Osteoclasts have all of the following functions except -
Locking of the knee involves which of the following?
During pregnancy, the increased size of the pituitary gland is primarily due to the enlargement of which hormone-secreting cells?
Gamma waves of REM sleep are associated with?
Which type of pain is characterized by unknown etiology?
Which of the following is not true about sleep -
Most recently identified taste sensation is?
Vibration sense is detected by ?
Stress induced hyperglycemia is mediated through which hormone:
NEET-PG 2015 - Physiology NEET-PG Practice Questions and MCQs
Question 111: Osteoclasts have all of the following functions except -
- A. Receptor for parathormone (Correct Answer)
- B. Ruffled border
- C. Bone resorption
- D. RANK ligand production
Explanation: ***Receptor for parathormone*** - **Osteoclasts** do not directly have receptors for **parathormone (PTH)**; instead, **osteoblasts** have PTH receptors. - When PTH binds to osteoblasts, they release factors (like **RANKL**) that stimulate osteoclast activity, thus indirectly regulating bone resorption. *Bone resorption* - **Osteoclasts** are specialized cells primarily responsible for **resorbing bone matrix**, a critical process in bone remodeling. - They secrete **acids and enzymes** to break down the mineral and organic components of bone. *Ruffled border* - The **ruffled border** is a characteristic morphological feature of active osteoclasts, representing a highly folded plasma membrane. - This specialized structure increases the surface area for the secretion of **protons and lysosomal enzymes** into the bone-resorbing compartment. *RANK ligand production* - **Osteoclasts** do not produce **RANK ligand (RANKL)**; rather, they have **RANK receptors** that bind to RANKL produced by **osteoblasts and stromal cells**. - The binding of RANKL to RANK is essential for the **differentiation, activation, and survival** of osteoclasts.
Question 112: Locking of the knee involves which of the following?
- A. Internal rotation of the tibia with the foot on the ground
- B. Contraction of the popliteus muscle
- C. Internal rotation of the femur with the foot on the ground (Correct Answer)
- D. External rotation of femur with the foot off the ground
Explanation: ***Internal rotation of the femur with the foot on the ground*** - When the foot is on the ground (closed kinematic chain), the **femur rotates internally on the tibia** during the end stages of knee extension. This creates a more stable, "locked" position of the knee. - This **terminal rotation of the femur** increases the contact area and tension in the cruciate ligaments, enhancing joint stability for weight-bearing. *Internal rotation of the tibia with the foot on the ground* - This describes the action of the **popliteus muscle** when "unlocking" the knee from full extension, not the locking mechanism itself. - With the foot on the ground, the tibia is fixed, and internal rotation would typically be a movement for unlocking, not locking. *Contraction of the popliteus muscle* - The **popliteus muscle** is primarily responsible for **unlocking the knee** from full extension, by causing internal rotation of the tibia (or external rotation of the femur). - Its contraction would lead to initial flexion of the knee, releasing the locked position, not establishing it. *External rotation of femur with the foot off the ground* - With the foot off the ground (open kinematic chain), **external rotation of the tibia** occurs during the final degrees of extension to lock the knee, not external rotation of the femur. - The locking mechanism requires specific relative rotation between femur and tibia; external rotation of the femur alone would not achieve the screw-home mechanism necessary for knee locking.
Question 113: During pregnancy, the increased size of the pituitary gland is primarily due to the enlargement of which hormone-secreting cells?
- A. Growth hormone
- B. Prolactin (Correct Answer)
- C. ACTH
- D. TSH
Explanation: ***Prolactin*** - During pregnancy, the number and size of **lactotrophs**, the cells that secrete prolactin, increase significantly due to high **estrogen** levels. - This **hyperplasia** and **hypertrophy** of lactotrophs contribute to the overall enlargement of the pituitary gland, preparing it for lactation. *Growth hormone* - While growth hormone is important, there isn't a primary enlargement of **somatotrophs** (GH-secreting cells) in the pituitary during pregnancy. - Furthermore, most circulating GH during pregnancy is **placental growth hormone**, rather than pituitary-derived. *ACTH* - Adrenocorticotropic hormone (ACTH) is secreted by **corticotrophs**, and these cells do not undergo prominent hypertrophy or hyperplasia during normal pregnancy. - While cortisol levels increase, this is largely due to factors other than increased pituitary ACTH cell size. *TSH* - Thyroid-stimulating hormone (TSH) is secreted by **thyrotrophs**, which do not notably enlarge during pregnancy. - Thyroid gland activity increases during pregnancy, but this is mediated by **hCG** and other mechanisms, not pituitary thyrotroph growth.
Question 114: Gamma waves of REM sleep are associated with?
- A. Dream consciousness and memory consolidation
- B. Deep subconscious processing
- C. Non-REM sleep
- D. Subconscious processing (Correct Answer)
Explanation: ***Subconscious processing*** - **Gamma waves (30-100 Hz)** during **REM sleep** represent high-frequency neural oscillations associated with **complex cognitive processing** occurring below the level of conscious awareness. - These waves reflect **integration of neural activity** across different brain regions, facilitating information processing and neural plasticity during sleep. - The term encompasses the underlying **neural mechanisms** that support dream generation and memory consolidation processes. *Dream consciousness and memory consolidation* - While **gamma waves** do correlate with dreaming and memory processes during **REM sleep**, these represent the **experiential and functional outcomes** rather than the primary neurophysiological association. - Dream consciousness is a **manifestation** of the underlying subconscious processing, not the direct association with gamma wave activity itself. *Deep subconscious processing* - The term "deep subconscious" is **non-specific** and lacks precise neurophysiological definition in the context of gamma wave activity. - While directionally correct, this option uses imprecise terminology compared to the more accurate "subconscious processing." *Non-REM sleep* - **Gamma waves** are characteristic of **waking states** and **REM sleep**, not non-REM sleep stages. - **Non-REM sleep** (stages N1, N2, N3) is dominated by **slower wave activity** including theta waves (stage N1), sleep spindles and K-complexes (stage N2), and delta waves (stage N3/deep sleep).
Question 115: Which type of pain is characterized by unknown etiology?
- A. Nociceptive pain
- B. Neuropathic pain
- C. Idiopathic pain (Correct Answer)
- D. Inflammatory pain
Explanation: ***Idiopathic pain*** - This term refers to pain where the **underlying cause** or pathology cannot be identified, despite thorough investigation. - It signifies that the **etiology is unknown**, fitting the description in the question directly. *Nociceptive pain* - This type of pain arises from the activation of **nociceptors** due to actual or threatened tissue damage. - Its etiology is typically clear, involving an injury, inflammation, or mechanical stress. *Neuropathic pain* - This pain results from damage or disease affecting the **somatosensory nervous system**. - The etiology is known to be nerve damage or dysfunction, not an unknown origin. *Inflammatory pain* - This pain is driven by the inflammatory process, involving the release of **pro-inflammatory mediators** at the site of tissue injury or infection. - The cause is directly linked to inflammation, making its etiology known.
Question 116: Which of the following is not true about sleep -
- A. Dreams come in REM sleep
- B. REM sleep comes earlier than NREM sleep (Correct Answer)
- C. REM sleep is also called paradoxical sleep
- D. Sleep walking comes in NREM sleep
Explanation: ***REM sleep comes earlier than NREM sleep*** - This statement is **incorrect** because the sleep cycle typically begins with **NREM (non-rapid eye movement) sleep**, specifically NREM stage 1, before progressing to NREM stages 2 and 3, and then finally entering REM sleep. - NREM sleep accounts for about **75% of total sleep time** and occurs prior to REM sleep in a typical nocturnal sleep episode. *Dreams come in REM sleep* - This statement is **true** as **vivid, memorable dreams** are most commonly associated with **REM sleep**. - During REM sleep, brain activity significantly increases, mimicking the awake state, which facilitates complex dream formation. *REM sleep is also called paradoxical sleep* - This statement is **true** because **REM sleep** is characterized by **high brain activity** (similar to wakefulness) and rapid eye movements, yet the body experiences **muscle atonia**, leading to a state of profound relaxation. - This paradoxical combination of an active brain and a paralyzed body gives it the name **paradoxical sleep**. *Sleep walking comes in NREM sleep* - This statement is **true** as **sleepwalking (somnambulism)** typically occurs during **slow-wave sleep**, which is **NREM stage 3 (deep sleep)**. - During this stage, arousal thresholds are very high, and complex motor behaviors can occur while the individual remains in a sleep state.
Question 117: Most recently identified taste sensation is?
- A. Sour
- B. Bitter
- C. Umami (Correct Answer)
- D. Sweet
Explanation: ***Umami*** - **Umami** is the most recently identified **fifth basic taste**, often described as a savory or meaty taste. - Its discovery and recognition as a distinct taste sensation occurred in the **early 20th century** by Kikunae Ikeda, who isolated glutamate from kombu. *Sour* - The sensation of **sourness** is one of the traditionally recognized basic tastes, identified much earlier than umami. - It is typically associated with **acids**, such as those found in lemons or vinegar. *Bitter* - **Bitterness** is another long-standing basic taste that serves an important protective function, often signaling potential toxins. - It is one of the earliest tastes understood and recognized, with receptors for a wide range of bitter compounds. *Sweet* - **Sweetness** is a fundamental and ancient taste, universally recognized as pleasurable and indicating energy-rich foods. - The perception of sweet taste, primarily from sugars, has been understood for centuries.
Question 118: Vibration sense is detected by ?
- A. Superficial receptors
- B. Free nerve endings
- C. Nociceptors
- D. Deep receptors (Correct Answer)
Explanation: ***Deep receptors*** - **Vibration sense** is primarily mediated by **Pacinian corpuscles** and **Meissner's corpuscles**, which are considered deep receptors. - **Pacinian corpuscles** are located in the **deep dermis** and **subcutaneous tissue** and are highly sensitive to **high-frequency vibration** (200-300 Hz). - **Meissner's corpuscles** in dermal papillae detect **lower frequency vibration** and are rapidly adapting mechanoreceptors. *Superficial receptors* - **Superficial receptors** like **Merkel cells** primarily detect **sustained touch** and **pressure**, providing information about texture. - While they contribute to tactile sensation, they are **slowly adapting** and not specialized for rapidly oscillating stimuli like vibration. *Free nerve endings* - **Free nerve endings** are unmyelinated or lightly myelinated nerve terminals that detect **pain**, **temperature**, and **crude touch**. - They are not specialized mechanoreceptors and lack the structural organization needed to transduce vibratory stimuli. *Nociceptors* - **Nociceptors** are specialized sensory receptors that detect **noxious (harmful) stimuli** and mediate the sensation of **pain**. - They respond to extreme temperatures, intense mechanical stress, or chemical irritants, not to non-painful vibration.
Question 119: Stress induced hyperglycemia is mediated through which hormone:
- A. Cortisol (Correct Answer)
- B. Epinephrine
- C. Insulin
- D. Growth hormone
Explanation: ***Cortisol*** - **Cortisol** is the **primary mediator** of stress-induced hyperglycemia among the counter-regulatory hormones - It promotes **gluconeogenesis** (formation of new glucose from amino acids and glycerol) in the liver - Stimulates **protein catabolism** in muscles, providing substrates for gluconeogenesis - Induces **insulin resistance** in peripheral tissues, reducing glucose uptake - Released as part of the **HPA axis response** to stress, with sustained elevation during prolonged stress - This is the **correct answer** for stress-induced hyperglycemia mediation *Epinephrine* - **Epinephrine** (adrenaline) is a potent hyperglycemic hormone but acts as an **acute, immediate response** to stress - Rapidly increases blood glucose through **glycogenolysis** (breakdown of glycogen) in liver and muscles - Stimulates **gluconeogenesis** and inhibits insulin secretion - Effects are **rapid but short-lived**, making it more of an emergency response rather than the sustained mediator - Works synergistically with cortisol but is not the primary sustained mediator *Growth hormone* - **Growth hormone** does contribute to hyperglycemia through **anti-insulin effects** and promoting lipolysis - Its hyperglycemic effects are **slower and less pronounced** compared to cortisol and epinephrine - Plays a role in **chronic stress** but is not the primary acute mediator - More important for **long-term metabolic adaptation** rather than immediate stress response *Insulin* - **Insulin** is a **glucose-lowering hormone** that facilitates glucose uptake into cells - During stress, insulin secretion is **suppressed** and tissues become **insulin-resistant** due to counter-regulatory hormones - It does **not mediate** stress-induced hyperglycemia; rather, its action is **opposed** by stress hormones - Decreased insulin action contributes to hyperglycemia but insulin itself is not the mediator