Integrative Physiology — MCQs

Integrative Physiology Indian Medical PG Practice Questions and MCQs

Question 11: What does GAS refer to?

A. Homeostasis
B. Adaptation to new situations
C. The pattern of physiological response to stress
D. The pathway of stress (autonomic nervous system) when aroused by a stressful situation (Correct Answer)

Explanation: **Explanation:** **General Adaptation Syndrome (GAS)**, a concept popularized by Hans Selye, describes the predictable three-stage physiological response the body undergoes when subjected to significant or prolonged stress. **Why Option D is Correct:** GAS refers to the specific **pathway of stress** involving the neuroendocrine system. When the body is aroused by a stressor, the **Autonomic Nervous System (ANS)**—specifically the sympathetic-adrenal-medullary (SAM) axis—is immediately activated (the "Alarm" stage). This triggers the "fight or flight" response, followed by the activation of the Hypothalamic-Pituitary-Adrenal (HPA) axis to maintain resistance. **Analysis of Incorrect Options:** * **Option A (Homeostasis):** While GAS aims to restore balance, homeostasis refers to the stable internal equilibrium of the body. GAS is the *process* of responding to a disruption of that equilibrium. * **Option B (Adaptation to new situations):** This is too broad. While adaptation occurs during the "Resistance" stage of GAS, the term specifically refers to the physiological stress response pattern, not general behavioral adaptation. * **Option C (The pattern of physiological response to stress):** While this is a common definition of GAS, in the context of medical examinations, the emphasis is often on the **functional pathway** (ANS and endocrine involvement) that mediates these responses. **High-Yield NEET-PG Pearls:** 1. **Three Stages of GAS:** * **Alarm Reaction:** Immediate sympathetic nervous system activation (Catecholamines). * **Resistance:** The body attempts to cope; HPA axis activation (Cortisol). * **Exhaustion:** Resources are depleted, leading to "diseases of adaptation" (e.g., hypertension, ulcers). 2. **Key Mediator:** Hans Selye identified **Cortisol** as the primary hormone driving the long-term resistance phase. 3. **Clinical Link:** Chronic GAS activation is linked to immunosuppression and psychosomatic disorders.

Question 12: Which of the following is an example of feed forward mechanism?

A. Temperature regulation (Correct Answer)
B. Vasoconstriction in response to cooling
C. Increase in cardiac output in response to anemia
D. HR increases from supine to standing

Explanation: ***Temperature regulation*** - Temperature regulation is the correct answer because it demonstrates **feed-forward control** through **anticipatory mechanisms** that act *before* core body temperature changes. - Classic feed-forward example: When **skin thermoreceptors** detect intense sunlight or environmental heat, the body initiates protective responses (behavioral changes like seeking shade, peripheral vasodilation, sweating) *before* core temperature rises. - This anticipatory control contrasts with feedback mechanisms that respond *after* detecting changes in the regulated variable. - The feed-forward component uses **peripheral sensors** and central command signals to proactively maintain **homeostasis**, preventing disturbances rather than correcting them. *Incorrect: HR increases from supine to standing* - This is a classic **negative feedback loop** controlled by the **baroreflex**. - Sequence: Standing → blood pools → BP drops → baroreceptors detect change → HR increases to restore BP. - The response occurs *after* detecting the disturbance (reactive, not anticipatory). *Incorrect: Vasoconstriction in response to cooling* - This is **negative feedback** to maintain core body temperature. - **Peripheral thermoreceptors** detect temperature drop → hypothalamus responds → **vasoconstriction** via **sympathetic stimulation** minimizes heat loss. - The response follows detection of cooling (reactive mechanism). *Incorrect: Increase in cardiac output in response to anemia* - This is homeostatic **negative feedback** compensating for reduced **oxygen delivery**. - Tissue hypoxia from anemia → increased **sympathetic drive** → elevated **Cardiac Output (CO)** to maximize oxygen transport. - The compensation occurs *after* oxygen delivery becomes inadequate.

Question 13: A neonate while suckling milk can respire without difficulty due to:

A. Small pharynx
B. Soft palate
C. High larynx (Correct Answer)
D. Small tongue

Explanation: ***High larynx*** - A neonate's **larynx** is positioned much higher in the neck compared to an adult, specifically near the **nasopharynx**. - This high position allows the **epiglottis** to overlap with the **soft palate**, creating a continuous air passage from the nose to the lungs even while milk is being swallowed in the oral cavity. *Small pharynx* - While neonates do have smaller anatomical structures, a "small pharynx" itself does not explain simultaneous breathing and suckling. - The critical factor is how the pharynx interacts with the larynx and soft palate, not just its size. *Soft palate* - The **soft palate** plays a crucial role by contacting the epiglottis, but it is its interaction with the high larynx that enables the dual function, not the soft palate in isolation. - The soft palate's ability to elevate and separate the oral and nasal cavities is important for swallowing, but its specific position relative to the larynx is key during suckling. *Small tongue* - A neonate's tongue is relatively large compared to the oral cavity, filling most of the space, which is actually beneficial for creating a seal around the nipple. - The size of the tongue does not directly account for the ability to respire during suckling; rather, it's about the **laryngeal positioning**.

Question 14: Which of the following is the most immediate cardiovascular response to acute stress?

A. Increased heart rate (Correct Answer)
B. Decreased heart rate
C. Release of cortisol
D. Decreased blood pressure

Explanation: ***Increased heart rate*** - The **sympathetic nervous system** is immediately activated during acute stress, leading to a rapid release of **catecholamines** (epinephrine and norepinephrine). - These hormones directly stimulate the heart, causing an almost instantaneous increase in its **rate and contractility**. *Decreased heart rate* - A decreased heart rate, or **bradycardia**, is characteristic of a **parasympathetic response**, which aims to conserve energy and promote rest. - This is the opposite of the "fight-or-flight" response seen in acute stress. *Release of cortisol* - **Cortisol** is a steroid hormone released by the adrenal cortex as part of the **hypothalamic-pituitary-adrenal (HPA) axis** response to stress. - While important in the stress response, its release and effects are **slower** and more sustained compared to the immediate cardiovascular changes mediated by the sympathetic nervous system. *Decreased blood pressure* - Acute stress typically causes an **increase in blood pressure** due to **vasoconstriction** and increased cardiac output. - A decrease in blood pressure (hypotension) would be an atypical and potentially dangerous response to acute stress, often indicative of shock or other severe conditions.

Practice by Chapter

Homeostatic Control Systems

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Stress Response and Adaptation

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Circadian Rhythms Integration

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Physiological Responses to Exercise

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Integrated Metabolic Regulation

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Thirst and Fluid Balance Integration

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Hunger and Satiety Regulation

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Physiological Basis of Behavior

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Systems Physiology Approach

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Physiological Biomarkers

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