Prediction

1. Exceeding the threshold depolarisation at the trigger zone DECREASES the likeliness of coevals of action potency.

2. Action possible amplitude: DOES NOT CHANGE with distance

3. Increasing frequence of stimulation to the trigger zone: DOES NOT increase the production of action potencies.

MATERIALS AND METHODS

Experiment 1: Consequence of Stimulus Strength on Action Potential Generation

1. Dependent Variable
Membrane potency

2. Independent Variable
Stimulus strength ( electromotive force )

3. Controlled Variables
Frequency of stimulation
Type of nerve cell

Experiment 2: Consequence of Frequency of Stimulation on Action Potential Generation

1. Dependent Variable
Membrane potency

2. Independent Variable
Frequency of stimulation

3. Controlled Variables
Type of nerve cell
Stimulus Strength ( electromotive force )

4. Which portion of the nerve cell was stimulated? Action potency is foremost generated in the dendrites of the nerve cell. or where the nerve cell receives the action potency of other nerve cells.

5. Where was membrane potency measured?

6. What was used to mensurate membrane potency?

Consequence

See Table 3: Membrane Potentials at Different Stimulation Voltages. by Location See Graph 1: Maximal depolarisation of membrane potency at axon knoll and axon after different stimulation electromotive forces.

1. What was the resting membrane potency ( no stimulation ) recorded in Table 3? The Resting Membrane Potential Voltage =-70 millivolt

2. At which stimulation electromotive force ( s ) did you see decrimental conductivity of ranked potency from axon knoll to axon? At 2V the graded possible went from 64. 8 – 73. 8

3. At what stimulus electromotive force ( s ) did an action potency occur? Action possible occurred at 6V

4. What was the membrane potency at the axon knoll when the action potency was generated? The membrane potency was 30. 2 at the axon knoll at 6V when action potency was generated.

5. For each of the stimulation electromotive forces. indicate whether it was sub-threshold. threshold. or suprathreshold. 2 V Subthreshold
4 V Subthreshold
6 V Threshold
8 V Threshold


See Table 4: Consequence of Supra-Threshold Stimulation Frequency on Action Potential Generation. See Graph 2: Number of action potencies generated at different times between simulations.

6. State the sum of clip between stimulations for each frequence of stimulation. 25 Hz 40 millisecond
50 Hz 20 millisecond
100 Hz 10 millisecond
200 Hz 5 millisecond
400 Hz 2. 5 millisecond



7. For each frequence of stimulation. bespeak whether the period between stimulation is longer or shorter than the length of an action potency. Length of action potency in pyramidic nerve cell is about 15-20 msecs ( millisecond ) 25 Hz thirster

50 Hz same
100 Hz shorter
200 Hz shorter
400 Hz shorter


8. Estimate the length of the stubborn period for the pyramidic nerve cell.

The length of refactory period was about 10 milliseconds between the 15-20 increasing the action potentials about duplicating them from 3 to 5.

Discussion

1. In Experiment 1. discuss why the amplitude of the action potency did non increase as stimulation electromotive force increased above threshold. All-or-none theory… . . Once the threshold is met. a refactory period is needed. All and so nil. repeat… . .

2. In Experiment 1. explain why the membrane potency between the axon knoll and axon either changed or did non alter with subthreshold stimulation. Differences of 1. 0 millivolt or less are non important. It did non alteration. Unless the depolarisation occurs. the Na ions can non come in created alteration. This lone happens at the threshold.

3. In Experiment 2. explain why the membrane potency between the axon knoll and axon either changed or did non alter with threshold stimulation. Differences of 1. 0 millivolt or less are non important. . It did non alteration. Unless the depolarisation occurs. the Na ions can non come in created alteration. This lone happens at the threshold.

4. In Experiment 2. explain why the figure of action potencies generated varied with increased stimulation frequence. Action potencies can happen more often as long there is a continued beginning of stimulation. every bit long as the comparative furnace lining period has been reached. which in experiment 2 the furnace lining period was complete.

5. Repeat your anticipations that were right and give the information from your experiment that supports them. Repeat your anticipations that were non right and rectify them. giving the information from your experiment that supports the rectification. 1 ) Exceeding threshold depolarisation does non alter the likeliness of an action potency being produced. Due to the demand for a stubborn period this is ( all or nil ) In the experiment from 6V-8V in the axon hillock the difference in amplitude went from 30. 2 to 30. 9 ( non a singular addition ) 2 ) Amplitude does non alter with distance. . From the experiment. the action possible amplitude does NOT alter as it propagates down the axon. ( The alteration was little at 0. 4. 0. 2 ) 3 ) Increasing frequence of stimulation of the trigger zone does non increases the production of the action potencies. This goes back to the threshold All or nil theory.

Application

1. ECF K degrees affect resting membrane potency. Hyperkalemia ( inordinate degrees of K in the blood ) and hypokalemia ( abnormally low blood K degrees ) both affect the map of nervousnesss and musculuss.

Explain how hyperkalemia will ab initio impact the resting membrane potency and the coevals of an action potency. Hyperkalemia depolarizes musculus cells. cut downing the membrane potency from –90 millivolt to about –80 millivolt. This brings the membrane potency closer to the threshold for coevals of an action potency. Hyperkalemia will ab initio increase irritability. since a lesser depolarizing stimulation is required to bring forth an action potency. But so due to the lessening in K+ weariness and less irritability set it in the nervousnesss and the musculuss.

Explain how hypokalemia will ab initio impact the resting membrane potency and the coevals of an action potency. Hypokalemia hyperpolarizes the musculus cells. This brings the membrane potency further from the threshold and ab initio causes fatigue so goes on to doing musculuss cramp and nervousnesss are over fire.

2. Tetrodotoxin. a toxin found in blowfish fish. Acts of the Apostless by suppressing voltage-gated Na channels. Eating improperly prepared blowfish fish sushi can be fatal because of intervention with action possible coevals. Explain how tetrodotoxin interferes with action possible coevals. TTX is a toxicant because it blocks voltage-gated Na channels in nervus membranes by adhering to a peptide group at the gap of the channel. This means that Na ions can non come in the cell. so that the nervousnesss do non fire and signals are non transmitted.

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