Neuroanatomy Practice Questions

Q: All of the following are true regarding the actions of endothelin-1 except?

Bronchodilation. **Explanation:** Endothelin-1 (ET-1) is one of the most potent endogenous **vasoconstrictors** known [1]. It is produced by vascular endothelial cells and acts primarily through two G-protein coupled receptors: $ET_A$ and $ET_B$ [1]. **Why Option A is the Correct Answer (The Exception):** Endothelin-1 does **not** cause bronchodilation. Instead, it is a potent **bronchoconstrictor**. It stimulates the contraction of airway smooth muscle and is often found in elevated levels in patients with asthma and COPD [2]. Therefore, "Bronchodilation" is the false statement. **Analysis of Incorrect Options:** * **B. Vasoconstriction:** This is the primary action of ET-1. By binding to $ET_A$ receptors on vascular smooth muscle, it causes profound and sustained vasoconstriction, increasing peripheral resistance and blood pressure [1]. * **C. Decreased GFR:** In the kidneys, ET-1 causes constriction of both afferent and efferent arterioles (with a preference for the afferent). This leads to reduced renal blood flow and a subsequent **decrease in Glomerular Filtration Rate (GFR)**. * **D. Inotropic effect:** ET-1 exerts a **positive inotropic effect** on the myocardium (increasing the force of contraction) and can also induce cardiac hypertrophy over time. **NEET-PG High-Yield Pearls:** * **Bosentan:** A non-selective endothelin receptor antagonist ($ET_A$ & $ET_B$) used clinically in the treatment of **Pulmonary Arterial Hypertension (PAH)**. * **Synthesis:** ET-1 is synthesized from "Big Endothelin" by the **Endothelin-Converting Enzyme (ECE)** [1]. * **Stimuli:** Its release is stimulated by thrombin, epinephrine, and low shear stress, while it is inhibited by Nitric Oxide (NO) and Prostacyclin ($PGI_2$).

Q: Which of the following conditions could be produced by fracture of the floor of the middle cranial cavity, causing severance of the greater petrosal nerve?

Dryness in the nose and palate. The **greater petrosal nerve** is the first branch of the facial nerve (CN VII), arising from the geniculate ganglion. It carries **preganglionic parasympathetic fibers** destined for the **pterygopalatine ganglion**. 1. **Why Option C is Correct:** After synapsing in the pterygopalatine ganglion, postganglionic fibers provide secretomotor supply to the **lacrimal gland** and the **mucous glands of the nasal cavity, paranasal sinuses, and palate**. Severance of this nerve leads to a loss of parasympathetic stimulation, resulting in decreased secretions and subsequent **dryness of the nose and palate**. 2. **Why Other Options are Incorrect:** * **Option A:** Severance would cause **decreased** (not increased) lacrimation (dry eye/xerophthalmia). * **Option B:** Taste from the epiglottis is carried by the **internal laryngeal nerve** (branch of Vagus, CN X). The greater petrosal nerve carries taste only from the soft palate. * **Option D:** The parotid gland receives its parasympathetic supply from the **glossopharyngeal nerve (CN IX)** via the lesser petrosal nerve and the otic ganglion. **High-Yield Clinical Pearls for NEET-PG:** * **Course:** The greater petrosal nerve passes through the **hiatus for the greater petrosal nerve** on the anterior surface of the petrous temporal bone (middle cranial fossa). * **Nerve of Pterygoid Canal (Vidian Nerve):** Formed by the union of the **greater petrosal nerve** (parasympathetic) and the **deep petrosal nerve** (sympathetic from the internal carotid plexus). * **Clinical Sign:** A lesion proximal to the geniculate ganglion (like a temporal bone fracture) presents with the

Q: All of the following are morphological features of apoptosis except?

Inflammation. **Explanation:** Apoptosis is a programmed, energy-dependent process of cell death designed to eliminate unwanted cells without eliciting a host response. The hallmark of apoptosis is that the **cell membrane remains intact**, preventing the leakage of cellular contents into the extracellular space. Consequently, there is **no inflammation** (Option C). In contrast, necrosis involves membrane rupture, leading to the release of lysosomal enzymes and pro-inflammatory signals. **Analysis of Options:** * **Cell Shrinkage (Option A):** This is a key feature. Unlike necrosis (where cells swell), apoptotic cells show dense cytoplasm and tightly packed organelles. * **Chromatin Condensation (Option B):** This is the most characteristic feature of apoptosis. Chromatin aggregates peripherally under the nuclear membrane (pyknosis), followed by nuclear fragmentation (karyorrhexis). * **Apoptotic Bodies (Option C):** The cell breaks into membrane-bound vesicles containing portions of cytoplasm and nucleus. These are rapidly cleared by macrophages via "eat-me" signals (like phosphatidylserine) before they can trigger an inflammatory response. **High-Yield NEET-PG Pearls:** 1. **Caspases:** These are the executioner proteases of apoptosis (Cysteine-Aspartic acid proteases). 2. **DNA Laddering:** On gel electrophoresis, apoptosis shows a "step-ladder" pattern due to internucleosomal cleavage of DNA by endonucleases (at 180-200 bp intervals). Necrosis shows a "smear" pattern. 3. **Bcl-2 Family:** Pro-apoptotic members include **Bax and Bak**; Anti-apoptotic members include **Bcl-2 and Bcl-xL**. 4. **Mitochondrial Pathway:** The release of **Cytochrome c** into the cytosol is the critical step in the intrinsic pathway.

Q: Which equation is used to measure the resting membrane potential in case of multiple ions?

Goldman equation. The resting membrane potential (RMP) is a fundamental concept in neurophysiology, representing the electrical potential difference across a cell membrane at rest. [1] ### **Explanation of the Correct Answer** **Option A (Goldman Equation):** The Goldman-Hodgkin-Katz (GHK) equation is the correct choice because it accounts for **multiple ions** (primarily $Na^+$, $K^+$, and $Cl^-$) simultaneously. Unlike simpler models, it considers two critical factors for each ion: 1. The **concentration gradient** across the membrane. [1] 2. The **relative permeability** ($P$) of the membrane to that specific ion. [1] Since the RMP of a neuron (typically -70 mV) is a collective result of all permeant ions, the Goldman equation provides the most accurate physiological measurement. ### **Explanation of Incorrect Options** * **Option B (Nernst Equation):** This equation calculates the **equilibrium potential for a single ion** only. [1] It determines the theoretical voltage at which the electrical and chemical gradients for one specific ion are perfectly balanced (e.g., -94 mV for $K^+$ or +61 mV for $Na^+$). It does not account for the membrane's simultaneous permeability to other ions. * **Options C & D:** These are incorrect as the two equations serve distinct purposes—one for individual ion equilibrium and the other for the total membrane potential. ### **NEET-PG High-Yield Pearls** * **The "K+ Rule":** The RMP is closest to the equilibrium potential of Potassium (-94 mV) because the resting membrane is 20–100 times more permeable to $K^+$ than to $Na^+$. * **The Na+-K+ Pump:** While the Goldman equation calculates the potential based on diffusion, the $Na^+$-$K^+$ ATPase pump is "electrogenic" and directly contributes about -4 mV to the RMP. * **Clinical Correlation:** Hypokalemia makes the RMP more negative (hyperpolarization), making neurons less excitable, which clinically manifests as muscle weakness or paralysis.

Q: Which nerve is associated with the 6th branchial arch?

Recurrent laryngeal nerve. The branchial (pharyngeal) arches are fundamental to head and neck development, with each arch associated with a specific cranial nerve branch. ### **Explanation of the Correct Answer** The **Recurrent Laryngeal Nerve (RLN)** is the nerve of the **6th branchial arch**. During development, the 6th arch gives rise to the intrinsic muscles of the larynx (except the cricothyroid) and the laryngeal cartilages (except the epiglottis). Because the RLN supplies these derivatives, it is embryologically tied to this arch [1, 3]. Its "recurrent" course is due to the descent of the heart and the transformation of the 6th arch arteries (forming the ductus arteriosus on the left and disappearing on the right) [1]. ### **Analysis of Incorrect Options** * **A, B, and C (Superior, Internal, and External Laryngeal Nerves):** These are all branches or components of the **Superior Laryngeal Nerve (SLN)**. The SLN is the nerve of the **4th branchial arch**. It supplies the cricothyroid muscle (via the external branch) and provides sensory innervation above the vocal cords (via the internal branch). ### **High-Yield NEET-PG Pearls** * **Arch-Nerve Correlation Table:** * **1st Arch:** Mandibular nerve ($V_3$) * **2nd Arch:** Facial nerve (VII) * **3rd Arch:** Glossopharyngeal nerve (IX) * **4th Arch:** Superior Laryngeal nerve (branch of X) * **6th Arch:** Recurrent Laryngeal nerve (branch of X) * **Muscles of 6th Arch:** All intrinsic muscles of the larynx **except** the cricothyroid. * **Clinical Correlation:** Injury to the RLN (often during thyroid surgery) leads to hoarseness of voice or respiratory distress if bilateral, as it controls the abductors of the vocal cords (Posterior Cricoarytenoid) [1, 3].

Q: Which of the following can cause a soft first heart sound (S1)?

All the above. The first heart sound (**S1**) is produced primarily by the closure of the atrioventricular valves (Mitral and Tricuspid) at the onset of ventricular systole [1]. The intensity of S1 depends on the mobility of the leaflets, the rate of pressure rise in the ventricles, and the distance between the heart and the stethoscope [1]. **Explanation of Options:** * **Mitral Regurgitation (C):** This is a classic valvular cause of a soft S1. In chronic MR, the mitral leaflets may fail to coapt properly or are structurally compromised, leading to inadequate "tensing" during closure. Additionally, the PR interval may be prolonged, or the leaflets may already be partially closed at the start of systole, reducing the sound intensity. * **Obesity (A) and Pleural Effusion (B):** These are **extracardiac factors**. S1 is "muffled" or softened because there is increased tissue or fluid (insulation) between the heart and the chest wall, which attenuates the transmission of sound waves to the stethoscope. **Why "All the Above" is Correct:** A soft S1 occurs whenever there is either a structural valvular defect (like MR or severe calcific MS), a physiological delay (long PR interval/First-degree heart block), or an anatomical barrier (obesity, emphysema, or pericardial/pleural effusion) that dampens sound transmission. **High-Yield Clinical Pearls for NEET-PG:** * **Loud S1:** Seen in Mitral Stenosis (pliable leaflets), short PR interval (Tachycardia, WPW syndrome), and hyperdynamic states (Anemia, Thyrotoxicosis). * **Variable S1:** A hallmark of **Atrial Fibrillation** and **Complete Heart Block** (due to varying PR intervals). * **Soft S1 in MI:** A soft S1 in the setting of an acute myocardial infarction may indicate poor ventricular contractility or the development of acute mitral regurgitation.

Question 1

All of the following are true regarding the actions of endothelin-1 except?

Accepted Answer

Bronchodilation

Answer

Vasoconstriction

Answer

Decreased GFR

Answer

Has inotrophic effect

Question 2

Which of the following conditions could be produced by fracture of the floor of the middle cranial cavity, causing severance of the greater petrosal nerve?

Accepted Answer

Dryness in the nose and palate

Answer

Increased lacrimal gland secretion

Answer

Loss of taste sensation in the epiglottis

Answer

Decreased parotid gland secretion

Question 3

Nephrocalcinosis is seen in which of the following conditions?

Accepted Answer

Hyperparathyroidism

Answer

Diabetes mellitus

Answer

Amyloidosis of kidney

Answer

End-stage renal disease

Question 4

All of the following are morphological features of apoptosis except?

Accepted Answer

Inflammation

Answer

Cell shrinkage

Answer

Chromatin condensation

Answer

Apoptotic bodies

Question 5

Which polyarthritic condition is not common?

Accepted Answer

Systemic lupus erythematosus (SLE)

Answer

Gout

Answer

Psoriatic arthritis

Answer

Ankylosing spondylitis

Question 6

The ability to recognize an unseen familiar object placed in the hand depends on the integrity of which neural pathway?

Accepted Answer

Posterior column

Answer

Posterior spinocerebellar tract

Answer

Spino-olivary tract

Answer

Spinospinal tract

Question 7

Which equation is used to measure the resting membrane potential in case of multiple ions?

Accepted Answer

Goldman equation

Answer

Nernst equation

Answer

Both Goldman and Nernst equations

Answer

Neither Goldman nor Nernst equation

Question 8

Which nerve is associated with the 6th branchial arch?

Accepted Answer

Recurrent laryngeal nerve

Answer

Superior laryngeal nerve

Answer

Internal laryngeal nerve

Answer

External laryngeal nerve

Question 9

Which of the following can cause a soft first heart sound (S1)?

Accepted Answer

All the above

Answer

Obesity

Answer

Pleural effusion

Answer

Mitral regurgitation

Question 10

What nerve supplies the skin over the parotid gland?

Accepted Answer

Greater auricular nerve

Answer

Retroauricular nerve

Answer

Greater occipital nerve

Answer

Facial nerve

Neuroanatomy — MCQs

Neuroanatomy — MCQs

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