Human Body Responses To the environment
You
will be
able
to…
Lesson Objectives
By the end of the lesson I can:
1. Plan and implement an
investigation
2. Recall how environmental
conditions affect the human
body
3. Explain how the body controls its
internal environment
Key Words
•
•
•
•
•
•
Vasodilation
Vasoconstriction
Homeostasis
Piloerection
Dilate
Capillaries
Put these events into order they occur
•Blood vessels vasodilate so more blood is carried to surface
to lose heat.
•Blood capillaries vasoconstrict so less blood is carried near
surface to keep in heat
•Sweating is reduced
•Sweating is increased
•Hairs stand up to trap warm air to act as an insulator
•Hairs lie flat
•No shivering
•Shivering – muscle action produces heat from respiration
Internal conditions that are controlled include;
•Water content
•Ion content
•Temperature
•Blood sugar level
Water is leaving the body all the time as we breathe out and
sweat. We lose any excess water in the urine (produced by the
kidneys). We also lose ions in sweat and urine.
We must keep out temperature constanst otherwise the
enzymes in the body will not work properly, if at all.
Sugar in the blood is the energy source for cells. The level of
sugar in our blood is controlled.
How does the body stay cool?
> Sweating
•
When you are hot, sweat glands are stimulated to
release sweat.
•
Heat energy from your skin is used to turn the liquid
sweat into gas - sweat evaporates.
•
Because heat is lost, your skin cools down.
> See this in action
How does the body stay cool?
> Sweating
Heat lost as
sweat
evaporates
Skin
Heat
How does the body stay cool?
> Vasodilation
•
Your blood carries most of the heat energy in
your body.
•
There are small blood vessels called capillaries
just underneath your skin.
•
When you are hot, these capillaries get wider
(dilate) so more blood comes close to the
surface of the skin and heat is lost.
•
This is why some people go red when they are
hot!
> See this in action
How does the body stay cool?
> Vasodilation
Heat loss
Skin
Capillaries
How does the body stay warm?
> Vasoconstriction
•
This is basically the opposite of vasodilation.
•
When you are cold, the capillaries near the
surface of your skin get narrower (constrict) and
some shut off.
•
This means less blood comes near the surface of
the skin and less heat is lost.
•
This is why your fingers and toes might go white
when they are cold!
> See this in action
How does the body stay warm?
> Vasoconstriction
Less heat loss
Skin
Capillaries
ARGH!
What do birds
do to keep warm
when it is cold?
I was
not
scared!
(phew!)
How does the body stay warm?
> Piloerection
•
When you are cold, the hairs on your skin stand up.
•
The hairs trap a layer of air next to the skin, which is
warmed by body heat and becomes an insulating layer.
•
This is sometimes called ‘goose bumps’.
•
The same principle applies to birds or mammals fluffing
themselves up.
> See this in action
How does the body stay warm?
> Piloerection
Trapped air
forms
insulation
Hairs
Skin
Aim:
The effects of insulation on heat loss
Equipment:
•
2 conical flasks of the same size
•
Boiling water
•
Cotton wool
•
2 thermometers
•
Timer or clock
•
Graph paper
Method:
1. Obtain 2 conical flasks
2. Wrap cotton wool round one flask and leave the other uncovered
3. Pour the same amount of boiling water into both flasks
4. Place a thermometer in each and record the temperature at 1 min intervals
for 15 mins
5. Record results in a suitable table and plot a graph (put temperature on the
vertical axis and time on the horizontal axis)
Time
(mins)
Temperature
(°C)
With
Time
(mins)
Without
Temperature
(°C)
With
0
6
1
7
2
8
3
9
4
10
5
Change temp (°C)
Without
What makes a good graph?
1. Use a Sharp Pencil and a Ruler
2. Label the axes with Quantity and Unit (e.g. Time /
minutes)
3. The scale on each axis must use up more than half
of the graph paper
For line graphs
Plot your points with crosses (X)
What is wrong with this graph?
A Line graph to show the effect of environmental
conditions on Alien body temperature
100
90
Temperature
80
70
60
50
40
30
20
10
0
0
2
4
6
Time
8
10
12
Results Analysis
What did you measure? What did your results show?
Conclusion:
What did you find out?
How does this link in with vasodilatation and vasoconstriction?
What effect did insulation have on the rate of heat loss?
Which flask lost heat faster and why?
Which structures in the mammal do you think acts in the same way as
the cotton wool?
Evaluation
How could you improve your experiment?
Was this a fair test? Were the results accurate?
What improvements could be made to further improve the reliability of
results?
HOMEOSTASIS research
Go to
http://www.teachersdomain.org/resource/tdc02.sci.life
.reg.bodycontrol/
Read the text on the right hand side then Press ‘VIEW’
HAVE YOU GOT WHAT IT TAKES TO CONTROL YOUR BODY MANUALLY?
Use the internet to research -how the body is controlled, -why its important
and -how it occurs.
You should include water, ion, temperature and blood sugar levels.
Place your research into a self-designed table on the computer and save it.
Human Body Responses To the environment
You
will be
able
to…
Lesson Objectives
By the end of the lesson I can:
1. Plan and implement an
investigation
2. Recall how environmental
conditions affect the human
body
3. Explain how the body controls its
internal environment