water balance

Water Balance7.6 Define gel electrophoresis. Briefly,

describe how it works.

Body adjusts for increased water intake by increasing _____________ output. Adjustments involve the nervous and

endocrine systems.

Regulating ADH – chemical response ADH: antidiuretic hormone – causes kidneys to

increase water reabsorption. ADH: produced by specialized nerve cells in the

hypothalamus. Pituitary gland: stores and releases ADH into blood. Osmoreceptors: specialized nerve receptors in the

hypothalamus. when blood solutes become more concentrated, increases blood’s osmotic pressure osmoreceptors shrink (losing water) nerve message sent to pituitary gland ADH released into blood reabsorbs more water from the nephrons osmotic pressure regulated.

Regulating ADH – behavioural response Shrunken osmoreceptors pituitary

releases ADH initiates thirst water consumed concentration of blood solutes decrease lower osmotic pressure fluids from blood to osmoreceptors swell nerve signal to nephrons less water reabsorbed.

ADH & the NEPHRON Proximal tubule very permeable to water

(85% of reabsorption occurs here). Descending loop of Henle is also permeable to water and ions.

Ascending loop of Henle and distal tubule is impermeable to water without ADH. Permeable to NaCl active transport of Na+

ions causes increase in ions in medulla (interstitual fluid).

15% of water filtered into nephron will be lost in urine if no ADH present

ADH: makes upper part of distal tubule permeable to water High [NaCl] in intercellular spaces

osmotic pressure increases water sucked out of nephron.

Kidneys and Blood Pressure Kidneys adjust blood volumes

adjusts blood pressure. Aldosterone: hormone that increases

Na+ reabsorption. Produced in the cortex or adrenal glands

(right above kidneys). As NaCl reabsorption increases, osmotic

gradient increases more water moves out of nephrons by osmosis.

Decrease in blood pressure Reduction of oxygen and nutrients to

tissues. Juxtaglomerular apparatus: (near

glomerulus) detects low blood pressure releases renin (enzyme that converts angiotensinogen to angiostensin)

Angiostensin: enzyme Constriction of blood vessels increase in blood

pressure. Stimulates the release of aldosterone from

adrenal gland.

pH Balance

Kidneys maintain pH balance Relatively constant: b/n 7.3 & 7.4 We eat acidic/basic foods Cellular respiration: CO2 production. ▪ Carbonic acid, weak acid, is produced. ▪ Buffer system: bicarbonate ion eliminates

extra H+.

Buffer system Kidneys help restore buffer. CO2 actively transported from

peritubular capillaries (surround the ______________) into cells surrounding the nephron

CO2 + H2O HCO3- and N+ ions. HCO3- back into blood. H+ recombind with phosphate ions or

ammonia excreted in urine.

Very Vague Summary...

Seatwork/Homework

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