Frog Nerve

b. What phenomena must take place for the small postsynaptic potentials to reach threshold and produce action potentials?

3) Increasing frequency of stimulation of the trigger zone does not increases the production of the action potentials. This goes back to the threshold All or nothing theory.

Encyclopedia of Nursing & Allied Health. Bioelectricity: Transmission of nerve impulses to muscle. Retrieved on 26 June 2011 from http://www.enotes.com/nursing-encyclopedia/bioelectricity

During the baseline measurement (Figure 1), when the setup was not actively manipulated, low amplitude, but still clearly visible signals where observed. This suggest that the skin contains receptors which constantly to respond to very subtle changes in the environment. Since the experimental conditions (temperature, air pressure, vibrations of the setup) were relatively stable throughout the baseline measurement, only receptors with a very low threshold of activation could respond. Since then only a relatively few number of primary sensory neurons are excited to the point that they fire APs, the amplitude of the CAPs that were measured were low.

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

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?

Differences in the electrical charge on each side of the cell membrane produce a resting potential which means that the neurons will have a resting potential of 70 millivolts.

Exercise 2: Skeletal Muscle Physiology: Activity 4: Tetanus in Isolated Skeletal Muscle Lab Report Pre-lab Quiz Results You scored 100% by answering 3 out of 3 questions correctly. 1. Stimulus frequency refers to You correctly answered: b. the rate that stimulating voltage pulses are applied to an isolated whole skeletal muscle. 2. Which of the following distinguishes a state of unfused tetanus from a state of complete (fused) tetanus? You correctly answered: d. Muscle tension increases and decreases during a state of unfused tetanus. 3. When the stimulus frequency reaches a value beyond which no further increases in force are generated by the muscle, the muscle has reached its You correctly answered: a. maximal tetanic tension.

9. Strong involuntary muscle reactions to shocks can occur in a amperage ranges as low as __________________.

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 findings of this experiment reinforced the hypothesis that the resting membrane potential is most influenced by the ion potassium. We were able to deduce this through the collection of a multitude of intracellular and extracellular recordings, such as the one shown below in Figure 1. This shows how this experiment was able to record every single resting membrane potential in all three different muscle groups under all six solutions.

1. Use your graph to answer and note that the dot in the graph turns red when you select that line in the table. What is the minimal, or threshold, stimulus? 0V.

The all-or-none principle states that the strength at which a muscle fiber or nerve may respond to a stimulus is independent of the strength of the stimulus. The axon hillock, or trigger zone, is the first place we see voltage gated ion channels. The action potentials from the trigger zone then go down the axon to the axon terminal. The action potential then communicates with it’s target.The nerve or muscle fiber will give a complete response if the stimulus exceeds the threshold potential, otherwise it will give no response at all. The “all” part of the all-or-none principle happens when the stimulus produces a depolarizing graded potential that is able to reach threshold and are constant in magnitude.If it does not reach threshold its returns

Experiment Data: Voltage 8.5 8.5 8.5 8.5 10 8.5 Length 75 75 75 75 75 75 Stimulus Single Multiple Multiple Multiple Multiple Multiple Active Force 1.83 2.39 2.54 3.89 4.00 5.72 Passive Force 0.00 0.00 0.00 0.00 0.00 0.00 Total Force 1.83 2.39 2.54 3.89 4.00 5.72

The compound action potential adds up all the action potentials that each individual neuron experiences in the sciatic nerve. Different stimulus amplitudes cause different neurons to fire an action potential; this is due to the fact that each neuron has a different threshold potential, or the minimum voltage the neuron needs to fire an action potential. The individual neuron action potential is an ‘all-or-nothing’ event, but the CAP, as a summation of different individual neurons, is not. The CAP amplitude will increase with larger stimulus potentials because more neurons with higher individual thresholds will be recruited. For this frog sciatic nerve, there are three fiber types, A, B, and C. A fibers are further divided, in the order of decreasing diameter, into α, β, γ, and δ fibers. There is an inverse relationship between the diameter of the nerve fiber and the threshold potential: the larger the diameter, the lower the threshold. Thus, as the largest fibers, the Aα neurons will be the first to be stimulated at a low stimulus potential, and the Aδ neuron fibers will be the last to be recruited. Because the sciatic nerve is mostly composed of A fibers, the recruitment of A-subtype nerve fibers are more readily distinguishable from the data. The minimum potential required to stimulate the Aα fibers was between 75 mV and 80 mV. Once the stimulus potential reached 90 mV, Aβ neurons were recruited and contributed to the increase in amplitude of the CAP. At a stimulus