| | so basically, tomorrow's the day. crazy cramming.
at first when i went to go pee, this is what i was thinking:
where did my pee come from?
the kidney, which is the most important part of the human excretory system, is made up of billions of nephrons. many nephrons = nephron tube. blood enters the glomerulus (many capillaries tangled into a ball), and the pressure forces water and solutes through the cappilary walls into the bowman's capsule (beginning of tube). solutes including glucose, salts, vitamins, nitrogenous wastes, and other small substances enter the capsule/filtrate and flow into the proximal convoluted tube. afterwards, this filtrate moves down the loop of Henle, and becomes more CONCENTRATED due to passive flow of H2O out of the tube. when the filtrate moves up the loop of Henle, it becomes more DILUTE b/c of passive & active transport of salts out the tube. however, there is also SELECTIVE SECRETION of salts from the outside fluid that join the filtrate. at the end of the loop, the interstitial fluids surrounding the nephron are still more concentrated with salts. as the filtrate goes to the collecting duct toward the renal pelvis, water passively moves out of the collecting duct and into the outside fluid. THIS RESULTING FLUID IS CONCENTRATED URINE. during this entire process, antidiuretic hormone (ADH) and aldosterone both help increase water absorption by increasing the permeability of the tube to water. this concentrated urine then enters the URETER and then the BLADDER and the URETHRA and finally out my penis and into the toilet.
that is where my pee came from.
OH MY GAWD. MY BRAIN IS GOING CRAZY. EVERYTHING I DO MUST RELATE BACK TO BIOLOGY. AHHHHHHH.
i am typing on the keyboard at this moment.
how am i allowed to feel the keyboard?
my hand is embedded with sensory neurons (afferent neurons) that help transmit nerve impulses from the brain to my finger. the transmission of a nerve impulse along a neuron from one end to the other occurs as a result of chemical changes across the membrane of the neuron. the unstimulated membrane is polarized, which means there is excess sodium on the outside and excess potassium ions on the inside. in response to the stimulus (typing on the keyboard), gated ion channels suddenly open and permit the Na+ on the outside to rush into the cell. this DEPOLARIZES the cell membrane (action potential has begun). REPOLARIZATION occurs when the potassium rushes outside the membrane to balance it out. however, too much K+ will accumulate, making it HYPERPOLARIZATION. the neuron goes through a refractory period but finally the impulse has been transmitted. the impulse goes fast because of SALTATORY CONDUCTION which is a result of jumping node to node in the NODS OF RANVIER. fuck, there are synapses too. AHHH. what the fuck is gamma aminobutyric acid. acetylcholine. norepinephrine. parasympathetic nervous sytem. AHHHHHH I AM SOOO SCREWED.
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| | Posted 5/13/2007 8:26 PM - 1 view - 5 comments
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