Lecture 5 & 6 Flashcards
Define Homeostasis ?
is the maintenance of a stable internal environment for the preservation of the normal functioning of cells.
eg.) body temp etc
What are cells surrounded by ?
Surrounded by ECF
1.) Ionic comnposition
2.)Solute concentration of ECF
3.)Health of cells is critical for normal function
Homeostasis of the ECF is the job of excretatory system
Define the chemical composition of the body ?
Body water -60% total body weight
Define body water divsions ?
Body water contains many dissolved ions/substances in solution called fluid
-ECF
subdivided into the plasma and interstitial fluid
-ICF
Hydrates interstitial space /Intertitium
How do species maintains maintains homeostasis of its ECF ?
Its environment :salt/fresh water,terrestrial
Its lifestyle
What do animals depend on to maintain ?
Depnd on excretory system
-volume,concentration and composition of their ECF and to excrete wastes eg.)urine
-Such systems use filtration ,secretion,and reabsorption to regulate
1.)Osmolarity
2.)Ionic composition of ECF
Define Osmosis ?
Water moves from a region of high water concentration to one of lower water concentration
-in order to maintain a homeostatic balance
1.) Remove excess fluid and retain specific ions or solutes.
2.) Conserve fluids and excrete excess ions or solutes
3.) Excrete waste products of nitrogen metabolism output:urine
What does osmosis require ?
1.)A semi-permeable membrane permitting water ,but not solute movement
2.)A difference in the solute concentration ( on either side)
In all animal excretory system there is no active system
Can water molecules diffuse across cell menbranes ?
yes despite being a polar molecule
slow process most passes through aquaporins
What are water channels ?
aqua porins
possess pores allowing water to pass from one side of the membrane to the other
found in tissues which transport large volumes of water per day
eg.) tubules of the kidney
What is osmotic pressure ?
amount of pressure that needs to be applied to just stop this movement
Solutes will displace water
lowering the water concentration
How does water move ?
water moves from the solution with a lower osmotic pressure into thr solution with higher osmotic pressure
Define Molarity ?
concentration of a substance expressed in moles per litre of that solution
Whta is Vant Hoffs law ?
is dependent on the toal number of dissolved particles present in solution which is measured in osmoles
Define Osmolarity ?
the meaure of solute concentration defined as the no of osmoles per litre of solution
Define Osmolality ?
number of osmoles per kg of solution
Define hyposmotic ?
low osmotic pressure
Define isotmotic ?
One that has the same osmotic pressure as that of the cells
Solutions isomotic to cells are not always isotonic in the long run;osmolarity and tonicity are related