Psyc 2560 note neurotransmission Ion responsible for resting membrane potential is potassium LEAK CHANNELS ALLOW POTASSIUM THROUGH AS POTASSIUM EXITS THE CELL -70 MILIVOT RESTING MEMBRANE RECEIVING CONSTANTLY SIGNALS TO FIRE OR NOT FIRE (inhibitory or excitatory) Sodium channels open only when membrane potential hits a certain threshold SODIUM RUSHES INTO THE CELL, SODIUM IONS MOVING AND THE MEMBRANE POTENTIAL BECOMES POSITIVE IT DRIVES THE MEMBRANE POTENTIAL TO POSITIVE DIRECTION POTASSIUM ARE VOLTAGE GATED JUST LIKE SODIUM, DIFFERENCE IS POTASSIUM CHANNELS OPEN AT +50 WHILE SODIUM OPENS UP AT -65 MILIVOLT ONCE POTASSIUM CHANNELS OPEN, THEY START RUSHING OUT OF THE CELL SODIUM CHANNELS CLOSE AND POTASSIUM STAYS OPEN AND POTASSIUM LEAVES THE CELL THROUGH THE OPENING AND IS GENERATING A VOLTAGE AS IT IS MOVING ACROSS A MEMBRANE AS IT GOES LOWER THERES A DELAY BEFORE IT FULLY CLOSES (REFRACTORY PERIOD) SOIDUM PUMPS WORKING HARD TO EXCESS SODIUM OUT FROM THE CELL AND POTASSIUM BACK INTO THE CELL. THEN IT IS AT EQUILIBRIUM THERE ARE TWO TYPES OF SYNAPSES CHEMICAL SYNAPES: METHOD OF COMMUNICATION IS THROUGH CHEMICAL EXCHANGE ACTION POTENTIAL THAT RUNS DOWN ITS AXON WITH ELECTRICAL IMPULSE IT REACHES THE ACTION TERMINUS IT INITATES A SEQUENCE OF EVENTS THAT LEAD TO A BINDING OF A BUBBLE OF NEUROTRANSMITTERS AND A RELAESE OF THEM INTO THE SYNAPTIC CLEFT, NEUROTRANSIMTTERS BINDS TO THE RECEPTORS ON THE POST SYNAPTIC CELL. CHEMICAL BECAUSE THE METHOD OF COMMUNICATION IS A NEUROTRANSMITTER MOLECULE THERE IS FULL COLAPSE FUSION OR KISS AND RUN EXOCYTOSIS IN FULL COLLAPSE IT FLOATS ALONG GETS A SIGNAL AND BINDS TO THE MEMBRANE OF THE AXON TERMINAL OF THE PRESYNAPTIC CELL AND IT SMUSHES ITSELF INTO THE MEMBRANE AND IT RELEASES ALL OF ITS CONTENTS INTO THE SYNAPTIC CLEFT KISS AND RUN IN CONTRAST THE VESSICLE COMES ALONG WITH THE SAME MOLECULAR MACHINERY THAT FULL COLAPSE USES AND INSTEAD OF SMUSHING ITSELF IT BINDS TO A PORT INSTEAD AND RELEASES THE NEUROTRANSMITTER AND ONCE IT RELEASES SOME NEUROTRANSMITTER IT DISCONNECTS AND FLOATS AWAY. ELECTRICAL SYNAPSE USES ELECTROCHEMICAL ENERGY TO COMMUNICATE THROUGH CHANNELS THAT CONNECT THE PRE-SYNAPTIC CELLS WITH THE POST SYNPATIC CELLS THAT ARE CALLED GAP JUNCTION CHANNELS THERE IS A DIRECT ROUTE OF SODIUM IONS FROM ONE CELL INTO ANOTHER THROUGH THE GAP JUNCTION CHANNELS AND IT IS MUCH FASTER AND YOU CAN SEE WHY CHEMICAL SLIDE: THE ACTION POTENTIAL CAUSES VOLTAGE GATED CALCIUM CHANNELS ARE RESPONSIVE TO THE SAME VOLTAGE AS THE POTASSIUM CHANNELS THE POSTITIVE MEMBRANE ACTION POTENTIAL TO CALCIUM AND IT SWINGS OPEN, IT IS THE MOLECULE THAT TELLS THE SYNPATIC VESICLE TO BIND EITHER FULLY OR TO THE PORT, THE VESSICLE THEN RELEASES ITS NEUROTRANSMITTER INTO THE CLEFT THE NEUROTRANSMITTER BINDS TO ONE OF THE RECEPTORS AND IT INITIATES A SEQUENCE OF EVENTS INTO THE POST SYNPATIC CELL THAT INVOLVE EITHER CHANGING THE MEMBRANE POTENTIAL GENEEXPRESSION OR BIOCHEMCIAL CASCADES ( LASTS WAY LONGER BUT SLOWER) IN CONTRAST THE ELECTRICAL SYNPASE GETS TRANSFERRED TO THE OTHER CELL THROUGH THE GAP JUNCTION CHANNEL DIRECTLY ALLOWING IT TO REACH THRESHOLD. ( MUCH FASTER BUT OVER MORE QUICKLY) THERE ARE 4 STEPS OF NEUROTRANSMISSION SYNTHESIS : THE MAKING/ BUILDING, THERE ARE LINES THAT GO FROM THE CELL BODY TO THE AXON TERMINAL AND ON TOP OF THESE LINES ARE MOLECULAR MOTORS (I.E TRAINS) LOADING THEMSELVES WITH THE VESICLE AND TAKE THEM DOWN AND TRANSPORT THE VESICLE TO THE TERMINAL. RELEASE: ACTION POTENTIAL COMES (POSITIVE MEMBRANE POTENTIAL) SWINGS OPEN THE DOORS OF THE CALCIUM CHANNEL, THE CALCIUM CHANNEL HAS A SENSOR THAT SENSES THE CHANGES IN THE VOLTAGE ONCE THE CALCIUM CHANNEL IS OPEN AND RUSHES INTO THE CELL CALCIUM THEN SWITCHES ON THESE MACHIENS THAT GRAB THE VESSICLE AND PULLS THE MEMBRANE VESSICLE EITHER FUSES FULLY OR BINDS TO THE PORT AND THE NEURO TRANSMITTER IS RELEASED INTO THE SYNAPTIC CLEFT • RECEPTOR ACTION: Once bound to postsynaptic receptors, NTs can: 1. Depolarize postsynaptic membrane (EPSP) 2. Hyperpolarize postsynaptic membrane (IPSP) 3. Make other changes that can affect the resting membrane potential 4. Generate new synapses 5. Bring other changes in cell • Through activation of genes LIGAN GATED RECEPTOR = FAST G-PROTEIN COUPLED RECEPTORS = SLOW DEACTIVIATION: NEUROTRANSMITTERS CAN BE RETURNED TO AXON TERMINALS FOR REUSE ENZYMES CAN BREAK APART AND INACTIVATE THE NEUROTRANSMITTERS NEUROTRANSMITTERS CAN DIFFUSE OUT OF THE SYNPATIC CLEFT 3 CLASSES OF NEUROTRANSMITTERS 1. Small-Molecule 2. Peptide 3. Gases GLUTAMATE IS THE PRIMARY EXCITATORY NEUROTRANSMITTER OF THE NERVOUS SYSTEM GABA IS THE PRIMARY INHIBATORY NEUROTRANSMITTER OF THE NERVOUS SYSTEM LISTEN AND REWATCH THE LAST TWO SLIDES TOO MUCH TO TYPE
