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Questions and Answers
Which enzyme is responsible for the breakdown of acetylcholine?
What is the abbreviation for the neurotransmitter involved in neuromuscular transmission?
What is the term for the graded potential generated at the postsynaptic membrane?
Where does the recycling of presynaptic vesicles occur?
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What is the process that recovers and recycles membrane components to an endosome compartment in the terminal?
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What triggers fusion and exocytosis of the synaptic vesicles?
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What inhibits vesicle exocytosis and neuromuscular transmission by cleaving SNARE proteins?
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What brings together the synaptic vesicle and pre-synaptic plasma membrane for fusion?
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What enzyme degrades ACh released into the synaptic cleft?
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What is synthesized from Acetyl Coenzyme A and Choline by Choline Acetyltransferase?
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What triggers the opening of ligand-gated ion channels in the motor end plate?
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What is transported into and concentrated in synaptic vesicles?
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What is taken back into the presynaptic terminal on a Na$^+$-choline cotransporter and recycled?
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What opens a non-specific cation channel, causing net Na$^+$ influx?
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What is the process of vesicle fusion with the pre-synaptic membrane that involves docking, priming, fusion, and exocytosis?
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Where are synaptic vesicles and their proteins synthesized?
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What is the most common type of synapse?
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What is the approximate delay for signal transmission across a chemical synapse?
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What stimulates the fusion of neurotransmitter-containing synaptic vesicles with the presynaptic plasma membrane?
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What causes the channels in the postsynaptic membrane to open or close?
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What initiates the transmission at a chemical synapse?
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What diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic cell membrane?
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What is the major functional component of a chemical synapse responsible for releasing neurotransmitter?
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What component of a chemical synapse is responsible for responding to the release of neurotransmitters?
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What is the functional connection between two neurons or between a neuron and another cell type?
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What type of synapse has no intercellular continuity, only response to release of neurotransmitters?
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What is the abbreviation for the neurotransmitter involved in neuromuscular transmission?
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What causes the fusion of neurotransmitter-containing synaptic vesicles with the presynaptic plasma membrane?
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What is the approximate delay for signal transmission across a chemical synapse?
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What is the major functional component of a chemical synapse responsible for releasing neurotransmitter?
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What diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic cell membrane?
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What opens a non-specific cation channel, causing net Na$^+$ influx?
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What is the process of vesicle fusion with the pre-synaptic membrane that involves docking, priming, fusion, and exocytosis?
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What is the abbreviation for the neurotransmitter involved in neuromuscular transmission?
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What enzyme degrades ACh released into the synaptic cleft?
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What is the term for the graded potential generated at the postsynaptic membrane?
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What causes the channels in the postsynaptic membrane to open or close?
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What is the process that recovers and recycles membrane components to an endosome compartment in the terminal?
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What is transported into and concentrated in synaptic vesicles?
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What brings together the synaptic vesicle and pre-synaptic plasma membrane for fusion?
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Study Notes
Synaptic Vesicle Fusion and Recycling Process
- Synaptic vesicles and their proteins are synthesized in the neuronal cell body and transported to nerve terminals
- ACh is taken up into the vesicles at the nerve terminal and translocates to the pre-synaptic membrane's active zone
- Ca2+ triggers fusion and exocytosis of the synaptic vesicles
- Endocytosis via clathrin-coating recovers and recycles membrane components to an endosome compartment in the terminal
- The process of vesicle fusion with the pre-synaptic membrane involves docking, priming, fusion, and exocytosis
- Botulinum toxin, a neurotoxin, cleaves SNARE proteins, inhibiting vesicle exocytosis and neuromuscular transmission
- SNARE proteins form a complex, bringing together the synaptic vesicle and pre-synaptic plasma membrane for fusion
- Acetylcholine is synthesized from Acetyl Coenzyme A and Choline by Choline Acetyltransferase, then transported into and concentrated in vesicles
- Acetylcholinesterase enzymatically degrades ACh released into the synaptic cleft
- Choline is taken back into the presynaptic terminal on a Na+-choline cotransporter and recycled
- Binding of Acetylcholine to Acetylcholine Receptors in the motor end plate triggers the opening of ligand-gated ion channels
- Nicotinic Acetylcholine Receptors on the post-synaptic membrane bind ACh, opening a non-specific cation channel, causing net Na+ influx
Chemical Synapse: Key Components and Signal Transmission
- Lectures recommended before physiology lectures: Gross Anatomy, Histology: Nervous Tissue, Muscle Physiology
- Synapse is a functional connection between two neurons or between a neuron & another cell type
- Nerve impulses (action potentials) transmitted from pre-synaptic cell to post-synaptic cell across the synapse
- Most common type of synapse is a chemical synapse
- In chemical synapses, electrical activity in presynaptic neuron stimulates release of neurotransmitter
- No intercellular continuity at chemical synapses, only response to release of neurotransmitters
- Signal transmission across a chemical synapse is delayed by about 0.5 ms
- Major functional components of a chemical synapse include: Pre-synaptic cell/neuron, Synapse/synaptic cleft, Post-synaptic cell, Axon terminal, Neurotransmitter, Receptor for neurotransmitter, Synaptic vesicles, Voltage-gated calcium channels
- Neurotransmitter diffuses across synaptic cleft and binds to specific receptors on postsynaptic cell membrane
- Binding of neurotransmitter to its receptors causes channels in postsynaptic membrane to open or close
- Transmission at chemical synapse initiated by arrival of action potential at presynaptic neuron terminal
- Elevation of presynaptic Ca2+ concentration stimulates fusion of neurotransmitter-containing synaptic vesicles with presynaptic plasma membrane
Neuromuscular Transmission: Key Points
- Acetylcholine receptors (AChRs) are divided into muscarinic AChRs & nicotinic AChRs.
- There are 5 subtypes of muscarinic receptors (M1-M5) and two subtypes of nicotinic receptors (Nn & Nm).
- Nm nicotinic AChRs are found in the neuromuscular junction (NMJ) and allow Na+ and K+ to flow through upon acetylcholine binding.
- Miniature End Plate Potentials (MEPPs) result from the spontaneous release of ACh from a single synaptic vesicle, causing a slight depolarization (~0.5 mV).
- End Plate Potentials (EPPs) occur when a nerve impulse stimulates the release of 100-200 vesicles, leading to a larger depolarization (~40 mV).
- EPPs are graded potentials, resulting from Na+ entry through nicotinic AChRs, and their magnitude decreases with distance from the site of origin.
- The delay in EPP generation represents the time required for ACh release, diffusion, and activation of postsynaptic AChRs.
- EPP depolarizes the membrane potential from -90 mV to threshold (-55 mV), activating voltage-gated sodium & potassium channels in the adjacent sarcolemma.
- Once initiated, the Action Potential propagates along the sarcolemma and T-tubules, leading to muscle cell contraction.
- There is a delay between the stimulation of the presynaptic motor neuron and the occurrence of EPP in the postsynaptic muscle cell.
- Neuromuscular transmission involves the propagation of the action potential in a motor neuron, presynaptic membrane depolarization, Ca2+ entry, and subsequent vesicle release and interaction with SNARE proteins.
- The process involves the activation of voltage-gated sodium & potassium channels, leading to action potential generation and muscle cell contraction.
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Description
Test your knowledge of synaptic vesicle fusion and recycling, key components and signal transmission in chemical synapses, and the fundamental points of neuromuscular transmission with this quiz. Brush up on neurotransmitter release, receptor binding, and the steps involved in neuromuscular junction signaling.
