<p>So far this summer, I’ve covered some Calculus and some Biology. </p>
<p>I’ve also been hitting the gym quite a bit. I’ve been doing 1 mile on the treadmill at 8.x MPH consistently for the past few days and I’ve done some weight lifting. I’ve been noticing some actual muscle now when I flex my arms, and it’s only been a week :D! And I noticed that today, during some strenuous activity, I barely got fatigued! Usually, I would be yawning and ready to pass out, but looks like my gym workouts are working :D. </p>
<p>Finally, I’ve also all but finished my FLVS courses - yay!! I’ve been working so fast that my teachers have told me to slow down :(. </p>
<p>Calculus:</p>
<p>Shells: use cross sections parallel to the axis of revolution. Integrate shell radius and shell height and multiply by 2pi. Done.
Parametric derivatives: just take the derivative of the two separate equations and put y’ on top of x’.
Arc length: just plug it into the formula
Force: integrate force over distance </p>
<p>Biology:
from memory </p>
<p>Steps in transmitting an impulse:</p>
<p>1) Resting potential. The voltage across the neuron is -70 mV. Sodium-potassium pumps in the membrane pump out Na+ and pump in K+. However, for every 3 sodium ions pumped out, 2 potassium ions are pumped in. So the inside of the neuron is negatively charged, and therefore there is a negative potential (voltage). </p>
<p>2) A stimulus will cause the neuron to open its Na+ gates. Letting in enough Na+ allows the neuron to reach its action potential, which is -50 mV. When the action potential is reached, Na+ floods in and the neuron is depolarized. </p>
<p>3) Repolarization. Potassium gates open. Potassium floods out according to its concentration gradient - remember, there was initially more K+ inside the neuron than outside. </p>
<p>4) Hyperpolarization. The neuron actually overshoots and the voltage drops down below -70 mV. </p>
<p>5) Refractory period. The neuron has to restore the Na+ and K+ concentrations because they’re switched now; because the K+ gates opened, there’s more K+ outside the neuron than inside. Oops. During this period the neuron doesn’t transmit anything. </p>
<p>Synapses:</p>
<p>A synapse is the gap between an axon and a dendrite. Axons send impulses. Dendrites receive signals. Basically, the impulse reaches the end of the axon and is transmitted by a neurotransmitter to the dendrite. </p>
<p>Myelin sheaths:</p>
<p>These insulate an axon. They do not cover the axon in its entirety though. The gaps are nodes of Ranvier. The impulses jump from node to node. Myelin sheaths enable faster impulse transmission.</p>