Homeostasis and Excretion

Homeostasis and Excretion
State that homeostasis involves maintaining the internal environment at a constant level or between narrow limits, including blood pH, oxygen and carbon dioxide concentrations, blood glucose, body temperature and water balance.
The internal environment consists of blood and tissue fluid. Cross reference with 2.3.3.
Explain that homeostasis involves monitoring levels of variables and correcting changes in levels by negative feedback mechanisms.
State that the nervous and the endocrine systems are both involved in homeostasis.
State that the nervous system consists of the central nervous system (CNS) and peripheral nerves and is composed of special cells called neurons that can carry electrical impulses rapidly.
No structural or functional division of the nervous system or details of impulse transmission or synapses are required.
Describe the control of body temperature including the transfer of heat in blood, the role of sweat glands and skin arterioles, and shivering.
State that the endocrine system consists of glands which release hormones that are transported in the blood.
The nature and action of hormones or direct comparisons between nerve and endocrine systems are not required.
Explain the control of blood glucose concentration, including the roles of glucagon, insulin and alpha and beta cells in the pancreatic islets.
Alpha islet cells produce glucagon; beta islet cells produce insulin. The regulation of glucose concentration within normal limits and the feedback mechanisms should be stressed. The effects of adrenaline are not required here.
Excretion
Define excretion.
Outline the need for excretion in all living organisms.
State that excretory products in plants include oxygen, and in animals they include carbon dioxide and nitrogenous compounds.
Discuss the relationship between the different nitrogenous waste products and habitat in mammals, birds and freshwater fish.
Surplus amino acids must be degraded to relatively harmless nitrogen-containing compounds. Freshwater fish can get rid of ammonia, although highly toxic (due to its basicity), because it can be diluted by the readily available water. Birds are unable to carry too much water so they excrete uric acid which is insoluble and expelled as a paste (most of the water is removed before excretion). Mammals excrete urea. Some desert mammals produce very concentrated urine (having a long loop of Henlé).
The Human Kidney
Outline the role of the kidney in excretion and the maintenance of water balance.
Draw the structure of the kidney.
Include the cortex, medulla, pelvis, ureter and renal blood vessels.
Draw the structure of a glomerulus and associated nephron.
Explain the process of ultrafiltration including blood pressure, fenestrated blood capillaries and basement membrane.
Define osmoregulation.
Osmoregulation -- the control of the water balance of the blood, tissue or cytoplasm of a living organism.
Explain the reabsorption of glucose, water and salts in the proximal convoluted tubule, including the roles of microvilli, osmosis and active transport.
Explain the roles of the loop of Henlé, medulla, collecting duct and ADH in maintaining the water balance of the blood.
Compare the composition of blood in the renal artery and renal vein, and compare the composition of glomerular filtrate and urine.
Outline the structure and action of kidney dialysis machines.