Anatomy
4 questionsSensory supply of the palm is from which nerves?
What is the anatomical significance of the Rhinion in relation to the osseocartilaginous junction?
Anal valve is found in which part of anal canal?
Which lymph nodes are involved in the lymphatic drainage of the lateral wall of the nose?
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 191: Sensory supply of the palm is from which nerves?
- A. Median nerve and Radial nerve
- B. Radial nerve and ulnar nerve
- C. Ulnar nerve and Median nerve (Correct Answer)
- D. Musculocutaneous nerve and Radial nerve
Explanation: **Ulnar nerve and Median nerve** *(Correct)* - The **median nerve** provides sensory innervation to the lateral palm, including the thumb, index, middle, and radial half of the ring finger [1]. - The **ulnar nerve** supplies sensory innervation to the medial palm, including the little finger and the ulnar half of the ring finger [1]. - Together, these two nerves provide complete sensory coverage of the palm [1]. *Median nerve and Radial nerve* (Incorrect) - While the **median nerve** innervates a significant portion of the palm, the **radial nerve** primarily supplies the dorsal aspect of the hand and a small area of the thenar eminence, not the entire palm. - The radial nerve's sensory supply to the palm is usually limited to a very small area at the base of the thumb. - This combination does not provide complete palmar sensory coverage. *Radial nerve and ulnar nerve* (Incorrect) - The **radial nerve** mainly supplies the dorsum of the hand and digits, with minimal palmar contribution, making this option incorrect for primary palmar sensory supply. - The **ulnar nerve** does innervate part of the palm, but the combination with the radial nerve for complete palmar supply is inaccurate. - The median nerve, not the radial nerve, is the other major contributor to palmar sensation. *Musculocutaneous nerve and Radial nerve* (Incorrect) - The **musculocutaneous nerve** primarily innervates the lateral aspect of the forearm (as the lateral antebrachial cutaneous nerve) and does not contribute to the sensory supply of the palm. - The **radial nerve** also has a limited role in palmar sensation. - Neither of these nerves provides significant sensory innervation to the palm.
Question 192: What is the anatomical significance of the Rhinion in relation to the osseocartilaginous junction?
- A. Nasion
- B. Rhinion (Correct Answer)
- C. Radix
- D. Columella
Explanation: ***Correct Answer: Rhinion*** - The **rhinion** is the **most prominent anterior point of the nasal bone**, often palpable as a slight bump or angulation on the dorsum of the nose. - It marks the anatomical location of the **osseocartilaginous junction** of the nasal dorsum, where the bony nasal framework transitions to the cartilaginous framework. - This is the key anatomical landmark that defines the transition from bone to cartilage in the external nose. *Incorrect: Nasion* - The **nasion** is located at the **root of the nose**, specifically at the most anterior and superior point of the nasofrontal suture. - It is a bony landmark and does not directly relate to the osseocartilaginous junction of the nasal dorsum. *Incorrect: Radix* - The **radix** (or nasal root) refers to the **uppermost part of the nose**, corresponding to the nasion. - It defines the point where the nose begins to project from the forehead and is a bony landmark, not directly related to the osseocartilaginous junction. *Incorrect: Columella* - The **columella** is the **fleshy, narrow strip of tissue that separates the nostrils**. - It forms the inferior segment of the nasal septum and is composed of skin, soft tissue, and the medial crura of the alar cartilages, thus having no direct relation to the osseocartilaginous junction of the nasal dorsum.
Question 193: Anal valve is found in which part of anal canal?
- A. Lower
- B. At anus
- C. Middle (Correct Answer)
- D. Upper
Explanation: ***Middle*** - The **anal valves** are crescentic folds located at the level of the **pectinate (dentate) line** in the middle portion of the anal canal. - They mark the inferior limit of the **anal columns** and form small recesses called **anal sinuses**. *Lower* - The lower part of the anal canal, below the pectinate line, is lined by **anoderm** and lacks anal valves. - This region is sensitive to pain due to somatic innervation. *At anus* - The anus refers to the external opening and perianal skin, which does not contain anal valves. - The anal canal transitions into the perianal skin at the anocutaneous line. *Upper* - The upper part of the anal canal, above the pectinate line, contains the **anal columns (columns of Morgagni)** but not the anal valves themselves, which are located at the base of these columns. - This region is lined by columnar epithelium and is relatively insensitive to pain.
Question 194: Which lymph nodes are involved in the lymphatic drainage of the lateral wall of the nose?
- A. Deep cervical nodes
- B. Retropharyngeal nodes
- C. Submandibular nodes
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - The lymphatic drainage from the **lateral wall of the nose** follows a sequential pathway involving **submandibular nodes**, **retropharyngeal nodes**, and ultimately the **deep cervical nodes**. - This question tests understanding of the complete lymphatic drainage pathway, not just the primary drainage site. - All three node groups are anatomically involved in draining lymph from the lateral nasal wall. **Drainage Pathway:** - **Submandibular nodes** (Primary): The anterior and middle portions of the lateral nasal wall drain primarily to the submandibular lymph nodes. - **Retropharyngeal nodes** (Secondary): The posterior portions of the lateral wall and areas near the nasal pharynx drain to retropharyngeal nodes. - **Deep cervical nodes** (Final pathway): Lymph from both submandibular and retropharyngeal nodes eventually drains into the deep cervical chain, particularly the jugulodigastric and juguloomohyoid nodes. *Why not just one node group?* - The lateral wall of the nose has an extensive lymphatic network with multiple drainage routes. - Different regions of the lateral wall have preferential drainage to different node groups. - Understanding the complete drainage pathway is clinically important for assessing spread of infections and malignancies from the nasal cavity.
Physiology
6 questionsMechanism by which Ach decreases heart rate is by:
Lesion of preoptic nucleus of hypothalamus is associated with which of the following conditions?
Which substrate is both secreted and filtered by the kidneys?
What is the average progressive velocity of human sperm under standard laboratory conditions?
What is the primary physiological effect of increased 2,3-DPG on hemoglobin?
Which sensory modalities are most directly affected by lesions of the primary somatosensory cortex?
NEET-PG 2012 - Physiology NEET-PG Practice Questions and MCQs
Question 191: Mechanism by which Ach decreases heart rate is by:
- A. Prolongation of action potential duration
- B. Reduction in calcium influx
- C. Inhibition of sympathetic activity
- D. Delayed diastolic depolarization (Correct Answer)
Explanation: ***Delayed diastolic depolarization*** - Acetylcholine (ACh) binding to muscarinic receptors on nodal cells increases **potassium permeability**, leading to a more negative maximal diastolic potential. - This slows the rate of **spontaneous depolarization** (pacemaker potential), thereby delaying the point at which the threshold for an action potential is reached and reducing heart rate. *Prolongation of action potential duration* - ACh typically **shortens** the action potential duration in atrial and nodal cells by increasing potassium efflux, which hyperpolarizes the cell and hastens repolarization. - A prolonged action potential duration would generally lead to a **slower heart rate** by increasing the refractory period, but this is achieved through different ionic mechanisms and is not the primary mechanism of ACh. *Reduction in calcium influx* - While ACh does reduce the inward **calcium current (ICa)** in nodal cells, contributing to a slower heart rate and weaker contractility, this effect primarily influences the upstroke and peak of the action potential. - The more **fundamentally important mechanism** for heart rate reduction is the impact on the pacemaker potential's slope, which is governed by altered ion conductances, predominantly potassium. *Inhibition of sympathetic activity* - ACh acts directly on **muscarinic receptors** on cardiac cells to decrease heart rate, which is a parasympathetic effect. - It does not directly inhibit sympathetic nerve activity but rather **counteracts sympathetic effects** by directly modulating cardiac cell physiology.
Question 192: Lesion of preoptic nucleus of hypothalamus is associated with which of the following conditions?
- A. Impaired thermoregulation
- B. Increased body temperature
- C. Hyperthermia (Correct Answer)
- D. Normal thermoregulation
Explanation: ***Hyperthermia*** - The **preoptic nucleus** of the anterior hypothalamus is the primary **heat-loss center** containing warm-sensitive neurons. - Lesion of this area impairs **heat dissipation mechanisms** (sweating, cutaneous vasodilation), preventing the body from lowering its temperature. - Results in **hyperthermia** - a pathological elevation of core body temperature due to failure of heat dissipation, not a change in set point. - This is the **most specific and clinically accurate** term for this condition. *Impaired thermoregulation* - While technically true, this is too **broad and non-specific**. - Impaired thermoregulation could refer to inability to either increase or decrease temperature. - In medical terminology, we use more specific terms like "hyperthermia" to describe the actual clinical condition. *Increased body temperature* - This is a **general descriptive term** rather than a specific clinical diagnosis. - While the body temperature is indeed increased, **hyperthermia** is the precise medical term that indicates the mechanism (impaired heat dissipation). - Less specific than "hyperthermia" for exam purposes. *Normal thermoregulation* - Clearly incorrect - a lesion in the primary thermoregulatory center would **abolish normal temperature control**. - The preoptic nucleus is essential for detecting and responding to temperature changes.
Question 193: Which substrate is both secreted and filtered by the kidneys?
- A. Glucose
- B. Urea
- C. Uric Acid (Correct Answer)
- D. Na+
Explanation: ***Uric Acid*** - **Uric acid** is freely **filtered** at the glomerulus. - It undergoes both **secretion** and reabsorption in the renal tubules, making it a substrate that is both secreted and filtered. *Glucose* - **Glucose** is freely **filtered** at the glomerulus but is almost completely **reabsorbed** in the proximal tubule under normal physiological conditions. - It is not actively secreted by the renal tubules. *Urea* - **Urea** is freely **filtered** at the glomerulus. - It undergoes **reabsorption** (especially in the medullary collecting duct) and some facilitated diffusion, but significant active secretion is not its primary handling mechanism. *Na+* - **Sodium (Na+)** is freely **filtered** at the glomerulus in large quantities. - Its renal handling is dominated by extensive **reabsorption** throughout the nephron, which is crucial for fluid balance and blood pressure regulation, with no active secretion.
Question 194: What is the average progressive velocity of human sperm under standard laboratory conditions?
- A. 1-3 mm/min (Correct Answer)
- B. 4-6 mm/min
- C. 6-9 mm/min
- D. 10-13 mm/min
Explanation: ***1-3 mm/min*** - The typical average progressive velocity of human sperm, categorized as **Grade A (rapid progressive)** motility, ranges from **25 micrometers/second or faster**, which translates to approximately 1-3 mm/minute. - This velocity is crucial for sperm to traverse the female reproductive tract and reach the ovum for fertilization. *4-6 mm/min* - This velocity range is significantly faster than the **average progressive velocity** observed in viable human sperm under standard laboratory conditions. - While some individual sperm may achieve higher speeds, this range is not representative of the **average progressive motility** of a healthy sperm population. *6-9 mm/min* - This progressive velocity is exceptionally high and not typically observed as the average for human sperm, even for highly motile sperm. - Such a high velocity would indicate an **abnormally fast movement** not compatible with biological norms for average progressive motility. *10-13 mm/min* - This range represents an extremely rapid progressive velocity for human sperm, well beyond physiological averages. - It does not align with the standard measurements for **progressive motility**, which are generally much lower.
Question 195: What is the primary physiological effect of increased 2,3-DPG on hemoglobin?
- A. Increased affinity of hemoglobin to oxygen
- B. Decreased affinity of hemoglobin to oxygen (Correct Answer)
- C. Left shift of oxygen-hemoglobin dissociation curve
- D. Right shift of oxygen-hemoglobin dissociation curve
Explanation: ***Decreased affinity of hemoglobin to oxygen*** - **2,3-Diphosphoglycerate (2,3-DPG)** binds to the beta subunits of deoxyhemoglobin, stabilizing the **deoxygenated state** and thus **reducing hemoglobin's affinity for oxygen**. - This is the **primary molecular mechanism** by which 2,3-DPG exerts its effect, facilitating **oxygen unloading** in peripheral tissues. - This decreased affinity manifests graphically as a **right shift** in the oxygen-hemoglobin dissociation curve. *Increased affinity of hemoglobin to oxygen* - This is incorrect because 2,3-DPG specifically works to **decrease hemoglobin's affinity** for oxygen, promoting oxygen release. - Increased affinity would mean oxygen is held more tightly, which is counterproductive for **oxygen delivery** to tissues. *Left shift of oxygen-hemoglobin dissociation curve* - A **left shift** indicates **increased affinity** of hemoglobin for oxygen, meaning oxygen is held more tightly. - Since 2,3-DPG decreases affinity, it causes a **right shift**, not a left shift. *Right shift of oxygen-hemoglobin dissociation curve* - While this is the **graphical representation** of 2,3-DPG's effect, it is a **consequence** of the primary molecular mechanism (decreased affinity). - A right shift signifies that for any given partial pressure of oxygen, hemoglobin is **less saturated** with oxygen, reflecting the decreased affinity caused by 2,3-DPG binding.
Question 196: Which sensory modalities are most directly affected by lesions of the primary somatosensory cortex?
- A. Pain, temperature, and touch
- B. Vibration and proprioception
- C. Localization and two-point discrimination (Correct Answer)
- D. All of the options
Explanation: ***Localization and two-point discrimination*** - Lesions in the **primary somatosensory cortex** (S1) lead to profoundly impaired **discriminative touch**, which includes the ability to precisely localize tactile stimuli and distinguish between two closely spaced points. - These are the **most characteristic deficits** of S1 lesions, representing the cortex's unique role in processing **spatial discrimination and fine sensory analysis**. - S1 is essential for the **integrative functions** that allow precise spatial mapping of sensory inputs. *Pain, temperature, and touch* - Basic touch perception is affected, but **pain and temperature** are primarily mediated by the **spinothalamic tracts** with substantial processing in the thalamus, insular cortex, and anterior cingulate cortex rather than S1. - Crude touch sensation remains relatively preserved with S1 lesions; it is the **discriminative quality** that is lost. - These modalities are NOT the most directly affected by isolated S1 lesions. *Vibration and proprioception* - **Vibration** and **proprioception** are indeed significantly impacted by S1 lesions as S1 receives thalamic projections from the **dorsal column-medial lemniscus (DCML) pathway**. - However, these modalities have substantial **subcortical representation** in the thalamus and can be partially preserved even with cortical damage. - In contrast, **localization and two-point discrimination** are purely cortical functions with no subcortical processing, making them the MOST directly and exclusively dependent on S1 integrity. *All of the options* - This is incorrect because pain and temperature perception is NOT most directly affected by S1 lesions—these are primarily processed by other pathways and cortical areas (spinothalamic system, insular cortex).