lecture 6: osmolarity and excretory system

What are the four main function of excretory systems?

1.Regulate volume of fluid in the body

2.Regulate overall osmolarity

3.Regulate individual solute (Ca2+, H+, Na+, glucose) concentrations

4.Eliminate nitrogenous wastes

Define osmoregulation 

The regulation of the chemical composition of body fluids

Define diffusion 

Movement of solutes down their concentration gradient 

Define osmosis 

Movement of water down its concentration gradient 

 Define osmolarity

The sum of concentrations of all solutes

Define isosmotic cell

Solute concentration is equal inside and outside of cell

Define hypoosmotic cell

Solute concentration is greater outside the cell, causing water to diffuse out and cell to shrink

Define hyperosmotic cell

Solute concentration is greater inside cell, causing water to diffuse in and cell to swell

Whats the diff between osmoregulators and osmoconformers

Osmoconformers match their internal solute concentration to their environment, saving energy but limiting their habitat. Osmoregulators actively maintain stable internal levels, requiring significant energy but allowing survival across diverse environments

Freshwater fish are generally _______ to their environment

hyperosmotic (Solute concentration is greater inside cell, causing water to diffuse in and cell to swell).

how do freshwater fish regulate osmolarity

freshwater fish are generally hyperosmotic.
Problem: They have enough water but not enough salt, so they must conserve ions and expel excess water. 

1. Strategies: 

   1. Do not drink excess water 

   2. Produce large volutes of dilute urine 

   3. Replenish ions through eating and reabsorption

   4.  Actively taking in salt through specialized gill cells

Saltwater fish are generally ____ to their environment. 

hypoosmotic (Solute concentration is greater outside the cell, causing water to diffuse out and cell to shrink)

how do saltwater fish regulate osmolarity

Saltwater fish are generally hypoosmotic to their environment

1. Problem: They lose water passively and must conserve it while expelling salt. 

   1. Strategies:

      1. Drink a lot of seawater 

      2. Eliminate excess ions via large intestine and kidney 

      3. Reabsorb as much water as possible in the kidneys 

      4. Actively excrete excess salt through specialized gill cells

      5. Produce small volumes of urine to conserve water

How do terrestrial animals regulate osmolarity?  

1. Body coverings to reduce water loss 

2. Behavioral changes: being active ar night or eating moist foods to conserve water

3. Metabolic water: water produced as a byproduct of metabolism is an important water source for some species 

4. Reabsorption in the kidneys: specialized kidneys aid in water retention 

Define what the excretory system is: 

Filters extracellular fluid to remove metabolic waste products.

Define filtrate 

Fluid squeezed out of blood from capillaries (glomerulus) and into the kidneys’ filtering units (nephrons- specically bowman’s capsule)

Define nephron 

Main function unit of the kidney, consisting of a renal tubules and surrounding blood vessels 

define glomerulus

a ball of capilarries where blood filtration occurs

define bowman’s capsule

A cuplike sac that has specialized cells that filter blood 

define proximal tube

filtrate passes through here and absorption of nutrients occurs

define distal tube

no nutrients absorbed, last stop until aquaporins and collecting duct

describe the role of the hoop of henle

sets up concentration gradient that helps collecting duct absorb or not absorb water. contributes to U/P ratio

What is U/P ratio 

Ratio of urine osmolarity to blood plasma osmolarity 

Describe the 3 U/P ratios

1. Dilute urine (U/P < 1): urine is More dilute than plasma. 

   1. Organism excretes more water than solutes. 

   2. Increases extracellular fluid osmolarity 

2. Normal urine production (U/P =1): urine and plasma has equal osmolarity

3. Concentrated urine production (U/P>1): urine is more concentrated than plasma. 

   1. Organisms retains more water

   2. Decreases extracellular fluid

where does filtration occur in the nephron

glomerulus and bownman’s capsule

where does reabsorption occur in the nephron

proximal renal tubule

where does secretion occur

distal tubule and collecting duct

what is diuresis. what does ADP production and amount. of open aquaporins look like

no h20 in reabsorbed in collecting duct. well hydrates, clear urine. low adp production, few aquporines opened

what is antidiuresis

h20 is reabosrbed (drawn out of urine). body is dehydrated. increased ADP production, many auaporins opened

All vertebrates can produce urine less concentrated than or equal to the extracellular fluid, however only _____ and ____ can produce urine more concentrated than the extracellular fluid allowing them to dilute their extracellular fluid. 

mammals;bird

How is the volume and the osmolarity of excreted urine regulated in amphibians? What is

the role of ADH in this process? How is this similar to and different from the process in