Part 3: Spinal Cord – Structure, Functions, Reflex Actions, Reflex Arc
Part 3 (25 MCQs) on Spinal Cord – Structure, Functions, Reflex Actions, Reflex Arc from Chapter 21: Neural Control and Coordination (NCERT Class 11 + NEET UG).
Part 3: Spinal Cord – Structure, Functions, Reflex Actions, Reflex Arc
Q1. The spinal cord in humans originates from:
a) Pons
b) Medulla oblongata
c) Cerebellum
d) Midbrain
Answer: b) Medulla oblongata
Explanation:
- ✅ (b) Spinal cord continues downward from medulla.
Q2. The spinal cord is enclosed in:
a) Cranium
b) Vertebral column
c) Sternum
d) Ribs
Answer: b) Vertebral column
Explanation:
- ✅ (b) Vertebral column protects spinal cord.
Q3. How many pairs of spinal nerves are present in humans?
a) 12
b) 24
c) 31
d) 33
Answer: c) 31
Explanation:
- ✅ (c) 31 pairs → mixed nerves (sensory + motor).
Q4. The butterfly-shaped area in spinal cord cross-section is:
a) White matter
b) Gray matter
c) Pia mater
d) CSF
Answer: b) Gray matter
Explanation:
- ✅ (b) Central gray matter (H/butterfly shape) surrounded by white matter.
Q5. White matter of spinal cord consists of:
a) Neuron cell bodies
b) Myelinated axons
c) Neuroglia only
d) Dendrites
Answer: b) Myelinated axons
Explanation:
- ✅ (b) White matter = myelinated nerve fibers.
Q6. The dorsal root of spinal nerve carries:
a) Motor impulses
b) Sensory impulses
c) Both
d) Autonomic impulses only
Answer: b) Sensory impulses
Explanation:
- ✅ (b) Dorsal root → afferent fibers → sensory input.
Q7. The ventral root of spinal nerve carries:
a) Sensory impulses
b) Motor impulses
c) Both
d) Reflex action
Answer: b) Motor impulses
Explanation:
- ✅ (b) Ventral root → efferent fibers → motor output.
Q8. Reflex action is:
a) Voluntary and slow
b) Involuntary and automatic
c) Only conscious
d) Only sympathetic
Answer: b) Involuntary and automatic
Explanation:
- ✅ (b) Reflex = rapid, involuntary response.
Q9. The functional unit of reflex is:
a) Neuron
b) Reflex arc
c) Spinal cord
d) Synapse
Answer: b) Reflex arc
Explanation:
- ✅ (b) Reflex arc = pathway of reflex action.
Q10. Knee-jerk reflex is an example of:
a) Polysynaptic reflex
b) Monosynaptic reflex
c) Conditioned reflex
d) Voluntary action
Answer: b) Monosynaptic reflex
Explanation:
- ✅ (b) Knee-jerk → involves only one synapse.
Q11. Withdrawal of hand from hot object is:
a) Voluntary reflex
b) Polysynaptic reflex
c) Monosynaptic reflex
d) Conditioned reflex
Answer: b) Polysynaptic reflex
Explanation:
- ✅ (b) Multiple interneurons involved in withdrawal reflex.
Q12. The center for reflex actions lies in:
a) Brain
b) Spinal cord
c) Hypothalamus
d) Cerebellum
Answer: b) Spinal cord
Explanation:
- ✅ (b) Reflexes are controlled by spinal cord (though brain aware).
Q13. Which of the following is NOT a component of reflex arc?
a) Receptor
b) Effector
c) Association neuron
d) Hormone
Answer: d) Hormone
Explanation:
- ✅ Reflex arc includes receptor, sensory neuron, interneuron, motor neuron, effector.
Q14. Conditioned reflex was first demonstrated by:
a) Darwin
b) Pavlov
c) Sherrington
d) Golgi
Answer: b) Pavlov
Explanation:
- ✅ (b) Ivan Pavlov demonstrated conditioned reflex in dogs (bell + food).
Q15. The meninges that directly cover the spinal cord are:
a) Pia mater
b) Arachnoid mater
c) Dura mater
d) All three
Answer: a) Pia mater
Explanation:
- ✅ (a) Pia mater → thin, innermost layer covering spinal cord.
Q16. Which part of spinal cord is responsible for higher processing of reflex?
a) White matter
b) Gray matter
c) Dorsal root
d) Ventral root
Answer: b) Gray matter
Explanation:
- ✅ (b) Reflex processing occurs in gray matter.
Q17. Which root of spinal nerve contains ganglion?
a) Ventral root
b) Dorsal root
c) Both
d) None
Answer: b) Dorsal root
Explanation:
- ✅ (b) Dorsal root ganglion = sensory neuron cell bodies.
Q18. Spinal cord ends in adults at the level of:
a) Thoracic vertebra
b) Lumbar vertebra (L1–L2)
c) Sacrum
d) Coccyx
Answer: b) Lumbar vertebra (L1–L2)
Explanation:
- ✅ (b) Spinal cord ends at L1–L2, continues as cauda equina.
Q19. Which tract carries motor commands from brain to spinal cord?
a) Ascending tract
b) Descending tract
c) Reflex arc
d) Autonomic nerves
Answer: b) Descending tract
Explanation:
- ✅ (b) Descending tracts carry motor impulses downward.
Q20. Which tract carries sensory input to brain?
a) Descending tract
b) Ascending tract
c) Reflex arc
d) Motor neurons
Answer: b) Ascending tract
Explanation:
- ✅ (b) Ascending tracts → sensory info to brain.
Q21. The effector in reflex action can be:
a) Muscle
b) Gland
c) Both a and b
d) None
Answer: c) Both a and b
Explanation:
- ✅ (c) Reflex → muscles (movement) or glands (secretion).
Q22. “All-or-none” principle of nerve conduction also applies to:
a) Reflex action
b) Muscle contraction
c) Both a and b
d) None
Answer: c) Both a and b
Explanation:
- ✅ (c) Either full response or none occurs.
Q23. The withdrawal reflex helps in:
a) Learning
b) Protection from injury
c) Maintaining posture
d) None
Answer: b) Protection from injury
Explanation:
- ✅ (b) Withdrawal from harmful stimulus → protective.
Q24. Conditioned reflex differs from simple reflex because:
a) It is inborn
b) It is acquired by learning
c) It is not related to CNS
d) It has no effector
Answer: b) It is acquired by learning
Explanation:
- ✅ (b) Conditioned reflex (e.g., Pavlov’s dog) is learned, not inborn.
Q25. Reflex arc that bypasses interneurons is:
a) Polysynaptic reflex
b) Monosynaptic reflex
c) Conditioned reflex
d) Complex reflex
Answer: b) Monosynaptic reflex
Explanation:
- ✅ (b) Monosynaptic reflex arc = sensory → motor neuron directly.
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