Understanding the origin and functions of spinal nerves is essential for B. Pharm students, linking anatomy to pharmacology and clinical practice. Spinal nerves arise from spinal cord segments via dorsal (sensory) and ventral (motor) roots, forming mixed nerves that give off dorsal and ventral rami and rami communicantes carrying somatic and autonomic fibers. Key concepts include dermatomes, myotomes, reflex arcs, sympathetic outflow (T1–L2), dorsal root ganglia, and pharmacologic modulation such as local anesthetics and neuromodulators. Grasping these topics clarifies radiculopathy, peripheral neuropathy, and drug effects on nerve conduction and autonomic function. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which structures combine to form a spinal nerve?
- Dorsal root and ventral root
- Dorsal horn and ventral horn
- Dorsal ramus and ventral ramus
- Anterior median fissure and posterior median sulcus
Correct Answer: Dorsal root and ventral root
Q2. How many pairs of spinal nerves are present in the adult human?
- 31 pairs
- 12 pairs
- 24 pairs
- 33 pairs
Correct Answer: 31 pairs
Q3. Which root contains the cell bodies of primary sensory neurons?
- Dorsal root (dorsal root ganglion)
- Ventral root (ventral horn)
- Dorsal ramus
- Ventral ramus
Correct Answer: Dorsal root (dorsal root ganglion)
Q4. The ventral root primarily carries which type of fibers?
- Motor efferent fibers
- Sensory afferent fibers
- Preganglionic sympathetic fibers only
- Postganglionic parasympathetic fibers only
Correct Answer: Motor efferent fibers
Q5. White rami communicantes contain which fibers?
- Preganglionic sympathetic myelinated fibers from T1–L2
- Postganglionic sympathetic unmyelinated fibers from all spinal levels
- Parasympathetic preganglionic fibers from S2–S4
- Sensory fibers for dermatomes
Correct Answer: Preganglionic sympathetic myelinated fibers from T1–L2
Q6. Which of the following best describes a dermatome?
- Skin area supplied mainly by a single spinal nerve
- Muscle group innervated by a single peripheral nerve
- Autonomic territory supplied by sympathetic chain
- Ventral ramus distribution only
Correct Answer: Skin area supplied mainly by a single spinal nerve
Q7. Which spinal level is classically associated with sensation of the thumb?
- C6
- C5
- C7
- C8
Correct Answer: C6
Q8. A lesion of a single spinal nerve root typically produces which pattern?
- Dermatomal sensory loss and myotomal weakness
- Complete limb paralysis with widespread skin loss
- Only autonomic dysfunction without sensory changes
- Isolated reflex hyperactivity without weakness
Correct Answer: Dermatomal sensory loss and myotomal weakness
Q9. Which neurotransmitter is released at the skeletal neuromuscular junction?
- Acetylcholine acting on nicotinic receptors
- Norepinephrine acting on alpha receptors
- Dopamine acting on D2 receptors
- GABA acting on GABA-A receptors
Correct Answer: Acetylcholine acting on nicotinic receptors
Q10. Which spinal segments give rise to the brachial plexus?
- C5–T1
- T1–T12
- L1–L4
- S1–S4
Correct Answer: C5–T1
Q11. Myotomes represent:
- Muscle groups primarily innervated by a single spinal segment
- Vascular territories of spinal nerves
- Only sensory distributions on the skin
- Autonomic ganglia chains
Correct Answer: Muscle groups primarily innervated by a single spinal segment
Q12. Local anesthetics primarily block nerve conduction by inhibiting:
- Voltage-gated sodium channels
- Voltage-gated potassium channels
- Acetylcholinesterase enzyme
- GABA reuptake transporters
Correct Answer: Voltage-gated sodium channels
Q13. Which fibers conduct pain and temperature from the periphery?
- A-delta and C fibers
- A-alpha fibers only
- A-beta fibers only
- B fibers exclusively
Correct Answer: A-delta and C fibers
Q14. The ventral ramus of a spinal nerve typically supplies:
- The anterior and lateral trunk and limbs
- The deep muscles of the back and skin overlying them
- Only autonomic fibers to viscera
- Cranial nerve functions
Correct Answer: The anterior and lateral trunk and limbs
Q15. Which clinical sign suggests a lower motor neuron lesion of a spinal nerve?
- Fasciculations and muscle atrophy
- Hyperreflexia and spasticity
- Babinski sign
- Clonus
Correct Answer: Fasciculations and muscle atrophy
Q16. Referred visceral pain from the heart is commonly perceived in which dermatome area?
- Left T1–T4 (medial arm and chest)
- Right C3–C5 (shoulder tip)
- Umbilical region (T10)
- Perineal region (S2–S4)
Correct Answer: Left T1–T4 (medial arm and chest)
Q17. Which structure contains cell bodies of preganglionic sympathetic neurons?
- Intermediolateral cell column of the spinal cord (lateral horn)
- Dorsal root ganglion
- Ventral horn motor neurons
- Sympathetic chain ganglia
Correct Answer: Intermediolateral cell column of the spinal cord (lateral horn)
Q18. Which pharmacologic agent is used to treat neuropathic pain by modulating calcium channels on neurons?
- Gabapentin
- Aspirin
- Propranolol
- Furosemide
Correct Answer: Gabapentin
Q19. Compression of a dorsal root ganglion most directly affects:
- Sensory transmission from the corresponding dermatome
- Sympathetic outflow to the limb
- Motor commands to the corresponding myotome
- Cerebellar coordination
Correct Answer: Sensory transmission from the corresponding dermatome
Q20. Which plexus arises from L4–S4 and supplies the lower limb?
- Sacral plexus
- Brachial plexus
- Cervical plexus
- Thoracic plexus
Correct Answer: Sacral plexus
Q21. Preganglionic parasympathetic fibers that contribute to pelvic organ function arise from which segments?
- S2–S4
- T1–T4
- L1–L2
- Cranial nerves only
Correct Answer: S2–S4
Q22. A positive straight-leg raise test indicates irritation of which nerve roots?
- L5–S1 nerve roots
- C5–C6 nerve roots
- T10–T12 nerve roots
- L1–L2 nerve roots
Correct Answer: L5–S1 nerve roots
Q23. Which of the following best distinguishes radiculopathy from peripheral neuropathy?
- Radiculopathy follows a single spinal root dermatome; peripheral neuropathy affects peripheral nerve distributions often bilaterally
- Radiculopathy is always bilateral; peripheral neuropathy is always unilateral
- Radiculopathy affects autonomic fibers only; peripheral neuropathy affects motor fibers only
- They are clinically identical and cannot be distinguished
Correct Answer: Radiculopathy follows a single spinal root dermatome; peripheral neuropathy affects peripheral nerve distributions often bilaterally
Q24. Which fiber type has the fastest conduction velocity in peripheral nerves?
- A-alpha motor fibers
- A-delta pain fibers
- C unmyelinated fibers
- A-beta sensory fibers
Correct Answer: A-alpha motor fibers
Q25. The dorsal ramus supplies which structures?
- Intrinsic back muscles and overlying skin
- Anterior thigh muscles and skin
- Visceral organs of the abdomen
- Lower limb flexor muscles only
Correct Answer: Intrinsic back muscles and overlying skin
Q26. Which mechanism explains how botulinum toxin affects neuromuscular transmission?
- Inhibits acetylcholine release at presynaptic terminals
- Blocks postsynaptic nicotinic receptors permanently
- Enhances acetylcholinesterase activity
- Opens voltage-gated sodium channels causing depolarization block
Correct Answer: Inhibits acetylcholine release at presynaptic terminals
Q27. Loss of the patellar (knee) reflex suggests involvement of which spinal segment?
- L4
- S1
- C7
- T12
Correct Answer: L4
Q28. Visceral afferent fibers conveying pain from pelvic viscera typically travel with:
- Parasympathetic pelvic splanchnic nerves to S2–S4 segments
- Somatic motor fibers to the ventral horn
- Sympathetic fibers only to T1–T4
- Cranial parasympathetic nerves only
Correct Answer: Parasympathetic pelvic splanchnic nerves to S2–S4 segments
Q29. In epidural anesthesia, blocking spinal nerve roots at the L3–L4 level typically produces:
- Analgesia and motor block in lower limbs depending on spread
- Complete anesthesia of the upper limb
- Loss of cranial nerve function
- Sensory loss confined to the face
Correct Answer: Analgesia and motor block in lower limbs depending on spread
Q30. Which finding indicates involvement of autonomic fibers in a spinal nerve lesion?
- Localized anhidrosis (loss of sweating) and vasomotor changes in the skin
- Isolated loss of tendon reflex only
- Exclusive hyperreflexia without sensory change
- Improved strength with exercise
Correct Answer: Localized anhidrosis (loss of sweating) and vasomotor changes in the skin
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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