As I’ve worked in a neuroscience lab over this summer, the important and illuminating parallels between computers and biological systems have become increasingly apparent to me. Perhaps most important to me is the digital nature of each machine. A logic switch on a circuit board is controlled by the presence or absence of a certain amount of voltage through one part of the circuit. The signals that run computers are discrete and on the simplest level, deviation from one of two states will only confuse the system.
For a long time, I thought of the regulation of an organism as one exponentially ramifying hierarchy whose agents elicited and were under the control of gradient signals. As my study of biochemistry and my research experience in neuroscience have continued, I’ve started to grasp the role of discrete signals in biology.
One of my favorite concepts in biology that also facilitates the understanding of computers, is of bistability. A bistable system has two states: on and off. When the switch is thrown to off, the system doesn’t randomly slide toward on, and vice versa. However, the on and off states are equally easy to reach. This equilibrium is achieved by an energetic or kinetic barrier between the two discrete states. An E. Coli cell must be either in the process of dividing or in cell cycle arrest.States between the two attitudes results in inefficient distribution of downstream cellular machinery and failure of the organism. It’s easy to achieve bistability in a circuit, but the mechanisms of how bistability is achieved in biology are more complex.
The action potential is a good example of how bistable switches can be achieved in biology. An axon is a long cylindrical capacitor that transmits charge in a basically digital manner. The axon starts in the off position, with sodium channels closed and the capacitor at a negative resting voltage. When charge influx flowing down the axon reaches a high enough level, voltage gated sodium channels open allowing charge to flow into the axon in an adjacent section. The charge influx is thus transmitted down the axon. After the action potential has passed, The membrane is locked at an especially negative potential, filtering out random noise in the form of weak depolarizations of the membrane.
Viewing biology as a logical processing circuit with emphasis on bistable mechanisms lends great power to the control and study of human health. In my research career, I would like to emphasize quantitative evaluation of the control of biological systems in my approach to science. I expect that keeping my eyes open to the similarities between all earthly machines will prove productive.