Download ELECTROCHEMICAL

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!!
A synaptic gap is about 20 A wide; 1A is
.0000001 mm—it’s very small
ANATOMY OF A NEURON
DENDRITE
CELL BODY
NUCLEUS
AXON HILLOCK
AXON
MYELIN SHEATH
NODES OF RANVIER
AXON 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 DENDRITES
AS 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.