I believe that while this model is widely used, it is too simplified to produce actual biological consciousness.Basics -- Biological Neural networks
One aspect that is overlooked is the influence of hormones on neuron firing levels. The brain is extremely sensitive to a number of different hormones, and while working, the hormone levels are in constant flux. Much of the hormones are produced through orders from the brain itself, thus causing it to be self-modifying, and some hormone production is caused by input external to the brain. A lot can be deduced about the state the brain is in by monitoring the hormone levels in different parts of the brain without reference to any neurons firing.