Free Neurons and Nerve Impulse MCQs with Answers

11. Neurotransmitters are released by

• A. Diffusion
• B. Exocytosis
• C. Endocytosis
• D. Osmosis

Explanation: Neurotransmitters are released by exocytosis of synaptic vesicles when Ca2+ enters the presynaptic terminal.

12. Acetylcholine is broken down by

• A. Acetylcholinesterase
• B. Monoamine oxidase
• C. COMT
• D. Peptidase

Explanation: Acetylcholinesterase in the synaptic cleft rapidly breaks down acetylcholine to terminate the signal.

13. The sympathetic nervous system

• A. Decreases heart rate
• B. Causes fight-or-flight response
• C. Stimulates digestion
• D. Constricts pupils

Explanation: The sympathetic division mediates fight-or-flight responses: increased heart rate, dilated pupils, inhibited digestion.

14. Which neurotransmitter is inhibitory in the CNS?

• A. Glutamate
• B. GABA
• C. Dopamine
• D. Serotonin

Explanation: GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the CNS, causing Cl- influx and hyperpolarization.

15. Parkinson's disease involves deficiency of

• A. Serotonin
• B. Dopamine
• C. GABA
• D. Acetylcholine

Explanation: Parkinson's disease results from degeneration of dopaminergic neurons in the substantia nigra, causing tremors and rigidity.

16. Nissl granule is a specialized structure in neuron formed by modification of:

• A. Golgi bodies & Smooth ER
• B. Peroxisome & Mitochondria
• C. Lysosome & Vacuole
• D. Ribosome & Rough ER

Explanation: Nissl granules are dense stacks of rough endoplasmic reticulum studded with ribosomes, which is why they stain so darkly and why they are concentrated in the cell body where protein synthesis for the whole neurone takes place. Smooth ER carries no ribosomes and handles lipid synthesis instead. Their disappearance after injury, called chromatolysis, is a standard sign of nerve cell damage.

17. The neurotransmitters are secreted by the neuron from:

• A. Axon ends
• B. Dendrite end
• C. Nissl's granules
• D. Cell body

Explanation: Vesicles of transmitter are stored in the swollen endings of the axon and released into the synaptic cleft when the impulse arrives. Dendrites carry the receptors that detect the transmitter on the other side of the synapse, which is why they are the tempting answer. This arrangement, with release on one side and reception on the other, is exactly what makes transmission one way.

18. Which part of the neuron typically receives incoming signals from other neurons?

• A. Axon
• B. Dendrites
• C. Myelin sheath
• D. Synaptic knob

Explanation: Dendrites are the short branched processes that carry receptors for neurotransmitter and conduct the resulting signal towards the cell body. The axon carries impulses away, and its synaptic knobs are where transmitter is released rather than received. Myelin is an insulating sheath that speeds conduction and plays no part in reception.

19. Which of the following cells possess Nissl's granules?

• A. Nerve cells
• B. WBC
• C. RBC
• D. Platelets

Explanation: Nissl granules are stacks of rough endoplasmic reticulum in the cell body of a neurone, supporting the heavy protein synthesis a nerve cell requires. Mature red blood cells have no nucleus and almost no organelles at all, and platelets are only cell fragments. Their loss after injury, called chromatolysis, is a recognised sign of neuronal damage.