BIOLOGY
Homeostasis
HOMEOSTASIS means keeping the same internal environment in the body . Your body
needs to maintain its internal environment so that your cells can function properly.
H2O
Things that need to stay
the same in the body
Water content
Temperature
Blood sugar levels
T
Salt levels
Feedback
D
R
AF
If your body detects a change in its
internal environment, it uses a FEEDBACK
MECHANISM to correct the imbalance.
• RECEPTORS detect a change.
• PROCESSING CENTRES receive
information and determine the correct
response.
• EFFECTORS produce the response. levels
too high
Which two of the following statements about
hormones is true?
(1 mark)
A Hormones travel along nerves.
BHormones are used to regulate cells and
organs.
CHormones act equally on all cells and
organs in the body.
D Hormones are produced by glands.
Hormones are chemical
messengers which travel in
the blood, so A is not true.
2.
Write down two things that your body
maintains using homeostasis
(2 marks)
Receptor
Processing centre
levels
increase
Effector
levels
decrease
Homeostasis systems
The NERVOUS system and ENDOCRINE
system work together to maintain
homeostasis. Communication between
receptors and effectors can be via
NERVE CELLS or HORMONES.
Hormones are secreted from GLANDS,
which are part of the endocrine system.
They travel in the blood and act on
specific body parts to produce a
response to bring the body back to a
normal condition.
You need to say what the word
means and why it is important.
Draft - subject to review
1.
Explain the meaning of the term
homeostasis. (2 marks)
levels
too low
5
biology
Thermoregulation
You need to know how your body REGULATES its temperature. The chemical reactions in
your body work best at 37°C which is normal body temperature.
37o
Decrease in temperature
Body temperature
too low
Body temperature
too high
Normal body
temperature
Body’s response to cold
Body’s response to heat
Here are three ways your body responds to
regulate a FALL in temperature:
Here are three ways your body responds to
regulate a RISE in temperature:
2
VASOCONSTRICTION –blood vessels
narrow, taking blood away from the
skin surface to reduce heat loss to
the environment.
OWERING BODY HAIR – this
1 Lincreases
heat loss from the skin.
VASODILATION – blood vessels close
2 to the skin surface widen so blood
T
RAISING BODY HAIR – goosebumps
help raise body hair which traps heat
on the surface of the skin.
AF
1
D
R
HIVERING – muscle contraction
3 Scauses
an increase in body heat.
Explain why a person’s face can go red when
they get hot. (2 marks)
When you get hot your blood vessels
dilate. This means that blood is brought
closer to the surface of the skin. This can
make your skin appear red.
Draft - subject to review
6
Increase in temperature
is brought closer to the skin surface
and excess body heat is lost to the
environment.
– evaporation of sweat on
3 StheWEATING
skin causes heat to be lost.
Detecting temperature
change
Your body has two ways of telling if it is
too hot or too cold:
RECEPTORS in the SKIN detect
changes in your skin temperature.
Receptors in your BRAIN detect
changes in your BLOOD temperature.
When this chef enters a walk-in freezer her body temperature falls.
Explain two ways her body responds to regulate this fall in
temperature.
(4 marks)
d to write down
The question says explain. You nee
d and describe how
two different responses to the col
y temperature.
each process helps to increase bod