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Lecture 39

BIOL 1082 Lecture Notes - Lecture 39: Membrane Potential, Excitatory Postsynaptic Potential, Motor NeuronPremium

3 pages100 viewsSpring 2018

Biological Sciences
Course Code
BIOL 1082

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Ch. 43 LO Part 2
Action potential, synapses, and PNS Textbook Reading: Concepts: 43.2-43.3 & 43.5
1. Describe how membrane potential can be altered in response to a stimulus.
Changes in the membrane potential occur because neurons contained gated ion
Gated Ion Channel: ion channels that open or close in response to stimuli.
o When gated ion channels are stimulated to open, ions flow across the
membrane changing the membrane potential.
o The increase in magnitude of the membrane potential is hyperpolarization. This
makes the inside of the membrane more negative.
Hyperpolarization results from any stimulus that increases the outflow of positive ions
of the inflow of negative ions.
o A reduction in the magnitude of membrane potential is depolarization.
Depolarization often occurs with sodium channels. If a stimulus causes the gated sodium
channels to open, the membrane's permeability to NA+ increases, NA+ diffuses into a
2. Distinguish between graded potentials and action action potential, identifying the
phases of the action potential and the causes of the voltage changes at the membrane level.
Graded potential- When the response to hyperpolarization or depolarization is just a
shift in membrane potential.
o Grade potential has a magnitude that varies with the strength of the stimulus. A
larger stimulus causes a greater change in the membrane potential.
o A larger stimulus produces a larger hyperpolarization. Which causes K+ to move
out the neuron. Making the cell more negative.
o A larger stimulus produces a large depolarization. Which causes NA+ to move in
making the cell less negative since positive ions are moving in.
o Graded potential induces a small electrical current that leaks out the neuron as it
flows along the membrane. As they leak the move further from neuron and time
passes, the grade potential decays.
Action potential- When depolarization shifts the membrane potential sufficiently, the
result is a massive change in membrane voltage.
o The membrane voltage is called an action potential.
o Action potentials have a constant magnitude and doesn't vary. They can
regenerate in adjacent regions of the membrane. Therefore, they can spread
along axons making them well suited for transmitting a signal over a long
3. Describe how action potentials are propagated, and sometimes accelerated, along axons.
Explain why action potentials are unidirectional and always travel without loss of signal.
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