Water Balance Flashcards
Homeostasis for water balance 3 points:
- all life depends on aqueous environment
- Animals must maintain water and electrolyte balance in different environments
- Balance: depends on intake and removal
Water and solutes are linked:
- osmolarity controls water flow
- Osmolarity: concentration of solutes in a solution (e.g ions, sugar, urea)
- Precise concentration of ions (electrolytes) required
Jellyfishes…
- Jelly fish is a osmoconfromer
- Most vertebrates and terrestrial invertebrates are osmoregulatory
Fish in salt water osmolarity in…
Gill tissue?
Seawater?
Gill tissue: lower osmolarity
Seawater: higher osmolarity
Urine has low water but some salt
Fish: Fresh water osmolarity in…
Gill tissue?
Freshwater?
Gill tissue: higher osmolarity
Freshwater: lower osmolarity
Metabolic waste is excreted into the surrounding water
Urine has low salt but large volumes of water
What do the Seawater/gill tissue gain/lose in fish in seawater
Gill tissues: Gain electrolytes by diffusion
Seawater: Lose electrolytes by active transport
What do the seawater/gill tissue gain/lose in fish in fresh water
Gill tissues: Gain electrolytes by active transport
Freshwater: Lose electrolytes by diffusion
Sharks are…
- are osmoconformers
Shark tissues have…
- Their tissues have a similar osmolarity as the surrounding seawater
- Relatively low salt concentration; high osmolarity due to high concentration of urea
- Salt is removed through the rectal gland
Bony fishes (salmon or sea bass) are…
- are osmoregulators
Bony fishe tissues maintains..
- Their tissues maintains lower osmolarity as the surrounding seawater
- Salt is removed by the same mechanism through chloride cells in their gills
The desert locust must conserve what?
- Locust must conserve water: must minimize water loss through the cuticle, as well as through breathing, or excretion
Desert locust parts and explain:
- Cuticle is very hydrophobic
- Organs are bathe in hemolymph: “open circulatory system
- Alimentary canal: fore, mid and hind gut
- Spiracle: opening that connects to tracheal system. Spiracles can be closed to prevent water loss
- Malpighian tubules filter hemolymph, releases filtrate into hind gut, water and minerals are reabsorbed
What are the 4 Common mechanisms
- Ions pumps build up osmotic pressure (active transport); water follows by osmosis
- Filtration is not very selective (size-based)
- Selective ion channels allow re-absorption
- Reabsorption is tightly regulated (response to hydration status)
How is electrolyte balance maintained?
Ions are moved either by active transport or passive transport (ion pumps, co-transporters, ion channels)
How is water balance maintained?
Water movements is driven by osmosis (differences in the osmolarity). Water movement is facilitated through some proteins (aquaporins) that make the membrane more permeable for water
How is nitrogenous waste eliminated?
Removal strategy depends on water availability.
Ammonia: easy to make, but is toxic and requires lots of water
Uric acid: most energy consuming synthesis; minimal water (solid waste)
Urea: some energy required; water soluble but harmless; contributes to osmolarity
Terrestrial vertebrates: osmoregulation through the kidney
- The kidney is composed of numerous nephrons
- A nephron is a tubular system that starts in the cortex and ends in the medulla
Nephron parts
Bowman’s capsule
Distal and proximal tube
Loop of henle
Loop of Henle parts
Descending/ascending limb
Has thin and thick ascending limb
Loop of Henle…
- extends from the cortex into the medulla and goes back up into the cortex
- Important feature: it has a gradient in osmolarity
Aldosterone is… and explain what it does
- is a steroid hormone
- released from the adrenal gland: lat. ad renam next to the kidney
- central role in the regulation of blood
- Na+ and K+ levels (→ of blood pressure)
Antidiuretic hormone (ADH) is also called… and is…
- also called vasopressin
- is a peptide hormone
- released from pituitary gland
- controls water retention
Diabetes Insipidus
Pituitary gland produces insufficient ADH, hence the kidneys make a lot of urine
