HL 2 Biology

6.5a Neurons


  • resting potential = an electrical potential across a cell membrane when not propagating an impulse
  • action potential – the localized reversal (depolarization) and then restoration (repolarization) of electrical potential between the inside and outside of a neuron as the impulse passes along it

Nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons.


Abnormal Action Potentials (p.255)

1 (a) The magnitude of the depolarization is lower and duration is longer to reach depolarization.

(b) The duration of the action potential is longer as re-polarization takes a longer time since high values cannot easily be reached.

2) The effects of reduced Na+ concentration on the action potential include the reduction of extra-cellular and lower electrochemical gradient. Also, the depolarization is taking place as the concentration difference.

3) THe effect of reduced Na+ concentration on the time taken to the return to the resting potential is lower as well as the pressure on K.

4)  The action potentials of shaker and normal fruit flies differ. The rate of re-polarization takes much longer in the mutant. In both the fruit flies, the final resting potential appeared to be the same group everywhere. Also, the magnitude to which the action potential is lower than in the mutant.Thus, the duration the action potential has in the mutant is longer.

5) Action potentials differ because of the potassium. It may be that the maximum depolarization is emphasized as they open early preventing maximum depolarization. Also, the movement of K ions is delayed and the opening wont send any longer and do not match and the gates are not open for a very long time.

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