Homeostasis is the maintenance of a constant internal environment
Keeping warm
1. Vasoconstriction- blood vessels
_______ and move away from
______ of skin
2. Hairs on skin become erect which
trap ______ which is an ________
3. Shivering- muscles moving rapidly
which generates heat by ________.
4. Thermoregulatory centre in brain
sends messages e.g. to put a jumper
on.
Cooling down
1. Vasodilation- blood vessels _______
and move towards ______ of skin
2. Hairs on skin lay flat.
3. Sweating- water _______ from the
surface of the skin using heat
energy from the surface of the skin
therefore cooling us down.
4. Thermoregulatory centre in brain
sends messages e.g. have a cold
drink
Can you explain why?
1. Imagine you have just walked out of the shower. Why do you feel chilly when you walk
from the bathroom to your bedroom?
2. What 3 ways can we get water into the body? 1.__________ 2.__________ 3._______
3. Why does a person who is dehydrated sweat less?
Explain these pictures:
Using the picture above explain:
1. What is filtered out of the blood and
how?__________________________
_______________________________
______________________________
2. What stays in the blood and
why?______________________________
__________________________________
3. What is completely reabsorbed into the
blood in healthy kidneys and
how?_____________________________
__________________________________
__________________________________
4. What else is reabsorbed and in what
amounts?__________________________
__________________________________
__________________________________
Active transport of glucose
Glucose is reabsorbed back into the
blood by active transport.
Active transport is special type of
diffusion where substances move from a
lower concentration to a higher
concentration (__________
concentration gradient). This process
uses ________ from respiration.
Compare osmosis, diffusion and active transport:
Kidney failure can be treated by either having dialysis of a kidney transplant
•
•
In dialysis the persons blood
flows between partially
permeable membranes. The
dialysis fluid contains same
concentration of useful
substances as the blood- so
glucose and mineral ions are not
lost. Urea diffuses out of blood.
Carried out at regular intervals
Summary of kidney function:
A healthy kidney produces urine by:
■ first filtering the blood
■ reabsorbing all the sugar
■ reabsorbing the dissolved ions needed by the body
■ reabsorbing as much water as the body needs
■ releasing urea, excess ions and water as urine.
Kidney transplants replace a diseased kidney with a normal one. The donor
kidney may be rejected by immune system because the antigens on the cells of
the donor (proteins on surface of cells) are different to the recipients therefore
the recipients antibodies may attack them as they appear foreign
Disadvantages of transplants:
any major surgery carries
some risk
the kidney may be rejected by
the body of the patient
a precise match of tissue type
is needed
there is a severe shortage of
donors
Advantage- can live a normal
life if all goes well
Disadvantages of dialysis:
they are expensive
the patient must have his or
her blood connected to the
machine for several hours
every week
patients must follow a very
rigid diet to avoid
complications
they only work for a limited
time for a patient
When blood glucose is high (after eating a meal)
Blood glucose is
controlled by
the pancreas
Insulin also
stimulates the
production of
glycogen- a
store of
glucose in the
liver
When blood glucose is low (missed lunch)
Glycogen is a
long chain of
glucose
molecules
Pancreas
makes another
hormone,
Glucagoncausing
glycogen to be
converted
back into
glucose to
raise blood
glucose levels