The Neuromuscular Junction (Nmj)

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| By Mgartz
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Quizzes Created: 8 | Total Attempts: 18,645
Questions: 20 | Attempts: 1,086

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The Neuromuscular Junction (Nmj) - Quiz


Questions and Answers
  • 1. 

    The Neuromuscular Junction (NMJ) A synapse between a motor neuron axon and the motor end plate (consists of excitable muscle fibers) Uses ___ as a transmitter

    • A.

      AChE

    • B.

      5-HT

    • C.

      NE

    • D.

      ACh

    Correct Answer
    D. ACh
    Explanation
    The correct answer is ACh. The neuromuscular junction is a synapse between a motor neuron axon and the motor end plate, which consists of excitable muscle fibers. It uses acetylcholine (ACh) as a transmitter. ACh is released from the motor neuron and binds to receptors on the motor end plate, causing the muscle fibers to contract.

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  • 2. 

    Mediate NMJ and autonomic ganglia function Are found on muscle endplates and peripheral ganglia Distinct subtypes exist at NMJ and autonomic ganglia pentameric ionotropic receptors (Similar to GABAA) Gate Na+ and K+ ions, and in some forms, Ca++ ions Net effect of activation is depolarization OF POSTSYNAPTIC CELL

    • A.

      Muscarinic receptors

    • B.

      Nicotinic receptors

    • C.

      Dopamine receptors

    • D.

      Serotonin receptors

    Correct Answer
    B. Nicotinic receptors
    Explanation
    Nicotinic receptors are the correct answer because they are known to mediate NMJ (neuromuscular junction) and autonomic ganglia function. They are found on muscle endplates and peripheral ganglia. Nicotinic receptors are pentameric ionotropic receptors, similar to GABAA receptors. They gate Na+, K+, and in some forms, Ca++ ions. Activation of nicotinic receptors leads to depolarization of the postsynaptic cell.

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  • 3. 

    ____________was the first widely used Neuromuscular Blocking Agents

    Correct Answer
    Curare
    Explanation
    Curare was the first widely used Neuromuscular Blocking Agent. Curare is a natural plant extract that has been used by indigenous tribes in South America for centuries as a poison for hunting. In the medical field, it was first introduced as a muscle relaxant during surgery in the 1940s. Curare works by blocking the transmission of nerve impulses to the muscles, leading to paralysis. Its introduction revolutionized anesthesia and surgical procedures by allowing better control over muscle relaxation. Today, synthetic derivatives of curare are commonly used in medical practice as Neuromuscular Blocking Agents.

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  • 4. 

    Two types of neuroblockin agents which one work by over-stimulating nicotinic receptors, causing muscle fiber membrane depolarization

    • A.

      Polarizing agents

    • B.

      Depolarizing agents

    • C.

      Competitive agents

    • D.

      Noncompetitive agents

    Correct Answer
    B. Depolarizing agents
    Explanation
    Depolarizing agents are neuroblocking agents that work by over-stimulating nicotinic receptors, leading to muscle fiber membrane depolarization. This causes a sustained muscle contraction, leading to paralysis. Polarizing agents, on the other hand, work by preventing depolarization of the muscle fiber membrane, while competitive and noncompetitive agents work by blocking the binding of acetylcholine to nicotinic receptors. Therefore, depolarizing agents are the correct answer in this case.

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  • 5. 

    Two types of neuroblockin agents which one work by antagonizing ACh receptors

    • A.

      Polarizing agents

    • B.

      Depolarizing agents

    • C.

      Competitive agents

    • D.

      Noncompetitive agents

    Correct Answer
    C. Competitive agents
    Explanation
    Competitive agents are neuroblocking agents that work by antagonizing ACh receptors. These agents compete with acetylcholine (ACh) for binding to the ACh receptors, preventing the activation of the receptors by ACh. This results in a decrease in the transmission of nerve impulses, leading to muscle relaxation and paralysis. Polarizing agents, depolarizing agents, and noncompetitive agents are not specifically mentioned as working by antagonizing ACh receptors, so they are not the correct answer.

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  • 6. 

    Neuromuscular blocking agents currently in use typically have a slow onset, and long duration of action

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    Neuromuscular blocking agents currently in use typically have a rapid onset, and short duration of action

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  • 7. 

    Currently only ____________ is used as a depolarizing neuromuscular blocking agent

    • A.

      Pancuronium

    • B.

      Succinylcholine

    • C.

      Vecuronium

    • D.

      Rocuronium

    Correct Answer
    B. Succinylcholine
    Explanation
    Succinylcholine is currently the only depolarizing neuromuscular blocking agent used. This means that it works by causing a depolarization of the motor end plate, resulting in muscle relaxation. Pancuronium, vecuronium, and rocuronium are all non-depolarizing neuromuscular blocking agents, which work by blocking the action of acetylcholine at the neuromuscular junction. Therefore, succinylcholine is the correct answer.

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  • 8. 

    Chemical makeup of neuromuscular blocking agents include:

    • A.

      Natural alkaloids and congeners

    • B.

      Ammonio steroids

    • C.

      Benzylisquinolones

    Correct Answer(s)
    A. Natural alkaloids and congeners
    B. Ammonio steroids
    C. Benzylisquinolones
    Explanation
    The correct answer is a list of different chemical makeups of neuromuscular blocking agents. These include natural alkaloids and congeners, ammonio steroids, and benzylisquinolones.

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  • 9. 

    Competitive agents tend to be ____, ____ molecules, ______ bottom

    Correct Answer(s)
    large, rigid, steroid
    Explanation
    Competitive agents are typically large molecules that are rigid in structure. Steroids, which are a type of organic compound, are known for their large size and rigidity. Therefore, the answer "large, rigid, steroid" accurately describes the characteristics of competitive agents.

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  • 10. 

    Natural or synthetic alkaloids are not often used because lots of ‘side effects’, including causing _________release_______ also have a relatively ______duration of action

    • A.

      Histamine, long

    • B.

      5-HT, long

    • C.

      Histamine, short

    • D.

      5-HT, short

    Correct Answer
    A. Histamine, long
    Explanation
    Natural or synthetic alkaloids are not often used because they can cause the release of histamine, which has a long duration of action. This means that the effects of histamine can last for a longer period of time, leading to potential side effects. Therefore, due to these side effects and the long duration of action of histamine, alkaloids are not commonly used.

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  • 11. 

    Pancuronium

    • A.

      Prototype ammonio steroid

    • B.

      No histamine release

    • C.

      Block muscarinic receptors, and causes tachycardia

    • D.

      Don’t have ganglionic blocking actions, don’t alter vagus nerve function

    • E.

      Prototype benzylisquinolone

    Correct Answer(s)
    A. Prototype ammonio steroid
    B. No histamine release
    C. Block muscarinic receptors, and causes tachycardia
    Explanation
    Pancuronium is a prototype ammonio steroid that does not release histamine. It blocks muscarinic receptors, which leads to tachycardia. It does not have ganglionic blocking actions and does not alter vagus nerve function.

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  • 12. 

    Atracurium

    • A.

      Prototype ammonio steroid

    • B.

      No histamine release

    • C.

      Block muscarinic receptors, and causes tachycardia

    • D.

      Don’t have ganglionic blocking actions, don’t alter vagus nerve function

    • E.

      Prototype benzylisquinolone

    Correct Answer
    E. Prototype benzylisquinolone
  • 13. 

    Benzylisquinolones

    • A.

      Prototype ammonio steroid

    • B.

      No histamine release

    • C.

      Block muscarinic receptors, and causes tachycardia

    • D.

      Don’t have ganglionic blocking actions, don’t alter vagus nerve function

    • E.

      Prototype benzylisquinolone

    Correct Answer
    D. Don’t have ganglionic blocking actions, don’t alter vagus nerve function
    Explanation
    The correct answer is that benzylisquinolones don't have ganglionic blocking actions and don't alter vagus nerve function. This means that benzylisquinolones do not affect the ganglia, which are clusters of nerve cell bodies outside the central nervous system, and do not interfere with the function of the vagus nerve, which is responsible for regulating various bodily functions. This information implies that benzylisquinolones have a specific mechanism of action that does not involve these particular effects on the nervous system.

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  • 14. 

    Neuromuscular Blocking Competitive Antagonists When applied directly to skeletal muscle, nicotinic agonists cause a localized _________

    Correct Answer
    paralytic effect
    Explanation
    Nicotinic agonists, when applied directly to skeletal muscle, bind to nicotinic acetylcholine receptors, leading to the activation of these receptors. This activation causes depolarization of the muscle cell membrane and subsequent muscle contraction. However, when nicotinic agonists are used in high concentrations or for a prolonged period, they can desensitize and eventually block the nicotinic receptors, resulting in a paralytic effect. This occurs because the agonists continuously stimulate the receptors, leading to a state of receptor desensitization and ultimately preventing muscle contraction.

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  • 15. 

    Neuromuscular Blocking Agent MOA: Depolarizing Agents

    • A.

      Depolarization effect on the postsynaptic muscle is long lasting

    • B.

      A short period of repetitive excitation and muscle twitching followed by…Blockade of neurotransmission and paralysis

    • C.

      Initial action of depolarizing agents is to cause opening of ion channels

    • D.

      All are true

    Correct Answer
    D. All are true
    Explanation
    The given answer states that all the statements provided are true. The statements mentioned in the question are as follows: depolarization effect on the postsynaptic muscle is long-lasting, a short period of repetitive excitation and muscle twitching followed by blockade of neurotransmission and paralysis, and the initial action of depolarizing agents is to cause the opening of ion channels. According to the answer, all of these statements are correct.

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  • 16. 

    Depolarization is achieved when muscle fibers are no longer responsive to ACh at With prolonged depolarization, muscle ____________, and Na+, Cl- and Ca++ are gained Depolarizing blockers are hydrolyzed by _____________

    • A.

      Postsynaptic cell

    • B.

      K+ is depleted

    • C.

      Butyrylcholinesterases

    • D.

      Presynaptic cell

    • E.

      K+ is increased

    Correct Answer(s)
    A. Postsynaptic cell
    B. K+ is depleted
    C. Butyrylcholinesterases
    Explanation
    Depolarization is achieved when muscle fibers are no longer responsive to ACh at the postsynaptic cell. With prolonged depolarization, muscle K+ is depleted, and Na+, Cl-, and Ca++ are gained. Depolarizing blockers are hydrolyzed by butyrylcholinesterases.

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  • 17. 

    What is true about NMJ Blocker Toxicity

    • A.

      Results in bronchospasm, hypotension, increased secretory activity

    • B.

      Can cause histamine release

    • C.

      Dangerous in patients with CHF who are taking diuretics, digoxin

    • D.

      Life threatening in individuals with ion regulation dysfunction

    • E.

      Dangerous in patients withsignificant burns, soft tissue damage, and in children

    • F.

      Cause a significant release of K+ from intracellular sites

    Correct Answer(s)
    A. Results in bronchospasm, hypotension, increased secretory activity
    B. Can cause histamine release
    C. Dangerous in patients with CHF who are taking diuretics, digoxin
    D. Life threatening in individuals with ion regulation dysfunction
    E. Dangerous in patients withsignificant burns, soft tissue damage, and in children
    F. Cause a significant release of K+ from intracellular sites
    Explanation
    NMJ (Neuromuscular Junction) Blocker Toxicity refers to the toxic effects of drugs that block the transmission of nerve impulses at the neuromuscular junction. These drugs can result in bronchospasm (constriction of the airways), hypotension (low blood pressure), and increased secretory activity. They can also cause histamine release, which can further contribute to bronchospasm and hypotension. NMJ Blocker Toxicity is particularly dangerous in patients with congestive heart failure (CHF) who are taking diuretics and digoxin, as it can exacerbate their condition. It can also be life-threatening in individuals with ion regulation dysfunction. Additionally, it is dangerous in patients with significant burns, soft tissue damage, and in children. These drugs can cause a significant release of potassium (K+) from intracellular sites, which can lead to hyperkalemia and further complications.

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  • 18. 

    Overdoses can be treated by AChE inhibitors like

    • A.

      Edrophonium

    • B.

      Neostigmine

    • C.

      Pyridostigmine

    • D.

      Atropine

    • E.

      Trimethaphan

    Correct Answer(s)
    A. Edrophonium
    B. Neostigmine
    C. Pyridostigmine
    Explanation
    AChE inhibitors like edrophonium, neostigmine, and pyridostigmine can be used to treat overdoses. These medications work by inhibiting the enzyme acetylcholinesterase, which breaks down acetylcholine in the body. By inhibiting this enzyme, the levels of acetylcholine can be increased, which can help counteract the effects of an overdose. Atropine and trimethaphan, on the other hand, are not AChE inhibitors and therefore would not be effective in treating overdoses.

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  • 19. 

    Step 1: activation of nAChRs, rapid depolarization of postsynaptic sites            Due to inward Na+ current (Ca++ current when neuronal nAChRs involved) Step 2: an action potential is caused in postganglionic neuron when threshold reached (mediated by nAChRs) Step 3: the action potential is followed by a slow IPSP, then a slow EPSP (mediated by mAChRs; does not occur in all ganglia) Step 4: a second late, slow EPSP follows (mediated by peptidergic release)  

    • A.

      Nicotinic Neurotransmission

    • B.

      Muscarinic Neurotransmission

    • C.

      Ganglionic Neurotransmission

    • D.

      Cholinergic Neurotransmission

    Correct Answer
    C. Ganglionic Neurotransmission
    Explanation
    The correct answer is "Ganglionic Neurotransmission" because the given steps describe the transmission of signals in the ganglia, which are clusters of nerve cells. The activation of nAChRs (nicotinic acetylcholine receptors) leads to the rapid depolarization of postsynaptic sites, causing an action potential in the postganglionic neuron. This is followed by slow IPSP (inhibitory postsynaptic potential) and EPSP (excitatory postsynaptic potential) mediated by mAChRs (muscarinic acetylcholine receptors). Additionally, a second late, slow EPSP is mediated by peptidergic release. This sequence of events represents the ganglionic neurotransmission in the nervous system.

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  • 20. 

    Nicotine

    • A.

      Has actions on both effector and chemosensory sites

    • B.

      Can rapidly cause receptor desensitization

    • C.

      Causes a transient stimulation of all autonomic ganglia

    • D.

      Ultimate response is due to summation of all nicotine’s effects on an organ/system

    • E.

      Pharmacological actions are complex, unpredictable

    Correct Answer(s)
    A. Has actions on both effector and chemosensory sites
    B. Can rapidly cause receptor desensitization
    C. Causes a transient stimulation of all autonomic ganglia
    D. Ultimate response is due to summation of all nicotine’s effects on an organ/system
    E. Pharmacological actions are complex, unpredictable
    Explanation
    Nicotine has actions on both effector and chemosensory sites, meaning it affects both the organs/systems it directly acts on and the sensory receptors involved in taste and smell. It can rapidly cause receptor desensitization, meaning that the receptors become less responsive to nicotine over time. This desensitization can lead to a decrease in the effects of nicotine. Nicotine also causes a transient stimulation of all autonomic ganglia, which are involved in the autonomic nervous system's control of involuntary bodily functions. The ultimate response to nicotine is due to the summation of all its effects on an organ/system. The pharmacological actions of nicotine are complex and unpredictable, making it difficult to predict its effects on the body.

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  • Current Version
  • Jan 03, 2024
    Quiz Edited by
    ProProfs Editorial Team
  • Feb 08, 2012
    Quiz Created by
    Mgartz
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