Neuromuscular Junction Specializations
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Questions and Answers

Which of the following is a structural specialization at the neuromuscular junction that supports the localization of a high density of ACh receptors?

  • Formation of junctional folds (correct)
  • Presence of voltage-activated Ca2+ channels
  • Clustering of synaptic vesicles
  • Expression of voltage-activated sodium channels

What is the role of voltage-activated Ca2+ channels at the presynaptic terminal of the neuromuscular junction?

  • To release acetylcholine from synaptic vesicles
  • To increase the surface area of the postsynaptic membrane
  • To provide the calcium needed for vesicle exocytosis (correct)
  • To depolarize the postsynaptic muscle fiber

What is the electrical event generated in the postsynaptic muscle fiber following a presynaptic action potential that is caused by the influx of cations through ACh receptor channels?

  • Action potential
  • Activation of Na+ channels
  • Depolarization of the postsynaptic
  • End-plate potential (correct)

Which one of these is responsible for depolarizing the muscle fiber membrane potential to threshold for activation of voltage-gated Na+ channels?

<p>Intracellular Ca2+ (A)</p> Signup and view all the answers

Why does a decrease in extracellular Ca2+ levels disrupt transmission at the neuromuscular junction?

<p>It reduces the driving force for Ca2+ influx into the presynaptic terminal (C)</p> Signup and view all the answers

What are the main types of ligand-gated ion channels for glutamate?

<p>AMPA, NMDA, and Kainate (KA) receptors (C)</p> Signup and view all the answers

What is the role of NMDA receptors in excitatory synaptic transmission?

<p>They elicit increases in intracellular calcium (A)</p> Signup and view all the answers

What is the main function of the presynaptic terminal at the neuromuscular junction?

<p>To release acetylcholine into the synaptic cleft (A)</p> Signup and view all the answers

What is the role of voltage-activated sodium channels at the postsynaptic muscle fiber?

<p>To generate an action potential (B)</p> Signup and view all the answers

What is the function of the junctional folds in the postsynaptic muscle fiber?

<p>To increase the surface area of the postsynaptic membrane (B)</p> Signup and view all the answers

What is the main function of voltage-activated Ca2+ channels at the presynaptic terminal?

<p>To release acetylcholine into the synaptic cleft (D)</p> Signup and view all the answers

What is the significance of the density of ACh receptors at the crests of the junction folds?

<p>It facilitates efficient activation of Na+ channels (C)</p> Signup and view all the answers

What is the role of synaptic vesicles at the presynaptic terminal?

<p>To release acetylcholine into the synaptic cleft (D)</p> Signup and view all the answers

What is the main function of the end-plate potential (EPP) in the postsynaptic muscle fiber?

<p>To generate an action potential (B)</p> Signup and view all the answers

What is the role of voltage-activated Ca2+ channels at the postsynaptic muscle fiber?

<p>To generate an action potential (B)</p> Signup and view all the answers

What is the significance of the active zones at the presynaptic terminal?

<p>They support the localization of synaptic vesicles (B)</p> Signup and view all the answers

What is the function of voltage-activated sodium channels at the presynaptic terminal?

<p>To generate an action potential (D)</p> Signup and view all the answers

Temporal summation refers to

<p>the process by which multiple EPSPs from a single presynaptic neuron add up over time to reach the threshold for an action potential in the postsynaptic neuron (C)</p> Signup and view all the answers

What is the role of synaptobrevin in synaptic vesicle fusion?

<p>Synaptobrevin induces a conformational change in SNARE proteins to drive fusion of the vesicle membrane with the plasma membrane (D)</p> Signup and view all the answers

What happens when extracellular calcium levels are decreased at the neuromuscular junction?

<p>The driving force for calcium influx during the presynaptic action potential is reduced (D)</p> Signup and view all the answers

Why do neurons in the central nervous system express different glutamate receptor subunits?

<p>To produce different types of glutamate receptors with unique functional properties (D)</p> Signup and view all the answers

What are the main roles of AMPA receptors in excitatory synaptic transmission?

<p>AMPA receptors produce postsynaptic depolarization at excitatory synapses (D)</p> Signup and view all the answers

What are the main roles of KA receptors in excitatory synaptic transmission?

<p>KA receptors produce postsynaptic depolarization at excitatory synapses (B)</p> Signup and view all the answers

What are the main roles of NMDA receptors in excitatory synaptic transmission?

<p>NMDA receptors produce postsynaptic depolarization at excitatory synapses (A)</p> Signup and view all the answers

What is the role of synaptotagmin in synaptic vesicle fusion?

<p>Synaptotagmin induces a conformational change in SNARE proteins to drive fusion of the vesicle membrane with the plasma membrane (B)</p> Signup and view all the answers

What is the role of AMPA receptors in producing postsynaptic depolarization?

<p>AMPA receptors have a high permeability to Ca2+ ions (C)</p> Signup and view all the answers

Why does a decrease in extracellular Ca2+ levels disrupt transmission at the neuromuscular junction?

<p>It decreases the release of synaptic vesicles (C)</p> Signup and view all the answers

What are the proteins in the presynaptic terminal responsible for guiding synaptic vesicles to the plasma membrane and preparing them for eventual release?

<p>SNARE proteins (C)</p> Signup and view all the answers

How does an action potential invading the presynaptic terminal of a motor neuron trigger synaptic vesicle fusion with the plasma membrane?

<p>Through the interaction of Synaptotagmin and SNARE proteins (B)</p> Signup and view all the answers

Why do neurons in the central nervous system express so many different glutamate receptor subunits?

<p>To create different types of glutamate receptors with unique functional properties (C)</p> Signup and view all the answers

What are the major types of ligand-gated ion channels for glutamate?

<p>AMPA, NMDA, and Kainate (KA) receptors (B)</p> Signup and view all the answers

What are the main roles of AMPA, NMDA, and KA receptors in excitatory synaptic transmission?

<p>AMPA receptors produce postsynaptic depolarization, KA receptors enhance transmitter release, and NMDA receptors regulate calcium-dependent signaling pathways (A)</p> Signup and view all the answers

What is temporal summation?

<p>The process of adding up postsynaptic potentials generated by rapid synaptic inputs (D)</p> Signup and view all the answers

What is the role of Synaptotagmin in synaptic vesicle fusion with the plasma membrane?

<p>It binds to the SNARE complex and induces a conformational change in the SNARE proteins (A)</p> Signup and view all the answers

What is the requirement for activation of NMDA receptors?

<p>Both glutamate binding and strong depolarization of the postsynaptic cell (D)</p> Signup and view all the answers

What is the ion channel of AMPA receptors highly permeable to?

<p>Na+ and K+ ions (D)</p> Signup and view all the answers

Which ion is excluded from entering the cell when GABAA receptors are activated?

<p>Na+ (A)</p> Signup and view all the answers

How many different types of GABAA receptors are there?

<p>19 (A)</p> Signup and view all the answers

Which GABAA receptor subtype generates an extra-synaptic pool of receptors?

<p>Synaptic, γ subunit-containing receptors (A)</p> Signup and view all the answers

Which GABAA receptor subtype mediates phasic inhibitory transmission?

<p>Extrasynaptic, δ subunit-containing receptors (B)</p> Signup and view all the answers

Which GABAA receptor subtype is persistently active and produces a persistent flux of Cl- into the cell?

<p>Extrasynaptic, δ subunit-containing receptors (B)</p> Signup and view all the answers

What is the main effect of activation of GABAA receptors?

<p>Hyperpolarization (A)</p> Signup and view all the answers

What is the role of sedative-hypnotic drugs on GABAergic, inhibitory synaptic transmission?

<p>Increase inhibitory transmission (A)</p> Signup and view all the answers

What is the role of anxiolytic drugs on GABAergic, inhibitory synaptic transmission?

<p>Increase inhibitory transmission (D)</p> Signup and view all the answers

Which ion is responsible for the hyperpolarization produced by GABAA receptor activation?

<p>Cl- (A)</p> Signup and view all the answers

What is the main role of GABAA receptors in inhibitory synaptic transmission?

<p>Both mediating phasic inhibition and generating an extra-synaptic pool of receptors (C)</p> Signup and view all the answers

Which type of drugs primarily act by enhancing the affinity of GABAA receptors for GABA?

<p>Benzodiazepine drugs (B)</p> Signup and view all the answers

What is the activity-dependent modulation of GABAergic inhibition mediated by endocannabinoids known as?

<p>Depolarization-induced suppression of inhibition (B)</p> Signup and view all the answers

What is the category of conditions and/or injuries to the peripheral nerves called?

<p>Peripheral neuropathy (C)</p> Signup and view all the answers

What is the term for damage to the axon and everything distal to the injury, including the axon and the myelin sheath?

<p>Axonopathy (D)</p> Signup and view all the answers

What is the term for damage to the cell body of a neuron?

<p>Neuronopathy (D)</p> Signup and view all the answers

What is the term for damage to the myelin sheath of a nerve?

<p>Segmental demyelination (A)</p> Signup and view all the answers

What is the better-understood form of retrograde synaptic transmission seen at some inhibitory synapses?

<p>Depolarization-induced suppression of inhibition (C)</p> Signup and view all the answers

What is the name of the endogenous compounds similar to tetrahydrocannabinol (THC) found in cannabis?

<p>Endocannabinoids (D)</p> Signup and view all the answers

What activates enzymatic pathways that convert membrane lipids into endocannabinoids at inhibitory synapses?

<p>Depolarization-induced suppression of inhibition (A)</p> Signup and view all the answers

What do endocannabinoids released from the postsynaptic cell do at inhibitory synapses?

<p>Activate presynaptic cannabinoid receptors (C)</p> Signup and view all the answers

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