Neuromuscular Junction Specializations

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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?

Intracellular Ca2+ Signup and view all the answers

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

It reduces the driving force for Ca2+ influx into the presynaptic terminal Signup and view all the answers

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

AMPA, NMDA, and Kainate (KA) receptors Signup and view all the answers

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

They elicit increases in intracellular calcium Signup and view all the answers

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

To release acetylcholine into the synaptic cleft Signup and view all the answers

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

To generate an action potential Signup and view all the answers

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

To increase the surface area of the postsynaptic membrane Signup and view all the answers

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

To release acetylcholine into the synaptic cleft Signup and view all the answers

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

It facilitates efficient activation of Na+ channels Signup and view all the answers

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

To release acetylcholine into the synaptic cleft Signup and view all the answers

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

To generate an action potential Signup and view all the answers

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

To generate an action potential Signup and view all the answers

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

They support the localization of synaptic vesicles Signup and view all the answers

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

To generate an action potential Signup and view all the answers

Temporal summation refers to

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 Signup and view all the answers

What is the role of synaptobrevin in synaptic vesicle fusion?

Synaptobrevin induces a conformational change in SNARE proteins to drive fusion of the vesicle membrane with the plasma membrane Signup and view all the answers

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

The driving force for calcium influx during the presynaptic action potential is reduced Signup and view all the answers

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

To produce different types of glutamate receptors with unique functional properties Signup and view all the answers

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

AMPA receptors produce postsynaptic depolarization at excitatory synapses Signup and view all the answers

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

KA receptors produce postsynaptic depolarization at excitatory synapses Signup and view all the answers

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

NMDA receptors produce postsynaptic depolarization at excitatory synapses Signup and view all the answers

What is the role of synaptotagmin in synaptic vesicle fusion?

Synaptotagmin induces a conformational change in SNARE proteins to drive fusion of the vesicle membrane with the plasma membrane Signup and view all the answers

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

AMPA receptors have a high permeability to Ca2+ ions Signup and view all the answers

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

It decreases the release of synaptic vesicles 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?

SNARE proteins 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?

Through the interaction of Synaptotagmin and SNARE proteins Signup and view all the answers

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

To create different types of glutamate receptors with unique functional properties Signup and view all the answers

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

AMPA, NMDA, and Kainate (KA) receptors Signup and view all the answers

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

AMPA receptors produce postsynaptic depolarization, KA receptors enhance transmitter release, and NMDA receptors regulate calcium-dependent signaling pathways Signup and view all the answers

What is temporal summation?

The process of adding up postsynaptic potentials generated by rapid synaptic inputs Signup and view all the answers

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

It binds to the SNARE complex and induces a conformational change in the SNARE proteins Signup and view all the answers

What is the requirement for activation of NMDA receptors?

Both glutamate binding and strong depolarization of the postsynaptic cell Signup and view all the answers

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

Na+ and K+ ions Signup and view all the answers

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

Na+ Signup and view all the answers

How many different types of GABAA receptors are there?

19 Signup and view all the answers

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

Synaptic, γ subunit-containing receptors Signup and view all the answers

Which GABAA receptor subtype mediates phasic inhibitory transmission?

Extrasynaptic, δ subunit-containing receptors Signup and view all the answers

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

Extrasynaptic, δ subunit-containing receptors Signup and view all the answers

What is the main effect of activation of GABAA receptors?

Hyperpolarization Signup and view all the answers

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

Increase inhibitory transmission Signup and view all the answers

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

Increase inhibitory transmission Signup and view all the answers

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

Cl- Signup and view all the answers

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

Both mediating phasic inhibition and generating an extra-synaptic pool of receptors Signup and view all the answers

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

Benzodiazepine drugs Signup and view all the answers

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

Depolarization-induced suppression of inhibition Signup and view all the answers

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

Peripheral neuropathy 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?

Axonopathy Signup and view all the answers

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

Neuronopathy Signup and view all the answers

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

Segmental demyelination Signup and view all the answers

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

Depolarization-induced suppression of inhibition Signup and view all the answers

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

Endocannabinoids Signup and view all the answers

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

Depolarization-induced suppression of inhibition Signup and view all the answers

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

Activate presynaptic cannabinoid receptors Signup and view all the answers

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?

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

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?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Temporal summation refers to

What is the role of synaptobrevin in synaptic vesicle fusion?

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

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

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

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

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

What is the role of synaptotagmin in synaptic vesicle fusion?

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

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

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

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

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

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

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

What is temporal summation?

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

What is the requirement for activation of NMDA receptors?

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

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

How many different types of GABAA receptors are there?

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

Which GABAA receptor subtype mediates phasic inhibitory transmission?

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

What is the main effect of activation of GABAA receptors?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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