Homeostatic control
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How do we maintain homeostasis?
The kidneys continuously regulate the chemical composition of the blood
How do you molecules move passively?
Move from where there is high concentration to where they are less of them down a concentration gradient
Define water potential
Describe how the movement of water molecules in a solution exert pressure on a membrane
Explain osmosis
Water moves from a high water potential to lower water potential through a differentially permeable membrane
When is a hypertonic solution formed?
Lowering the water potential
How is the water potential lowered?
High concentration of sorts decreases the number of free water molecules
When is a hypotonic solution form?
Increasing the water potential of a solution
How is water potential increased?
Present of a lower concentration of solute in a solution of water – does not decrease the number free water molecules
Define an isotonic solution
Solutions on both sides of a membrane are the same and have the same number free water molecules
What is the water potential of pure water?
0
What happens when molecules move actively?
They combine with a carrier molecule and may move against the concentration gradient - need energy
Regulation of water content
• Osmoregulation • Hormone ADH
Define osmoregulation
Maintains the correct balance between the water and solid content of the body fluids
What is osmoregulation controlled by?
Kidney and skin
How do the cells function properly?
• Amount of water • Concentration of solutes
What does too little water cause?
Dehydration of the cells
What does too much water cause?
Cells to burst
What is the concentration of solutes in the sound is determined?
The osmolarity (osmotic pressure) of body fluids
Define osmolarity
The number of solid particles dissolved in 1 L of water
What happens when there is a greater concentration of solutes?
Greater the osmolarity and greater the tenancy forwarder to move in the strong solution – hypertonic
What percentage of the body is water is returned from the kidneys into the bloodstream?
99%
Where is most of the body is water reabsorbed from?
Proximal tubule Descending limb of loop of Henle
What does the kidney do when the fluid intake is low?
Conserves water - more concentrated urine
ADH
Antidiuretic hormone