Download Homeostasis and kidneys

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Saving energy?
Sayid has decided to save energy by staying in bed all day.
How much of his energy do you think this will save?
Surprisingly, the answer is only about 30%.
The other 70% keeps his body temperature at 37 °C
(98.6 °F), and the solutions around his cells at just the
right concentration.
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What is homeostasis?
The body uses so much energy, even during sleep, because
it must maintain a constant internal environment.
This process of keeping things the same is called
homeostasis.
A series of automatic
control systems ensures
that the body maintains
a constant temperature
and steady levels of
water, ions and blood
sugar.
Homeostasis allows the
body’s cells to work at
their optimum.
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Keeping comfortable
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The organs of homeostasis
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Why is water important?
The human body is about 60-70% water.
Water molecules and ions constantly
move in and out of cells, and are essential
for all life processes.
Dehydration (loss of too much water
from the body) damages cells.
How is water gained and lost?
 Water is produced by the body during respiration, and
absorbed from food and drink.
 Water is lost from the body in exhaled air, sweat, urine
and feces.
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What is osmosis?
Osmosis is the diffusion of water molecules from a low
concentration solution to high concentration solution,
across a partially-permeable membrane.
A partially-permeable membrane has holes in it that permit
water molecules through but are too small to allow larger
molecules through. Osmosis can be demonstrated using
dialysis tubing filled with a solution and placed in a beaker
of pure water.
partiallypermeable
membrane
(dialysis tubing)
water
glucose
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Dilute vs. concentrated
During osmosis, water molecules diffuse from pure water or
dilute solution to more concentrated solutions.
 Dilute solutions have a high concentration of
water molecules.
 Concentrated solutions have a low concentration
of water molecules.
pure water
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dilute solution
concentrated
solution
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Predicting osmosis
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Osmosis in action
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Remember what the cell membrane looks like:
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Osmosis and cells
Plant and animal cells are surrounded by a partiallypermeable plasma membrane. This allows water and other
small molecules to diffuse across.
Plant cells additionally have a strong cell wall surrounding
the membrane which offers support and protection.
plasma
membrane
cell wall
plant cell
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red blood cell
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Osmosis and plant cells
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Osmosis and animal cells
Animal cells do not have a cell wall. This means they
respond differently to plant cells to the gain and loss of
water.
In dilute solutions, osmosis can
cause animals cells, such as red
blood cells, to swell up and burst.
This is called lysis.
In concentrated solutions, water
loss causes the cells to shrink.
When this happens to red blood
cells, it is called crenation.
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Osmosis and animal cells
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Factors that affect Passive Transport:
•
Whether a molecule can move
through the membrane depends on:
the size of the molecule
the type of molecule (polar or
nonpolar, ions, etc.)
•
Molecules move by one of the following
methods: diffusion, facilitated diffusion, or
osmosis.
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Egg in hypertonic solution
Water moved out of
the egg to try to dilute
the solutes outside of
the egg and make the
external environment
have a higher water
concentration to match
the inside.
Chicken egg in syrup
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Egg in hypotonic solution
Chicken egg in tap water
(or vinegar)
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Water moved into the
egg to reduce the
water concentration
compared to solutes
outside of the egg and
make the external
environment have a
lower water
concentration to match
the inside.
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Osmosis and animal cells
In order to remain healthy, animal cells need to maintain
an isotonic water balance. This means that the water
concentration both inside and outside the cell are equal.
hypothalamus
The concentration of water
and salt in the blood are
controlled by the kidneys.
The kidneys are controlled
by the portion of the brain
called the hypothalamus.
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Waste removal
Several organs are important in removing waste from the body.
The lungs remove
carbon dioxide.
The skin provides
a surface for small
amounts of water
and salt to move
out of the body.
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The liver
converts excess
protein into urea.
The kidneys
remove unwanted
substances such
as urea, excess
water and salt.
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What is urea?
Excess amino acids in the body are
broken down by the liver, producing
a waste substance called urea.
This process is important because
it converts toxic ammonia to urea,
which is done using carbon dioxide.
Once formed, urea is transported by the
circulatory system to the kidneys.
The kidneys filter the blood, removing
urea and excess water and salt, which
forms urine. Urine is stored in the bladder
before being excreted from the body.
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What are the different parts of a kidney?
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Labeling the kidney
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How does the kidney work?
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Stages in the nephron
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Controlling water content
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Regulating water content
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Analysing urine
Changes in the colour, clarity, pH and the presence of certain
substances in urine can help doctors diagnose medical
conditions:
 Protein or red blood cells in
urine can indicate kidney
damage or disease, as these
substances would not normally
filter through the glomerulus.
 Glucose in urine is often an
indication of diabetes. A person
with diabetes will have a high
level of glucose in the blood.
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Which sample?
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Controlling blood glucose
Between meals, blood glucose levels are topped up from
stored deposits in the liver and muscles.
After a meal, blood glucose rises but quickly returns to
normal. Where does the excess go? Why not leave it in
the blood?
Excess glucose makes the blood plasma and
tissue fluid around cells too concentrated.
This can severely damage cells, for example,
causing crenation in red blood cells.
However, low blood sugar levels can be
equally as dangerous, as it can make cells
swell up and burst. This is called lysis.
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