Percentage of COHb that usually causes death:
Why do eyebrows not grow beyond a certain length?
Haarscheiben Cells in epidermis are responsible for
Hormone primarily responsible for blood pressure regulation following acute blood loss is:
Which of the following actions of GH is mediated by IGF-1?
NEET-PG 2013 - Physiology NEET-PG Practice Questions and MCQs
Question 91: Percentage of COHb that usually causes death:
- A. > 70%
- B. > 60%
- C. > 80% (Correct Answer)
- D. > 50%
Explanation: ***> 80%*** - While significant symptoms occur at lower levels, **COHb levels above 80%** typically cause profound central nervous system depression leading to **cardiac arrest and death**. - This level indicates almost complete displacement of oxygen from hemoglobin, leading to severe **tissue hypoxia**. *> 70%* - At **COHb levels above 70%**, individuals are often in a **coma**, experiencing severe **cardiac dysfunction** and respiratory failure. - Death is highly probable at this level, though it is not the universally accepted threshold for lethality as higher percentages are more definitive for causing death. *> 60%* - At **COHb levels above 60%**, patients typically experience **coma, convulsions**, and significant **cardiovascular compromise**. - While extremely dangerous and often fatal, **COHb levels above 80%** are more reliably associated with death. *> 50%* - At **COHb levels above 50%**, individuals often experience **coma, seizures**, and severe **metabolic acidosis**. - While critical and life-threatening, death is less common at this percentage compared to those above 70% or 80%, as aggressive medical intervention may still be effective.
Question 92: Why do eyebrows not grow beyond a certain length?
- A. Telogen phase
- B. Anagen phase (Correct Answer)
- C. Catagen phase
- D. Exogen phase
Explanation: **Anagen phase** - The **anagen phase**, or growing phase, is significantly shorter for eyebrow hairs (typically 30-45 days) compared to scalp hair (2-7 years), which limits their maximum length. - The duration of this active growth phase **determines the ultimate length** hair can reach before it transitions to resting and shedding. *Telogen phase* - The **telogen phase** is a **resting phase** where the hair follicle is completely inactive; it does not contribute to the hair's growth or final length. - During this phase, the old hair is shed to make way for new hair growth, but it is not the phase that dictates the maximum length. *Catagen phase* - The **catagen phase** is a **transitional phase** lasting about 2-3 weeks, during which hair growth stops and the hair follicle shrinks. - This phase prepares the hair for resting and shedding but does not directly limit how long the hair grows. *Exogen phase* - The **exogen phase** is when a hair is **shed from the follicle**, often aided by activities like washing or brushing. - This phase is responsible for hair shedding, not for limiting the maximum length hair can attain.
Question 93: Haarscheiben Cells in epidermis are responsible for
- A. Pressure
- B. Touch (Correct Answer)
- C. Proprioception
- D. Temperature
Explanation: ***Touch*** - **Haarscheiben cells**, also known as **Merkel cells**, are specialized epidermal cells associated with nerve endings. - They are primarily responsible for sensing **light touch** and **discriminative touch**, playing a crucial role in tactile sensation. *Pressure* - While Merkel cells contribute to touch sensation, the primary receptors for **deep pressure** and vibration are **Pacinian corpuscles**, located deeper in the dermis and hypodermis. - Light pressure can be detected by other mechanoreceptors such as **Meissner's corpuscles**. *Proprioception* - **Proprioception** refers to the sense of body position and movement. - Receptors for proprioception are mainly located in **muscles, tendons, and joints** (e.g., muscle spindles, Golgi tendon organs), not primarily in the epidermis. *Temperature* - **Temperature sensation** is mediated by **thermoreceptors**, which are free nerve endings in the skin. - These receptors (e.g., Krause end bulbs for cold, Ruffini endings for warmth) are distinct from Haarscheiben/Merkel cells.
Question 94: Hormone primarily responsible for blood pressure regulation following acute blood loss is:
- A. Aldosterone
- B. ANP
- C. Epinephrine
- D. ADH (Correct Answer)
Explanation: ***ADH*** - **Antidiuretic hormone (ADH)**, also known as **vasopressin**, is released in response to decreased blood volume and pressure detected by **baroreceptors**. - Its primary role is to increase water reabsorption in the **renal collecting ducts** and cause **vasoconstriction**, both of which help restore blood volume and pressure. - This makes ADH the key **hormonal mechanism** for BP regulation following acute blood loss. *Aldosterone* - **Aldosterone** is crucial for long-term **blood pressure regulation** by increasing sodium and water reabsorption in the kidneys. - While important for volume restoration, its effects are **slower** (hours) and more focused on electrolyte balance rather than immediate BP stabilization after acute blood loss. *ANP* - **Atrial natriuretic peptide (ANP)** is released in response to **atrial stretch** due to increased blood volume and acts to lower blood pressure. - It promotes **vasodilation** and **sodium/water excretion**, counteracting the body's efforts to raise blood pressure after blood loss. - ANP levels are **suppressed** during hypovolemia. *Epinephrine* - **Epinephrine** increases heart rate and cardiac contractility, and causes vasoconstriction, providing an immediate increase in blood pressure. - However, it's primarily a **catecholamine** (not a classic hormone) part of the **sympathetic nervous system** response, and while it acts immediately, ADH provides the sustained hormonal BP regulation.
Question 95: Which of the following actions of GH is mediated by IGF-1?
- A. Na+ retention
- B. decreases insulin
- C. Antilipolysis (Correct Answer)
- D. Lipolysis
Explanation: ***Antilipolysis*** * **Insulin-like growth factor 1 (IGF-1)**, stimulated by GH, plays a role in reducing **lipolysis** indirectly. * IGF-1 promotes **anabolic processes** and nutrient storage, which can lead to decreased fat breakdown. *Na+ retention* * **Na+ retention** is more directly influenced by hormones like **aldosterone** and **ADH**, not IGF-1. * While GH can exert some influence on fluid and electrolyte balance, this specific action is not primarily mediated by IGF-1. *decreases insulin* * IGF-1 and GH generally tend to **increase insulin sensitivity** in some tissues or antagonize insulin effects indirectly. * IGF-1's primary metabolic role is not to decrease insulin itself directly. *Lipolysis* * **Growth hormone (GH)** directly promotes **lipolysis**, breaking down fat for energy. * However, the question specifically asks for actions mediated by **IGF-1**, which has an opposite, antilipolytic effect.