Biology 1012: Lecture Outline for Chapter 42:

Topics:

I. Challenges to Water and Electrolyte Balance in Different Environments

II.  Water and Electrolyte Balance in Aquatic Animals

III.  Water and Electrolyte Balance in Terrestrial Insects

IV.  Water and Electrolyte Balance in Terrestrial Vertebrates

I. Challenges to Water and Electrolyte Balance in Different Environments

• How do animals live in environments of varying osmolarity (salt concentration)?
  
  • Osmoconformers

 

• Osmoregulators

 

• What are Electrolytes?

• How do Animals transport water and electrolytes?

•   Many Animals rely on Passive Transport.  How does it work?

   

  • Diffusion

   

  • Osmosis

•  When do animals use Active Transport?     

What mechanisms are used for Active Transport?

 

  Pumps

  Cotransporters

Symporters

Antiporters

How do Animals Osmoregulate?

Osmoregulation in Salt water

Marine Fish: Hypotonic to ocean

Problems:

Lose water by osmosis
Gain electrolytes by diffusion

Solutions

Drink water
Reduced amount of urine
Excrete electrolytes by active transport

Osmoregulation in Fresh Water

Freshwater Fish: Hypertonic to ocean

Problems:

gain water by osmosis
Loose electrolytes by diffusion

Solutions

Don’t Drink water
Lots of of urine
Add electrolytes by diet and active transport

Osmoregulation on Land

Land Animals

Problems:

lose water by evaporation and urine
Lose electrolytes by urine

Solutions

Drink water
regulate urine production
Add electrolytes by diet

II.  Water and Electrolyte Balance in Aquatic Animals

The Shark Rectal Gland as a Model

What does it do?

How does it work?

In Vitro studies (outside the body)

How can you confirm it still works when removed from the shark's body?

How does it concentrate electrolyter?

Facilitated by: Sodium/Potassium Pump (Na+/K+-ATPase)

Where is Na+/K+-ATPase located?

 

Diagram how this works on the model below.

 

Model of Salt Excretion in Rectal Gland.

Explain what is happening at each of the steps above.

1.

2.

3.

4.

 

 

Other Animals Use Processes Similar to Sharks

1.  How do Marine Birds excrete salt

 

 

2. How do fish move electrolytes against a concentration gradient?

 

 

Location of chloride cells varies:

Freshwater Fish:  On lamellae

Saltwater Fish:  Base of gill filaments

 

 

III.  Water and electrolyte balance in Terrestrial Insects

 

Insect Strategies:

 How do insects minimize Water loss?

 

 

Getting rid of waste nitrogenous wastes.

 

What types of Nitrogenous Wastes are produced by animals?

 

What type of nitrogenous waste do insects produce?   How does this help them conserve water?

 

 

Insect Excretory Systems:  Maintaining Homeostasis

 

Insects have Hemolymph instead of blood.  

 

How does the insect excretory system work?

 

Malphigian Tubules

 

 What is the mechanism for forming Pre Urine?

 

 

How does the Hindgut aid in maintaining homeostasis?

 

 

 

 

IV.  Water and Electrolyte Balance in Terrestrial Vertebrates

How do land dwelling animals regulate the osmolarity of their tissues?

Regulate water intake

 

Conserve water

 

Carefully control the excretion of water, electrolytes, and nitrogenous wastes.

 

 

The Structure of mammalian kidneys.

Nephron Structure

Glomerulus

Proximal Tubule

Loop of Henle

Distal Tubule

Collecting Duct

 

 

How does a kidney work?

1. Filtration - Glomerulus and Bowman's Capsule

 

2. Reabsorbtion: Proximal Tubule

3. Concentration: Loop of Henle

• Loops through a concentration gradient
  
• Descending Limb (impermeable to ions)
  
• H2O diffuses out
  
• Ascending Limb (impermeable to water)
  
• Lower part: Na+ and Cl- diffuse out
  Upper part: Na+ and Cl- actively transported out
  
• What happens to the water and salts that are pulled out of the loop of Henle?
  

4. Adjusting urine osmolarity: Distal Tubule and Collecting Duct

• Adjust final water and salt concentration of urine

• H2O, Na+ and Cl- reabsorbed.
  

 

How Much Urine do you make?

How is urine output adjusted?

Hormone regulated

Aldosterone (Adrenal Glands)

ADH (Antidiuretic hormone) (Brain)

 

Questions:

Nicotine stimulates ADH release, therefore the more you smoke, the ____ urine you will produce.

1. More
2. Less

You’ve noticed that your friend has to make many more trips to the bathroom when she drinks alcoholic beverages than when she drinks non-alcoholic drinks. This suggests that alcohol might _________ ADH release.

1.stimulate
2. inhibit
3. have no effect on