Homeostasis and Excretion.txt

Homeostasis is the maintenance of a constant internal environment within the body

Temperature - increased by shivering, lost by sweating

Water content - increased by drinking, lost by sweating and urine

Blood glucose - increased and decreased by hormones

Homeostasis is necessary if an organism is to be independent of its surroundings and if its metabolism is to function efficiently

Hairs flatten, sweat evaporates, erector muscle relaxes, blood capillaries dilate

Nerves in skin, blood flowing in brain

Exercise, absorbing heat

• Move into shade
• Wear less clothing
• Drink cool water

• Hairs are upright
• Erector muscle contracts
• Blood capillaries contract

Heat loss from body to surroundings

Exercise, shivering to increase respiration, seek heat source

Regulates temperature, excretory organ sweat (urea water salt)

Lungs, control levels of co2, oxygen, water vapour

Kidneys, control urea, water and salt levels

Pancreas and liver, control blood sugar levels

Excretion is the removal of waste products of metabolism from the body

• Kidneys - urea, water and salt
• Lungs - co2 and water vapour
• Skin - sweat (urea water and salt)

Brings oxygenated blood to pelvic trgion

Blood supply to the kidney

Filters the blood, reabsorbs any useful substances

Transfers urine from kidney to bladder

Stores urine

Controls opening and closing of bladder (release of urine)

Passes urine out of the body

Passes any reabsorbs substances from kidneys back to bloodstream

Returns deoxygenated blood to the heart

• Urea is produced in the liver
• Amino acids are broken down to make urea
• Process is called deamination

Outer cortex

Small molecules glucose, amino acids, water, salts, urea filter out

Blood vessels reabsorb back useful nutrients from tubes

Urea excess salts and water continue down onto bladder

Red blood cells, white blood cells, lipids and proteins

Renal artery divided into GLOMERULUS at top

Bowmans capsule surrounds each. Smaller molecules are forced under pressure out of plasma into lumen of capsule, forming GLOMERULAR FILTRATE

All but large proteins and blood cells are filtered

Proximal convoluted tubule, glucose, amino acids, salts and water back into blood

Food molecules by active transport

Water by osmosis from loop of henle

Urea, salt and water pass as urine into bladder

Kidney regulates amount of water in body by regulating amount of urine produced

Anti-diuretic hormone

Controls whether distal tubule and collecting ducts reabsorb water or not

ADH is secreted from pituitary gland

More water reabsorbed only small volume of urine is produced

Turns of ADH production

Large volume of urine