the maintenance of a constant internal
environment
Homeothermic/endoithermic
animals can keep their
temperature almost constant
even though their environment
changes
Poikilothermic/exothermic animals cannot
Temperature Regulation
Top layer - epidermis
Cells in the epidermis were made in the
MALPIGHIAN LAYER Cellls ar constantly dividing
by mitosis. The new cells made move
towards the surface of the skin as they go
they die and fill up with a protein - KERATIN forming the CORNIFIED LAYER.
Some cells in the epidermis contain a dark brown pigment - MELANIN. This
absorbs harmful UV rays in sunlight
The epidermis folds in forming hair follicles. hairs are made of
keratin.
A SEBACEOUS GLAND opens from the side of each hair follicle
these make an oily substance called SEBUM which keeps the hair and
skin soft and supple
Bottom layer - dermis
Mostly made of connective tissue which contains elastic fibres and collagen fibres.
Sweat glands secrete sweat
Blood vessels and nerve endings
A layer of fat called ADIPOSE TISSUE below the
dermis helps insulate the body
The HYPOTHALAMUS is a part of the brain that coordinates the
activities of parts of the body that can bring about temperature
change
It acts as a thermostat and works by sending electrical
impulses along nerves to parts of the body
When hot.....
Hair lies flat
Vasodilation
Sweat
When cold......
Muscles work
Metabolism may increase
Hair stands up
Vasoconstriction
Negative Feedback
Where the hypothalamus stops the skin from acting to reduce or conserve heat
Control of blood glucose content
Cells need steady supply of glucose to carry out respiration
Carried out by the LIVER and PANCREAS
Scattered throughout the pancreas are ISLETS OF
LANGERHANS. They make two hormones called glucagon and
insulin
Insulin lowers blood sugar
the liver cells absorb glucose from the blood.
Some is used for respiration, but some is
stored in the liver as the insoluble
polysaccharide glycogen
Glucagon raises blood sugar
The liver cells break down glycogen into glucose
Excretion
Deamination
Kidneys -Ultra filtration
the removal of toxic materilals, the waste
products of metabolism andsubstances of
excess requirements