Give two reasonsthat may account for the continuous firing of a
postsynapticneuron.

1.Continuous diffusion of negatively charged ions into the postsynaptic neurons , which  leads to continuous reversal of charges (hyperpolarization) and therefore continuous firing of action potential

2. Inhibition of hydrolytic enzymes e.g (acetycholinesterase)   that  metabolize activities of  cholinergic   neurotransmitters  e,g acetycholine at post synaptic cleft. leading to firing of action potential.

Explanation:

Neuron whose dendrites  transmits action potential to the  neuromuscular junction is called presynaptic neuron. While  neuron that  transmit action potential away from the neuronal synaptic junction, or from the neuromuscular  junction to the cell body of adjacent neuron or to effectors (gland and muscles) are called  post synaptic  neuron.

The more  negatively charged ions that diffused into the post synsptic neuron, the more depolarization, and the greater the frequency of action potential produced

The inhibition of  activities of hydrolytic enzyme which metabolize cholinergic neurotransmitter leads to  continuous   excitatory activities  of cholinergic neurotransmitters   on  the receptors at the postsynaptic neuron, and the more  action potential

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."