Neurobiology and Genetics of Mental Disorders Practice Questions

Q: What are the most important receptors implicated in schizophrenia?

D2. **Explanation:** The neurobiology of schizophrenia is primarily explained by the **Dopamine Hypothesis**, which posits that symptoms arise from dysregulated dopaminergic activity. Specifically, the **Dopamine D2 receptor** is the most critical target because: 1. **Hyperdopaminergia** in the mesolimbic pathway (excess D2 stimulation) is associated with **positive symptoms** (hallucinations, delusions). 2. All currently available antipsychotics (both typical and atypical) share the common property of being **D2 receptor antagonists**. The clinical potency of typical antipsychotics (e.g., Haloperidol) is directly proportional to their D2 receptor binding affinity. **Analysis of Incorrect Options:** * **GABAA & GABAB (Options A & B):** While GABAergic dysfunction (inhibitory deficits) is observed in schizophrenia research, these receptors are not the primary targets for treatment. GABA receptors are more centrally involved in the mechanism of benzodiazepines and the pathophysiology of anxiety and seizure disorders. * **5-HT1 (Option D):** While serotonin (5-HT) plays a role in schizophrenia (especially **5-HT2A** antagonism in atypical antipsychotics like Clozapine), 5-HT1 is not the primary receptor implicated in the core disease process or the standard mechanism of antipsychotic efficacy. **NEET-PG Clinical Pearls:** * **Mesolimbic Pathway:** Increased D2 activity → Positive symptoms. * **Mesocortical Pathway:** Decreased D1/D2 activity → Negative symptoms (apathy, withdrawal). * **Nigrostriatal Pathway:** D2 blockade here by antipsychotics leads to **Extrapyramidal Side Effects (EPS)**. * **Tuberoinfundibular Pathway:** D2 blockade here leads to **Hyperprolactinemia**.

Q: Disorientation is a common symptom in which of the following conditions?

Organic brain syndrome. ### Explanation **Correct Answer: B. Organic brain syndrome** **1. Why Organic Brain Syndrome is Correct:** Disorientation (to time, place, or person) is a hallmark feature of **Organic Brain Syndromes (OBS)**, such as Delirium and Dementia. In psychiatry, "organic" refers to conditions caused by identifiable physiological or structural brain dysfunction (e.g., metabolic imbalances, infections, or neurodegeneration). Disorientation occurs because these conditions impair the **sensorium** and cognitive functions. In Delirium, disorientation is typically acute and fluctuating, whereas in Dementia, it is progressive. **2. Why the Other Options are Incorrect:** * **A. Schizophrenia:** This is a functional psychotic disorder. While patients may be preoccupied with hallucinations or delusions, their **sensorium remains clear**. They are generally oriented to time, place, and person unless they are in a state of extreme catatonic stupor or severe chronic deterioration. * **C. Depression:** This is a mood disorder. While severe depression (Melancholia) can cause "pseudodementia" (memory complaints), patients remain oriented. * **D. Mania:** Patients with mania are hyper-attentive and easily distracted, but they do not lose the basic orientation of their surroundings unless the condition is complicated by delirium (Delirious Mania). **3. Clinical Pearls for NEET-PG:** * **The "Clouding of Consciousness":** This is the pathognomonic feature of Delirium. If a question mentions "fluctuating levels of consciousness" and "disorientation," always think of an organic cause. * **Order of Disorientation:** In organic states, orientation to **Time** is usually lost first, followed by **Place**, and lastly **Person**. * **Functional vs. Organic:** The presence of disorientation is one of the most reliable clinical markers to differentiate organic psychiatric disorders from functional ones (like Schizophrenia or Bipolar Disorder).

Q: Which of the following psychiatric illnesses is common in a patient with stroke?

Depression. **Explanation:** **Post-Stroke Depression (PSD)** is the most common neuropsychiatric complication following a stroke, affecting approximately **30% to 35%** of survivors. 1. **Why Depression is Correct:** The etiology of PSD is multifactorial, involving both **biological factors** (disruption of amine pathways, particularly serotonin and norepinephrine, due to ischemic injury) and **psychosocial factors** (reaction to new physical disability and loss of independence). Studies indicate that lesions in the **left frontal cortex** and **left basal ganglia** are more strongly associated with the development of severe depression. 2. **Why Other Options are Incorrect:** * **Schizophrenia:** This is a primary psychotic disorder with a typical onset in late adolescence or early adulthood. While "post-stroke psychosis" can occur, it is rare compared to mood disorders. * **Bipolar Disorder:** Post-stroke mania is significantly less common than depression and is usually associated with lesions in the **right hemisphere** (specifically the temporal or orbitofrontal cortex). * **Psychosis:** While strokes can cause hallucinations or delusions (organic psychosis), the prevalence is low (approx. 4-5%) compared to the high incidence of depressive symptoms. **High-Yield Clinical Pearls for NEET-PG:** * **Treatment:** SSRIs (e.g., Sertraline, Fluoxetine) are the first-line treatment for PSD and have been shown to improve both mood and motor recovery. * **Location Correlation:** Left-sided lesions (Frontal) → Depression; Right-sided lesions → Mania/Indifference. * **Differential:** Always rule out **Vascular Dementia** if cognitive decline is prominent alongside mood changes.

Q: A 45-year-old male presents with blood work showing increased homovanillic acid (HVA). Which of the following conditions is this patient most likely to exhibit?

Schizophrenia. **Explanation:** The correct answer is **Schizophrenia**. This question tests your knowledge of neurotransmitter metabolites and their clinical significance in psychiatry. **1. Why Schizophrenia is Correct:** Homovanillic acid (HVA) is the primary metabolic byproduct of **Dopamine**. According to the **Dopamine Hypothesis of Schizophrenia**, the condition is associated with overactivity of dopaminergic pathways (specifically the mesolimbic pathway). Increased dopamine turnover leads to elevated levels of HVA in the cerebrospinal fluid (CSF) and plasma. Therefore, high HVA is a biochemical marker often associated with psychotic disorders like schizophrenia. **2. Why the Other Options are Incorrect:** * **Depression:** This is primarily associated with decreased levels of **5-HIAA** (a metabolite of Serotonin) and **MHPG** (a metabolite of Norepinephrine). While dopamine can be involved, elevated HVA is not a hallmark. * **Parkinson’s Disease:** This condition involves the degeneration of dopaminergic neurons in the substantia nigra. Consequently, patients with Parkinson's would show **decreased** levels of HVA due to dopamine deficiency. * **Poorly controlled chronic conditions:** This is a non-specific distractor and does not correlate with a specific increase in HVA. **Clinical Pearls for NEET-PG:** * **HVA (Homovanillic Acid):** Metabolite of Dopamine (High in Schizophrenia/Mania; Low in Parkinson’s). * **5-HIAA (5-Hydroxyindoleacetic Acid):** Metabolite of Serotonin (Low levels in CSF are strongly linked to **impulsivity and completed suicide**). * **VMA (Vanillylmandelic Acid):** Urinary metabolite of Epinephrine/Norepinephrine (High in **Pheochromocytoma**). * **MHPG:** Metabolite of Norepinephrine (Used to study depressive subtypes).

Q: Disorientation to time and space is characteristic of which of the following?

Delirium. **Explanation:** **Delirium** (Option D) is the correct answer because it is characterized by an acute decline in cognitive function, specifically involving a **clouding of consciousness** and impairment in **attention and orientation**. Disorientation to time and space is a hallmark feature of delirium, often fluctuating throughout the day (sundowning). It is a medical emergency usually caused by an underlying organic condition (e.g., infection, metabolic imbalance, or drug toxicity). **Why other options are incorrect:** * **Hallucinations (A):** These are sensory perceptions in the absence of an external stimulus (e.g., hearing voices). While they can occur *during* delirium, they are disturbances of perception, not orientation. * **Illusion (B):** This is a misinterpretation of a real external stimulus (e.g., mistaking a rope for a snake). Like hallucinations, these are perceptual disturbances. * **Delusion (C):** This is a fixed, false belief that is not shaken by logic and is out of keeping with the patient’s cultural background. It is a disorder of **thought content**, not orientation. **High-Yield Clinical Pearls for NEET-PG:** * **Orientation Loss Sequence:** In progressive cognitive decline, orientation to **Time** is lost first, followed by **Place**, and lastly **Person**. * **Delirium vs. Dementia:** Delirium is acute, reversible, and features fluctuating consciousness; Dementia is chronic, progressive, and consciousness remains clear until late stages. * **Visual Hallucinations:** While auditory hallucinations are common in Schizophrenia, **visual hallucinations** are highly suggestive of organic brain syndromes like Delirium. * **EEG Finding:** In delirium, the EEG typically shows generalized **slowing** of background activity (except in Delirium Tremens, where it shows low-voltage fast activity).

Q: Exercise is prescribed as an adjuvant treatment for depression. What is the most probable mechanism of action?

Raising endorphin levels. **Explanation:** **Mechanism of the Correct Answer (C):** The antidepressant effect of exercise is primarily attributed to the **"Endorphin Hypothesis."** During vigorous physical activity, the pituitary gland and hypothalamus increase the synthesis and release of **beta-endorphins**. These endogenous opioid peptides bind to mu-opioid receptors in the brain, leading to analgesia and a state of euphoria (often termed the "runner's high"). Furthermore, exercise stimulates **neurogenesis** and increases levels of **Brain-Derived Neurotrophic Factor (BDNF)**, which helps reverse the hippocampal atrophy often seen in chronic depression. **Analysis of Incorrect Options:** * **A & B (Pulse Pressure and Hemodynamics):** While exercise improves cardiovascular efficiency and stroke volume, these are physiological adaptations of the circulatory system. They do not have a direct, evidence-based neurochemical link to the pathophysiology of mood disorders. * **D (Inducing Good Sleep):** Although exercise improves sleep hygiene and circadian rhythms (which is beneficial for mental health), it is considered a secondary effect rather than the primary biochemical mechanism for treating depression. **NEET-PG High-Yield Pearls:** * **Neurotransmitters:** Exercise also increases the availability of serotonin, dopamine, and norepinephrine in the synaptic cleft, mimicking the action of traditional antidepressants. * **HPA Axis:** Regular exercise helps regulate the Hypothalamic-Pituitary-Adrenal (HPA) axis, reducing the baseline levels of **cortisol**, which is typically elevated in depressed patients. * **BDNF:** Remember that BDNF is the key molecule for **synaptic plasticity**; its deficiency is a core feature of the "Neurotrophic Hypothesis of Depression."

Q: Acute organic psychosis may be associated with all of the following diseases EXCEPT?

Arteriosclerosis. **Explanation:** The core concept in this question is the distinction between **Acute** and **Chronic** organic brain syndromes. **Why Arteriosclerosis is the Correct Answer:** Arteriosclerosis is a chronic, progressive degenerative process. In the brain, it leads to gradual vascular insufficiency, resulting in **Multi-infarct Dementia** or Chronic Organic Brain Syndrome. The onset of psychiatric symptoms (cognitive decline, personality changes) is insidious and long-term, rather than acute. Therefore, it is not typically associated with "Acute Organic Psychosis." **Analysis of Incorrect Options:** * **Head Injury:** Traumatic brain injury can cause sudden cerebral dysfunction, leading to acute post-traumatic psychosis or delirium. * **Meningitis:** Acute infections of the CNS cause rapid inflammation, often presenting with an acute organic brain syndrome characterized by clouding of consciousness, agitation, and hallucinations. * **Delirium Tremens:** This is a severe, acute manifestation of alcohol withdrawal. It is a medical emergency characterized by sudden onset of autonomic hyperactivity, vivid hallucinations, and global confusion (a classic example of acute organic psychosis). **NEET-PG High-Yield Pearls:** 1. **Acute Organic Brain Syndrome** is synonymous with **Delirium**. It is characterized by a fluctuating level of consciousness and is usually reversible. 2. **Chronic Organic Brain Syndrome** is synonymous with **Dementia**. It is characterized by a clear sensorium (conscious) but with permanent cognitive deficits. 3. **Visual Hallucinations** are the most common type of hallucination in organic psychoses (unlike Schizophrenia, where auditory hallucinations predominate). 4. Always rule out hypoglycemia, electrolyte imbalances, and infections in any patient presenting with sudden-onset psychosis.

Question 1

What are the most important receptors implicated in schizophrenia?

Accepted Answer

D2

Answer

GABAA

Answer

GABAB

Answer

5-HT1

Question 2

Disorientation is a common symptom in which of the following conditions?

Accepted Answer

Organic brain syndrome

Answer

Schizophrenia

Answer

Depression

Answer

Mania

Question 3

A 25-year-old male patient sustains a serious head injury in an automobile accident. He had been aggressive and assaultive. He also makes inappropriate suggestive comments to the nurses and masturbates a great deal. The area(s) of the brain most likely to be affected in this patient is (are) the:

Accepted Answer

amygdala

Answer

right parietal lobe

Answer

basal ganglia

Answer

hippocampus

Question 4

Which of the following psychiatric illnesses is common in a patient with stroke?

Accepted Answer

Depression

Answer

Schizophrenia

Answer

Bipolar disorder

Answer

Psychosis

Question 5

A 45-year-old male presents with blood work showing increased homovanillic acid (HVA). Which of the following conditions is this patient most likely to exhibit?

Accepted Answer

Schizophrenia

Answer

Poorly controlled chronic conditions

Answer

Depression

Answer

Parkinson's disease

Question 6

Disorientation to time and space is characteristic of which of the following?

Accepted Answer

Delirium

Answer

Hallucinations

Answer

Illusion

Answer

Delusion

Question 7

Which of the following disorders has been shown to be genetically transmitted by single autosomal dominant genes?

Accepted Answer

Huntington's disease

Answer

Catatonic schizophrenia

Answer

Phenylketonuria

Answer

Creutzfeldt-Jakob disease

Question 8

Exercise is prescribed as an adjuvant treatment for depression. What is the most probable mechanism of action?

Accepted Answer

Raising endorphin levels

Answer

Increasing pulse pressure

Answer

Improving hemodynamics

Answer

Inducing good sleep

Question 9

Acute organic psychosis may be associated with all of the following diseases EXCEPT?

Accepted Answer

Arteriosclerosis

Answer

Head injury

Answer

Meningitis

Answer

Delirium tremens

Question 10

Amnesia is a common finding in which of the following conditions?

Accepted Answer

Head injury

Answer

Mania

Answer

Schizophrenia

Answer

Psychiatric state

Neurobiology and Genetics of Mental Disorders — MCQs

Neurobiology and Genetics of Mental Disorders — MCQs

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