Anatomy
4 questionsWhich of the following is derived from endoderm?
Sympathetic supply to the heart arises from which of the following spinal segments?
Ophthalmic artery is a branch of:
Primordial germ cells are derived from:
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 121: Which of the following is derived from endoderm?
- A. Gall bladder (Correct Answer)
- B. Lens
- C. Spleen
- D. Lymph nodes
Explanation: ***Gall bladder*** - The **gallbladder**, along with other organs of the **gastrointestinal tract** such as the liver, pancreas, and epithelial lining of the digestive and respiratory systems, originates from the **endoderm** [1]. - The endoderm forms the primitive gut tube, from which these accessory digestive organs bud off. *Lens* - The **lens of the eye** is derived from the **surface ectoderm**, which invaginates to form the lens vesicle. - This contrasts with the neural ectoderm, which forms the neural tube and retina. *Spleen* - The **spleen** is derived from the **mesoderm**, specifically from mesenchymal cells in the dorsal mesentery of the stomach. - It is involved in blood filtration and immune responses, making it a lymphoid organ. *Lymph nodes* - **Lymph nodes** are primarily derived from the **mesoderm**, specifically from specialized mesenchymal cells that form their connective tissue capsule and stroma. - The immune cells within the lymph nodes, such as lymphocytes, originate from hematopoietic stem cells that migrate into these developing structures.
Question 122: 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 123: Ophthalmic artery is a branch of:
- A. Cavernous part of ICA
- B. Cerebral part of ICA (Correct Answer)
- C. MCA
- D. Facial artery
Explanation: ***Cerebral part of ICA*** - The **ophthalmic artery** is typically the first major branch off the **internal carotid artery (ICA)** once it exits the cavernous sinus and enters the cranial cavity. - This segment of the ICA is also known as the supraclinoid or **cerebral part**, underscoring its proximity to the brain. *Cavernous part of ICA* - The **cavernous part of the ICA** is located within the cavernous sinus and typically gives off smaller branches such as the **meningohypophyseal trunk** and the **inferolateral trunk**, which supply structures within and around the sinus. - The ophthalmic artery emerges after the ICA exits the cavernous sinus, not from within it. *MCA* - The **middle cerebral artery (MCA)** is a major terminal branch of the internal carotid artery, supplying large parts of the cerebrum. - It does not give rise to the ophthalmic artery, which branches off the ICA before the ICA bifurcates into the MCA and anterior cerebral artery. *Facial artery* - The **facial artery** is a branch of the **external carotid artery**, supplying structures of the face. - The ophthalmic artery is a primary supply to the orbit and is derived from the internal carotid artery, a completely separate vascular system.
Question 124: Primordial germ cells are derived from:
- A. Neural crest
- B. Genital ridge
- C. Somatopleuritic mesoderm
- D. Yolk sac (Correct Answer)
Explanation: ***Yolk sac*** - **Primordial germ cells (PGCs)** arise from **epiblast** cells but are first identifiable in the wall of the **yolk sac** during the **3rd week** of development. - From the yolk sac, they migrate during the **4th-6th week** through the dorsal mesentery to reach the developing **genital ridges** (gonads) where they form **gametes** [2]. - The yolk sac is considered the site where PGCs are recognized and begin their journey to the gonads. *Neural crest* - Neural crest cells are multipotent cells that migrate to various locations and differentiate into structures like **neurons**, **glial cells**, **melanocytes**, and **facial cartilage**, not germ cells. - They arise from the dorsal part of the **neural tube** during neurulation. *Genital ridge* - The genital ridge is the embryonic structure that develops into the **gonads** (testes or ovaries) [1]. - Primordial germ cells migrate *to* the genital ridge, but they do not originate *from* it — it is their destination, not their source. *Somatopleuritic mesoderm* - **Somatopleuritic mesoderm** (somatic mesoderm) forms the **parietal layer** of serous membranes, the dermis of the body wall, and the skeletal elements of the limbs. - It does not give rise to **primordial germ cells**.
Anesthesiology
1 questionsWhich of the following is true about coeliac plexus block?
NEET-PG 2012 - Anesthesiology NEET-PG Practice Questions and MCQs
Question 121: Which of the following is true about coeliac plexus block?
- A. Usually done unilaterally
- B. Most common side effects include diarrhea and hypotension (Correct Answer)
- C. Located retroperitoneally at the level of L3
- D. Useful for painful conditions of the lower abdomen
Explanation: ***Most common side effects include diarrhea and hypotension*** - A coeliac plexus block interrupts **sympathetic innervation** to the upper abdominal organs, which can lead to parasympathetic dominance. - This imbalance often results in **increased gastrointestinal motility (diarrhea)** and **vasodilation (hypotension)** as common side effects. *Located retroperitoneally at the level of L3* - The coeliac plexus is typically located **retroperitoneally** at the level of the **T12-L1 vertebrae**, not L3. - Its position is generally superior to the renal arteries, which are closer to L1-L2. *Usually done unilaterally* - A coeliac plexus block is almost always performed **bilaterally** or with a single posterior approach aiming for bilateral spread to effectively block the plexus. - The coeliac plexus is an extensive network, and a unilateral block would likely provide inadequate pain relief. *Useful for painful conditions of the lower abdomen* - The coeliac plexus primarily innervates **upper abdominal organs** (e.g., pancreas, liver, stomach, small intestine, kidneys, adrenal glands). - It is therefore generally **ineffective for lower abdominal pain**, which is innervated by different sympathetic plexuses (e.g., superior and inferior hypogastric plexuses).
Dental
1 questionsStability of alveoli is maintained by:
NEET-PG 2012 - Dental NEET-PG Practice Questions and MCQs
Question 121: 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.
Physiology
4 questionsMechanism by which Ach decreases heart rate is by:
Damage to the striatum primarily affects which type of memory?
Salty taste is due to?
What is the primary factor that determines the resting membrane potential in a nerve fiber?
NEET-PG 2012 - Physiology NEET-PG Practice Questions and MCQs
Question 121: 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 122: Damage to the striatum primarily affects which type of memory?
- A. Memory of how to perform tasks (Correct Answer)
- B. Memory for recent events
- C. Memory for past experiences
- D. Memory for facts and events
Explanation: ***Memory of how to perform tasks*** - The **striatum**, a component of the **basal ganglia**, is crucial for **procedural memory**, which is the memory of how to perform skills and habitual tasks. - Damage to this area can impair the ability to learn new motor skills or execute previously learned ones, even if the person remembers the task explicitly. *Memory for recent events* - This type of memory, often referred to as **episodic memory**, relies heavily on the **hippocampus** and medial temporal lobe structures. - Damage to the striatum typically does not directly affect the recall of recent events or experiences. *Memory for past experiences* - **Autobiographical memory**, which includes past experiences, primarily involves widespread cortical networks, particularly in the **temporal and frontal lobes**. - While broad brain damage can affect this, the striatum's primary role is not in the storage or retrieval of experiential memories. *Memory for facts and events* - This describes **declarative memory**, which is subdivided into **semantic memory** (facts) and **episodic memory** (events). - These are largely mediated by the **hippocampus**, **medial temporal lobes**, and various cortical areas, not primarily the striatum.
Question 123: 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.
Question 124: What is the primary factor that determines the resting membrane potential in a nerve fiber?
- A. Is equal to the resting potential of cardiac muscle fibers.
- B. Can be accurately measured using intracellular electrodes.
- C. Increases with elevated extracellular potassium concentration.
- D. Is primarily determined by the equilibrium potential of potassium ions. (Correct Answer)
Explanation: ***Is primarily determined by the equilibrium potential of potassium ions*** - The **resting membrane potential** of a nerve fiber is predominantly set by the efflux of **potassium ions** through leak channels, bringing the membrane potential close to potassium's equilibrium potential. - The high permeability of the nerve membrane to **potassium** at rest means that K+ movement is the most significant factor influencing the potential. *Is equal to the resting potential of cardiac muscle fibers* - **Cardiac muscle fibers** have a distinct resting potential (around -80 to -90 mV) influenced by different ion channels and regulatory mechanisms compared to nerve fibers (around -70 mV). - While both involve potassium currents, their specific conductances and the contribution of other ions differ significantly. *Can be accurately measured using intracellular electrodes* - While **intracellular electrodes** are indeed used to measure the resting membrane potential, this statement describes a measurement method, not the *primary factor* that determines the potential itself. - The method of measurement does not explain the underlying biophysical mechanisms that establish the potential. *Increases with elevated extracellular potassium concentration* - An **elevated extracellular potassium concentration** would make the resting membrane potential *less negative* (depolarize) rather than "increase" it in the typical sense of a more positive value. - This is because a higher external K+ reduces the concentration gradient for potassium efflux, bringing the membrane potential closer to zero.