Homeostasis

Pusat Persediaan Sains dan Teknologi

UMS

What is homeostasis

• Maintenance of a constant environment by the body.

• Body works best when it has suitable/optimum/correct;

• 1) Temperature• 2) Water level• 3) Glucose level

Body Temperature

• Mammal: constant body temp.• Human: 370C• Animals with a large surface area compared to

their volume will lose heat faster than animals with a small surface area.

• The temperature is monitored by central thermoreceptors in the hypothalamus (Your Brain!)

How to be cool?

How to be cool?

1) Sweating• When your body is hot, sweat glands are

stimulated to release sweat.• The liquid sweat turns into a gas (it

evaporates)• To do this, it needs heat.• It gets that heat from your skin.• As your skin loses heat, it cools down.

How to be cool?

2) Vasodilation• Your blood carries most of the heat energy

around your body.• There are capillaries underneath your skin that

can be filled with blood if you get too hot.• This brings the blood closer to the surface of

the skin so more heat can be lost.• This is why you look red when you are hot!

How to be hot (read: warm)?

1) Vasoconstriction• This is the opposite of vasodilation• The capillaries underneath your skin get

constricted (shut off).• This takes the blood away from the surface of

the skin so less heat can be lost.

How to be hot (read: warm)?

2) Piloerection• This is when the hairs on your skin “stand

up” .• It is sometimes called “goose bumps” or

“chicken skin”!• The hairs trap a layer of air next to the skin

which is then warmed by the body heat• The air becomes an insulating layer.

Goosebumps

How to be hot (read: warm)?

• 3) Shivering• Muscle will contract and relax. Producing

metabolic heat.

Blood Sugar

• Our body need sugar as fuel. • Blood sugar is regulated by 2 important

hormones;• 1) Glucagon• 2) Insulin• Both excreted by pancreas

How to be sweet (and a sweetheart)?

• If there is not enough sugar in blood, glycogen will be converted to glucose by glucagon.

• If there is too much sugar in blood, insulin converts excess sugar to glycogen

• Location: Liver.

Diabetes

• Diabetes mellitus: Metabolic disorder, not enough insulin.

• Type 1: No insulin is produced• Occurs when a person (usually teen) unable to

produce insulin due to disease (genetic)• Type 2: Lack of insulin• Occurs when pancreas cells fail to produce enough

insulin due to aging (40 and above)• High blood concentration is called hyperglycaemia.

Water level

• Kidneys control water level• Urea is a waste product that is made when the

LIVER breaks down proteins that are not needed by the body.

Inside Kidney

How to clean (your blood)?

• 1) Filtration• The blood is filtered in glomerulus• All the small particle run into tubule• The kidney tubule contains lots of glucose,

salt, water, urea.

How to clean (your blood)?

• 2) Absorption• The sugar is reabsorbed back to capillary and

will be used in respiration• Then water and ions too will be reabsorbed,

depend on the demand by the body. • Concentrated urine vs. Dilute urine

How to clean (your blood)?

• 3) Excretion• Everything that is left in the kidney tubule is

waste:• All the urea• Excess water• Store in bladder later excreted through

urethra. Called urine.

What happen if your kidneys fail?