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Action Potential Terms

Action Potential Terms. Electrochemical gradient : the sum of chemical and electrical forces acting across the membrane, Resting potential : the charge(-70 mV) of the neuron membrane when the neuron is at rest

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Action Potential Terms

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  1. Action Potential Terms • Electrochemical gradient: the sum of chemical and electrical forces acting across the membrane, • Resting potential: the charge(-70 mV) of the neuron membrane when the neuron is at rest • Graded potentials (local potentials): changes in the membrane potential that cannot travel far from the site of stimulation, causes a change in neuron charge Na+ gates open due to stimulus and the neuron becomes more positive(-65 mV or higher)

  2. Action Potential Terms • Depolarization: any change in the resting potential toward (0 mV) • Local current: movement of positive charges through a membrane • Hyperpolarization: increase of negative charge due to the loss of Na+ (-75 mV or less)

  3. Action Potential Terms • Repolarization: the process of restoring the normal resting potential (-70 mV) • Threshold: a depolarization that causes sodium channels to open (-60 to –55 mV) • All-or-none principle: no matter how big or small the depolarization when the threshold is exceeded an action potential will occur • Refractory period: the time it takes from an action potential to a stabilized normal resting potential

  4. Action Potential Generation • Neurotransmitters released by presynaptic cell into synapse • Neurotransmitters cause Na+ channels to open on post synaptic cell membrane • Na+ influx causes depolarization and a local current develops • Local current travels through neuron membrane of the dendrites and/or cell body until sufficient depolarization can cause threshold to be reached, area that is first depolarized on the axon is called the initial segment

  5. Action Potential Generation • When threshold is exceeded a large scale activation of Na+ channels occurs and leads to rapid depolarization and an action potential is sent down the axon • As the membrane potential approaches +30mV the Na+ channels become inactive and close

  6. Action Potential Generation • At the same time K+ channels open and cause it to flow out of the cell decreasing the positive charge to shift the membrane back to resting potential levels • The K+ channels remain open until the cell is hyperpolarized (-80 to –85mV) then they close the sodium-potassium pumps quickly returns the neuron to it resting potential state (now the action potential is over)

  7. Class/HW • BYGO’s Pg 461 #11-17 • Draw fig 12.13 (a) label and describe all 8 steps in your own words

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