7.6: Water Balance• Antidiuretic hormone (ADH): causes the

kidneys to increase water reabsorption• Regulating ADH:1. water intake2. [blood solute]3. blood osmotic pressure and is sensed by

osmoreceptors in the hypothalamus4. hypothalamus cells shrink; nerve message is

sent to the pituitary gland to release ADH; initiates sensation of thirst

5. ADH is carried to the kidneys and signals the reabsorption of water

6. This produces a more concentrated urine

Osmotic Pressure (H2O balance – Regulating ADH)

• high osmotic pressure = when there is little water in blood (dehydrated) … this causes water to rush out of cells to enter bloodstream.

• A hormone, antidiuretic hormone (ADH), helps regulate the osmotic pressure of bodily fluids by causing the kidneys to increase water reabsorption

Communication between hypothalamus and pituitary gland.* ADH secretion triggers reabsorption of water at the kidney.

Animation: Hormonal Communication

behavioural change

Osmoreceptors in hypothalamus (brain)-detect osmotic changeHow? (blood: water = solutes = shrinkage of cells in hypothalamus as water leaves)

hormonal change

Creates the sensation of thirst

ADH (hormone made in hypothalamus, stored in pituitary) Released to the bloodstream

= drink more= osmotic pressure

ADH to kidneys via blood= increase in water uptake

How? makes the usually impermeable distal tubule and collecting duct permeable to water water is ‘sucked’ out because of high NaCl concentration in intercellular spaces

= osmoreceptors swell

= in ADH

Kidneys and Blood Pressure1. low blood volume and low blood pressure2.sensed by blood pressure receptors in

juxtaglomerular apparatus3. renin is released to convert angiotensinogen into

angiotensin4.angiotensin constricts blood vessels and

simulates release of aldosterone from adrenal gland

5.aldosterone is carried to the kidneys6.nephrons increase Na+ and H2O reabsorption

Blood Pressure (Adjusting Blood Volume)

• a hormone aldosterone, produced in the adrenal glands (located above kidneys), acts on the nephrons to increase Na+ reabsorption.

water = blood pressure = O2 to tissues so…

• receptors near glomerulus detect blood pressure change

• = release renin (enzyme) which converts the plasma protein angiotensinogen into angiotensin (enzyme)

• * angiotensin has 2 roles: • vasoconstriction (constriction of blood vessels) • stimulates the release of aldosterone which increases reabsorption

of NaCl/H2O at the nephron

• in blood pressure

pH Balance

• The pH of our body is 7.3 7.5• Cell respiration releases H+ ions into the blood

which decreases pH• So… our buffer system:• H+ + HCO3- H2CO3 H2O + CO2• But this removes HCO3- ions so we have to get

more of them• So… 2 things happen (in different parts of the

kidney) to replace the HCO3-

CO2 (taken in actively) HCO3- (out to blood ) peritubule

capillary

interstitial fluid

CO2 + H2O HCO3- + H+

(makes more bicarbonate – sends it back to blood)

tubule cells

H+ + HPO42- pee

H+ + NH3 pee (the H+ ions combine with either

phosphate or ammonia – flushed out in filtrate)

lumen of tubule

Section 7.6, pp. 356, #1-8

Kidney DiseaseDiabetes Insipidus• kidneys don't concentrate urine well

Symptoms• frequent urination• strong thirst response

Causes• inadequate production of ________.• may be caused by head injury or brain tumours.• Medication containing lithium

Treatment:• drink large volumes of water

Diabetes Mellitus

• islet cells of the pancreas produce little or no insulin

Symptoms• frequent urination• extreme thirst• lack of energy• vision problems

Treatment• insulin replacement therapy• oral hypoglycemic medication

Blood Sugar

Animation: Blood Sugar Regulation in Diabetics

Bright's Disease (Nephritis)• grouping of diseases characterized by the

inflammation of the nephrons. One type of nephritis changes the permeability of the glomerulus allowing proteins to pass into the nephron. This causes an increase in urine production.

Kidney Stones• caused by the precipitation of mineral solutes

from the blood• sharp stones can damage tissues• Extracorporeal shock-wave lithotripsy (ESWL)

breaks stones into smaller fragments that can be voided through the excretory system

Diabetes Mellitus

inadequate secretion of insulinblood sugar levels rise

you pee out lots of glucosethis messes up the osmotic pressure and more water is lost = lots of peeing

must drink a lot

Diabetes Insipidus

destruction of ADH producing cells in the hypothalamus (not able to control water reabsorption)

urine output increasesyou must drink a lot

Bright’s Disease

“inflammation of the nephron” = altered permeabilitylots of characteristicsstart peeing out large molecules like proteinsproteins in tubule = osmotic issues = lots more peeing

Kidney Stones

precipitation of mineral solutes from the bloodOuch! some can be destroyed by ultrasound

Dialysis Technology

the exchange of substances across a semipermeable membrane

• haeomodialysis a tube is connected to a vein and blood is removed from the body

the blood goes into a dialysis machine (in the tube) and passes through various environments(solutions) that remove toxins from the blood

essentially a “man made” kidney.

• peritoneal dialysis pump dialysis fluids into abdominal cavity (~2 L)

the selectively permeable membranes of the cavity allow toxins to go into the fluid

fluid is removed and new fluid pumped in• wastes diffuse from the plasma into the

peritoneum and is filtered into the dialysis fluid• accumulated wastes are drained off and

replaced several times a day• performed at home (2-6 hours)• neither provide the hormones that kidneys do so

they have to be injected

Kidney Transplant

• 85 % successful• new kidney is placed lower in the pelvis

and attached to blood vessels and ureter• old kidney is not removed• patient must receive immunosuppressant

drugs forever • Section 7.7, pp. 362, #1-10• Review: pp. 367, #1-8; pp. 368, #1-13, 15,

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