Lecture 26/Osmoregulation

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c. Regulation of blood composition (pH, ions)
- Na+, H+, K+, Mg++, Ca++, Cl-, HCO3-

There may be conflicts between these. For example, between the need to conserve H₂O and to use it to excrete wastes.

The kidney also performs 2 additional functions:
d. Retention of nutrients such as glucose and amino acids

e. Secretion of hormones

(e.g. erythropoietin which is required for the formation of RBCs).

The first step in the production of urine is the filtrationof small molecules (including water, sugar, salts and wastes) out of the capillaries under pressure - this is nonselective. Some substanes are then reabsorbedfrom the fluid by active transport, while others are added it by secretion. (see 44.14)

6. Juxtamedullary nephron
Endotherms, mammals and birds, contain a specialized structure, the juxtamedullary nephronthat greatly increases the ability of the kidney to concentrate urine and thus conserve water. The structure and function of the human kidney will be the focus of our discussion next time.

(Campbell, 4th, pp.879-898, p.150)
Review:
1. Campbell, pp 891-892, Self-quiz 1-4, 7,8, Challenge Q 1,2
2. What challenges await a salmon as it proceeds from the ocean into the rivers and streams to spawn? What body organs will have to be modifed to meet those challenges?
3. What do you predict will happen to the rate of the contractile vacuole of a Paramecium (pumping out water) if salt is gradually added to the water surrounding it?

4. Could a human marooned at sea on a life raft survive by drinking sea water? How about by eating captured fish? For each, why or why not?


			c. Regulation of blood composition (pH, ions) - Na+, H+, K+, Mg++, Ca++, Cl-, HCO3-
		There may be conflicts between these. For example, between the need to conserve H₂O and to use it to excrete wastes. The kidney also performs 2 additional functions: d. Retention of nutrients such as glucose and amino acids
			e. Secretion of hormones
		(e.g. erythropoietin which is required for the formation of RBCs). The first step in the production of urine is the filtrationof small molecules (including water, sugar, salts and wastes) out of the capillaries under pressure - this is nonselective. Some substanes are then reabsorbedfrom the fluid by active transport, while others are added it by secretion. (see 44.14) 6. Juxtamedullary nephron Endotherms, mammals and birds, contain a specialized structure, the juxtamedullary nephronthat greatly increases the ability of the kidney to concentrate urine and thus conserve water. The structure and function of the human kidney will be the focus of our discussion next time. (Campbell, 4th, pp.879-898, p.150) Review: 1. Campbell, pp 891-892, Self-quiz 1-4, 7,8, Challenge Q 1,2 2. What challenges await a salmon as it proceeds from the ocean into the rivers and streams to spawn? What body organs will have to be modifed to meet those challenges? 3. What do you predict will happen to the rate of the contractile vacuole of a Paramecium (pumping out water) if salt is gradually added to the water surrounding it? 4. Could a human marooned at sea on a life raft survive by drinking sea water? How about by eating captured fish? For each, why or why not?