Anerve impulse travels from the axon hillock to the synaptic terminals by propagating a series of action potentials along the axon. the speed of conduction increases with the diameter of the axon and, in many vertebrate axons, with myelination. action potentials in axons insulated by myelination appear to jump from one node of ranvier to the next, a process called saltatory conduction. if an action potential lasts from the beginning of the rising phase to the point of maximal undershoot, what is the maximum frequency at which a neuron could fire action potentials? (assume that the neuron can fire only one action potential at a time and that the refractory period following the action potential is negligible.)0.0023 events per second (hz)
0.0046 events per second (hz)
220 events per second (hz)
430 events per second (hz)

The best answer to the question: What is the maximum frequency at which a neuron could fire action potentials, (taking into account that an action potential lasts from the beginning of the rising phase to the point of maximal undershoot), would be: 430 events per second (Hz).

Explanation:

The reason for this being the answer comes from the explanation given in the question itself, when first they give us the information that an action potential, especially in myelinated neurons, takes time first to be generated, to reach firing point and then to be propagated. That is without mentioning the time it takes the neuron to be ready to fire a new action potential. The information says that the neuron can only fire one action potential at a time, and even if the refractory period is taken as negligible, there are only so many times that a same neuron can deporalize and generate action potentials repetitively. This number of events produced, per second, would be, given the conditions set by the question itself, 430 event per second (Hz).

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.