In the second week, we got familiar with some new matters, for example we learned how neurons can be categorized. One categorization which we had never heard of it was that neurons can be classified based on their dendrites or neurotransmitters. The other one was about synapses, we did not know that there are electrical synapses in addition to chemical synapses. Symmetric synapse and asymmetric synapse which are excitatory and inhibitory, respectively, was as well new information to us.
Another interesting subject was how information travel within the human body. The mechanism for communication in our body is pretty similar to what we have in our telephone/telegraph communication system. For instance, axons fairly resemble the telephone wire or action potentials can play the role of Morse code traveling in telegraph wire. However, there are some differences like the insulation level of pathways or the type of suspension in which wire/axon is suspended (air .vs salty fluid). It was these differences that drew our attention towards some new concepts like excitable membrane, resting membrane potential. To understand the aforementioned concepts we need to study water as the main ingredients of both intra and extracellular fluid. By assessing the water molecule, we realized that polar molecules like Na+Cl– tends to dissolve in water, and that is where ions were introduced. We learned that there are two types of ions, cations with positive charge and anions with negative charge, which both are functioning as charge carriers in physiological systems.
Next, ion channels were brought up and we learned how the ion channels work. There were three types of channel including Potassium (permeable to K+), Sodium (permeable to Na+) and Calcium channels (permeable to Ca2+). Expectedly, we needed something to move the ions and enable them to go through the membrane, what we were looking for was actually some enzymes known as ion pumps. We have ion channels, let’s say a bridge and we have the means of crossing (ion pumps) and what we are missing to complete the mechanism of ionic movement are some forces to drive the ions across. Diffusion and Electricity are the two determining forces that help the ions with their migration through the membrane. we saw that diffusion comes from the imbalance of concentration and Electricity is made by zero conductance of membrane which leads to accumulation of charged ions on both sides of the membrane, and that explains membrane potential. Following the ionic movement topic, some questions were asked, for example after the action potential, how long does it take for the ion pumps to normalize the concentrations of K+ and Na+ back to normal? Or if the speed of the action potential could be increased in our neurons how it would affect us? Would it just make our reflexes better and our thinking more effective?
Ruhoollah, Maria and Väinö