Biolog 42 - Chapter 42: The Internal Environment A. Gains...

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Chapter 42: The Internal Environment A. Gains and Losses in Water and Solutes - Homeostasis: an animal’s composition and volume of its internal environment must be maintained at tolerable ranges. -Vertebrates have a urinary system, kidneys to help maintain balance. -Freshwater fishes and amphibians gain water and lose solutes continually, marine fishes contain less salt and continually lose water by osmosis. -vertebrates on land do not lose water by osmosis, but instead they lose it in controlled ways such as urinary excretion. -mammals lose solutes mainly in sweats, respiration, and urinary excretion. B. Urinary System -the human urinary system consists of two kidneys, two ureters, a urinary bladder and a urethra. -Urine forms in the kidneys, then enters one of two ureters. Stretch receptors inside the bladder wall are stimulated when urine expands and fills the sac. -the functional units of human kidney are millions of nephrons, and two sets of blood capillaries that interact with one another. -urine is formed by three processes: glomerular filtration, tubular reabsorption and tubular secretion. -glomerular filtration nonselectively moves water, ions and solutes from blood into Bowman’s capsule. Ions and some nutrients are actively and passively transported outward into interstitial fluid as filtrate flows through the proximal tubule in tubular reabsorption. -In tubular secretion, transporters move hydrogen, potassium, urea and wastes out of
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This note was uploaded on 12/03/2011 for the course CHEM BIO P 101 taught by Professor Kk during the Spring '11 term at Rochester.

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Biolog 42 - Chapter 42: The Internal Environment A. Gains...

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