was named after the Latin for ‘tough body’. The hypothalamus, located below the thalamus, was named after its position. Finally, the putamen, a structure involved in movement control, comes from the Latin word for ‘that which falls off in pruning’. These etymologies provide insight into the history and development of our understanding of the brain’s structures.

Mitmachen involves manipulating a patient’s body into a specific posture, even if they resist. Mitgehen is a more severe form of mitmachen, where even slight pressure can cause the patient to move in any direction, similar to an anglepoise effect. Hypnagogic hallucinations are a common occurrence when falling asleep, while chorea is characterized by sudden and jerky movements that resemble purposeful actions. Echopraxia refers to the imitation of another person’s movements.