Key Points From Last Lecture

Homeostasis is made possible by physiological negative feedback loops

Osmoregulation: Evolutionary trend towards greater control of osmoregulation, waste secretion

Outline/Key Points:

Kidneys filter blood, regulate osmolarity (two functions)

- Human kidneys

- Concentration gradient/kidney function

Water/salt needs of different animals are different

- Too much water/too little salt

- Too little water/too much salt

The Kidney Filters Wastes from Blood, and is the Effecter of Osmoregulation

Fig 32_13

The Kidney performs two functions - osmoregulation and recovery of valuable materials

Low salt concentration - No water crosses tubule

High salt concentration - allows passive diffusion of water out of waste - birds and mammals

Active recovery of valuable materials

The Kidney is an Effecter in a Negative Feedback Loop Allowing Osmoregulation

Pg 626

Organisms Face Different Challenges to Osmoregulation Based on their Environment

Fig 32_10

Either too little or too much water/salt

Marine environments are analogous to deserts

In freshwater environments salts and minerals are limited

Three Types of Nitrogenous Waste

Fig 32_14

Type of waste and the amount of dilutions follows phylogeny

Too Much Water/Too Little Salt

Bodies are saltier than environment = water moves in salt moves out

Fig 32_8

Too Little Water/Too Much Salt

Environment is saltier than body = water moves out salt moves in

Fig 32_8

Additional Physiological Adaptations Involved in Osmoregulation

Fig 32_9

Fig 32_12

Urea is deteoxified, used to raise osmolarity of blood which prevents water loss

Salt in diet, specialized organ to eliminate salt

Elasmobranch (marine) Marine bird