makes the voltage drop below -70 mv. When this occurs, the K+ gates close. Resting potential occurs after this at -70 mv (Andrews, Brains and Neurons) Messages travel from one neuron to another in a process that begins when an action potential travels down the axon, enters the terminal branches, spreads depolarization. Following this votage-gated Calcium channels are activated, calcium permeability increases and Ca influx results. Synaptic vesicles containing neurotransmitters now fuse with the neuron membrane becuase of increased intracellular calcium. Neurtrasmittitters are now released into synaptic clefts. It takes approximetly .3-3 seconds to diffuse. This deceleration is called the 'synaptic delay'. Depending on the nature of the receptor, either positive or negative ions will flow into the postsynaptic neuron. If the neurotransmitter gates a positive channel, sodium will flux and a excitatory postsynaptic potential occurs. And exitatory postsynaptic potential is a small depolarizing potential. If the neurotransmitter opens potassium or chlorine channels, the ions flow in or out (potassium out and chlorine in). This will cause an inhibitory postsynaptic potential. An inhibitory postsynaptic potential is a graded hyperpolarization. Reuptake of neurotransmitters by the presynaptic neuron clears away the neurotransmitter by the presynaptic neuron clears awy the neurtranmitters in the cleft. Finally, neurotransmitters are taken back in (Andrews, Nuerons and Nueral Communications) 3Describe with examples how cognitive science can be said to have three (separate but related) levels of description and explanation. Describe briefly this tri-level hypothesis. Describe examples of research that can naturally be subsumed under each one of the three levels. In 1982, David Marr theorized that in order to to describe cognitive science entirely, one would have to descibe the three levels of cognitive science. These seperate yet re...
