Briefly explain the difference between the absolute refractory period and the relative refractory period.
Absolute refractory period is the time period when an action potential cannot be initiated even if there is a large stimulus that is effected. The absolute refractory lasts until the resting potential throughout the threshold and action potential time period (Sherwood, 2012).
The relative refractory period is the time period during which the second action potential is restrained though its action can take place. The relative refractive period can only be triggered by an occurrence that would be considered stronger than the usual events (Sherwood, 2012).
2. A neuron is able to maintain a negative intracellular charge even though there is approximately 20 times as many positively charged potassium ions inside the cell relative to outside the cell at this time. This phenomenon is enabled by the action potential and the availability of reduced non gated channels for the transport of Na + in comparison to the number of K+ non gated channels. Na + therefore have lower permeability regardless of the high concentration gradient between the two opposing ions on the different sides of the membranes. For a steady resting potential to be achieved, the difference in charges of the two ions has to be maintained through the Na+ / K+ pump (Siegel and Sapru). The K+ ions are therefore able to maintain a high concentration which could be as high as 20 times in relation to the Na + ions. Moving Na+ ions into the intracellular surface is movement against a concentration gradient which would equal active transport. Active transport requires a lot of ATP use because a protein pump would have to be used to move the Na + ions (Siegel and Sapru: Kolb and Whishaw, 2011).
Kolb, B. and Whishaw, Q. (2011). Principles of Neuroscience: An Introduction to Brain and
Behavior. 3rd edition. London: Worth.
Sherwood, L. (2012). Human Physiology: From Cells to Systems. Ohio: Cengage brain.
Siegel, A. & Sapru, H. (2010). Essential Neuroscience. Netherlands: Wolters Kluwer.