Neuroscience-Chapter 2 Flashcards
What do electrical signals arise from?
Ion fluxes and non-uniform distribution of ions through the neuron’s semi-permeable membrane
Is the resting potential of a membrane negative or positive?
Negative (between -40 and -90 mV)
What are receptor potentials?
Activation of sensory neurons by external stimuli
What are synaptic potentials?
Electrical signals that travel along axons (“spikes” or “impulses”)
What happens when a current makes the membrane potential more negative? (Hyperpolarization)
Nothing
What happens when current makes the membrane potential more positive? (Depolarization)
An action potential may or may not occur
What is the purpose of an action potential?
Boosts electrical signals of axons so that electrical signals do not degrade over the length of the axon
Why do neurons need action potentials?
Because axons are leaky and not good conductors
Why are electrical signals generated?
Differences in concentrations of specific ions across nerve cell membranes and selective permeability to these ions
How is the ion concentration gradient established?
Active transporters and ion channels
What is electrochemical equilibrium?
An exact balance between the concentration gradient that causes K to move from inside to outside and the opposing electrical gradient that tries to stop K from leaving the membrane
Is the number of ions that need to flow to produce an action potential significant?
No
How can equilibrium potential be predicted?
The Nernst Equation
What is the Nernst equation?
E=(58/z)log[x(out)/x(in)]
Would the membrane potential be negative or positive if the membrane was more permeable to K than Na?
Negative
As K moves outside the cell, does it create a positive or negative membrane potential?
Negative
What is the Goldman equation used for?
To determine the voltage across a membrane when it is permeable to more than one ion
How does an action potential work?
The resting potential is negative until the membrane potential is depolarized by synaptic action. The permeability to Na increases, making the membrane potential more positive. An action potential occurs. Once the action potential is gone, permeability to K is restored and permeability to Na inactivates and the membrane potential returns to resting level.
What did Alan Hodgkin and Bernard Katz do?
Altered the concentration of K in a squid neuron and showed that the membrane of a resting neuron is more permeable to K.
Is there a higher concentration of Na on the outside of a neuron or the inside?
Outside
What happens during an undershoot?
The membrane potential is hyperpolarized because K permeability, which is even greater than at rest. Hyperpolarization eventually subsides.
