Question

• What is a resting potential? Is it positive or negative?
• The resting potential is mainly due to the main _____-charged large molecules stuck inside the neuron.
• The Na+/K+ pump pushes Na+ _____ of the cell and K+ ____ of the cell (in or out for each ion)
• Where is K+ concentrated, inside or outside of the neuron?
• Where is Na+ concentrated, inside or outside of the neuron?
• The action potential starts with an rise in membrane voltage. This is due to ___ (an ion) going ___ (in/out) of the neuron.
• The action potential then has a quick drop in membrane voltage. This is due to ___ going ___ of the neuron (Figure 4-18)
• What is a voltage-gated channel? What are the two main types of voltage-gated channels that contribute to action potentials?
• What is temporal summation? How is it different from spatial summation?
• What is an EPSP? What is an IPSP? Are they resting potentials, graded potentials, or action potentials?

Answer 1

1. The resting membrane potential is is the potential difference that exists across the plasma membrane of a cell under resting conditions. The RMP of a typical neuron is -70 mV. So it is negative.

2. The resting potential is mainly due to the negatively charged large molecule stuck inside the neutron.

3. The Na+/K+ pump pushes Na+ into the cell and K+ out of the cell.

4. K+ is concentrated more inside the neuron.

5. Na+ is concentrated more outside the neuron.

6. The action potential starts with a rise in membrane voltage. This is due to Na+ ion going into the neuron.

7. The action potential then has a quick drop in membrane voltage. This is due to K+ ion going out of the neuron.

8. Voltage-gated channels are the channels that open in response to a voltage stimulus i.e. a change in membrane potential. Na+ voltage-gated channels and K+ voltage-gated channels are the two channels that contribute to the action potential.

9. Temporal summation is summation of postsynaptic potentials resulting from the buildup of neurotransmitters released by a single presynaptic neuron at different times.

It is different from spatial summation by the fact that spatial summation results from buildup of neurotransmitters released by a number of presynaptic neurons at the same time.

10. An EPSP ( Excitatory Postsynaptic Potential) is a depolarizing graded potential that brings the membrane potential close to the threshold, causing it to be less negative, so that an action potential is generated.

An IPSP ( Inhibitory Postsynaptic Potential) is a hyperpolarizing graded potential that brings the membrane potential away from the threshold causing it to be more negative.

EPSP and IPSP are graded potentials.