It can be shown that the constant rm, and ra can be written as follows, Rm Tm = % (13) p Ta = 1ra2 (14) Where Rm is membrane resistance per unit area, a is the radius of the dendrite, and ,o is the resistivity of the cytoplasm which is the inverse of conductivity or. Question 17: Redene A in terms of a, Rm, and ,0 using the equations aboue. Discuss how the dendrite radius and cytoplasm resistivity eect the potential in dendrites and ulti- mately neuron signalling. Question 18: Alzheimer's disease is characterized by the accumulation of the -amyloid peptide (A) in the brain. It if formed from the breakdown of amyloid precursor proteins (APP). The build up of A5 in the brain effects the ion channels in neurons in multiple ways. In one study, it was shown that the A build up causes a decrease in sodium channels present in dendrites. As shown in gure 1, sodium ion channels control the influx of current into the dendrite. How would the leak ion channels (say potassium) resistance and thus the number of potassium channels need to change such that the dendrites ability to activate an action potential is not changed due to the build up of A5 1