BIOLOGY 1A Lecture Notes - Lecture 33: Renal Artery, Renal Cortex, Collecting Duct System
THE KIDNEYS AND OSMOREGULATION
Overview of form of excretory system:
Blood supply via Renal artery
-
Exchange of ions occurs within the kidney
-
Excretion of unwanted substances via the urinary system
-
Kidney- form and function
Overview- regulates ionic composition
Determines the ionic composition of the body (concentration of Na+, K+, Ca2
+, H+, phosphate)
i.
Strategy:
Filters an enormous amount of plasma- 180 liters
1)
Reabsorbs ions the body needs back into the blood
2)
Secretes some urine but also waste products and toxins into the urine
3)
Excretes excess water and ions in urine (1-2 liters)
4)
ii.
a.
b.
I.
Nephron: key structural and functional unit of kidney
Nephron Types: each kidney has 10^6 nephrons
Tubule with a bulb and a collecting duct that collects urine to send to ureter
Cortical (short): primarily in renal cortex
1.
Juxtamedullary (long): deeper loop into medulla of kidney
2.
a.
Different steps occur at different locations of a nephron:
Filtration= blood pressure forces filtration of water and solutes
In bowman's capsule, ions removed from blood 1)
Not all blood, some gets diverted and into nephron2)
1.
Reabsorption= valuable substances returned to the blood
Take ions and put back into blood1)
2.
Secretion= addition of toxins and ions to urine
Some ions and toxins have transporters that remove from blood and
secrete into urine
1)
3.
Excretion= urination4.
5.
b.
II.
Osmoregulation: a primary function of kidney is homeostatic regulation of osmolarity=
concentration of ions in the blood
Homeostatically regulation of solute and water are critical for survival a.
Osmosis= flow of water through a selectively permeable membrane from a region
of low solute concentration to high solute concentration
Always extracellular fluid compared to intracellular fluid1.
b.
Hyperosmotic: [Ions]ECF > [Ions]ICF
Concentration of ECF is greater than concentration ICF
§
c.
Iso-osmotic: [Ions]ECF= [Ions]ICF
Concentration of ECF equal to concentration ICF
§
d.
Hypo-osmotic: [Ions]ECF<[Ions]ICF
Concentration of ECF less than concentration ICF
§
e.
What happens when you drink water?
Water is absorbed into extracellular fluid1.
Lowers the concentration of extracellular fluid relative to intracellular fluid
Hypoosmotic1)
2.
Water moves into cells, causing them to swell3.
f.
Negative feedback to maintain osmolarity: example of homeostasis
Normal blood osmolarity= 300 mOsm/L1.
Blood osmolarity increases (such as after sweating) 2.
Hypothalamus contains osmosensers that detect3.
Hypothalamus generates thirst--> drink water4.
g.
III.
Nephron form and function
a.
Renal artery enters Bowman's capsule which contains the glomerulus. Blood enters
vasa recta (one with each nephron) where exchange of ions happens. Then it drains
into the veins to the renal vein to the heart
b.
Branch of renal artery gets broken into capillary bed (glomerulus)
§
FILTRATION in glomerulus= network of capillaries
§
Bowman's capsule is entry into nephron
§
Ions become filtrate. Then reabsorption of some ions back into blood
§
c.
The directions of flow:
Filtration: 1600 L/day of blood passes through kidney and 180 L/day water
enters glomerular filtrate
So most of blood does not get filtered; just not all at the same time□
(Blood--> lumen/filtrate)□
§
Most water and dissolved solutes returned to the blood by reabsorption
(lumen/filtrate-->blood)
Reabsorption can be by active or passive transport□
§
When ions are re-absorbed, urine is more dilute; when water is re-absorbed,
urine is more concentrated
§
Critical function of kidney is secretion (blood-->filtrate) and excretion in urine
of harmful substances and (nitrogenous wastes) urea
§
d.
Absorption of ions and water happen at different locations of the nephron
Proximal tubule: ions and water reabsorbed through active and passive
transport
□
Descending loop: reabsorption of water□
Loop of Henle □
Ascending loop: reabsorption of salt, filtrate gets more dilute□
Deep in medulla: high concentration of filtrate because high
concentration of solutes in filtrate
□
Distal tubule: secretion □
Collecting duct: where urine concentration is determined
Control how much water gets reabsorbed
®
Permeable to urea only at this point
®
□
1.
e.
Two regulators of concentration of urine:
Osmolarity: How much water can be reabsorbed depends on osmolarity of
extracellular fluid
HUGE gradient of osmolarity in the kidney which is critical for its
function
1)
High osmolarity dependent on urea= metabolic waste generated from
breakdown of proteins
2)
1.
The number of water channels (aquaporins)2.
f.
Antidiuretic hormone (ADH or vasopressin) stimulates water reabsorption
Normal blood osmolarity= 300 mOsm/L1.
Blood osmolarity increases2.
Osmoreceptors in hypothalamus release ADH
Posterior pituitary releases ADH which causes water reabsorption in the
collecting tube
1)
3.
g.
Posterior pituitary secretes ADH (anti diuretic hormone)1.
Receptors for ADH are on collecting duct2.
ADH binds to increase water channels to reabsorb water
Dehydrated--> increase more water channels to reabsorb water and
concentrate urine
1)
3.
h.
ADH signaling promotes aquaporin exocytosis to the plasma membrane
1.
ADH binds to receptor which is a GPCR which causes a cascade of signaling
Increase of cAMP which binds to protein kinase A (enzyme) which takes
storage vesicles which fuse to membrane and water can be pulled back
into the body to counteract the dehydration
1)
2.
i.
People who are starving do not have enough protein in their diet. They often die
from dehydration. Why?
j.
IV.
Lecture 33-4/16
Monday, April 16, 2018
4:18 PM
THE KIDNEYS AND OSMOREGULATION
Overview of form of excretory system:
Blood supply via Renal artery
-
Exchange of ions occurs within the kidney
-
Excretion of unwanted substances via the urinary system
-
Kidney- form and function
Overview- regulates ionic composition
Determines the ionic composition of the body (concentration of Na+, K+, Ca2
+, H+, phosphate)
i.
Strategy:
Filters an enormous amount of plasma- 180 liters
1)
Reabsorbs ions the body needs back into the blood
2)
Secretes some urine but also waste products and toxins into the urine
3)
Excretes excess water and ions in urine (1-2 liters)
4)
ii.
a.
b.
I.
Nephron: key structural and functional unit of kidney
Nephron Types: each kidney has 10^6 nephrons
Tubule with a bulb and a collecting duct that collects urine to send to ureter
Cortical (short): primarily in renal cortex
1.
Juxtamedullary (long): deeper loop into medulla of kidney
2.
a.
Different steps occur at different locations of a nephron:
Filtration= blood pressure forces filtration of water and solutes
In bowman's capsule, ions removed from blood 1)
Not all blood, some gets diverted and into nephron2)
1.
Reabsorption= valuable substances returned to the blood
Take ions and put back into blood1)
2.
Secretion= addition of toxins and ions to urine
Some ions and toxins have transporters that remove from blood and
secrete into urine
1)
3.
Excretion= urination4.
5.
b.
II.
Osmoregulation: a primary function of kidney is homeostatic regulation of osmolarity=
concentration of ions in the blood
Homeostatically regulation of solute and water are critical for survival a.
Osmosis= flow of water through a selectively permeable membrane from a region
of low solute concentration to high solute concentration
Always extracellular fluid compared to intracellular fluid1.
b.
Hyperosmotic: [Ions]ECF > [Ions]ICF
Concentration of ECF is greater than concentration ICF
§
c.
Iso-osmotic: [Ions]ECF= [Ions]ICF
Concentration of ECF equal to concentration ICF
§
d.
Hypo-osmotic: [Ions]ECF<[Ions]ICF
Concentration of ECF less than concentration ICF
§
e.
What happens when you drink water?
Water is absorbed into extracellular fluid1.
Lowers the concentration of extracellular fluid relative to intracellular fluid
Hypoosmotic1)
2.
Water moves into cells, causing them to swell3.
f.
Negative feedback to maintain osmolarity: example of homeostasis
Normal blood osmolarity= 300 mOsm/L1.
Blood osmolarity increases (such as after sweating) 2.
Hypothalamus contains osmosensers that detect3.
Hypothalamus generates thirst--> drink water4.
g.
III.
Nephron form and function
a.
Renal artery enters Bowman's capsule which contains the glomerulus. Blood enters
vasa recta (one with each nephron) where exchange of ions happens. Then it drains
into the veins to the renal vein to the heart
b.
Branch of renal artery gets broken into capillary bed (glomerulus)
§
FILTRATION in glomerulus= network of capillaries
§
Bowman's capsule is entry into nephron
§
Ions become filtrate. Then reabsorption of some ions back into blood
§
c.
The directions of flow:
Filtration: 1600 L/day of blood passes through kidney and 180 L/day water
enters glomerular filtrate
So most of blood does not get filtered; just not all at the same time□
(Blood--> lumen/filtrate)□
§
Most water and dissolved solutes returned to the blood by reabsorption
(lumen/filtrate-->blood)
Reabsorption can be by active or passive transport□
§
When ions are re-absorbed, urine is more dilute; when water is re-absorbed,
urine is more concentrated
§
Critical function of kidney is secretion (blood-->filtrate) and excretion in urine
of harmful substances and (nitrogenous wastes) urea
§
d.
Absorption of ions and water happen at different locations of the nephron
Proximal tubule: ions and water reabsorbed through active and passive
transport
□
Descending loop: reabsorption of water□
Loop of Henle □
Ascending loop: reabsorption of salt, filtrate gets more dilute□
Deep in medulla: high concentration of filtrate because high
concentration of solutes in filtrate
□
Distal tubule: secretion □
Collecting duct: where urine concentration is determined
Control how much water gets reabsorbed
®
Permeable to urea only at this point
®
□
1.
e.
Two regulators of concentration of urine:
Osmolarity: How much water can be reabsorbed depends on osmolarity of
extracellular fluid
HUGE gradient of osmolarity in the kidney which is critical for its
function
1)
High osmolarity dependent on urea= metabolic waste generated from
breakdown of proteins
2)
1.
The number of water channels (aquaporins)2.
f.
Antidiuretic hormone (ADH or vasopressin) stimulates water reabsorption
Normal blood osmolarity= 300 mOsm/L1.
Blood osmolarity increases2.
Osmoreceptors in hypothalamus release ADH
Posterior pituitary releases ADH which causes water reabsorption in the
collecting tube
1)
3.
g.
Posterior pituitary secretes ADH (anti diuretic hormone)1.
Receptors for ADH are on collecting duct2.
ADH binds to increase water channels to reabsorb water
Dehydrated--> increase more water channels to reabsorb water and
concentrate urine
1)
3.
h.
ADH signaling promotes aquaporin exocytosis to the plasma membrane
1.
ADH binds to receptor which is a GPCR which causes a cascade of signaling
Increase of cAMP which binds to protein kinase A (enzyme) which takes
storage vesicles which fuse to membrane and water can be pulled back
into the body to counteract the dehydration
1)
2.
i.
People who are starving do not have enough protein in their diet. They often die
from dehydration. Why?
j.
IV.
Lecture 33-4/16
Monday, April 16, 2018
4:18 PM
THE KIDNEYS AND OSMOREGULATION
Overview of form of excretory system:
Blood supply via Renal artery
-
Exchange of ions occurs within the kidney
-
Excretion of unwanted substances via the urinary system
-
Kidney- form and function
Overview- regulates ionic composition
Determines the ionic composition of the body (concentration of Na+, K+, Ca2
+, H+, phosphate)
i.
Strategy:
Filters an enormous amount of plasma- 180 liters1)
Reabsorbs ions the body needs back into the blood2)
Secretes some urine but also waste products and toxins into the urine3)
Excretes excess water and ions in urine (1-2 liters)4)
ii.
a.
b.
I.
Nephron: key structural and functional unit of kidney
Nephron Types: each kidney has 10^6 nephrons
Tubule with a bulb and a collecting duct that collects urine to send to ureter
Cortical (short): primarily in renal cortex1.
Juxtamedullary (long): deeper loop into medulla of kidney
2.
a.
Different steps occur at different locations of a nephron:
Filtration= blood pressure forces filtration of water and solutes
In bowman's capsule, ions removed from blood
1)
Not all blood, some gets diverted and into nephron
2)
1.
Reabsorption= valuable substances returned to the blood
Take ions and put back into blood
1)
2.
Secretion= addition of toxins and ions to urine
Some ions and toxins have transporters that remove from blood and
secrete into urine
1)
3.
Excretion= urination
4.
5.
b.
II.
Osmoregulation: a primary function of kidney is homeostatic regulation of osmolarity=
concentration of ions in the blood
Homeostatically regulation of solute and water are critical for survival
a.
Osmosis= flow of water through a selectively permeable membrane from a region
of low solute concentration to high solute concentration
Always extracellular fluid compared to intracellular fluid
1.
b.
Hyperosmotic: [Ions]ECF > [Ions]ICF
Concentration of ECF is greater than concentration ICF
§
c.
Iso-osmotic: [Ions]ECF= [Ions]ICF
Concentration of ECF equal to concentration ICF
§
d.
Hypo-osmotic: [Ions]ECF<[Ions]ICF
Concentration of ECF less than concentration ICF
§
e.
What happens when you drink water?
Water is absorbed into extracellular fluid
1.
Lowers the concentration of extracellular fluid relative to intracellular fluid
Hypoosmotic
1)
2.
Water moves into cells, causing them to swell
3.
f.
Negative feedback to maintain osmolarity: example of homeostasis
Normal blood osmolarity= 300 mOsm/L1.
Blood osmolarity increases (such as after sweating) 2.
Hypothalamus contains osmosensers that detect3.
Hypothalamus generates thirst--> drink water4.
g.
III.
Nephron form and function
a.
Renal artery enters Bowman's capsule which contains the glomerulus. Blood enters
vasa recta (one with each nephron) where exchange of ions happens. Then it drains
into the veins to the renal vein to the heart
b.
Branch of renal artery gets broken into capillary bed (glomerulus)
§
FILTRATION in glomerulus= network of capillaries
§
Bowman's capsule is entry into nephron
§
Ions become filtrate. Then reabsorption of some ions back into blood
§
c.
The directions of flow:
Filtration: 1600 L/day of blood passes through kidney and 180 L/day water
enters glomerular filtrate
So most of blood does not get filtered; just not all at the same time□
(Blood--> lumen/filtrate)□
§
Most water and dissolved solutes returned to the blood by reabsorption
(lumen/filtrate-->blood)
Reabsorption can be by active or passive transport□
§
When ions are re-absorbed, urine is more dilute; when water is re-absorbed,
urine is more concentrated
§
Critical function of kidney is secretion (blood-->filtrate) and excretion in urine
of harmful substances and (nitrogenous wastes) urea
§
d.
Absorption of ions and water happen at different locations of the nephron
Proximal tubule: ions and water reabsorbed through active and passive
transport
□
Descending loop: reabsorption of water□
Loop of Henle □
Ascending loop: reabsorption of salt, filtrate gets more dilute□
Deep in medulla: high concentration of filtrate because high
concentration of solutes in filtrate
□
Distal tubule: secretion □
Collecting duct: where urine concentration is determined
Control how much water gets reabsorbed
®
Permeable to urea only at this point
®
□
1.
e.
Two regulators of concentration of urine:
Osmolarity: How much water can be reabsorbed depends on osmolarity of
extracellular fluid
HUGE gradient of osmolarity in the kidney which is critical for its
function
1)
High osmolarity dependent on urea= metabolic waste generated from
breakdown of proteins
2)
1.
The number of water channels (aquaporins)2.
f.
Antidiuretic hormone (ADH or vasopressin) stimulates water reabsorption
Normal blood osmolarity= 300 mOsm/L1.
Blood osmolarity increases2.
Osmoreceptors in hypothalamus release ADH
Posterior pituitary releases ADH which causes water reabsorption in the
collecting tube
1)
3.
g.
Posterior pituitary secretes ADH (anti diuretic hormone)1.
Receptors for ADH are on collecting duct2.
ADH binds to increase water channels to reabsorb water
Dehydrated--> increase more water channels to reabsorb water and
concentrate urine
1)
3.
h.
ADH signaling promotes aquaporin exocytosis to the plasma membrane
1.
ADH binds to receptor which is a GPCR which causes a cascade of signaling
Increase of cAMP which binds to protein kinase A (enzyme) which takes
storage vesicles which fuse to membrane and water can be pulled back
into the body to counteract the dehydration
1)
2.
i.
People who are starving do not have enough protein in their diet. They often die
from dehydration. Why?
j.
IV.
Lecture 33-4/16
Monday, April 16, 2018 4:18 PM
Document Summary
Excretion of unwanted substances via the urinary system. Determines the ionic composition of the body (concentration of na+, k+, ca2. Filters an enormous amount of plasma- 180 liters. Reabsorbs ions the body needs back into the blood. Secretes some urine but also waste products and toxins into the urine. Excretes excess water and ions in urine (1-2 liters) b. Nephron: key structural and functional unit of kidney. Nephron types: each kidney has 10^6 nephrons a. Tubule with a bulb and a collecting duct that collects urine to send to ureter. Juxtamedullary (long): deeper loop into medulla of kidney. Juxtamedullary (long): deeper loop into medulla of kidney b. Different steps occur at different locations of a nephron: Filtration= blood pressure forces filtration of water and solutes. Not all blood, some gets diverted and into nephron. Secretion= addition of toxins and ions to urine. Some ions and toxins have transporters that remove from blood and secrete into urine.
