5. Hard cards

• Connexon or Hemichannel


  Transcellular protein composed of six connexins
• Connexins


  Transmembrane proteins that make up hemichannels and allow neurons connected with electrical synapses to share cytoplasm
• Gap junction


  When the connexons of two cells make contact, how they share signals electrically
• Chemical synapse


  Presynaptic cell releases neurotransmitters to the postsynaptic cells, which are just random nearby cells that pick them up
• Neuromuscular junction (NMJ)


  Chemical synapse releasing acetylcholine between a motor neuron and muscle tissue that causes the muscle to contract
• Acetylcholine


  Chemical signalling molecule released from motor neurons to muscle tissue that causes the muscle to contract
• Charcot-Marie-Tooth disease


  Rare genetic disease resulting in weakness and deformed feet that causes the PNS to be damaged because of issues with the gene that makes the connexin Cx32 that helps build myelin
• Small vesicles are found almost exclusively in the axon terminals, while large dense-core vesicles are found in cell bodies, all along the axon, and the terminal
• Vesicular transporter


  Giant transmembrane proteins that take neurotransmitter molecules from the intracellular space of the axon terminal and pump them into vesicles. They're usually specialized to a specific type or class of neurotransmitters
• Vesicular ATP-ase


  Like ATP in a sodium-potassium pump but for H+, for each of these used one proton is dragged in
• Antiporter


  v-ATP-ase, because it pushes H+ until it has a gradient where it flows naturally out, dragging the desired neurotransmitters inside
• Readily releasable pool (RRP)


  Vesicles located close to the cell membrane of the axon terminal and might be already "docked" (coat proteins might interact with membrane proteins), first vesicles to fuse with the membrane and release their contents at an action potential
• Recycling pool


  Vesicles that have already been depleted due to release and are further inside of the cell, being refilled. It requires more intense stimulation from an action potential to get them to release their contents
• Reserve pool


  Most vesicles are in this group, the furthest from the cell membrane that requires the most intense stimulation to get them to release their contents
• V-SNAREs


  Proteins expressed on vesicles for regulating the release of neurotransmitters
• T-SNAREs


  Proteins expressed on the cytoplasmic side of the axon terminal that are the target for the vesicle to fuse to
• Syntaxin and SNAP-25


  Examples of t-SNAREs
• Synaptobevrin and synaptotagmin

  Examples of v-SNAREs
• Botulism (botulinum toxin)


  Toxin that selectively cleaves the SNARE proteins so that neurotransmitters can't be released and paralysis ensues. An infection of the toxin can lead to fatal respiratory failure
• Synaptotagmin


  v-SNARE protein capable of sensing augmented Ca2+ levels, which turn out to be the go-ahead for neurotransmitter release
• SNARE complex


  t-SNAREs and v-SNAREs interacting with each other in the hightened presence of Ca2+ causing the vesicle to get closer and closer to the membrane until they fuse
• Active or orthosteric site


  Specific series of amino acid residues that are shaped to allow molecules of neurotransmitter to bind to the receptor
• Ionotropic receptors or ligand-gated ion channels


  These channels only open when a chemical binds to their active site on the extracellular side of the protein, and then they let their specific ions in, which changes the Vm drastically and within milliseconds
• G proteins


  Proteins on the inside of the cell which induce changes in neuronal excitability through the action of second messenger signalling molecules
• Metabotropic receptors


  Transmembrane proteins that contain 7 alpha helix motifs with an N-terminus on the outside (3 loops in the cell and 3 loops out). Because of this pattern they are also called seven-transmembrane receptors, or 7-TM
• Guanosine triphosphate


  GTP, similar to ATP, is also a source of energy when one of the phosphate groups breaks off. Activates GPCR when it binds to it and inactivates GPCR once it's hydrolyzed into GDP
• G protein-coupled receptors


  GPCR, also known as metabotropic receptors
• Metabotropic receptor


  They get activated by neurotransmitters, and when they do, GTP replaces GDP on the coupled G-protein, giving it energy to go affect the metabolic process in other parts of the cell
• Heterotrimic


  Word used to describe how g-proteins generally have 3 subunits; alpha, beta, and gamma
• Gas 


  G alpha subunit that is excitatory. Results in increased activity of adenylate cyclase (AC) which causes elevated levels of cyclic AMP (cAMP), which in turn activates protein kinase a
• Kinase


  Enzyme that phosphorylates other proteins
• Protein kinase A


  Activated by the chain reaction caused by the gas subunits of a g-protein, phosphorylates protein targets that increase cell excitation (e.g. causes a receptor to stay open for longer when activated by a molecule of glutamate, which makes one glutamate molecule cause more excitation), which leads to increased transmission over a few hours. It also can change the transcription of some genes, which can lead to the synthesis of different proteins
• Gai 


  G alpha subunit that causes a decrease in excitability by decreasing adenylate cyclase (AC), which decreases cyclic AMP (cAMP), which in turn decreases levels on protein kinase A
• Enzyme phospholipase C (PLC)


  Breaks down phospholipid membrane molecule PIP2 into IP3 and DAG
• Soluble inositol triphosphate (IP3)


  Liberates Ca2+ from the intracellular stores, which depolarizes the cell and activates calcium-dependant precesses which are usually excitatory
• Membrane-embedded diacylgylcerol (DAG)


  Activates protein kinase C (PKC), an enzyme with substrates that increases neurotransmitter release probability or decreases potassium channel concordance
• Presynaptic receptors


  Neuron receptors that are at the end of the axon terminal instead of a dendrite, and are often inhibitory and serve a self-regulatory function
• Autoreceptors


  Presynaptically-expressed receptors that respond to the same neurotransmitter that is released
• Glutamate


  Most common neurotransmitter in the brain by volume
• vGluT


  Presence identifies glutamatergic neurons