Anatomy
3 questionsSympathetic supply to the heart arises from which of the following spinal segments?
Which structure is located immediately posterior to the head of the pancreas?
Which statement accurately describes a characteristic of synovial joints?
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 381: Sympathetic supply to the heart arises from which of the following spinal segments?
- A. T1 to T5 (Correct Answer)
- B. T2 to T6
- C. T3 to T7
- D. T4 to T8
Explanation: The preganglionic sympathetic fibers that innervate the heart originate from the lateral horns of the thoracic spinal segments T1 to T5. These fibers synapse in the cervical and upper thoracic sympathetic ganglia, from which postganglionic fibers extend to the heart. While there is some overlap, the primary and most significant sympathetic innervation to the heart stems predominantly from T1 to T5, making T2 to T6 a less precise answer. Including T6 would extend past the typical primary cardiac sympathetic innervation, which largely concludes at T5. This range is too caudal and largely beyond the principal segments providing sympathetic innervation to the heart. Segments T6-T8 are more involved in sympathetic supply to abdominal organs and other structures rather than direct cardiac control.
Question 382: Which structure is located immediately posterior to the head of the pancreas?
- A. Portal vein (Correct Answer)
- B. Splenic artery
- C. Inferior mesenteric vein
- D. Coeliac trunk
Explanation: ***Portal vein*** - The **portal vein** is formed by the union of the **splenic vein** and the **superior mesenteric vein** (SMV) posterior to the **neck** of the pancreas [1]. - It then runs in a **groove on the posterior surface** of the head of the pancreas, lying anterior to the **inferior vena cava** (IVC). - Among the given options, the portal vein has the most direct posterior relationship to the head of the pancreas. *Splenic artery* - The **splenic artery** runs along the **superior border** of the pancreas, following its body and tail. - It does not lie posterior to the head of the pancreas. - It is a branch of the **celiac trunk** and supplies the spleen. *Inferior mesenteric vein* - The **inferior mesenteric vein** typically drains into the **splenic vein** or the junction of the splenic and superior mesenteric veins. - It ascends **anterior** to the left kidney and does not lie immediately posterior to the head of the pancreas. *Coeliac trunk* - The **celiac trunk** originates from the **abdominal aorta** at the level of T12-L1 vertebra. - It lies **superior and anterior** to the pancreas, giving off the splenic artery, common hepatic artery, and left gastric artery. - It is not located posterior to the head of the pancreas.
Question 383: Which statement accurately describes a characteristic of synovial joints?
- A. Hyaline cartilage covers the articular surfaces of synovial joints. (Correct Answer)
- B. The metacarpo-phalangeal joint is a condyloid joint.
- C. Cartilage can sometimes divide the joint into two cavities.
- D. Stability is inversely proportional to mobility in synovial joints.
Explanation: ***Hyaline cartilage covers the articular surfaces of synovial joints.*** - The articular surfaces of bones within a **synovial joint** are covered by a thin layer of **hyaline cartilage**, providing a smooth, low-friction surface for movement [1]. - This **articular cartilage** absorbs shock and protects the underlying bone from wear and tear [1]. - This is a **universal structural characteristic** of all synovial joints, making it the most accurate answer. *The metacarpo-phalangeal joint is a condyloid joint.* - While this statement is factually true (MCP joints are indeed **condyloid/ellipsoid joints** allowing movement in two planes), it describes a **specific type** of synovial joint, not a general characteristic of all synovial joints. - The question asks for a characteristic that describes synovial joints as a category, not an example of one specific joint classification. - This makes it incorrect as the best answer to this question. *Cartilage can sometimes divide the joint into two cavities.* - This statement refers to an **articular disc** or **meniscus**, which is a fibrocartilaginous structure that can partially or completely divide a synovial joint cavity. - This feature is present in **some** synovial joints (like the knee or temporomandibular joint) but is **not universal**. - Since it's not a characteristic of all synovial joints, it's not the best answer. *Stability is inversely proportional to mobility in synovial joints.* - Generally, there is an **inverse relationship** between **stability** and **mobility** in joints; joints designed for great mobility (e.g., shoulder) tend to be less stable, and vice-versa (e.g., hip). - However, this describes a **functional principle** or trade-off rather than a **structural characteristic** that defines synovial joints. - While true, it's not the defining characteristic being asked for in this question.
Dental
1 questionsStability of alveoli is maintained by:
NEET-PG 2012 - Dental NEET-PG Practice Questions and MCQs
Question 381: Stability of alveoli is maintained by:
- A. Negative intrapleural pressure
- B. Residual air in alveoli
- C. Compliance of the lungs
- D. Reduced surface tension by surfactant (Correct Answer)
Explanation: ***Reduced surface tension by surfactant*** - **Surfactant** (a mixture of lipoproteins) reduces the **surface tension** at the air-liquid interface within the alveoli, preventing their collapse at the end of expiration. - This reduction in surface tension helps to maintain the **stability** and patency of the smaller alveoli, preventing them from emptying into larger ones. *Compliance of the lungs* - **Compliance** refers to the distensibility of the lungs and chest wall, indicating how easily they can be stretched. - While pulmonary compliance is important for easy breathing, it does not directly maintain the stability of individual alveoli in preventing their collapse. *Negative intrapleural pressure* - **Negative intrapleural pressure** helps to keep the lungs expanded by creating a vacuum between the visceral and parietal pleura, pulling the lungs outwards. - This pressure prevents the lung as a whole from collapsing but does not directly prevent the collapse of individual alveoli due to surface tension. *Residual air in alveoli* - **Residual volume** is the amount of air remaining in the lungs after a maximal exhalation. - While residual air prevents the complete collapse of the lungs, it is surface tension reduction by surfactant that specifically maintains the stability of individual alveoli against collapse forces.
Obstetrics and Gynecology
1 questionsWhich structure do cytotrophoblasts invade during implantation?
NEET-PG 2012 - Obstetrics and Gynecology NEET-PG Practice Questions and MCQs
Question 381: Which structure do cytotrophoblasts invade during implantation?
- A. Decidua capsularis
- B. Decidua vera
- C. Decidua basalis (Correct Answer)
- D. Decidua parietalis
Explanation: ***Decidua basalis*** - The **cytotrophoblasts** invade the maternal **decidua basalis**, which is the portion of the **endometrium** directly underlying the implanted embryo, forming the maternal component of the **placenta**. - This invasion is crucial for establishing the **placenta** and allowing for nutrient and waste exchange between the mother and the fetus. *Decidua parietalis* - The **decidua parietalis** is the portion of the **endometrium** lining the rest of the **uterine cavity**, not directly involved in the immediate implantation site. - It plays a role later in pregnancy, fusing with the **decidua capsularis** as the **embryo** grows. *Decidua capsularis* - The **decidua capsularis** is the portion of the endometrium that overlies the implanted embryo, separating it from the uterine lumen. - It does not undergo invasion by the **cytotrophoblasts** in the same way the **decidua basalis** does. *Decidua vera* - The **decidua vera** is another term for the **decidua parietalis**, referring to the endometrial lining of the uterine cavity that is not involved in the implantation site. - It is not directly invaded by **cytotrophoblasts** during implantation.
Physiology
5 questionsMechanism by which Ach decreases heart rate is by:
Which one of the following is the CORRECT statement regarding coronary blood flow?
Lesion of preoptic nucleus of hypothalamus is associated with which of the following conditions?
Which part of the brain is responsible for setting posture before planned movement?
Salty taste is due to?
NEET-PG 2012 - Physiology NEET-PG Practice Questions and MCQs
Question 381: 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 382: Which one of the following is the CORRECT statement regarding coronary blood flow?
- A. Coronary blood flow is directly related to perfusion pressure and inversely related to resistance (Correct Answer)
- B. Coronary blood flow is inversely related to perfusion pressure and directly related to resistance
- C. Coronary blood flow is directly related to perfusion pressure and also to resistance
- D. Coronary blood flow is inversely related to both pressure and resistance
Explanation: ***Coronary blood flow is directly related to perfusion pressure and inversely related to resistance*** - According to Ohm's law, **blood flow** is directly proportional to the **pressure gradient (perfusion pressure)** and inversely proportional to the **vascular resistance**. - This fundamental principle applies to coronary circulation, meaning higher pressure drives more flow, while higher resistance impedes it. *Coronary blood flow is inversely related to perfusion pressure and directly related to resistance* - This statement contradicts the basic principles of **fluid dynamics** and **Ohm's law**, where a higher pressure gradient generally leads to increased flow. - Direct proportionality to resistance would imply that increased obstruction leads to increased flow, which is physiologically incorrect. *Coronary blood flow is directly related to perfusion pressure and also to resistance* - While a direct relationship with **perfusion pressure** is correct, directly relating flow to **resistance** is incorrect. - Increased resistance, such as that caused by **atherosclerosis**, reduces blood flow, not increases it. *Coronary blood flow is inversely related to both pressure and resistance* - An inverse relationship with **pressure** is incorrect as an increase in the driving pressure should increase flow. - An inverse relationship with **resistance** is correct, but the inverse relationship with pressure makes the entire statement incorrect.
Question 383: 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 384: Which part of the brain is responsible for setting posture before planned movement?
- A. Motor cortex
- B. Frontal eye fields
- C. Premotor cortex
- D. Supplementary motor cortex (Correct Answer)
Explanation: ***Supplementary motor cortex*** - The **supplementary motor cortex (SMA)** is responsible for **anticipatory postural adjustments** that occur before voluntary movements - It plays a key role in **internal generation and planning of complex motor sequences** - SMA activation precedes movement, ensuring **postural stability and coordination** - Essential for **bilateral coordination** and **motor programming** *Premotor cortex* - The **premotor cortex** is primarily involved in **externally guided movements** and selection of movements based on sensory cues - While it participates in motor planning, it is more focused on **sensory-motor integration** rather than anticipatory postural control *Motor cortex* - The **primary motor cortex** executes voluntary movements by sending signals directly to spinal motor neurons - Responsible for **fine motor control** and determining the **force and direction** of muscle contractions - Functions in **movement execution** rather than preparatory postural adjustments *Frontal eye fields* - The **frontal eye fields** control **voluntary saccadic eye movements** and visual attention - Not involved in trunk or limb **postural preparation** for planned movements
Question 385: Salty taste is due to?
- A. Sodium ion channels (Correct Answer)
- B. Calcium ion channels
- C. G-protein coupled receptors
- D. Proton channels
Explanation: ***Sodium ion channels*** - The sensation of **salty taste** is primarily mediated by the direct influx of **sodium ions (Na+)** into taste receptor cells. - This influx leads to **depolarization** of the cell membrane, triggering neurotransmitter release and signaling to the brain. *Calcium ion channels* - While calcium ions are crucial for various cellular processes, including **neurotransmitter release**, they are not the primary initiators of the salty taste transduction pathway. - Calcium channels are more directly involved in the sensation of **umami** and **sweet tastes**, often via G-protein coupled receptors. *G-protein coupled receptors* - **G-protein coupled receptors (GPCRs)** are responsible for the transduction of **sweet, bitter, and umami tastes**. - They are not involved in the direct detection of **saline compounds**, which operate through ion channels. *Proton channels* - **Proton channels (H+)** are primarily involved in the sensation of **sour taste**. - The influx of protons causes intracellular acidification, leading to cell depolarization.