9.3 MAINTAINING THE EXCRETORY SYSTEM
Read p.316-325 and answer the questions that follow.
1. What is osmotic pressure?
Osmotic pressure is the force generated as water moves by osmosis.
2. What are osmoreceptors?
Osmoreceptors are cells that are sensitive to osmotic pressure and detect
changes in water levels.
3. Draw a flow chart that describes how osmotic pressure is regulated when
you are dehydrated.
Increased
osmotic
pressure
dehydrated
Decreased
osmotic
pressure to
normal
Osmoreceptors in
hypothamalmus
tell pituitary gland
to release ADH
(antidiuretic
hormone)
Increased
reabsorption of
water into
blood
ADH travels
through blood to
kidneys
Kidneys increase
their
permeability in
distal tubule and
collecting duct
4. Draw a flow chart that describes how osmotic pressure is regulated when
your plasma is too dilute of ions.
Plasma too
dilute
Decreased
osmotic
pressure
Osmotic
pressure
increases to
normal
Osmoreceptors
in hypothalamus
prevent the
release of ADH
Solute
concentration in
blood increases
Distal tubule and
collecting tube
become less
permeable to
water
More water is
secreted in urine
5. What is diabetes insipidus?
Diabetes insipidus is an insufficient release of ADH. If you don’t have enough
ADH, water cannot be reabsorbed and so you will have excessive amounts of
urinating and dehydration. To restore water reabsorption you can take
synthetic ADH.
6. How does alcohol affect urine production?
Alcohol stimulates urine production by also decreasing ADH production,
which in turn leads to water loss through urine.
7. Explain how aldosterone controls the concentration of sodium within the
blood.
Aldosterone is the hormone that increases the reabsorption of sodium
and water and the release (secretion) of potassium (K+) in the kidney.
Decreased
concentration
of sodium in
blood
Hormone
aldosterone
secreted by the
adrenal glands
above the kidneys
If K+ concentration
high then it is
secreted from blood
into distal tubule and
collecting ducts
Distal tubule and
collecting duct
reabsorb Na+
Water and Clions follow Na+
passively
Net gain of ions
and water into
the blood
8. How do the respiratory and excretory systems work together to regulate
blood pH?
The kidneys keep blood pH within normal limits. They reabsorb HCO3(bicarbonate ions), and excrete H+ ions as needed to maintain the pH at
about 7.4. The chemical reactions that act to maintain a constant pH are
linked to the respiratory system because H2CO3 (carbonic acid) reacts
in solution to form carbon dioxide and water. Therefore, levels of
H2CO3 are linked to levels of CO2, which are regulated by breathing.
9. What are kidney stones? What is the treatment method for kidney stones?
Kidney stones usually occur due to excess calcium in the urine. When the
chemicals within the urine crystallize they can form a kidney stone. The
stones can be passed through the urinary tract, or be broken down with
medications. Ultrasound waves can also be used to break them down if they
are less than 20 mm in diameter. If they are larger surgery to remove them
may be needed.
10. What is renal insufficiency?
Renal insufficiency occurs when kidney’s cannot maintain homeostasis due to
damaged nephrons.
11. What is dialysis?
Dialysis refers to the diffusion of dissolved substances through a semipermeable membrane. Substances more concentrated in the blood will move
into the dialysate; substances more concentrated in the dialysate will move
into the blood. *** want to maintain homeostasis.
12. Identify the two types of renal dialysis and briefly describe their similarities
and differences.
1. HEMODIALYSIS = artificial semi-permeable membrane is attached to a
person’s artery and vein in their arm; it acts as an exterior artificial
kidney.
2. PERIOTONEAL DIALYSIS = the lining of the intestine (peritoneum) acts
as the semi-permeable membrane; dialysate is introduced to the
abdominal cavity, where the large surface area and rich supply of
capillaries of peritoneum slowly filter the blood.
13. Why is kidney transplant considered a cure for a serious kidney disorder,
while renal dialysis is not?
Dialysis enables people with kidney disease to live their lives in a relatively
unchanged way. However, dialysis is not a cure and it is not intended to be a
long-term solution to the problem of kidney disease. Individuals with kidney
functions of ten percent or less will eventually have to replace their kidneys.
14. What factors could affect the short-term and long-term success of a kidney
transplant?
The short-term success would depend on the availability of organs for
transplantation, surviving surgery, and contracting an infection. Long-term
success depends on the success of anti-rejection drugs and solving the
problem that caused the original kidney disease.