Use a for loop with inter if conditions. It will be more easy to answer your question if you can write this part in more detail " I need to get spikes at the O/P when the integral exceeds the set threshold say 1, and reset the integrator. "

The website of the Goldman Lab (University of California) contains tutorials of neuronal modelling. I attach you the information related to the integrate and fire model, containing the generating mcode of the model. You would only have to change the input signals (i.e., consider that a sinusoid is also treated as an array by Matlab).

http://neuroscience.ucdavis.edu/goldman/Tutorials_files/Integrate%26Fire.pdf

Thank you , it worked well.