Weekly Pathology Exam - July 24, 2026 (Section A: MCQs)

Question 1

What neurotransmitter is associated with runner's high?

Accepted Answer

Endorphins — Endorphins are endogenous opioid peptides that are released during strenuous exercise and are responsible for the euphoric feeling known as 'runner's high'.

Question 2

What neurotransmitter is associated with anxiety disorders?

Accepted Answer

GABA — Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system. Reduced GABAergic activity is linked to increased neuronal excitability and is implicated in anxiety disorders.

Question 3

Where do neurons store the genetic information they use to code and build all the proteins required for their functions?

Accepted Answer

Nucleus — Neurons, like all eukaryotic cells, store their genetic information in the form of DNA within the nucleus. This DNA is transcribed into RNA, which is then translated into proteins.

Question 4

Which of the following are major inhibitory neurotransmitters, causing inhibitory postsynaptic potentials (IPSPs)?

Accepted Answer

GABA and Glycine — GABA (gamma-aminobutyric acid) and Glycine are the primary inhibitory neurotransmitters in the central nervous system. Their binding to receptors on the postsynaptic neuron leads to an influx of negative ions or efflux of positive ions, hyperpolarizing the membrane and making it less likely to fire an action potential (IPSP).

Question 5

The effect of tetrodotoxin (puffer fish poison) on axons demonstrates

Accepted Answer

The importance of ion channels in action potential generation — Tetrodotoxin blocks voltage-gated sodium channels, which are crucial for the rapid depolarization phase of the action potential. Its ability to block nerve conduction highlights the essential role of these ion channels in generating action potentials.

Question 6

What neurotransmitter is associated with mood disorders?

Accepted Answer

Serotonin — Serotonin plays a significant role in regulating mood, appetite, and sleep. Dysregulation of serotonin levels and signaling is strongly implicated in the pathophysiology of mood disorders like depression and anxiety.

Question 7

Which of the following is not true?

Accepted Answer

All neurotransmitters bind to the same type of receptor. — Neurotransmitters bind to specific receptors, and there are many different types of neurotransmitter receptors, each with unique signaling properties.

Question 8

What neurotransmitter is associated with insomnia?

Accepted Answer

Melatonin — While GABAergic systems are involved in promoting sleep, Melatonin is a hormone that plays a crucial role in regulating the sleep-wake cycle. Disruptions in melatonin production or signaling can contribute to insomnia.

Question 9

What neurotransmitter is associated with seizures?

Accepted Answer

Glutamate — Seizures are characterized by excessive and synchronous neuronal firing. Glutamate, the primary excitatory neurotransmitter, is involved in this hyperexcitability. Imbalances between excitatory (glutamate) and inhibitory (GABA) neurotransmission can lead to seizures.

Question 10

What is one of the functions of Dopamine?

Accepted Answer

Control of motor movement and reward pathways — Dopamine is a key neurotransmitter involved in motor control (its deficiency is linked to Parkinson's disease), motivation, reward, pleasure, and reinforcement.

Question 11

What is one of the functions of Endorphins?

Accepted Answer

Inhibition of pain perception — Endorphins are endogenous opioid peptides that act as natural painkillers and are involved in the body's response to stress and pain, as well as contributing to feelings of pleasure and well-being.

Question 12

What neurotransmitter is associated with Parkinson's disease?

Accepted Answer

Dopamine — Parkinson's disease is characterized by the progressive loss of dopaminergic neurons in the substantia nigra, leading to a deficiency in dopamine. This deficiency results in the motor symptoms of the disease.

Question 13

A 28-year-old woman presents with fatigue and pallor. Complete blood count shows low haemoglobin level and peripheral blood film shows microcytic hypochromic red blood cells. What is the most likely diagnosis?

Accepted Answer

Iron deficiency anemia — Microcytic hypochromic red blood cells are characteristic of iron deficiency anemia, where there is insufficient iron to synthesize hemoglobin, leading to small (microcytic) and pale (hypochromic) red blood cells. Fatigue and pallor are common symptoms of anemia.

Question 14

The primary site of haematopoiesis in adults is:

Accepted Answer

Bone marrow — In healthy adults, the bone marrow, particularly the red marrow within flat and long bones, is the primary site for the production of all blood cell lineages (hematopoiesis).

Question 15

Which blood cell type is primarily responsible for defence against parasitic infections?

Accepted Answer

Eosinophils — Eosinophils are granulocytes that play a significant role in the immune response against parasitic infections and in allergic reactions. They release cytotoxic proteins and enzymes that are effective against larger pathogens like parasites.

Question 16

Which clotting factor is deficient in Haemophilia A?

Accepted Answer

Factor VIII — Hemophilia A is an inherited bleeding disorder caused by a deficiency in Factor VIII, a crucial protein in the coagulation cascade that helps blood to clot.

Question 17

A patient presents with recurrent infections, petechiae, and anaemia. A bone marrow biopsy shows reduced cellularity. What is the most likely diagnosis?

Accepted Answer

Aplastic anemia — Reduced cellularity in the bone marrow, along with pancytopenia (leading to recurrent infections from low white cells, petechiae from low platelets, and anemia from low red cells), is characteristic of aplastic anemia, a condition where the bone marrow fails to produce sufficient blood cells.

Question 18

Haemopoiesis is the process of:

Accepted Answer

Formation and development of blood cells — Hematopoiesis is the complex process by which all types of blood cells, including white blood cells, red blood cells, and platelets, are produced and developed from hematopoietic stem cells.

Question 19

A 62-year-old man presents with fatigue, fever and bruising. His full blood count shows WCC 40 × 10⁹/L with 25% circulating blasts, Hb 90 g/L and platelets 50 × 10⁹/L. Which investigation is required to definitively diagnose acute myeloid leukaemia?

Accepted Answer

Bone marrow biopsy with cytochemistry and immunophenotyping — While a peripheral blood smear can show blasts, a definitive diagnosis of Acute Myeloid Leukemia (AML) requires a bone marrow biopsy. Cytochemical stains (like MPO) and immunophenotyping are essential to confirm the myeloid lineage of the blasts and classify the AML subtype.

Question 20

Which cytochemical stain is most useful to confirm lymphoblasts in suspected ALL?

Accepted Answer

Periodic Acid-Schiff (PAS) — The Periodic Acid-Schiff (PAS) stain demonstrates glycogen granules, which are often present in lymphoblasts of Acute Lymphoblastic Leukemia (ALL). Myeloperoxidase, esterase, and lysozyme stains are more characteristic of myeloid blasts.

Question 21

A patient receiving chemotherapy shows a drop in neutrophil count. This condition is termed:

Accepted Answer

Neutropenia — Neutropenia is a condition characterized by a lower-than-normal number of neutrophils, a type of white blood cell. Chemotherapy often causes myelosuppression, leading to neutropenia and an increased risk of infection.

Question 22

Which chromosomal translocation is pathognomonic of chronic myeloid leukaemia?

Accepted Answer

t(9;22) - Philadelphia chromosome — The t(9;22) translocation, resulting in the Philadelphia chromosome (BCR-ABL fusion gene), is the hallmark genetic abnormality found in over 95% of patients with Chronic Myeloid Leukemia (CML).

Question 23

Thrombopoietin primarily regulates the production of:

Accepted Answer

Platelets — Thrombopoietin (TPO) is the main hormone that stimulates the production of platelets (thrombocytes) from megakaryocytes in the bone marrow.

Question 24

Which of the following is a stem cell marker used to identify haematopoietic stem cells?

Accepted Answer

CD34 — CD34 is a transmembrane glycoprotein that is expressed on hematopoietic stem cells, progenitor cells, and endothelial cells. It is widely used as a marker for identifying and isolating hematopoietic stem cells.

Question 25

What neurotransmitter is primarily associated with the euphoric feeling experienced during a 'runner's high'?

Accepted Answer

Endorphins — Endorphins are endogenous opioid peptides that are released during strenuous exercise and are responsible for the euphoric feeling known as 'runner's high'.

Question 26

Which neurotransmitter system is most implicated in the pathophysiology of anxiety disorders?

Accepted Answer

GABA — Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system. Reduced GABAergic activity is linked to increased neuronal excitability and is implicated in anxiety disorders.

Question 27

Where do neurons store the genetic information they use to code and build all the proteins required for their functions?

Accepted Answer

Nucleus — Neurons, like all eukaryotic cells, store their genetic information in the form of DNA within the nucleus. This DNA is transcribed into RNA, which is then translated into proteins.

Question 28

Which of the following are major inhibitory neurotransmitters, causing inhibitory postsynaptic potentials (IPSPs)?

Accepted Answer

GABA and Glycine — GABA (gamma-aminobutyric acid) and Glycine are the primary inhibitory neurotransmitters in the central nervous system. Their binding to receptors on the postsynaptic neuron leads to an influx of negative ions or efflux of positive ions, hyperpolarizing the membrane and making it less likely to fire an action potential (IPSP).

Question 29

The effect of tetrodotoxin (puffer fish poison) on axons demonstrates:

Accepted Answer

The importance of ion channels in action potential generation — Tetrodotoxin blocks voltage-gated sodium channels, which are crucial for the rapid depolarization phase of the action potential. Its ability to block nerve conduction highlights the essential role of these ion channels in generating action potentials.

Question 30

Which neurotransmitter is most commonly associated with the regulation of mood, and its dysregulation is implicated in mood disorders like depression?

Accepted Answer

Serotonin — Serotonin plays a significant role in regulating mood, appetite, and sleep. Dysregulation of serotonin levels and signaling is strongly implicated in the pathophysiology of mood disorders like depression and anxiety.

Question 31

Which of the following statements is NOT true regarding neurotransmitters?

Accepted Answer

All neurotransmitters bind to the same type of receptor. — Neurotransmitters bind to specific receptors, and there are many different types of neurotransmitter receptors, each with unique signaling properties.

Question 32

Which neurotransmitter system is heavily involved in regulating sleep-wake cycles and is often implicated in insomnia?

Accepted Answer

Melatonin — While GABAergic systems are involved in promoting sleep, Melatonin is a hormone that plays a crucial role in regulating the sleep-wake cycle. Disruptions in melatonin production or signaling can contribute to insomnia.

Question 33

Which neurotransmitter plays a critical role in mediating excitatory neurotransmission and is implicated in the hyperexcitability seen in certain seizure disorders?

Accepted Answer

Glutamate — Glutamate, the primary excitatory neurotransmitter, is involved in the hyperexcitability seen in certain seizure disorders. Imbalances between excitatory (glutamate) and inhibitory (GABA) neurotransmission can lead to seizures.

Question 34

What is one of the primary functions of Dopamine in the brain?

Accepted Answer

Control of motor movement and reward pathways — Dopamine is a key neurotransmitter involved in motor control (its deficiency is linked to Parkinson's disease), motivation, reward, pleasure, and reinforcement.

Question 35

What is one of the primary functions of Endorphins?

Accepted Answer

Inhibition of pain perception — Endorphins are endogenous opioid peptides that act as natural painkillers and are involved in the body's response to stress and pain, as well as contributing to feelings of pleasure and well-being.

Question 36

Which neurotransmitter deficiency is strongly associated with Parkinson's disease?

Accepted Answer

Dopamine — Parkinson's disease is characterized by the progressive loss of dopaminergic neurons in the substantia nigra, leading to a deficiency in dopamine. This deficiency results in the motor symptoms of the disease.

Question 37

A 35-year-old man has no clinical evidence for bleeding and he feels fine. As part of a pre-operative workup for a hernia repair, laboratory studies show Hgb 14.8 g/dL, Hct 45%, MCV 96 fL, and WBC count 8500/microliter, and platelet count 275,000/microliter. His prothrombin time is normal, but the partial thromboplastin time is prolonged. A deficiency of which of the following coagulation factors is most likely be associated with these findings?

Accepted Answer

Factor VIII — A prolonged PTT with a normal PT suggests a defect in the intrinsic or common pathway of coagulation. Factor VIII deficiency (Hemophilia A) is a common inherited disorder that causes a prolonged PTT but a normal PT. Factors VII and X are involved in the extrinsic and common pathways, respectively, and would affect PT. Factor XIII is involved in clot stabilization.

Question 38

A 20-year-old man is actively bleeding from multiple sites during surgery. He has a CBC that shows a WBC count of 4500/microliter, Hgb 7.6 g/dL, Hct 23.9%, MCV 98 fL, and platelet count 75,000/microliter. His prothrombin time is 30 seconds and partial thromboplastin time 63 seconds. What is the best blood product to use for him in this situation?

Accepted Answer

Fresh frozen plasma (FFP) — This patient has evidence of significant coagulopathy (prolonged PT and PTT) and potentially thrombocytopenia (platelet count 75,000/microliter, which is low in the context of active bleeding), along with anemia. Fresh frozen plasma (FFP) contains all clotting factors and is the best choice to rapidly correct coagulopathy. Packed red blood cells would address anemia, cryoprecipitate would provide fibrinogen and Factor VIII (useful in specific coagulopathies but not the primary choice here), and platelets would address thrombocytopenia, but FFP addresses the systemic clotting factor deficiency indicated by the prolonged PT and PTT.

Question 39

A 31-year-old woman has oozing of blood from mucous membranes over the past 3 days. Laboratory studies show a platelet count of 10,000/microliter. She receives 6 units of platelets. An hour following this transfusion, her platelet count is 2,000/microliter. What is the most probable explanation for the change in pre- to post-transfusion platelet count?

Accepted Answer

Rapid platelet consumption — A poor response to platelet transfusion (less than 20% increase in platelet count) with a very low post-transfusion count despite adequate infusion strongly suggests rapid platelet consumption or destruction. While splenomegaly can trap platelets, and DIC is a possibility, alloimmune destruction is a specific cause of refractoriness to transfusion. However, 'rapid platelet consumption' is a broader, yet highly probable explanation, especially if there's an underlying condition causing high platelet turnover or activation, such as severe infection, trauma, or thrombotic microangiopathy (which can be a cause of DIC). Given the options, rapid consumption is the most direct explanation for the rapid drop, suggesting the transfused platelets are being used up or destroyed quickly.

Question 40

A 12-year-old boy has had multiple episodes of bleeding since infancy. It is characterized by hemarthroses and decreased joint mobility. His prothrombin time (PT) is normal, but the partial thromboplastin time (PTT) is elevated. When his plasma is mixed with normal plasma, the PTT is not elevated. His platelet count is normal. Which of the following is the most likely cause for his illness?

Accepted Answer

Hemophilia A — The presentation of bleeding since infancy, hemarthroses, normal PT, elevated PTT, and normal platelet count are classic signs of Hemophilia A (Factor VIII deficiency). The mixing study normalization suggests an intrinsic factor deficiency rather than an inhibitor (autoantibody).

Question 41

A 64-year-old nursing home patient receiving tube feedings is admitted with fever of two days' duration accompanied by a cough productive of yellowish sputum. On admission his temperature is 37.4°C. A sputum gram stain shows 4+ gram positive diplococci. He is also found to have a total serum protein of 9.4 g/dl with serum albumin of 3.8 g/dl. Which of the following underlying diseases do these findings most strongly suggest that he has?

Accepted Answer

Pneumonia — The presence of fever, productive cough with gram-positive diplococci on sputum gram stain, and elevated total serum protein (likely due to inflammatory response) are highly suggestive of pneumonia. The patient's age and condition (nursing home, tube feedings) increase his risk. While COPD can predispose to pneumonia, the acute symptoms and gram stain findings point directly to an infectious process of the lung. Heart failure and diabetes mellitus are less directly supported by these acute findings.

Question 42

A 44-year-old man has had congestive heart failure for 2 years. His serum ferritin is markedly elevated. His CBC shows WBC count 6300/microliter, Hgb 7.8 g/dL, Hct 22.6%, MCV 69 fL, and platelet count 177,000/microliter. A hemoglobin electrophoresis reveals 2% Hgb A, 8% Hgb A2, and 90% Hgb F. Which of the following hematologic conditions is he most likely to have?

Accepted Answer

Beta thalassemia major — The patient has microcytic anemia (low MCV), elevated ferritin (suggesting iron overload, common in chronic transfusions or ineffective erythropoiesis), and a high percentage of fetal hemoglobin (Hb F) with very little adult hemoglobin (Hb A). This pattern is highly characteristic of Beta thalassemia major, where the production of beta-globin chains is severely impaired, leading to ineffective erythropoiesis and a compensatory increase in Hb F. While congestive heart failure is present, the hematologic findings are the key.

Question 43

A study of blood product therapy is done. One product is identified that carries the greatest risk for infection. This blood product has the shortest shelf life, and it must be used as quickly as possible for transfusion. Which of the following products is best described by these findings?

Accepted Answer

Platelets — Platelets have the shortest shelf life of blood products (typically 5-7 days under refrigeration and agitation) and are highly susceptible to bacterial contamination due to their storage conditions. While all blood products carry some risk of infection, platelets are considered to have a higher risk due to these factors.

Question 44

An 81-year-old previously healthy woman has had a 2 kg weight loss without dieting over the past 2 months. She reports no other problems. On examination there are no abnormal findings. Laboratory studies show a serum alkaline phosphatase of 200 U/L. Which of the following diseases is she most likely to have?

Accepted Answer

Metastatic malignancy — Unexplained weight loss in an elderly individual, especially when accompanied by an elevated alkaline phosphatase (which can be elevated in various liver and bone conditions), is highly suspicious for malignancy. Metastatic disease to the liver or bone can cause elevated alkaline phosphatase and constitutional symptoms like weight loss. Acute viral hepatitis typically presents with jaundice and other signs of liver inflammation. Cholelithiasis might cause pain or jaundice but not typically weight loss and elevated ALP in this manner. Primary biliary cirrhosis is a chronic condition and the presentation doesn't fit as well as malignancy.

Question 45

A 17-year-old boy has developed a mild fever with sore throat over the past day. On physical examination he has generalized lymphadenopathy. Laboratory studies show a CD4 lymphocyte count of 375/microliter. He is most likely to be infected with which of the following agents?

Accepted Answer

Epstein-Barr virus (EBV) — The constellation of symptoms: fever, sore throat, generalized lymphadenopathy, and a CD4 count that is moderately reduced (normal is 500-1500/microliter) is highly suggestive of infectious mononucleosis, which is typically caused by the Epstein-Barr virus (EBV). HTLV-1 is associated with adult T-cell leukemia/lymphoma. CMV can cause mononucleosis-like illness but is often less severe and lymphadenopathy may be less prominent. HSV causes pharyngitis but not typically generalized lymphadenopathy and reduced CD4 counts of this magnitude.

Question 46

A 62-year-old healthy woman has a pre-operative workup for an elective surgery. A serum glucose is ordered and is of 120 mg/dl. Four hours later that day, another glucose test is ordered unnecessarily, and the value is noted to be 124 mg/dl. Which of the following best explains the difference in these two values on this woman?

Accepted Answer

Physiological diurnal variation — A fasting glucose of 120 mg/dL is considered pre-diabetic or borderline. However, glucose levels naturally fluctuate throughout the day. Without knowing when the first and second tests were taken relative to meals, and given the small increase, it is plausible that the second reading reflects a normal postprandial rise in blood glucose after a meal or snack consumed between the tests. Significant diabetes mellitus would typically present with higher fasting or random glucose levels and potentially larger fluctuations. Diurnal variation exists but usually within a narrower range, and laboratory error is possible but less likely to explain a small, consistent increase.

Question 47

A healthy 27 year old male donates blood. He completes the questionnaire and interview with no exclusions noted. The presence of which of the following infectious agents will not routinely tested for on his blood collected for transfusion?

Accepted Answer

Human T-lymphotropic virus type 1 — Routine screening of donated blood in most countries includes tests for HIV-1, Hepatitis C virus (HCV), and West Nile virus (WNV). While HTLV-1 can cause disease, it is not as commonly screened for routinely as the other agents listed, though it may be screened for in certain geographic regions or for specific blood products. Regulations for blood screening can vary, but HIV, HCV, and WNV are standard.

Question 48

A 33-year-old woman has had multiple episodes of deep venous thrombosis over the past year. Last week she had a transient ischemic attack. On examination there are no abnormal findings. Laboratory studies show a prolonged prothrombin and partial thromboplastin time. When her plasma is mixed in a ratio of 1:1 with normal plasma, neither the PT nor the PTT normalize. Which of the following conditions is she most likely to have?

Accepted Answer

Antiphospholipid syndrome — Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by the presence of antiphospholipid antibodies, which can lead to recurrent arterial and venous thrombosis, and pregnancy morbidity. The prolonged PT and PTT that do not correct upon mixing with normal plasma is a characteristic finding in some patients with APS due to the presence of lupus anticoagulants, which interfere with the clotting assays. While hemophilia A and Factor XI deficiency cause prolonged PTT, they would typically correct with mixing studies, and their thrombotic risk is lower than their bleeding risk. Von Willebrand disease primarily affects platelet function and the PTT may be normal or mildly prolonged.

Question 49

Which lipoprotein is responsible for transporting dietary triglycerides from the intestines to tissues?

Accepted Answer

Chylomicrons — Chylomicrons are large lipoprotein particles synthesized in the intestinal cells. They are primarily composed of triglycerides and are responsible for the transport of dietary fats from the intestines to peripheral tissues, such as adipose tissue and muscle.

Question 50

What is the primary function of HDL cholesterol?

Accepted Answer

Transporting cholesterol from peripheral tissues to the liver — High-density lipoprotein (HDL) cholesterol is often referred to as 'good cholesterol' because it plays a crucial role in reverse cholesterol transport. It picks up excess cholesterol from peripheral tissues and transports it back to the liver for excretion.

Weekly Pathology Exam - July 24, 2026 (Section A: MCQs)

Questions, Answers & Explanations