Neurohumoral transmission in CNS MCQs With Answer

Neurohumoral transmission in CNS MCQs With Answer

Neurohumoral transmission in the central nervous system (CNS) describes how neurons and non-neuronal cells communicate using neurotransmitters, neuromodulators, and gaseous messengers. This topic covers synaptic and volume transmission, synthesis, vesicular storage (VMAT, VAChT, VGLUT), release mechanisms (SNAREs, synaptotagmin, Ca2+), receptor families (ionotropic and metabotropic GPCRs), reuptake transporters (DAT, SERT, NET), and degradative enzymes (AChE, MAO, COMT). Understanding these processes links molecular pharmacology to therapeutic drug targets—antidepressants, antipsychotics, anxiolytics, cholinesterase inhibitors, and neuromodulatory agents. Designed for B.Pharm students, this set emphasizes mechanisms, drug action points, and clinical relevance. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the primary role of synaptotagmin in neurohumoral transmission?

• Packaging neurotransmitters into vesicles
• Acting as a Ca2+ sensor to trigger vesicle fusion
• Cleaving neurotransmitters in the synaptic cleft
• Transporting neurotransmitters across the blood–brain barrier

Correct Answer: Acting as a Ca2+ sensor to trigger vesicle fusion

Q2. Which transporter is responsible for vesicular uptake of monoamines like dopamine and norepinephrine?

• VAChT
• VGLUT
• VMAT
• SERT

Correct Answer: VMAT

Q3. Volume transmission in the CNS is best described as:

• Fast point-to-point synaptic transmission across a narrow cleft
• Diffuse signaling where neurochemicals spread through extracellular fluid to act at distant sites
• Transmission exclusively mediated by gap junctions
• Only hormonal signaling via the systemic circulation

Correct Answer: Diffuse signaling where neurochemicals spread through extracellular fluid to act at distant sites

Q4. Which enzyme primarily degrades acetylcholine in the synaptic cleft?

• Monoamine oxidase (MAO)
• Acetylcholinesterase (AChE)
• Catechol-O-methyltransferase (COMT)
• Glutamate decarboxylase (GAD)

Correct Answer: Acetylcholinesterase (AChE)

Q5. Which receptor type is an ionotropic receptor mediating fast excitatory transmission by glutamate?

• Muscarinic M2 receptor
• NMDA receptor
• D2 dopamine receptor
• CB1 cannabinoid receptor

Correct Answer: NMDA receptor

Q6. Select the correct pairing of reuptake transporter and neurotransmitter.

• SERT — Dopamine
• DAT — Serotonin
• NET — Norepinephrine
• GLT-1 — GABA

Correct Answer: NET — Norepinephrine

Q7. Endocannabinoids modulate synaptic transmission primarily by:

• Increasing vesicular neurotransmitter loading
• Acting as retrograde messengers to inhibit presynaptic neurotransmitter release
• Activating postsynaptic NMDA receptors
• Directly blocking voltage-gated sodium channels

Correct Answer: Acting as retrograde messengers to inhibit presynaptic neurotransmitter release

Q8. Which gaseous neurotransmitter diffuses freely and activates guanylate cyclase in target cells?

• Acetylcholine
• Nitric oxide (NO)
• Serotonin
• Substance P

Correct Answer: Nitric oxide (NO)

Q9. Which of the following is a characteristic feature of GPCR-mediated neuromodulation?

• Direct pore formation for ion flow
• Fast millisecond ion flux like ionotropic receptors
• Activation of second messenger cascades (cAMP, IP3/DAG)
• Irreversible activation after ligand binding

Correct Answer: Activation of second messenger cascades (cAMP, IP3/DAG)

Q10. Which process best explains quantal release at chemical synapses?

• Neurotransmitter diffusion through gap junctions
• Release of discrete vesicle-sized packets of neurotransmitter
• Continuous leak of transmitter from presynaptic membrane
• Synthesis of transmitter in the synaptic cleft

Correct Answer: Release of discrete vesicle-sized packets of neurotransmitter

Q11. Which protein complex is directly involved in vesicle docking and fusion at presynaptic terminals?

• SNARE complex
• Na+/K+ ATPase
• Tubulin polymerase
• Cyclooxygenase

Correct Answer: SNARE complex

Q12. Monoamine oxidase inhibitors (MAOIs) increase synaptic monoamines by inhibiting:

• Vesicular monoamine transporter (VMAT)
• Enzymatic breakdown of monoamines in presynaptic terminals
• Reuptake via DAT, SERT, and NET directly
• Synthesis of monoamines from precursors

Correct Answer: Enzymatic breakdown of monoamines in presynaptic terminals

Q13. Which neurotransmitter is synthesized from tryptophan and is a target of SSRIs?

• Dopamine
• Serotonin (5-HT)
• Norepinephrine
• GABA

Correct Answer: Serotonin (5-HT)

Q14. Which statement best differentiates neuromodulators from classical neurotransmitters?

• Neuromodulators only act at ionotropic receptors
• Neuromodulators produce longer-lasting, diffuse effects via GPCRs and volume transmission
• Classical neurotransmitters never bind receptors
• Neuromodulators are stored in synaptic cleft proteins

Correct Answer: Neuromodulators produce longer-lasting, diffuse effects via GPCRs and volume transmission

Q15. GABA-A receptors are best described as:

• Metabotropic GPCRs that increase cAMP
• Ionotropic chloride channels mediating fast inhibition
• Voltage-gated potassium channels
• Presynaptic transporters for GABA uptake

Correct Answer: Ionotropic chloride channels mediating fast inhibition

Q16. Which drug class enhances GABA-A receptor activity and is used as anxiolytics and sedatives?

• SSRIs
• Benzodiazepines
• Tricyclic antidepressants
• MAO inhibitors

Correct Answer: Benzodiazepines

Q17. Which transporter is primarily responsible for clearing glutamate from the synaptic cleft to prevent excitotoxicity?

• SERT
• EAAT (e.g., GLT-1)
• NET
• GAT-1

Correct Answer: EAAT (e.g., GLT-1)

Q18. Which receptor subtype mediates fast skeletal neuromuscular transmission?

• Muscarinic M1 receptor
• Nicotinic acetylcholine receptor (nAChR)
• MOP opioid receptor
• CB2 cannabinoid receptor

Correct Answer: Nicotinic acetylcholine receptor (nAChR)

Q19. Which protein loads acetylcholine into synaptic vesicles?

• VAChT
• VMAT
• VGLUT
• Choline acetyltransferase (ChAT)

Correct Answer: VAChT

Q20. The locus coeruleus is the principal source of which neuromodulator in the brain?

• Serotonin
• Dopamine
• Norepinephrine
• Acetylcholine

Correct Answer: Norepinephrine

Q21. Which mechanism is a common target for antidepressant drugs such as SSRIs and SNRIs?

• Inhibition of acetylcholinesterase
• Blockade of voltage-gated calcium channels
• Inhibition of neurotransmitter reuptake transporters (SERT/NET)
• Activation of GABA-A receptors

Correct Answer: Inhibition of neurotransmitter reuptake transporters (SERT/NET)

Q22. Which peptide acts as a neurotransmitter/neuromodulator involved in pain transmission and is a target for analgesics?

• Substance P
• Glutamate
• GABA
• Dopamine

Correct Answer: Substance P

Q23. Which receptor property allows NMDA receptors to act as coincidence detectors in synaptic plasticity?

• Block by Mg2+ at resting membrane potential and voltage-dependent relief upon depolarization
• Constitutive opening independent of ligand or voltage
• Exclusive coupling to Gi proteins
• Rapid desensitization preventing long-term potentiation

Correct Answer: Block by Mg2+ at resting membrane potential and voltage-dependent relief upon depolarization

Q24. Which transport protein is targeted by cocaine to increase synaptic dopamine?

• SERT
• DAT
• VAChT
• EAAT

Correct Answer: DAT

Q25. Retrograde signaling in the CNS commonly involves which of the following?

• Presynaptic release of glutamate acting on postsynaptic NMDA receptors
• Postsynaptic release of diffusible signals (e.g., endocannabinoids, NO) acting on presynaptic terminals
• Axonal transport of vesicles to the soma
• Direct electrical coupling only

Correct Answer: Postsynaptic release of diffusible signals (e.g., endocannabinoids, NO) acting on presynaptic terminals

Q26. Which enzyme synthesizes GABA from glutamate?

• Tyrosine hydroxylase
• Glutamate decarboxylase (GAD)
• Choline acetyltransferase (ChAT)
• Phenylethanolamine N-methyltransferase (PNMT)

Correct Answer: Glutamate decarboxylase (GAD)

Q27. In the context of neurohumoral pharmacology, COMT primarily metabolizes which class of compounds?

• Peptide neurotransmitters
• Catecholamines (e.g., dopamine, norepinephrine)
• Gaseous transmitters like NO
• Endocannabinoids

Correct Answer: Catecholamines (e.g., dopamine, norepinephrine)

Q28. Astrocytes contribute to neurohumoral transmission by:

• Generating action potentials to propagate signals
• Uptaking neurotransmitters, modulating extracellular ions, and releasing gliotransmitters
• Forming myelin around axons
• Producing dopamine in the substantia nigra

Correct Answer: Uptaking neurotransmitters, modulating extracellular ions, and releasing gliotransmitters

Q29. Which statement best describes the blood–brain barrier (BBB) relevance to neurohumoral pharmacology?

• All neuroactive drugs freely cross the BBB regardless of size or polarity
• The BBB restricts many drugs; lipophilicity, transporters, and efflux pumps determine CNS penetration
• BBB is only a concern for peptide hormones, not small molecules
• The BBB actively transports all neurotransmitters into the brain

Correct Answer: The BBB restricts many drugs; lipophilicity, transporters, and efflux pumps determine CNS penetration

Q30. Which drug mechanism is used to treat myasthenia gravis by enhancing neuromuscular transmission?

• NMDA receptor antagonism
• Acetylcholinesterase inhibition
• Blocking nicotinic receptors
• Inhibiting VMAT

Correct Answer: Acetylcholinesterase inhibition

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com