16.3 Regulatory Functions of the Kidneys
1. Intro
a. One of the kidneys main functions is to ______________ the watersalt ______________ within normal limits.
b. This is how they also maintain blood ______________ and blood
______________.
2. Process of Water Reabsorption
a. Reabsorption requires:
i. Reabsorption of ______________
ii. Establishing a ______________ gradient
iii. Water is ______________
b. Reabsorption of Salt
i. Salts are ions in the ______________ and include
1. ______________ Na+
2. ______________ K+
3. ______________ ions HCO34. ______________ Mg+
ii. Almost all salt filtered in the ______________ is
______________ from the ______________ back into the
______________
1. 67% in the ______________ tubule
2. 25% in the ______________ limb of the loop of the
nephron
3. Rest is absorbed by the ______________ convoluted
tubule and ______________ duct
iii. Hormones ______________e reabsorption
1. Aldosterone
a. Secreted by ______________ cortex
b. Promotes ______________ of K+ and
______________ of Na+
c. Na+ ______________ causes H2O to follow;
increases blood ______________ and blood
pressure
2. Renin
a. Secreted by ______________ apparatus
b. Stimulates ______________ cortex to secrete
______________
3. Atrial ______________hormone (ANH)
a. Secreted by ______________ of the heart when
cardiac cells are ______________due to high
blood ______________
b. Promotes ______________ of renin, which
promotes the adrenal ______________ to secrete
______________
c. Establishment of Solute Gradient
i. Happens in the long loop of the nephron (Loop of Henle)
1. Penetrates deep into ______________
2. Has ______________ and ascending limb
3. Salt _____________ diffuses out of the ________portion
4. Upper portion ______________ extrudes salt out into
the tissue of the outer renal medulla
5. The concentration of salt is ______________ as you go
deeper into the ______________ (hypertonic)
d. Reabsorption of Water
i. Occurs due to ______________ gradient within renal
______________
ii. Countercurrent mechanism
1. Water ______________ out as the loop descends
2. Remaining fluid in loop continues to be ______-tonic as
it descends due to ______________ concentration in the
renal medulla, therefore water keeps diffusing out
iii. Fluid enters the ______________ duct from the distal
convoluted ______________
1. Hypo________ to renal cortex
2. ______________ transport of salt out of ascending limb
has decreased osmolarity of the ______________
3. At this point, the filtrate is ________-tonic compared to
general body fluids
a. Good if excess water needs to be _____________
b. Urine will be _________-tonic
4. Production of _______-tonic urine
a. Needed if body is ______________ (reabsorb as
much water as possible)
b. ______________ hormone (ADH) is excreted by
______________ gland
i. Diuresis means ______________ amount
of urine (e.g. coffee is a diuretic = increases
volume of urine produced and dehydrated
you)
ii. Makes collecting duct ______________ to
water
iii. More ADH is produced during sleep,
presumably to help interrupt your sleep less
– why first urine of the day is more
______________
e. Diuretics
i. ______________ flow of urine
ii. Alcohol consumption inhibits _________ production
iii. Caffeine ______________ the glomerular filtration _________
and decreases the tubular ______________ of Na+
iv. Diuretic drugs counteract ______________ blood pressure by
decreasing blood volume by ______________ active transport
o f Na+ at the Loop of Henle
v. Also abused by athletes to ______________ water volume to:
1. Lose weight quickly
2. Look more “cut” for bodybuilding competition
3. Can cause irregular heartbeat, dehydration, and even
death
p.307 #1-3
16.3 Regulatory Functions of the Kidneys
1. Intro
a. One of the kidneys main functions is to maintain the water-salt
balance within normal limits.
b. This is how they also maintain blood pressure and blood volume.
2. Process of Water Reabsorption
a. Reabsorption requires:
i. Reabsorption of salt
ii. Establishing a solute gradient
iii. Water is reabsorbed
b. Reabsorption of Salt
i. Salts are ions in the blood and include
1. sodium Na+
2. potassium K+
3. bicarbonate ions HCO34. magnesium Mg+
ii. Almost all salt filtered in the glomerulus is reabsorbed from
the filtrate back into the blood
1. 67% in the proximal tubule
2. 25% in the ascending limb of the loop of the nephron
3. Rest is absorbed by the distal convoluted tubule and
collecting duct
iii. Hormones regulate reabsorption
1. Aldosterone
a. Secreted by adrenal cortex
b. Promotes excretion of K+ and reabsorption of Na+
c. Na+ reabsorption causes H2O to follow; increases
blood volume and blood pressure
2. Renin
a. Secreted by juxtaglomerular apparatus
b. Stimulated adrenal cortex to secrete aldosterone
3. Atrial natriuretic hormone (ANH)
a. Secreted by atria of the heart when cardiac cells
are stretched due to high blood volume
b. Promotes secretion of renin, which promotes the
adrenal cortex to secrete aldosterone
c. Establishment of Solute Gradient
i. Happens in the long loop of the nephron (Loop of Henle)
1. Penetrates deep into medulla
2. Has descending and ascending limb
3. Salt passively diffuses out of the lower portion
4. Upper portion actively extrudes salt out into the tissue
of the outer renal medulla
5. The concentration of salt is greater as you go deeper
into the medulla (hypertonic)
d. Reabsorption of Water
i. Occurs due to osmotic gradient within renal medulla
ii. Countercurrent mechanism
1. Water diffuses out as the loop descends
2. Remaining fluid in loop continues to be hypotonic as it
descends due to increasing concentration in the renal
medulla, therefore water keeps diffusing out
iii. Fluid enters the collecting duct from the distal convoluted
tubule
1. Hypotonic to renal cortex
2. Active transport of salt out of ascending limb has
decreased osmolarity of the filtrate
3. At this point, the filtrate is hypotonic compared to
general body fluids
a. Good if excess water needs to be excreted
b. Urine will be hypotonic
4. Production of hypertonic urine
a. Needed if body is dehydrated (reabsorb as much
water as possible)
b. Antidiuretic hormone (ADH) is excreted by
pituitary gland
i. Diuresis means increased amount of urine
(e.g. coffee is a diuretic = increases volume
of urine produced and dehydrated you)
ii. Makes collecting duct impermeable to
water
iii. More ADH is produced during sleep,
presumably to help interrupt your sleep less
– why first urine of the day is more
concentrated
e. Diuretics
i. Increase flow of urine
ii. Alcohol consumption inhibits ADH production
iii. Caffeine increases the glomerular filtration rate and decreases
the tubular reabsorption of Na+
iv. Diuretic drugs counteract high blood pressure by decreasing
blood volume by inhibiting active transport of Na+ at the Loop
of Henle
v. Also abused by athletes to decrease water volume to:
1. Lose weight quickly
2. Look more “cut” for bodybuilding competition
3. Can cause irregular heartbeat, dehydration, and even
death
p.307 #1-3
16.3 Regulatory Functions of the Kidneys (cont’d)
3. Acid-Base Balance
a. Normal body pH = _________
i. Optimum pH for ____________ (such as cellular enzymes)
b. __________ = above 7.4 (alkaline means basic; basic pH >7)
c. __________ = below 7.4
d. The body will stop functioning if pH not near-normal due to protein
__________
e. Foods and products of __________ add basic or acidic substances to
blood
i. Cellular respiration produces carbon dioxide which combines
with water to form ____________________
ii. Fermentation adds __________ acid (product of anaerobic
respiration – happens when heart rate is above the aerobic
zone)
f. Buffers
i. A buffer is a chemical or combination of chemicals that can
take up excess ____ or ____ ions
ii. Combination of __________ acid (H2CO3) and __________ ions
(HCO3-) is one of the most important blood buffers
1. Reduces __________: H+ + HCO3-  __________
2. Reduces __________: OH- + H2CO3  HCO3- + H2O
iii. Buffers __________ prevent significant pH changes until more
__________ solutions come from the __________ capillaries
(lungs)
g. Respiratory Center
i. __________ __________ (part of the brain) regulates
__________ rate
ii. Breathing rate __________ as H+ concentration __________
and the following reaction takes place in the pulmonary
capillaries:
H+ + HCO3- __________  H2O + __________
iii. When CO2 is exhaled, the reaction shifts to the __________,
__________H+ concentration in the blood
h. The Kidneys
i. Kidneys act __________ to adjust pH compared to the other
two (buffers and breathing)
ii. More __________ effect than other two
iii. Kidneys:
1. reabsorb __________ (bicarbonate ions)
2. excrete __________ (hydrogen ions)
iv. Urine is usually __________ (acidic/basic)
p.308 #1-2
16.3 Regulatory Functions of the Kidneys (cont’d)
4. Acid-Base Balance
a. Normal body pH = 7.4
i. Optimum pH for proteins (such as cellular enzymes)
b. Alkalosis = above 7.4 (alkaline means basic; basic pH >7)
c. Acidosis = below 7.4
d. The body will stop functioning if pH not near-normal due to protein
denaturation
e. Foods and products of metabolism add basic or acidic substances to
blood
i. Cellular respiration produces carbon dioxide which combines
with water to form carbonic acid
ii. Fermentation adds lactic acid (product of anaerobic respiration
– happens when heart rate is above the aerobic zone)
f. Buffers
i. A buffer is a chemical or combination of chemicals that can
take up excess H+ or OH- ions
ii. Combination of carbonic acid (H2CO3) and bicarbonate ions
(HCO3-) is one of the most important blood buffers
1. Reduces acidity: H+ + HCO3-  H2CO3
2. Reduces alkalinity: OH- + H2CO3  HCO3- + H2O
iii. Buffers temporarily prevent significant pH changes until more
permanent solutions come from the pulmonary capillaries
(lungs)
g. Respiratory Center
i. Medulla oblongata (part of the brain) regulates breathing rate
ii. Breathing rate increases as H+ concentration increases and the
following reaction takes place in the pulmonary capillaries:
H+ + HCO3- H2CO3  H2O + CO2
iii. When CO2 is exhaled, the reaction shifts to the right,
decreasing H+ concentration in the blood
h. The Kidneys
i. Kidneys act slower to adjust pH compared to the other two
(buffers and breathing)
ii. More powerful effect than other two
iii. Kidneys:
1. reabsorb HCO3- (bicarbonate ions)
2. excrete H+ (hydrogen ions)
iv. Urine is usually acidic