Research suggests that learning may involve:
1. ca²⁺ influx into a postsynaptic cell, causing biochemical changes and enhanced response to stimulation.
2. strengthening the sodium-potassium pump.
3. changes in action potential duration caused by blocking voltage-gated k⁺ channels.
4. synaptic changes caused by decreasing the size of the synaptic cleft and increasing the effectiveness of neurotransmitter diffusion.
5. synaptic changes causing slower reuptake of neurotransmitter from the synaptic cleft.

This is the amino acid cysteine. circle the amine group, put a box aroundthe carboxylic acid group and use a different colored pencil/pen to circle the sidechain (r group). h o | ||nh2— c- c-oh | ch2 | sh

The kidney filters potentially toxic substances in the blood, and thus “clears” the blood of those substances. this clearance function is dependent upon and proportional to the diffusion gradient of the substance across filtering capillaries, i.e. if the concentration of the substance is doubled, twice as much will be cleared from each ml of blood that is filtered. suppose that the body produces a constant amount of a substance x per unit of time. the kidneys eliminate substance x at a rate directly proportional to the concentration of the substance and the volume of blood cleared each minute (c): elimination = c × [x], where [x] is the steady-state concentration of substance x. imagine an individual with an initial concentration of x equal to [x]0 who develops kidney disease. her baseline clearance c0 drops to one half of the original (½c0). what is the new steady state concentration of x? (for simplicity, assume that substance x is 100% filtered by the kidney).

Did the vinegar diffuse all the way to the center of any of the cubes? if so, which ones? what does this tell you about surface area-to-volume ratio and the diffusion rate?