Stress Response and Adaptation — MCQs
Cortisol increases all of the following components except:
Which neurotransmitter deficit is MOST consistently implicated as the primary mechanism in the pathophysiology of depression?
In surgical stress all hormones are increased except:
Which hormone is NOT increased in stress?
A patient with a pheochromocytoma is secreting large amounts of norepinephrine into the bloodstream. In a normal individual, this compound is usually released from the adrenal medulla in response to which of the following?
The following marked recordings in GIT are produced by:
The image shows migrating motor complexes in various parts of gut. Identify the correct statement.
A patient with chronic heart failure shows elevated ADH levels despite low serum osmolality (270 mOsm/kg) and hyponatremia (125 mEq/L). Critically evaluating this paradox, which represents the most physiologically sound explanation?
A 30-year-old woman participates in a hot yoga session (40°C ambient temperature) for 90 minutes. She maintains normal core temperature throughout. Analyzing her integrated physiological response, which combination of mechanisms is most critical for her thermoregulation?
A researcher studying metabolic responses observes that during prolonged fasting, brain metabolism shifts partially from glucose to ketone bodies, while RBCs continue using only glucose. What is the fundamental physiological principle explaining this difference?
Stress Response and Adaptation Indian Medical PG Practice Questions and MCQs
Question 1: Cortisol increases all of the following components except:
- A. Monocytes
- B. RBCs
- C. Platelets
- D. Eosinophils (Correct Answer)
Explanation: ***Eosinophils*** - Cortisol causes **eosinopenia** (a decrease in eosinophils) by increasing their sequestration in tissues and promoting their apoptosis. - This effect is a classic indicator of stress and can be observed in conditions of elevated endogenous or exogenous cortisol. *Monocytes* - Cortisol typically causes a **mild monocytosis** (increase in circulating monocytes), although this effect can vary. - It impacts the trafficking and differentiation of monocytes, leading to their transient increase in the bloodstream. *RBCs* - Cortisol can lead to a slight **increase in red blood cell (RBC) count** or hemoglobin concentration. - This effect is partly due to hemoconcentration and partly by promoting erythropoiesis. *Platelets* - Cortisol generally causes a **thrombocytosis** (increase in platelet count). - This effect is thought to be mediated by various factors, including cytokine interactions and direct effects on megakaryopoiesis.
Question 2: Which neurotransmitter deficit is MOST consistently implicated as the primary mechanism in the pathophysiology of depression?
- A. Norepinephrine
- B. GABA
- C. Serotonin (Correct Answer)
- D. Dopamine
Explanation: ***Serotonin (decreased levels)*** - The **monoamine hypothesis** of depression suggests that a functional deficit of neurotransmitters is central to its pathophysiology, with **serotonin (5-HT) most consistently highlighted as the primary driver**. - Reduced levels of serotonin in the synaptic cleft lead to impaired neurotransmission, affecting **mood**, **sleep**, **appetite**, and **cognitive functions**. - Most **selective serotonergic antidepressants (SSRIs)** target this pathway as first-line treatment, underscoring serotonin's central role. *Norepinephrine (decreased levels)* - **Norepinephrine** is another monoamine neurotransmitter implicated in depression, and its deficiency contributes to depressive symptoms. - Low norepinephrine levels are linked to symptoms like **fatigue**, **difficulty concentrating**, and **anhedonia**. - However, while important, **decreased serotonin is more consistently emphasized as the primary pathophysiological mechanism** in most contemporary models of depression. *GABA (reduced levels)* - **GABA (gamma-aminobutyric acid)** is the primary inhibitory neurotransmitter in the brain; reduced levels are associated more strongly with **anxiety disorders** and seizure disorders. - While GABAergic system dysfunction can contribute to certain depressive symptoms, it is not considered a primary mechanism for the core pathophysiology of depression. *Dopamine (increased levels)* - **Increased dopamine levels** are more commonly associated with conditions like **schizophrenia** (mesolimbic pathway) and **mania**, not depression. - Conversely, **decreased** dopamine levels (particularly in the mesocortical pathway) are linked to anhedonia and lack of motivation in depression, making this option factually incorrect.
Question 3: In surgical stress all hormones are increased except:
- A. Insulin (Correct Answer)
- B. Epinephrine
- C. ACTH
- D. Cortisol
Explanation: ***Insulin*** - While other **stress hormones** increase, **insulin** levels typically **decrease** or remain stable due to increased **insulin resistance** during surgical stress. - This physiological response aims to maintain **blood glucose** levels for energy during heightened metabolic demands. *Epinephrine* - **Epinephrine** (adrenaline) is a key **catecholamine** released during surgical stress, leading to a "fight or flight" response. - It increases **heart rate**, **blood pressure**, and promotes **gluconeogenesis** to supply quick energy. *ACTH* - **Adrenocorticotropic hormone (ACTH)** is released from the **pituitary gland** in response to surgical stress. - **ACTH** stimulates the adrenal cortex to produce **cortisol**, a critical stress hormone. *Cortisol* - **Cortisol** levels significantly rise during surgical stress, mediated by **ACTH** release. - It plays a crucial role in **modulating inflammation**, **glucose metabolism**, and maintaining **hemodynamic stability**.
Question 4: Which hormone is NOT increased in stress?
- A. Glucagon
- B. Insulin (Correct Answer)
- C. Cortisol
- D. Epinephrine
Explanation: ***Insulin*** - Insulin levels generally **decrease** during acute stress. This allows for increased availability of glucose for tissues, such as the brain and muscles, during "fight or flight" responses. - The sympathetic nervous system activity during stress **inhibits insulin secretion** from pancreatic beta cells. *Glucagon* - **Glucagon levels increase** during stress to promote **hepatic glucose production** (glycogenolysis and gluconeogenesis), ensuring a readily available energy supply. - This rise in glucagon is part of the counter-regulatory response to maintain blood glucose stability during stressful conditions. *Cortisol* - **Cortisol levels significantly increase** during stress as part of the **hypothalamic-pituitary-adrenal (HPA) axis** activation. - Cortisol mobilizes energy stores, suppresses the immune system, and prepares the body for prolonged stress. *Epinephrine* - **Epinephrine (adrenaline) levels increase rapidly** during acute stress as part of the **sympathetic nervous system** response. - It triggers the "fight or flight" response, increasing heart rate, blood pressure, and diverting blood flow to essential organs, while also promoting glucose release.
Question 5: A patient with a pheochromocytoma is secreting large amounts of norepinephrine into the bloodstream. In a normal individual, this compound is usually released from the adrenal medulla in response to which of the following?
- A. Acetylcholine (Correct Answer)
- B. Normetanephrine
- C. Metanephrine
- D. Epinephrine
Explanation: ***Acetylcholine*** - **Acetylcholine** is the primary neurotransmitter released by **preganglionic sympathetic fibers** that innervate the adrenal medulla. - Upon binding to **nicotinic receptors** on chromaffin cells, acetylcholine stimulates the release of catecholamines, including norepinephrine and epinephrine, into the bloodstream. *Normetanephrine* - **Normetanephrine** is a metabolite of **norepinephrine**, not a hormone that triggers its release. - It is formed by the action of **catechol-O-methyltransferase (COMT)** on norepinephrine. *Metanephrine* - **Metanephrine** is a metabolite of **epinephrine**, not a substance that stimulates catecholamine release from the adrenal medulla. - Like normetanephrine, it is also formed by the action of **COMT**. *Epinephrine* - **Epinephrine** (adrenaline) is a hormone primarily produced and released by the **adrenal medulla**, alongside norepinephrine. - While both are catecholamines, epinephrine does not trigger its own release or the release of norepinephrine in this context; instead, their release is stimulated by acetylcholine.
Question 6: The following marked recordings in GIT are produced by:
- A. Smooth muscle
- B. Interstitial cells of Cajal (Correct Answer)
- C. Myenteric plexus
- D. Parasympathetic stimulation
Explanation: ***Interstitial cells of Cajal*** - The image displays characteristic **slow waves** (also known as basal electrical rhythm) and superimposed **spike potentials** in the gastrointestinal tract, which are generated by the interstitial cells of Cajal (ICCs). - ICCs act as **pacemaker cells** in the GI tract, initiating the bioelectrical activity that dictates the rhythm of smooth muscle contractions. *Smooth muscle* - While GI smooth muscle cells contract in response to these electrical activities, they **do not generate the slow waves or spike potentials** themselves. - Smooth muscle cells are responsible for **muscle tension**, as shown in the lower tracing, which is directly triggered by the spike potentials. *Myenteric plexus* - The myenteric plexus primarily consists of **neurons** that regulate GI motility and secretions, influencing the activity of smooth muscle cells and ICCs. - It does not directly produce the characteristic slow waves or spike potentials observed as the intrinsic electrical rhythm. *Parasympathetic stimulation* - Parasympathetic stimulation, primarily via the **vagus nerve**, generally **increases the frequency and amplitude** of slow waves and spike potentials. - However, it modulates the activity rather than initiating the intrinsic electrical rhythm itself.
Question 7: The image shows migrating motor complexes in various parts of gut. Identify the correct statement.
- A. Triggered by secretin
- B. Occur every 100 minutes (Correct Answer)
- C. Phase 3 has least activity
- D. Intake of meal exaggerates the migrating motor complex
Explanation: ***Occur every 100 minutes*** - The Migrating Motor Complex (MMC) is a pattern of electromechanical activity observed in the gastrointestinal tract during fasting, typically occurring in cycles of **approximately 90-120 minutes**, or about every 100 minutes. - This cyclical activity during the interdigestive period serves to **clear residual indigestible material and bacteria** from the small intestine into the colon. *Triggered by secretin* - The MMC is primarily triggered by **motilin**, a polypeptide hormone that increases gastrointestinal motility. - **Secretin** is known to inhibit gastric acid secretion and stimulate bicarbonate and water secretion from the pancreas and bile ducts, but it is not the primary trigger for MMC. *Phase 3 has least activity* - Phase 3 of the MMC is characterized by a **burst of intense, regular propagated contractions** that sweep from the stomach to the ileum, often referred to as the "housekeeping wave." - This phase exhibits the **most vigorous motor activity**, not the least, as seen by the high-amplitude spike bursts in the image. *Intake of meal exaggerates the migrating motor complex* - The MMC is a **fasting phenomenon** and is **abolished or inhibited by the intake of a meal**. - Feeding initiates a different motor pattern characterized by continuous, irregular contractions, which serve to mix and propel chyme through the digestive tract.
Question 8: A patient with chronic heart failure shows elevated ADH levels despite low serum osmolality (270 mOsm/kg) and hyponatremia (125 mEq/L). Critically evaluating this paradox, which represents the most physiologically sound explanation?
- A. Osmoreceptor dysfunction causing inappropriate ADH secretion
- B. Syndrome of inappropriate ADH secretion (SIADH) from cardiac medications
- C. Non-osmotic stimuli (baroreceptors sensing decreased effective volume) override osmotic inhibition (Correct Answer)
- D. Primary polydipsia causing dilutional hyponatremia with secondary ADH elevation
Explanation: ***Non-osmotic stimuli (baroreceptors sensing decreased effective volume) override osmotic inhibition*** - In **heart failure**, the **effective arterial blood volume** (EABV) is low, which activates **high-pressure baroreceptors** in the carotid sinus and aortic arch. - This **non-osmotic stimulus** for ADH release is a potent physiological trigger that prioritizes **hemodynamic stability** and volume over plasma osmolality, leading to **hyponatremia**. *Osmoreceptor dysfunction causing inappropriate ADH secretion* - **Osmoreceptors** in the hypothalamus remain functional; however, their inhibitory signal is ignored in the presence of strong **hemodynamic signals**. - This is a physiological response to **perceived hypovolemia**, not a primary pathological dysfunction of the osmoreceptors themselves. *Syndrome of inappropriate ADH secretion (SIADH) from cardiac medications* - While some medications can cause **SIADH**, the patient's underlying **heart failure** provides a more direct physiological explanation involving **low EABV**. - Unlike SIADH, which is characterized by **euvolemia**, heart failure typically presents with **hypervolemia** despite the decreased effective circulating volume. *Primary polydipsia causing dilutional hyponatremia with secondary ADH elevation* - In **primary polydipsia**, excessive water intake should normally **suppress ADH** levels to near zero as the body attempts to excrete the excess water. - **Secondary ADH elevation** would not occur in polydipsia unless there was a co-existing cause for volume depletion or SIADH.
Question 9: A 30-year-old woman participates in a hot yoga session (40°C ambient temperature) for 90 minutes. She maintains normal core temperature throughout. Analyzing her integrated physiological response, which combination of mechanisms is most critical for her thermoregulation?
- A. Evaporative cooling through sweating with increased skin blood flow and decreased splanchnic flow (Correct Answer)
- B. Radiation and conduction as primary heat loss with minimal sweating
- C. Behavioral thermoregulation alone without autonomic involvement
- D. Decreased metabolic rate with peripheral vasoconstriction
Explanation: ***Evaporative cooling through sweating with increased skin blood flow and decreased splanchnic flow*** - When the ambient temperature (**40°C**) exceeds the body's skin temperature, **evaporation** of sweat becomes the only effective way to lose heat from the body. - This process is supported by **sympathetic-mediated vasodilation** to the skin to facilitate heat transfer and a compensatory **vasoconstriction** of splanchnic and renal beds to maintain blood pressure. *Radiation and conduction as primary heat loss with minimal sweating* - **Radiation** and **conduction** only work effectively if the environment is cooler than the body; at 40°C, these mechanisms actually lead to **heat gain**. - Intense physical activity in high heat requires significant **sweating** to prevent hyperthermia, making minimal sweating physiologically impossible here. *Behavioral thermoregulation alone without autonomic involvement* - **Behavioral thermoregulation** (like removing clothes) is insufficient during 90 minutes of active yoga without **autonomic** responses like sweating and heart rate changes. - The **hypothalamus** triggers involuntary autonomic responses, such as **sympathetic cholinergic** activation of sweat glands, which are essential for survival in this scenario. *Decreased metabolic rate with peripheral vasoconstriction* - **Metabolic rate** actually tends to increase during exercise (yoga) and high heat due to the **Q10 effect** and muscular work. - **Peripheral vasoconstriction** is a response to cold; in high heat, the body must **vasodilate** skin vessels to dissipate heat to the environment.
Question 10: A researcher studying metabolic responses observes that during prolonged fasting, brain metabolism shifts partially from glucose to ketone bodies, while RBCs continue using only glucose. What is the fundamental physiological principle explaining this difference?
- A. Brain has higher glucose transporter density
- B. RBCs lack mitochondria and cannot metabolize ketones (Correct Answer)
- C. RBCs preferentially use anaerobic glycolysis for ATP
- D. RBCs lack insulin receptors while brain has them
Explanation: ***RBCs lack mitochondria and cannot metabolize ketones*** - **Ketone body utilization** (ketolysis) requires **mitochondria** to convert beta-hydroxybutyrate and acetoacetate into **acetyl-CoA** for the **TCA cycle**. - Since **RBCs lack mitochondria**, they are incapable of **aerobic respiration** or ketolysis and must rely exclusively on **anaerobic glycolysis** for energy. *Brain has higher glucose transporter density* - While the brain utilizes **GLUT1** and **GLUT3** for glucose uptake, transporter density does not explain the inability of RBCs to use **ketone bodies**. - Higher transporter density prioritizes **glucose delivery** to the brain but does not restrict other tissues from metabolic adaptation. *RBCs preferentially use anaerobic glycolysis for ATP* - It is not a matter of preference but a **physiological necessity**, as RBCs cannot perform **oxidative phosphorylation** due to the absence of mitochondria. - This term explains *how* they get energy from glucose but does not explain *why* they cannot switch to **ketone bodies** during fasting. *RBCs lack insulin receptors while brain has them* - Glucose uptake in both RBCs and the brain is primarily **insulin-independent**, mediated by **GLUT1** and **GLUT3** respectively. - The presence or absence of **insulin receptors** does not determine the capacity of a cell to metabolize **ketone bodies** versus glucose.
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