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Published byShawn Potterfield Modified over 10 years ago
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a b c
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Need to think about this question 2 ways
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1. within neurons – 2. between neurons-
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Neuron receiving info Information traveling down neuron
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within neurons – electrically between neurons – chemically Synapse – space between neurons
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developed Golgi Stain first determined space between neurons synapse
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the resting state the active state neuron is firing action potential the refractory state
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giant squid axon
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inside of the axon has a slightly negative charge relative to outside the axon called the membrane potential usually around -70mV
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inside of the axon has a slightly negative charge relative to outside the axon called the membrane potential why?
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action potential or spike
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see depolarization (change from negative inside neuron to more positive)
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action potential or spike
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see depolarization (change from negative inside neuron to more positive) threshold – if a great enough depolarization occurs, an action potential will occur action potential – very quick – milliseconds Other terms – spike, firing, generating an AP
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action potential or spike
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Hyperpolarization return to negative this is the refractory or recovery period
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action potential or spike
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All axons and cells have a membrane thin lipid (fat) bilayer The membranes have channels (to allow ions in or out) Ions – molecules with a charge These channels can be open or shut
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Ions flowing across the membrane causes the changes in the potential Ions are molecules that contain a positive or negative charge anion – negative charge cation – positive charge
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Na+ sodium HIGHER CONCENTRATION OUTSIDE THE AXON Cl- chloride HIGHER CONCENTRATION OUTSIDE AXON K+potassium higher concentration inside the axon A- anions -large (-) molecules with a negative charge (stuck inside the axon)
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INSIDE AXON (intracellular) OUTSIDE AXON (EXTRACELLULAR FLUID) Na+ Na+ and Cl- are in higher concentration in the extracellular fluid Cl- Neuron at Rest Na+ Cl- A-
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INSIDE AXON OUTSIDE AXON (EXTRACELLULAR FLUID) Na+ A- K+ and negative anions are in higher concentration in the intracellular or inside the axon Cl- K+ Cl- K+ Neuron at Rest K+ A- Na+ Cl- K+
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concentration gradient – ions diffuse from higher concentration to lower concentration
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example of concentration forces
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Na+ K+ Cl- What would each ion do if the ion channel opened based on the concentration gradient?
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concentration gradient – ions diffuse from higher concentration to lower concentration electrical gradient - opposite charges attract so ions are attracted to an environment that has a charge that is opposite of the charge they carry!
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example of electrostatic forces
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Na+ K+ Cl- What would each ion do if the ion channel opened based on electrostatic forces ?
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INSIDE AXON (intracellular) OUTSIDE AXON (EXTRACELLULAR FLUID) Na+ Na+ and Cl- are in higher concentration in the extracellular fluid Cl- Axon depolarizing Na+ Cl- A-
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opening of Na+ channels and influx of Na+ ions
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lidocaine, novocaine, cocaine TTX – tetrototoxin Sagitoxin- red tides
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Na+ K+ Cl- Concentration Gradient Electrical Gradient after the AP (+ intracellular)
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INSIDE AXON OUTSIDE AXON (EXTRACELLULAR FLUID) Na+ A- K+ and negative anions are in higher concentration in the intracellular or inside the axon Cl- K+ Cl- K+ Neuron at Rest K+ A- Na+ Cl- K+
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Sodium-potassium pump – active force that exchanges 3 Na+ inside for 2 K+ outside
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INSIDE AXON OUTSIDE AXON (EXTRACELLULAR FLUID) Na+ A- K+ and negative anions are in higher concentration in the intracellular or inside the axon Cl- K+ Cl- K+ After the action potential K+ A- Na+ Cl- K+ Na+
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myelin sheath (80% fat and 20% protein) produced by glia
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http://www.blackwellpublishing.com/matthews/channel.html
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nodes of ranvier
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myelin sheath (80% fat and 20% protein) produced by glia nodes of ranvier
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myelin sheath (80% fat and 20% protein) produced by glia nodes of ranvier saltatory conduction (200 ft/sec)
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http://www.blackwellpublishing.com/matthews/actionp.html
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speed, efficiency of neurotransmission
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disease: Multiple Sclerosis progressive, autoimmune disease onset ~ 20 years of age early symptoms: motor symptoms, such as weakness, leg dragging, stiffness, a tendency to drop things, a feeling of heaviness, clumsiness,
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What about communication between neurons?
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