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ELECTROCHEMICAL NEUROTRANSMISSION. There are 100 trillion neurons Each of them connect, interact with as many as 1,000 other neurons across a gap called the SYNAPSE So maybe there are 100 quadrillion synapses in the brain!! - PowerPoint PPT Presentation
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ELECTROCHEMICAL NEUROTRANSMISSION
There are 100 trillion neuronsEach of them connect, interact with as many as
1,000 other neurons across a gap called theSYNAPSE
So maybe there are 100 quadrillion synapses in the brain!!
A synaptic gap is about 20 A wide; 1A is .0000001 mm—it’s very small
ANATOMY OF A NEURON
DENDRITECELL BODYNUCLEUSAXON HILLOCKAXONMYELIN SHEATHNODES OF RANVIERAXON BOUTON
DENDRITES ARE THE “RECEIVING” END OF THE NEURON
AXONS ARE THE “SENDING” END OF THE NEURON
AXON HILLCOK ADDS UP (SUMMATES) INFORMATION COMING IN TO THE RECEIVING END OF THE NEURON—THE DENDRITESAS WELL AS THE CELL BODY
THE “MESSAGES” (AT THE RECEIVING END) TELL THE NEURON TO PASS ITS CHARGE (INFORMATION) ALONG ITS AXON TO ITS “SENDING” END, OR NOT
“YES” AND “NO” MESSAGES ARE SUMMATED AT THE AXON HILLOCK; SPATIALLY, TEMPORALLY
IF/WHEN THE AXON DECIDES “YES, I’M GOING TO PASS MY MESSAGE ALONG”, THE “ELECTRO” PART OF ELECTRO CHEMICAL NEUROTRANSMISSION BEGINS
COMMUNICATION AMONG NEURONS OCCURS VIA:
ELECTRO (within the neuron)CHEMICAL (between neurons)
NEUROTRANSMISSION
“ELECTRO” PART
AXONS AT REST HAVE IONS UNEVENLY DISTRIBUTED ACROSS THEIR MEMBRANES;THAT IS, THERE ARE MORE NEGATIVELY CHARGED IONS INSIDE THE AXON THAN OUTSIDE
THIS CREATES A TENSION ACROSS THE MEMBRANE
IN ADDITION, Na+ (sodium) and K+ (potassium) ARE ALSO UNEVENLY DISTRIBUTED ACROSS THE MEMBRANE
SODIUM IS MORE HIGHLY CONCENTRATED ON THE OUTSIDE OF THE AXON MEMBRANE
POTASSIUM IS MORE HIGHLY CONCENTRATEDL ON THE INSIDE OF THE AXON MEMBRANE
WHEN THE AXON HILLOCK DECIDES, “YES, I WANT TO PASS MY MESSAGE DOWN MY AXON TO COMMUNICATE WITH OTHER NEURONS AT THE END OF MY AXON”, “MAGIC” HAPPENS
THE AXON MEMBRANES OPEN UP AND BECOME PERMEABLE TO THE UNEVEN DISTRIBUTION OF + AND – IONS AND THEY SEEK EQUILIBRIUM DOWN THEIR ELECTROSTATIC GRADIENT
IN ADDITION, K+ AND Na+ SEEK EQUILIBRIUM DOWN THEIR CONCENTRATION GRADIENT; CALLED THE SODIUM-POTASSIUM PUMP
THE EXCHANGE OF + AND – IONS AND THE EXCHANGE OF K+ AND Na+ CAUSES MOVEMENT OF THE “MESSAGE” DOWN THE LENGTH OF THE AXON
THIS OCCURS MORE QUICKLY IN MYELINATED AXONS THAN NON-MYELINATED
WHEN THIS ACTIVITY REACHES THE END BOUTON,
THE “CHEMICAL” PART OF ELECTROCHEMICAL NEUROTRANSMISSION BEGINS
NEUROTRANSMITTERS ARE:
Synthesized in cell body;
Stored in vesicles in end boutons;
Released into the synapse;
Travel across the synapse to the
Receptor on the post-synaptic neuron; and then the signal is
Terminated—either through enzymatic degradation or reuptake.