07_Synaptic Physiology Synchronous Session.pptx.pdf

Synaptic Physiology Synchronous Session John Thomas Y. Chuatak, MD How many connexons comprise 1 gap junction in a electrical synapse? A. 0.5 B. 1 C. 2 D. 6 How many connexons comprise 1 gap junction in a electrical synapse? A. 0.5 B. 1 C. 2 D. 6 Which neurotransmitter is invo...

Synaptic Physiology Synchronous Session John Thomas Y. Chuatak, MD How many connexons comprise 1 gap junction in a electrical synapse? A. 0.5 B. 1 C. 2 D. 6 How many connexons comprise 1 gap junction in a electrical synapse? A. 0.5 B. 1 C. 2 D. 6 Which neurotransmitter is involved in the neuromuscular junction? A. Acetylcholine B. Glutamate C. Gamma-aminobutyric acid (GABA) D. Serotonin Which neurotransmitter is involved in the neuromuscular junction? A. Acetylcholine B. Glutamate C. Gamma-aminobutyric acid (GABA) D. Serotonin  A 43 year old female harvested mussels on the beach near their hotel and prepared them in a soup which they ate between midnight and 2 a.m as part of a group. Approximately 1–2 hours later, she experienced vomiting, diarrhea, facial numbness, ataxia, arm and leg weakness. Her companions also experienced similar symptoms. https://panlasangpinoy.com/tinolang-tahong/ Saxitoxin poisoning The botulinum toxin blocks vesicle exocytosis. Which of the following statements is true? A. The botulinum toxin prevents action potential from reaching the presynaptic terminal B. The botulinum toxin prevents the opening of voltage gated calcium channels C. The botulinum toxin blocks the action of acetylcholinesterase D. The botulinum toxin prevents the activation of postsynaptic receptors Vacuolar-type H pump catalyzes the inward movement of H+ into the vesicle, coupled to the hydrolysis of cytosolic ATP to ADP and inorganic phosphate Neurotransmitter transport proteins mediate the exchange of neurotransmitters in the cytosol for H+ in the vesicle SLC18, SLC17, SLC32 SNARE proteins SNAP Receptor Proteins comprise the force-generating molecular machinery for membrane-membrane fusion. Comprised of v-SNAREs (from the vesicle membrane) and t-SNAREs (from the target membrane) v-SNARE t-SNARE Synaptobrevin Syntaxin-1 SNAP-25 Synaptotagmin Calcium sensor for exocytosis Docking after docking of the vesicle near the presynaptic membrane, Sec-1/Munc18, Munc13, and RIM catalyze assembly of the partial SNARE complex. Priming Stage 1 The free helical ends of synaptobrevin, syntaxin, and SNAP-25 begin to coil around each other to form a four helix bundle—the trans-SNARE complex—formed by four ~70–amino-acid SNARE helix motifs, one Priming Stage 1 The result, called priming stage 1, is a ternary SNARE complex with an extraordinarily stable rod-shaped structure of intertwined α helices. As the energetically favorable coiling of the three SNAREs continues in a Priming Stage 2 Next, a cytosolic protein called complexin inserts into the trans-SNARE complex, preventing spontaneous fusion. Priming Stage 2 Next, a cytosolic protein called complexin inserts into the trans-SNARE complex, preventing spontaneous fusion.  As Ca2+ enters through voltage-gated Ca2+ channels located in register with the active zone of the presynaptic membrane—it binds to multiple sites on the C2 domains of synaptotagmin.  These Ca2+-bound C2 domains promote the binding of synaptotagmin to acidic phospholipids in the presynaptic membrane and also displace the complexin, thereby reversing the block to fusion. Fusion-pore opening These events trigger the actual membrane fusion event, accompanied by fusion-pore opening and the beginning of transmitter release. Fusion completion Following fusion completion, as the plasma-membrane Ca-ATPase (PMCA) extrudes Ca2+ across the plasma membrane and as mitochondria take up Ca2+, [Ca2+]i rapidly falls, causing synaptotagmin to Fusion completion The soluble α-SNAP (soluble NSF attachment protein) binds to the SNARE complex and promotes the binding of NSF (N-ethylmaleimide–sensi tive factor, a homohexameric ATPase), which uses the Fusion completion The now-free synaptobrevin presumably undergoes recycling endocytosis, whereas the syntaxin and SNAP-25 on the presynaptic membrane are available for the next round of vesicle fusion The botulinum toxin blocks vesicle exocytosis. Which of the following statements is true? A. The botulinum toxin prevents action potential from reaching the presynaptic terminal B. The botulinum toxin prevents the opening of voltage gated calcium channels C. The botulinum toxin blocks the action of acetylcholinesterase D. The botulinum toxin prevents the activation of postsynaptic receptors  A 64-year-old man who’s admitted to the hospital with a 3-month history of shortness of breath, fatigue, and difficulty standing up from a chair. He said his legs felt weak, and he’d been having trouble climbing the stairs in his house for the past month, especially in the evening. His medical history is significant for about 40 pack-years of smoking since the age of 25, chest imaging is performed and the CT scan shows a subcarinal mass. A bronchoscopic biopsy is performed and demonstrates small cell carcinoma. He’s referred to medical oncology and neurology, and the neurologist orders the antibody study, the voltage-gated calcium channel, which is positive, suggesting Lambert-Eaton myasthenic syndrome, or LEMS. https://www.onclive.com/view/lems-case-review In Lambert-Eaton myasthenic syndrome, there is an increase in muscle strength due to the allowance of more calcium into the presynaptic terminal causing the release of more acetylcholine. This phenomenon is most similar to which of the following phenomena in synaptic modulation? A. Potentiation B. Depression C. Presynaptic Inhibition D. Spatial summation In Lambert-Eaton myasthenic syndrome, there is an increase in muscle strength due to the allowance of more calcium into the presynaptic terminal causing the release of more acetylcholine. This phenomenon is most similar to which of the following phenomena in synaptic modulation? A. Potentiation B. Depression C. Presynaptic Inhibition D. Spatial summation Thank you!