HOMEOSTASIS
1. Homeostasis in mammals
Homeostasis is the process of maintaining constant internal body conditions– important as it
ensures optimal conditions for enzyme action and cell function
Most homeostatic control mechanisms in organisms use negative feedback to maintain homeostatic
balance
Negative feedback control loops involve:
o A receptor (or sensor) – to detect a stimulus that is involved with a condition / physiological
factor
o A coordination system (nervous system and endocrine system) – to transfer
information between different parts of the body
o An effector (muscles and glands) – to carry out a response
Homeostasis in mammals relies on two different coordination systems to transfer information
between different parts of the body:
o Nervous system – information is transmitted as electrical impulses that travel
along neurones
o Endocrine system – information is transmitted as chemical
messengers called hormones that travel in the blood
1.1 Production of urea
Excess amino acid can’t be stored – transported to liver for deamination
the amino group is removed from each amino acid
o The amino group (-NH2) of an amino acid is removed, together with an extra hydrogen atom
to form ammonia (NH3) – highly soluble and toxic, can combine with water to form alkaline
ammonium hydroxide and alter blood pH, affect cell signalling
o Ammonia combines with carbon dioxide to for urea and water
o The remaining keto acid converted to pyruvate or Acetyl CoA that enter Krebs cycle to
be respired, be converted to glucose, or converted to glycogen / fat for storage
, 1.2 Structure of kidney
Renal artery – carries oxygenated blood containing urea and salts to kidneys
Renal vein – carries deoxygenated blood, that has urea and excess salts removed away from kidneys
Kidney – regulates water content of blood and filters blood. Ureter – carries urine from kidney to
bladder. Bladder – store urine. Urethra – releases urine outside the body
Fibrous capsule – tough outside layer of kidney
Nephrons – tiny tubes, that is responsible for the formation of urine
Each glomerulus is supplied with blood by an afferent arteriole (carries blood from renal artery). The
capillaries of the glomerulus rejoin to form an efferent arteriole (flows into the renal vein)
1. Homeostasis in mammals
Homeostasis is the process of maintaining constant internal body conditions– important as it
ensures optimal conditions for enzyme action and cell function
Most homeostatic control mechanisms in organisms use negative feedback to maintain homeostatic
balance
Negative feedback control loops involve:
o A receptor (or sensor) – to detect a stimulus that is involved with a condition / physiological
factor
o A coordination system (nervous system and endocrine system) – to transfer
information between different parts of the body
o An effector (muscles and glands) – to carry out a response
Homeostasis in mammals relies on two different coordination systems to transfer information
between different parts of the body:
o Nervous system – information is transmitted as electrical impulses that travel
along neurones
o Endocrine system – information is transmitted as chemical
messengers called hormones that travel in the blood
1.1 Production of urea
Excess amino acid can’t be stored – transported to liver for deamination
the amino group is removed from each amino acid
o The amino group (-NH2) of an amino acid is removed, together with an extra hydrogen atom
to form ammonia (NH3) – highly soluble and toxic, can combine with water to form alkaline
ammonium hydroxide and alter blood pH, affect cell signalling
o Ammonia combines with carbon dioxide to for urea and water
o The remaining keto acid converted to pyruvate or Acetyl CoA that enter Krebs cycle to
be respired, be converted to glucose, or converted to glycogen / fat for storage
, 1.2 Structure of kidney
Renal artery – carries oxygenated blood containing urea and salts to kidneys
Renal vein – carries deoxygenated blood, that has urea and excess salts removed away from kidneys
Kidney – regulates water content of blood and filters blood. Ureter – carries urine from kidney to
bladder. Bladder – store urine. Urethra – releases urine outside the body
Fibrous capsule – tough outside layer of kidney
Nephrons – tiny tubes, that is responsible for the formation of urine
Each glomerulus is supplied with blood by an afferent arteriole (carries blood from renal artery). The
capillaries of the glomerulus rejoin to form an efferent arteriole (flows into the renal vein)
