Neurohumoral transmission links neuronal signaling and hormonal control to regulate body functions—an essential topic for B.Pharm students. This area covers neurotransmitters, receptors, synaptic and neuroeffector junction mechanisms, and hormone-driven second-messenger pathways that determine drug responses. Core keywords include neurotransmitters, synaptic transmission, GPCRs, ionotropic receptors, neuromodulation, second messengers (cAMP, IP3/DAG), reuptake, enzymatic degradation (MAO, COMT), cholinergic and adrenergic systems, neuromuscular junctions, receptor desensitization, and pharmacological modulation (agonists, antagonists, enzyme inhibitors). Mastery helps predict therapeutic effects, adverse reactions, and targets for new agents. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What best describes neurohumoral transmission?
- Direct electrical coupling between endocrine cells
- Communication combining neuronal release of chemical mediators and hormonal signaling
- Hormone release solely from endocrine glands without neural input
- Only synaptic transmission at the neuromuscular junction
Correct Answer: Communication combining neuronal release of chemical mediators and hormonal signaling
Q2. Which enzyme primarily degrades norepinephrine in the synaptic cleft and periphery?
- Acetylcholinesterase
- Catechol-O-methyltransferase (COMT)
- Monoamine oxidase (MAO)
- Choline acetyltransferase
Correct Answer: Monoamine oxidase (MAO)
Q3. Which receptor type mediates fast synaptic transmission via ligand-gated ion channels?
- G protein-coupled receptors (GPCRs)
- Tyrosine kinase receptors
- Ionotropic receptors
- Nuclear hormone receptors
Correct Answer: Ionotropic receptors
Q4. Which second messenger is classically increased by stimulatory beta-adrenergic receptor activation?
- cAMP
- IP3
- DAG
- cGMP
Correct Answer: cAMP
Q5. What is the primary action of monoamine oxidase inhibitors (MAOIs) in neurohumoral systems?
- Block neurotransmitter reuptake into vesicles
- Prevent enzymatic breakdown of monoamines, increasing synaptic levels
- Activate autoreceptors to decrease release
- Inhibit postsynaptic receptor signaling directly
Correct Answer: Prevent enzymatic breakdown of monoamines, increasing synaptic levels
Q6. Which is a characteristic of neuromodulators compared with classical neurotransmitters?
- They act only at ionotropic receptors
- They typically produce rapid postsynaptic currents lasting milliseconds
- They often act on GPCRs and diffuse to affect many neurons
- They are stored exclusively in small clear synaptic vesicles
Correct Answer: They often act on GPCRs and diffuse to affect many neurons
Q7. Which mechanism terminates acetylcholine action at the neuromuscular junction?
- Reuptake by presynaptic transporter
- Hydrolysis by acetylcholinesterase
- Degradation by COMT
- Diffusion into blood and hormone clearance
Correct Answer: Hydrolysis by acetylcholinesterase
Q8. A drug that occupies a receptor and produces less than maximal response is called a:
- Full agonist
- Inverse agonist
- Partial agonist
- Neutral antagonist
Correct Answer: Partial agonist
Q9. Which process describes reduced receptor responsiveness after continued agonist exposure?
- Receptor up-regulation
- Receptor desensitization (tachyphylaxis)
- Facilitation
- Potentiation
Correct Answer: Receptor desensitization (tachyphylaxis)
Q10. Which transporter is primarily responsible for serotonin reuptake into presynaptic terminals?
- DAT (dopamine transporter)
- SERT (serotonin transporter)
- NET (norepinephrine transporter)
- VAChT (vesicular acetylcholine transporter)
Correct Answer: SERT (serotonin transporter)
Q11. What is the role of autoreceptors on presynaptic terminals?
- Enhance neurotransmitter synthesis permanently
- Provide negative feedback to inhibit further transmitter release
- Transport neurotransmitter into postsynaptic cell
- Activate second messenger cascades in the postsynaptic neuron
Correct Answer: Provide negative feedback to inhibit further transmitter release
Q12. Which drug class increases synaptic serotonin by blocking its reuptake?
- Beta-blockers
- SSRIs (selective serotonin reuptake inhibitors)
- MAO-B inhibitors
- Acetylcholinesterase inhibitors
Correct Answer: SSRIs (selective serotonin reuptake inhibitors)
Q13. Which molecule acts as a gaseous neurotransmitter and diffuses freely across membranes?
- Acetylcholine
- Nitric oxide (NO)
- Dopamine
- ATP
Correct Answer: Nitric oxide (NO)
Q14. Which adrenergic receptor subtype primarily mediates increased heart rate and contractility?
- Alpha-1
- Beta-1
- Beta-2
- Alpha-2
Correct Answer: Beta-1
Q15. Quantal release refers to:
- Continuous leakage of ions across the membrane
- Release of neurotransmitter in discrete packets (vesicles)
- Hormone secretion from endocrine glands only
- Electrical coupling strength between neurons
Correct Answer: Release of neurotransmitter in discrete packets (vesicles)
Q16. Which enzyme synthesizes acetylcholine from choline and acetyl-CoA?
- Choline acetyltransferase (ChAT)
- Acetylcholinesterase (AChE)
- Tyrosine hydroxylase
- Phenylethanolamine N-methyltransferase
Correct Answer: Choline acetyltransferase (ChAT)
Q17. Which statement best describes GPCR signaling in neurohumoral transmission?
- GPCRs are ion channels that open upon ligand binding
- GPCR activation engages heterotrimeric G proteins to modulate second messengers
- GPCRs directly phosphorylate intracellular proteins
- GPCRs only mediate genomic effects via nuclear translocation
Correct Answer: GPCR activation engages heterotrimeric G proteins to modulate second messengers
Q18. In synaptic plasticity, long-term potentiation (LTP) is primarily associated with:
- Decreased postsynaptic AMPA receptor density
- Enhanced synaptic strength, often via NMDA receptor-dependent mechanisms
- Permanent loss of synapses
- Exclusive presynaptic inhibition of release
Correct Answer: Enhanced synaptic strength, often via NMDA receptor-dependent mechanisms
Q19. Which pharmacological agent would increase acetylcholine levels at synapses by inhibiting breakdown?
- Neostigmine (acetylcholinesterase inhibitor)
- Propranolol (beta-blocker)
- Fluoxetine (SSRI)
- Reserpine (vesicular monoamine transporter inhibitor)
Correct Answer: Neostigmine (acetylcholinesterase inhibitor)
Q20. What is the primary effect of presynaptic uptake inhibition on neurotransmission?
- Decrease synaptic neurotransmitter concentration
- Increase extracellular neurotransmitter concentration and prolong signaling
- Enhance enzymatic degradation in the synaptic cleft
- Block vesicular release mechanisms directly
Correct Answer: Increase extracellular neurotransmitter concentration and prolong signaling
Q21. Which drug class blocks beta-adrenergic receptors to reduce cardiac workload?
- ACE inhibitors
- Beta-blockers
- Calcium channel activators
- Monoamine oxidase inhibitors
Correct Answer: Beta-blockers
Q22. Which process allows rapid removal of neurotransmitter from the synaptic cleft in many central synapses?
- Endocytosis of postsynaptic receptors
- Active reuptake into presynaptic terminals or glia
- Conversion into DNA within the synapse
- Diffusion into intracellular mitochondria
Correct Answer: Active reuptake into presynaptic terminals or glia
Q23. Which receptor subtype is ionotropic among cholinergic receptors?
- Muscarinic M2
- Nicotinic
- Muscarinic M1
- Beta-adrenergic
Correct Answer: Nicotinic
Q24. Which term describes a drug that stabilizes a receptor in its inactive conformation, reducing constitutive activity?
- Partial agonist
- Inverse agonist
- Neutral agonist
- Allosteric enhancer
Correct Answer: Inverse agonist
Q25. Which factor most restricts penetration of many drugs into the brain, affecting neurohumoral drug action?
- Liver metabolism
- Blood-brain barrier (BBB)
- Gastric pH
- Renal glomerular filtration
Correct Answer: Blood-brain barrier (BBB)
Q26. Which is a common effect of activating presynaptic alpha-2 adrenergic receptors?
- Increased neurotransmitter release
- Inhibition of neurotransmitter release via feedback
- Postsynaptic depolarization
- Conversion of NE to epinephrine
Correct Answer: Inhibition of neurotransmitter release via feedback
Q27. Which enzyme catalyzes the rate-limiting step in catecholamine synthesis?
- Tyrosine hydroxylase
- Monoamine oxidase
- Dopamine beta-hydroxylase
- Phenylethanolamine N-methyltransferase
Correct Answer: Tyrosine hydroxylase
Q28. Which concept explains how a small amount of neurotransmitter can produce a large cellular response?
- Pharmacokinetics
- Second-messenger amplification
- First-pass metabolism
- Receptor sequestration
Correct Answer: Second-messenger amplification
Q29. At the neuromuscular junction, miniature end plate potentials (MEPPs) reflect:
- Action potential propagation failure
- Spontaneous release of single vesicles of acetylcholine
- Postsynaptic receptor down-regulation
- Hormonal modulation of muscle metabolism
Correct Answer: Spontaneous release of single vesicles of acetylcholine
Q30. Which pharmacological strategy increases synaptic norepinephrine by preventing vesicular storage?
- SSRIs
- Reserpine (VMAT inhibitor)
- Beta-2 agonists
- Acetylcholinesterase inhibitors
Correct Answer: Reserpine (VMAT inhibitor)
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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