Comparative Nervous System — MCQs
Which parasite is most characteristically known for its larval forms residing primarily in muscle tissue?
Which of the following statements correctly describes Group B sympathetic postganglionic nerve fibers?
The mechanism of hearing and memory, include all, EXCEPT:
Which of the following statements about Helminths is false?
What structures are derived from the neural crest?
Sensory supply of the palm is from which nerves?
Which nerve gives sensory supply to the region marked with an arrow?
All are true about the triangle marked green except:
Malleus and incus are derived from?
At 30 days of intrauterine life, what is the expected developmental milestone?
Comparative Nervous System Indian Medical PG Practice Questions and MCQs
Question 1: Which parasite is most characteristically known for its larval forms residing primarily in muscle tissue?
- A. Taenia solium
- B. Echinococcus granulosus
- C. Trichinella spiralis (Correct Answer)
- D. All of the options
Explanation: ***Trichinella spiralis*** - This parasite is renowned for its **larval forms** that encyst primarily in **striated muscle tissue** of its hosts, causing trichinosis. - Humans typically acquire the infection by consuming **undercooked meat**, especially pork and wild game, containing these encysted larvae. *Taenia solium* - While *Taenia solium* can cause **cysticercosis** in humans, where larvae (cysticerci) encyst in tissues, their primary target is often the **central nervous system**, eyes, and subcutaneous tissue, rather than muscle as the predominant site. - Infection occurs by ingesting *T. solium* **eggs**, not larvae in meat, and pigs serve as the intermediate host for muscle cyst formation. *Echinococcus granulosus* - This parasite causes **hydatid disease** where large cysts (hydatid cysts) develop, most commonly in the **liver** and **lungs**, although they can occur in other organs. - The disease is acquired by ingesting **eggs** from dog feces, and the larval stage does not primarily reside in muscle tissue. *All of the options* - This option is incorrect because while *Taenia solium* and *Echinococcus granulosus* have larval stages that can reside in various tissues, only **Trichinella spiralis** is primarily characterized by its larvae encysting in muscle tissue.
Question 2: Which of the following statements correctly describes Group B sympathetic postganglionic nerve fibers?
- A. Myelinated fibers that are parasympathetic postganglionic.
- B. Unmyelinated fibers primarily conveying pain.
- C. Myelinated fibers associated with the autonomic nervous system. (Correct Answer)
- D. Myelinated fibers that are sympathetic postganglionic.
Explanation: ***Myelinated fibers associated with the autonomic nervous system.*** * **Group B fibers** are **myelinated autonomic nerve fibers** that serve as **preganglionic neurons** in both sympathetic and parasympathetic divisions of the autonomic nervous system. * These fibers have a diameter of approximately **1-3 μm** and conduction velocity of **3-15 m/s**. * The key characteristic is that they are **preganglionic autonomic fibers**, not postganglionic. * This is the most accurate description among the given options. *Myelinated fibers that are sympathetic postganglionic.* * This is **incorrect** because **sympathetic postganglionic fibers** are predominantly **unmyelinated Group C fibers**, not myelinated Group B fibers. * Group B fibers represent **preganglionic** autonomic neurons, not postganglionic. * The question stem itself contains an error in referring to "Group B sympathetic postganglionic" as this combination does not exist in standard classification. *Unmyelinated fibers primarily conveying pain.* * This description refers to **Group C fibers**, which are **unmyelinated** and primarily transmit **slow pain**, temperature, and postganglionic autonomic signals. * Group C fibers have conduction velocities of **0.5-2 m/s**, much slower than Group B fibers. *Myelinated fibers that are parasympathetic postganglionic.* * This is **incorrect** because **parasympathetic postganglionic fibers** are also **unmyelinated Group C fibers**. * Like sympathetic postganglionic neurons, parasympathetic postganglionic fibers lack significant myelination. * Group B fibers are **preganglionic**, serving both sympathetic and parasympathetic divisions.
Question 3: The mechanism of hearing and memory, include all, EXCEPT:
- A. Spatial Reorganization of synapse
- B. Changes in level of neurotransmitter at synapse
- C. Increasing protein synthesis
- D. Recruitment by multiplication of neurons (Correct Answer)
Explanation: ***Recruitment by multiplication of neurons*** - The **brain's capacity for learning and memory** primarily involves changes in existing neural circuits, not the multiplication of neurons in the adult brain for new information processing. - While neurogenesis occurs in specific brain regions (e.g., hippocampus), it is not a widespread mechanism for acquiring or storing specific memories or the rapid processing involved in hearing. *Spatial Reorganization of synapse* - This refers to the **restructuring of synaptic connections**, which is a crucial mechanism for long-term potentiation and depression, fundamental to learning and memory formation. - Changes in the **number or location of synapses** can alter neural pathways and strengthen or weaken signal transmission. *Changes in level of neurotransmitter at synapse* - Alterations in the **amount of neurotransmitter released** or the **sensitivity of postsynaptic receptors** significantly impact synaptic strength and neuronal communication. - This short-term and long-term modulation is vital for processes like habituation, sensitization, and long-term potentiation, integral to memory and sensory processing. *Increasing protein synthesis* - **New protein synthesis** is essential for the consolidation of long-term memories and for the structural changes underlying synaptic plasticity. - These proteins can range from enzymes that modify synaptic transmission to structural proteins that alter dendritic spine morphology, enabling lasting changes in neural circuits.
Question 4: Which of the following statements about Helminths is false?
- A. Alimentary canal is complete in Nematodes
- B. Nematodes have separate sexes
- C. Body cavity is present in trematodes (Correct Answer)
- D. Alimentary canal is present but incomplete in trematodes
Explanation: ***Body cavity is present in trematodes*** - Trematodes are **flatworms** (Platyhelminthes), which are **acoelomate**, meaning they lack a true body cavity or coelom. - Their internal organs are embedded in a **parenchymal tissue** rather than being suspended within a fluid-filled cavity. *Alimentary canal is complete in Nematodes* - **Nematodes** (roundworms) possess a **complete alimentary canal**, with a distinct mouth, intestine, and anus. - This allows for **unidirectional flow of food** and waste through their digestive system. *Nematodes have separate sexes* - **Nematodes** are generally **dioecious**, meaning they have separate male and female individuals. - This sexual dimorphism is a characteristic feature for most species within this phylum. *Alimentary canal is Present but incomplete* - The statement refers to the digestive system of **Platyhelminthes** (flatworms) like trematodes and cestodes, where the alimentary canal is present but **incomplete** (lacking an anus). - This means they have a **single opening** that serves as both mouth and anus for digestion.
Question 5: What structures are derived from the neural crest?
- A. Melanocytes
- B. Dental papillae
- C. Adrenal medulla
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - The **neural crest** is a multipotent, migratory cell population that contributes to the formation of many diverse tissues and organs during vertebrate development. - Neural crest cells give rise to a wide array of derivatives, including components of the nervous system, pigment cells, skeletal and connective tissues of the head and face, and endocrine glands [1]. *Melanocytes* - **Melanocytes**, the pigment-producing cells found in the skin, hair, eyes, and other tissues, are derived from the **neural crest** [2]. - These cells migrate extensively during development from the neural crest to their final destinations throughout the body. - Neural crest-derived melanocytes produce melanin, which provides pigmentation and protection against UV radiation [2]. *Dental papillae* - The **dental papilla** is crucial for tooth development and is formed from **ectomesenchymal cells** that are derived from the cranial neural crest. - These cells differentiate into the odontoblasts that produce dentin and also contribute to the pulp of the tooth. *Adrenal medulla* - The cells of the **adrenal medulla**, which produce catecholamines like epinephrine and norepinephrine, are specialized **postganglionic sympathetic neurons** derived from the neural crest. - They develop from neuroectodermal cells that migrate to the developing adrenal gland.
Question 6: 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 7: Which nerve gives sensory supply to the region marked with an arrow?
- A. Radial nerve (Correct Answer)
- B. Median nerve
- C. Ulnar nerve
- D. Posterior interosseous nerve
Explanation: ***Radial nerve*** - The image shows the **dorsal (back) aspect of the hand**, specifically the region over the **anatomical snuffbox** or the dorsal part of the thumb and first web space. - The **superficial branch of the radial nerve** provides sensory innervation to this area, including the dorsal aspect of the thumb, index, and half of the middle finger, extending to the dorsal hand. *Median nerve* - The **median nerve** primarily provides sensory innervation to the **palmar aspect** of the lateral three and a half digits (thumb, index, middle, and radial half of the ring finger) and the corresponding palm. - It does not innervate the dorsal hand in the region indicated. *Ulnar nerve* - The **ulnar nerve** innervates the **medial 1.5 digits** (pinky and ulnar half of the ring finger) on both the palmar and dorsal aspects of the hand, as well as the ulnar part of the palm and dorsum of the hand. - The highlighted region is on the radial side of the hand, not the ulnar side. *Posterior interosseous nerve* - The **posterior interosseous nerve** is a **motor nerve** that innervates the muscles in the posterior compartment of the forearm. - It does **not provide sensory innervation** to any part of the hand.
Question 8: All are true about the triangle marked green except:
- A. Localised pain in this area after fall on outstretched hand indicates fracture of scaphoid
- B. Cephalic vein in this area is used to make Ciminobrescia fistula in hemodialysis
- C. Medial border is formed by tendon of abductor pollicis longus and extensor pollicis brevis (Correct Answer)
- D. Superficial branch of radial nerve runs to provide innervation to 3.5 digits
Explanation: ***Medial border is formed by tendon of abductor pollicis longus and extensor pollicis brevis*** - This statement is incorrect because the **medial border of the anatomical snuffbox** is formed by the tendon of the **extensor pollicis longus**. - The **lateral border** of the anatomical snuffbox is formed by the tendons of the **abductor pollicis longus** and **extensor pollicis brevis**. *Localised pain in this area after fall on outstretched hand indicates fracture of scaphoid* - The anatomical snuffbox is a crucial site for palpating the **scaphoid bone**, which is frequently fractured in falls on an **outstretched hand**. - **Tenderness in the anatomical snuffbox** following such an injury is a strong clinical indicator of a scaphoid fracture, even if initial X-rays are negative. *Cephalic vein in this area is used to make Ciminobrescia fistula in hemodialysis* - The anatomical snuffbox region provides access to the **cephalic vein**, which is a common site for creating an **arteriovenous fistula (AV fistula)**, also known as a Cimino-Brescia fistula. - An AV fistula connects the radial artery to the cephalic vein, providing robust venous access for **hemodialysis**. *Superficial branch of radial nerve runs to provide innervation to 31/2 digits* - The **superficial branch of the radial nerve** traverses the anatomical snuffbox region to provide **sensory innervation** to the dorsal aspect of the lateral 3.5 digits (thumb, index finger, middle finger, and radial half of the ring finger) as well as the associated dorsal hand. - This nerve is susceptible to injury in this area due to its superficial location.
Question 9: Malleus and incus are derived from?
- A. 3rd Arch
- B. 4th Arch
- C. 1st Arch (Correct Answer)
- D. 2nd Arch
Explanation: ***1st Arch*** - The **malleus** and **incus** are ossicles of the middle ear that develop from the **cartilage of the first pharyngeal arch** (Meckel's cartilage). - This arch also contributes to the development of the **mandible** and muscles of mastication. *2nd Arch* - The **second pharyngeal arch** (Reichert's cartilage) gives rise to the **stapes**, a different ossicle of the middle ear. - It also forms the **styloid process**, **lesser cornu of the hyoid**, and muscles of facial expression. *3rd Arch* - The **third pharyngeal arch** contributes to the development of the **greater cornu of the hyoid bone** and the **stylopharyngeus muscle**. - It plays no direct role in the formation of the malleus or incus. *4th Arch* - The **fourth pharyngeal arch** contributes to the formation of the **thyroid cartilage**, **cricoid cartilage**, and muscles of the pharynx and larynx. - It is not involved in the development of the ear ossicles.
Question 10: At 30 days of intrauterine life, what is the expected developmental milestone?
- A. Optic vesicle appears (Correct Answer)
- B. Heart starts beating
- C. Cerebellum develops
- D. Pinna appears
Explanation: Optic vesicle appears - The **optic vesicle** is an outpocketing from the diencephalon that appears around **day 22-28** of development. - At approximately **30 days** (end of 4th week/early 5th week), the optic vesicle is actively present and beginning to invaginate to form the optic cup. - Among the given options, this represents the developmental structure most characteristically associated with the **late 4th week/30-day timeframe** in embryology milestones. *Heart starts beating* - The primitive heart tube begins to beat around **day 22-23** of gestation. - By 30 days, the heart has already been beating for over a week, making this an earlier milestone rather than one expected "at" 30 days. *Cerebellum develops* - The cerebellum develops later, primarily during the **second and third months** (weeks 8-12) of gestation as the metencephalon differentiates. - Major cerebellar development occurs well after 30 days. *Pinna appears* - The external ear (pinna) begins forming around the **sixth week** (~42 days) from six auricular hillocks.
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