Conduction Velocity Lab

If the frequency of action potentials in the excitatory presynaptic cell increases than the number of action potentials in the postsynaptic cell will increase as well. This is due to temporal summation of EPSP at very frequent times. This causes the postsynaptic cell to produce many action potential in succession.

Action potentials can occur more frequently as long there is a continued source of stimulation, as long as the relative refractory period has been reached, which in experiment 2 the refractory period was complete.

The more stimuli per second, the greater the force generated by the muscle due to a

If the nerve impulse is not released than it will not cause an action potential.

Results were taken immediately after performing the experiment. For subject 1, we began with the finger. In two out of six pressure points applied to subject 1 (finger), he recorded an improper result. Those points happened to be very

Write a brief description of the three slides (Neuron, Spinal Cord Smear and C.S of Myelinated Nerve Fibers) as though you were explaining it to someone who cannot see the slide.

This stage is called repolarisation. The K+ channels then close, the sodium-potassium pump restarts, restoring the normal distribution of ions either side of the cell surface membrane and thus restoring the resting potential. In response to this the Na+ channels in that area would open up, allowing Na+ ions to flood into the cell and thus reducing the resting potential of the cells. If the resting potential of the cell drops to the threshold level, then an action potential has been generated and an impulse will be fired.

Discussion Questions: (Hint: Read the discussion of sensory and motor PATHWAYS in Chapter 15 and pay careful attention to where they cross over from right side to left side)

3. A nerve is a bundle of axons, and some nerves are less sensitive to lidocaine. If a nerve, rather than an axon, had been used in the lidocaine experiment, the responses recorded at R1 and R2 would be the sum of all the action potentials (called a compound action potential). Would the response at R2 after lidocaine application necessarily be zero? Why or why not?

1. Using the information provided in the Introduction and your observations from Part 1, hypothesize as to the type of electrolyte the following solutions would be. Justify the hypothesis from a chemical standpoint.

During an absolute refractory period, a second stimulus will not produce a second action potential no matter how strong the stimulus is. Absolute refractory period corresponds to the period when Na+ channels are open (often just a millisecond or less). During a relative refractory period,

The action potential at R1 (or R2) stayed the same as I increased the stimulus above the threshold voltage. My results did not compare well with my prediction because I predicted that the peak value of the action potential would increase.

The effective refractory period is the time in which the cell is incapable of responding to a second stimulus between the phases of 0-3.5, while the relative refractory period is the time in which the cell is making preparations to receive stimulus between phase 3.5-4.

When the dendrite of the neuron receives a stimulus, and when the stimulus depolarizes the cell to its action potential threshold of -55mV an action potential will occur. If the neuron does not reach this threshold level, then no action

| |Contraction amplitude |Contraction amplitude with the |Effect of nerve stimulation on the contraction amplitude |