Guiding Questions week 3

Action Potentials

Differentiate between graded potentials and action potentials.

Where in the neuron do action potentials occur?

How does the strength of the stimulus effect the amplitude of the action potential? Why are they all-or-none?

increasing the stimulus strength causes an increase in the frequency of an action potential.

Explain how ion permeability changes during the rising phase and falling phase of an action potential.

What is the stimulus for opening EACH of the channels used during an action potential?

A stimulus from a sensory cell or another neuron causes the target cell to depolarize toward the threshold potential. If the threshold of excitation is reached, all Na⁺ channels open and the membrane depolarizes. At the peak action potential, K⁺ channels open and K⁺ begins to leave the cell.

What is the order of stimulus, opening and closing of all of these channels?

How is the resting membrane potential reestablished after an action potential?

Hint, we did this for our in-class activity! Can you visualize what’s happening with each of the channels?

Voltage gated Na+ channels in the axon contain two gates. What are they? How are they triggered?

What are the absolute and relative refractory periods?

How does the inactivation gate on the Na+ channel cause the absolute refractory period?

What causes the relative refractory period?

How are action potentials conducted along the length of the neuron?

Why don’t action potentials lose amplitude along the length of the axon?

If action potentials all have the same amplitude, how do action potentials transmit the intensity of the signal (to phrase it a different way, how do neurons alter the amount of neurotransmitter release based on the size of the stimulus?)?

Explain how myelin increases conduction speed down the length of an axon.

Explain the mechanism of salutatory conduction

What is the effect of demyelination? What are the symptoms of demyelination diseases (multiple sclerosis).

 

Synaptic Transmission

Draw and label the components of a synapse. Be sure to label the following structures: presynaptic cell, axon terminal, synaptic cleft, and postsynaptic cell (either neuronal or non neuronal)

What is the difference between a chemical and electrical synapse?

What is the trigger for neurotransmitter release from a synapse? Outline the steps of synaptic transmission.

How is neurotransmitter release terminated?

How is synaptic activity terminated (be sure to talk about all three mechanisms)?

Differentiate between “FAST” receptors and “SLOW” receptors on a post synaptic cell.

Explain how neurotransmitter binding to a fast receptor might cause an EPSP in the post synaptic cell. How about and IPSP?

Explain how a neurotransmitter binding to a slow receptor might cause an EPSP in the post synaptic cell. How about an IPSP?