NEET-PG 2013 Practice Questions

Q: Which muscle is the deepest in the anterior neck region?

Longus colli. ***Longus colli*** - The **longus colli** muscle is the **deepest muscle** located in the anterior neck region, running along the front of the cervical vertebral column from C1 to T3. - It lies in the **prevertebral layer**, deep to all other anterior neck structures including the carotid sheath, visceral compartment, and superficial muscles. - Its position directly anterior to the vertebral bodies makes it the deepest anterior neck muscle. *Platysma* - The platysma is the **most superficial muscle** of the neck, located just beneath the skin in the superficial fascia. - It is not a deep muscle and lies superficial to all other neck muscles. *Sternocleidomastoid* - The sternocleidomastoid is enclosed within the **investing layer of deep cervical fascia**, making it relatively superficial. - While prominent in the anterior and lateral neck, it is not the deepest anterior neck muscle. *Trapezius* - The trapezius is a large, **superficial muscle of the back and posterior neck**. - It is not located in the anterior neck and is a superficial, not deep, muscle.

Q: The primary oocyte remains arrested in which stage until ovulation?

Diplotene stage. ***Diplotene stage*** - The primary oocyte enters **meiosis I** during fetal development but arrests in the **prophase I substage of diplotene**. - This arrest is maintained until **puberty** and **ovulation**, when hormonal surges trigger the completion of meiosis I. *Pachytene stage* - The **pachytene stage** of prophase I is when **crossing over** (recombination) occurs between homologous chromosomes. - While an important step in meiosis, it precedes the **diplotene arrest** point. *Metaphase* - **Metaphase** is a stage where chromosomes align at the metaphase plate, either in meiosis I or meiosis II. - The primary oocyte's arrest occurs much earlier, during **prophase I**, not metaphase. *Telophase* - **Telophase** is the final stage of mitosis or meiosis where chromosomes decondense and nuclear envelopes reform. - The oocyte's initial arrest point is in **prophase I**, long before telophase.

Q: What is the mechanism by which mercury causes damage?

Binds to -SH groups of enzymes. ***Binds to -SH groups of enzymes*** - Mercury, particularly its inorganic and organic forms, has a high affinity for **sulfhydryl (-SH) groups** found in **cysteine residues** of proteins and enzymes. - This binding disrupts the **tertiary structure** and **catalytic activity** of vital enzymes, leading to widespread cellular dysfunction and toxicity. *Causes toxicity through various mechanisms (not specific to -SH binding)* - While mercury can indeed cause toxicity through various mechanisms, the **most prominent and fundamental mechanism** underpins many of these downstream effects. - This option is too general and does not pinpoint the primary molecular interaction responsible for mercury's widespread cellular damage. *Indirectly inhibits the electron transport chain (ETC) by enzyme disruption* - This statement is partially true in that mercury's enzyme disruption can affect the ETC, but it's an **indirect consequence** rather than the primary mechanism itself. - The direct mechanism involves the initial binding to -SH groups, which then leads to the dysfunction of enzymes, including those involved in the ETC. *Indirectly inhibits protein synthesis by disrupting enzyme function* - Similar to ETC inhibition, mercury's disruption of enzyme function can ultimately impair protein synthesis, but this is an **effect down the causal chain**. - The initial and direct molecular interaction is the binding to sulfhydryl groups of key enzymes involved in various cellular processes, including protein synthesis.

Q: Ninhydrin test is used for?

Amino acids. ***Amino acids*** - The **ninhydrin test** is a chemical test used to detect the presence of **amino acids** and primary and secondary amines. - It produces a **purple-blue color** when it reacts with most amino acids, due to the formation of a colored complex called Ruhemann's purple. *Bile salts* - The detection of **bile salts** typically involves tests like Hay's test or Pettenkofer's test, which are distinct from the ninhydrin reaction. - These tests rely on the physical or chemical properties of bile salts, such as changes in surface tension or specific color reactions with sulfuric acid. *Nucleic acid* - **Nucleic acids** (DNA and RNA) are detected using specific tests like the **diphenylamine test** (for DNA) or orcinol test (for RNA). - These tests target the deoxyribose or ribose sugars present in their structures and result in different color changes compared to ninhydrin. *Lipids* - **Lipids** are typically identified using tests that exploit their nonpolar nature, such as the **emulsion test** or solubility tests in organic solvents. - Their detection does not involve ninhydrin, as they lack the primary or secondary amine groups that react with this reagent.

Q: Which one of the following is the most common CNS tumor associated with type I neurofibromatosis?

Optic nerve glioma. ***Optic nerve glioma*** - **Optic nerve gliomas** are the most frequently encountered central nervous system tumors in patients with **Type 1 neurofibromatosis (NF1)**, occurring in about 15% of individuals. - They are typically low-grade **astrocytomas** and can cause vision loss and proptosis depending on their size and location. *Meningioma* - While more common in **Type 2 neurofibromatosis (NF2)**, meningiomas can occur in NF1, but are not the most common CNS tumor. - Meningiomas are tumors that arise from the **meninges**, the membranes surrounding the brain and spinal cord. *Acoustic schwannoma* - **Bilateral acoustic schwannomas (vestibular schwannomas)** are the hallmark feature of **Type 2 neurofibromatosis (NF2)**, not NF1 [1]. - These tumors arise from the Schwann cells of the **vestibulocochlear nerve** and can cause hearing loss and balance issues [1]. *Low grade astrocytoma* - While optic nerve gliomas are a type of low-grade astrocytoma, this option is too general; **optic nerve glioma** is the specific and most common presentation in NF1. - Other forms of low-grade astrocytomas can occur in NF1 but are not as universally characteristic as optic nerve gliomas.

Q: What is the primary condition associated with positive anti-dsDNA antibodies?

SLE. ***SLE*** - **Anti-dsDNA antibodies** are a highly specific marker for **Systemic Lupus Erythematosus (SLE)** and are included in its diagnostic criteria [1]. - The levels of **anti-dsDNA antibodies** can also correlate with disease activity, particularly in cases of **lupus nephritis** [1]. *RA* - **Rheumatoid Arthritis (RA)** is primarily associated with **rheumatoid factor (RF)** and **anti-citrullinated protein antibodies (ACPA)** or **anti-CCP antibodies**. - While ANA (antinuclear antibodies) can be positive in RA, **anti-dsDNA antibodies** are not a characteristic serological marker [1]. *Scleroderma* - **Scleroderma**, or systemic sclerosis, is characterized by specific antibodies such as **anti-Scl-70 (topoisomerase I)**, **anti-centromere antibodies**, and **anti-RNA polymerase III antibodies**, depending on the subtype. - **Anti-dsDNA antibodies** are not typically found in scleroderma and do not play a role in its diagnosis [1]. *PAN* - **Polyarteritis Nodosa (PAN)** is a **necrotizing vasculitis** of medium-sized arteries and is not associated with **anti-dsDNA antibodies**. - PAN is generally considered an **ANCA-negative vasculitis**, and its diagnosis relies more on clinical features, angiography, and biopsy findings.

Q: Which of the following is classified as an antispasmodic agent?

Dicyclomine. ***Dicyclomine*** - **Dicyclomine** is an **anticholinergic** medication that works by blocking muscarinic receptors, thereby reducing smooth muscle spasm in the gastrointestinal tract. - It is commonly used to treat symptoms of **irritable bowel syndrome (IBS)**, such as abdominal pain and cramping. *Physostigmine* - **Physostigmine** is a **cholinesterase inhibitor** that increases the concentration of acetylcholine at the synaptic cleft. - It is used to treat **anticholinergic poisoning** by reversing the effects of anticholinergic drugs, rather than acting as an antispasmodic itself. *Tropicamide* - **Tropicamide** is an **anticholinergic** agent primarily used as a **mydriatic** (pupil dilator) and **cycloplegic** (paralyzes the ciliary muscle) for ophthalmic examinations. - Its action is localized to the eye and it does not have significant systemic antispasmodic effects. *None of the options* - This option is incorrect because one of the listed medications is indeed classified as an antispasmodic agent. - When "None of the options" appears as a choice, it should only be selected if all other options are clearly incorrect.

Q: LH surge is associated with?

Increased estrogen & decreased progesterone. ***Increased estrogen & decreased progesterone*** - The **LH surge** is triggered by a significant rise in **estrogen** levels from the dominant follicle, indicating ovarian readiness. - At the time of the LH surge, **progesterone** levels remain low; they only begin to rise significantly after ovulation, when the corpus luteum forms. *Increased estrogen & increased progesterone* - While **estrogen** levels are high, **progesterone** only significantly increases *after* ovulation, as the corpus luteum develops. - High estrogen *and* high progesterone together are typically seen in the **luteal phase**, not at the peak of the LH surge. *Decreased estrogen & increased progesterone* - A decrease in **estrogen** would suppress LH, not trigger a surge. - Increased **progesterone** would also inhibit LH release via negative feedback in the follicular phase if it were to occur pre-ovulation. *Decreased estrogen & decreased progesterone* - Both **decreased estrogen** and **decreased progesterone** would lead to low FSH/LH levels and would not promote an LH surge or ovulation. - This hormonal profile is more characteristic of the very early follicular phase or menopause.

Q: What is the primary action observed in the withdrawal reflex?

Flexion. ***Flexion*** - The **withdrawal reflex** is a protective reflex that causes the affected limb to **flex** and withdraw from a painful stimulus. - This **flexion** is mediated by the contraction of flexor muscles and relaxation of extensor muscles, moving the limb away from danger. *Extension* - **Extension** is the opposite of flexion and would move the limb closer to or maintain its position relative to the painful stimulus. - This action is typically observed in the **crossed extensor reflex**, where the contralateral limb extends to support the body, not in the direct withdrawal of the stimulated limb. *Flexion followed by extension* - While **flexion** is the primary action, it is not typically followed immediately by extension within the same limb in a simple withdrawal reflex. - If a coordinated movement were to occur, such as shifting weight, the **crossed extensor reflex** would involve extension in the opposite limb. *Not applicable* - The withdrawal reflex involves a clear and defined muscle action which is **flexion**, making "not applicable" incorrect. - This reflex is a fundamental component of the nervous system's response to noxious stimuli.

Q: What type of reflex is the righting reflex?

Vestibular reflex. ***Vestibular reflex*** - The **righting reflex** is primarily mediated by the **vestibular system** (labyrinthine apparatus), which detects changes in head position and movement in space. - This reflex helps maintain proper **head and body orientation** relative to gravity, ensuring balance and stability. - Note: Righting reflexes are actually a group of **postural reflexes** that also involve visual, neck proprioceptive, and body proprioceptive inputs, but the **vestibular (labyrinthine) component is the most important** and is often emphasized in medical education. *Cochlear reflex* - The **cochlea** is primarily involved in **hearing**, translating sound vibrations into electrical signals. - The cochlear reflex, such as the **stapedial reflex**, is an auditory protective reflex that dampens loud sounds, not involved in postural control or spatial orientation. *Spinal reflex* - A **spinal reflex** is mediated solely by the **spinal cord** without supraspinal integration (e.g., knee jerk, withdrawal reflex). - The righting reflex requires integration at the **brainstem and higher centers**, involving the vestibular nuclei, and cannot function through spinal cord alone. *None of the options* - This option is incorrect for exam purposes, as the righting reflex is conventionally taught as primarily a **vestibular-mediated postural reflex**. - The vestibular system is the key sensory component for detecting head position changes that trigger righting responses.

Question 1

Which muscle is the deepest in the anterior neck region?

Accepted Answer

Longus colli

Answer

Sternocleidomastoid

Answer

Platysma

Answer

Trapezius

Question 2

The primary oocyte remains arrested in which stage until ovulation?

Accepted Answer

Diplotene stage

Answer

Pachytene stage

Answer

Metaphase

Answer

Telophase

Question 3

What is the mechanism by which mercury causes damage?

Accepted Answer

Binds to -SH groups of enzymes

Answer

Causes toxicity through various mechanisms

Answer

Inhibits electron transport chain

Answer

Inhibits protein synthesis

Question 4

Ninhydrin test is used for?

Accepted Answer

Amino acids

Answer

Bile salts

Answer

Nucleic acid

Answer

Lipids

Question 5

Which one of the following is the most common CNS tumor associated with type I neurofibromatosis?

Accepted Answer

Optic nerve glioma

Answer

Meningioma

Answer

Acoustic schwannoma

Answer

Low grade astrocytoma

Question 6

What is the primary condition associated with positive anti-dsDNA antibodies?

Accepted Answer

SLE

Answer

RA

Answer

Scleroderma

Answer

PAN

Question 7

Which of the following is classified as an antispasmodic agent?

Accepted Answer

Dicyclomine

Answer

Physostigmine

Answer

Tropicamide

Answer

None of the options

Question 8

LH surge is associated with?

Accepted Answer

Increased estrogen & decreased progesterone

Answer

Increased estrogen & increased progesterone

Answer

Decreased estrogen & increased progesterone

Answer

Decreased estrogen & decreased progesterone

Question 9

What is the primary action observed in the withdrawal reflex?

Accepted Answer

Flexion

Answer

Extension

Answer

Flexion followed by extension

Answer

Not applicable

Question 10

What type of reflex is the righting reflex?

Accepted Answer

Vestibular reflex

Answer

Cochlear reflex

Answer

Spinal reflex

Answer

None of the options

NEET-PG 2013

Anatomy

Biochemistry

Internal Medicine

Pharmacology

Physiology