Who’s urine? MATCH UP!
Normal diet
Drunk plenty
of water
Has been exercising but
not drunk anything
Title - Homeostasis
Learning Objective
To be able to explain how our
bodies control water content.
Learning Outcome
• Homeostasis involves making sure that
our bodies have the correct levels of 4
key things.
• Can you name two of them?
What is Homeostasis?
Homeostasis involves maintaining a
constant environment in the body
• Homeostasis makes sure our body has
the correct levels of;
Temperature
Water
Carbon dioxide
Oxygen
B2 : How does the body control water balance?
In
Out
Food
and drink Breath
Our bodies need a balanced water level to keep the
Water
madeconcentration
in respiration Sweat
internal
of our cells at the correct level for
them to work properly.
Faeces
Urine
The kidneys
Kidneys do two main jobs:
1. Remove waste urea from the blood.
2. Keep a balance of other chemicals in the blood – including water.
How kidneys work
Filtering all small molecules from the blood.
Reabsorbing all of the glucose.
Reabsorbing as much salt as the body needs.
Reabsorbing as much water as the body needs.
Excreting the remaining urea, excess water and salt as urine, which is stored in
the bladder.
Water balance
The concentration of blood plasma is monitored as it passes through the
brain.
If the blood is too dilute then kidneys excrete more water in the urine.
If the blood is too concentrated then kidneys excrete less water in the
urine.
The amount of water in the blood depends on: external temperature, exercise,
intake of fluids and salts.
ADH and water balance.
The concentration of urine is controlled by a hormone
called ADH (anti-diuretic hormone).
It is released into the bloodstream by the pituitary gland.
Blood too
concentrated –
detected in
brain
ADH secreted
by pituitary
gland
ADH causes
kidneys to
reabsorb more
water to blood
Water Balance
Normal blood
concentration
Blood too dilute
– detected in
brain
Normal blood
concentration
ADH not
secreted by
pituitary gland
kidneys
reabsorb less
water to blood
TITLE: Controlling Water Content
Outcomes: create a think board on homeostasis and
water balance.
Which hormone controls water content
in the body?
How do the Kidneys help keep water in the
body balanced?
Where is it released from?
(C)
What 3 main things can effect the
concentration of urine?
(D)
Draw a flow diagram of how the
Explain in as much detail as possible (use as
concentration of urine is controlled by a many science key words as you can) how
hormone
Alcohol and Ecstasy affect ADH production
(B)
(A)
True/False Quiz!
•
•
•
•
•
•
Your urine is always the same. FALSE
The pituitary gland monitors blood plasma. TRUE
TRUE
Homeostasis maintains a constant internal environment.
The liver helps balance water and waste in the body. FALSE
Alcohol suppresses ADH production. TRUE Dehydration
Ecstasy increases ADH production. TRUE Drowning
Which is the odd one out?
bacteria
virus
fungus
B2 past EXAM questions!
• I will be round to mark them as you go ready to put
into your progress folder.
ALL must do 2 exam questions
SOME will do more so can pick their highest grade for progress folder
FEW will do all exam questions for a PRIZE!
Exam Question (hard)
3 marks – pick from the following
• number of bacteria after 2 hours is 12 800 (or 1.28 x 104),
which is a sufficient number to cause food poisoning
• idea that if conditions were not optimum the actual
number may be lower than this
• idea that not enough data/evidence/information, or would
need to measure more things, to conclude that person will
definitely get food poisoning
• idea of immune response against bacteria or toxins / acid in
stomach destroying bacteria or toxins
Testing Urine
• Draw the following table in your books neatly.
Sample
Protein
Sugar
A
B
C
• Test the 3 urine samples for protein and for sugar using the
equipment available.
• EXTENSION: explain in as much detail as possible what
homeostasis is and how water content is controlled in the body.
Drug Trials
• Outcomes: create a Powerpoint on the use of
drug trials in medical science.
Include information on the following:
- Laboratory testing on human cells [C]
- Laboratory testing on animals [C-B]
- Human clinical trials [A]
- ‘blind trails’ (you’ll need to know what a placebo is)
- ‘double blind trials’
- ‘open label trials’
Homeostasis
• How hot do you think our core body temperature is?
• 370c
How do we maintain our body
temperature in hot environment
Red cheeks
Hairs lie flat
Sweating
Controlling body temperature
• If the body
temperature gets too
high, the blood flows
closer to the skin.
• This is the reason why
we get red cheeks.
Sweating
•
•
When your body is hot, sweat glands are
stimulated to release sweat.
The liquid sweat turns into a gas.
Sweating
The
skin
Effects of overheating
• Being to hot is dangerous.
• If too much water is lost through sweating,
the body becomes d_ h _d_ a _ _d.
• This can lead to heat stroke and even death.
How do we maintain our body
temperature in a cold environment?
Shiver
Hairs stand on end
Respire more
Respire
more
Effects of being too cold
• If the body temperature
fall too low, sweating
stops and the muscles
begin to s _ _ ver.
• Hypothermia is when the
body temperature falls
too far below 37oc.
• This causes
unconsciousness and
sometimes death
Body temperature readings
• Where on the body can body
temperature readings be taken from?
ANUS
MOUTH
SKIN
SURFACE
FINGER
EAR
Task
• Complete the worksheet.
• If you need help put your hand up.