W1L2 Osmosis and diffusion

Principles of homeostasis & physiological regulation

Explain the distribution of fluid compartments inside the human body, including intracellular and extracellular fluids

The human body's water is distributed into two main fluid compartments: intracellular fluid (ICF) and extracellular fluid (ECF).

~ 2/3 of the body's water is contained within cells (ICF),

while the remaining 1/3 is outside cells (ECF). The ECF is further divided into interstitial fluid (surrounding cells) and plasma (the fluid component of blood).

Intrcellular fluid (ICF) refers to the fluid inside the cell, cytoplasm 

Compare and contrast the ionic composition of intracellular and extracellular fluids

Intracellular and extracellular fluids have distinct ionic compositions.

Extracellular fluid (ECF) is high in sodium (Na⁺) and chloride ions (Cl^-), low in Potassium(K⁺)

while intracellular fluid (ICF) is high in potassium (K⁺), low in sodium (Na⁺ ) and lots of protein

Proteins are also a significant component of both, but their concentrations differ. 

Describe the role of barriers (cell membrane and capillary wall)

Both the cell membrane and the capillary wall act as barriers, controlling the movement of substances in and out of cells and tissues.

• The cell membrane, a phospholipid bilayer, regulates what enters and exits the cell.

• separates the interstitial fluid (type of ECF) from the Intracellular Fluid (ICF)

• Capillary wall, controls the movement of substances between the bloodstream and surrounding tissues

• Capillary wall separates the plasma (type of ECF) from the interstitial fluid (type of ECF)

Apply the concepts of concentration gradients to predict the direction of ion movement between fluid compartments

Ions move across fluid compartments based on their concentration gradients, tending to move from areas of high concentration to areas of low concentration.

This movement can be influenced by other factors like electrical charge differences (electrochemical gradient) and membrane permeability. 

Differentiate between osmosis and diffusion as passive transport processes

Both osmosis and diffusion are passive transport processes, meaning they don't require the cell to expend energy. However, they differ in what moves and the presence of a membrane.

Diffusion is the movement of any substance from a region of higher concentration to lower concentration,

while osmosis is the movement of water across a semipermeable membrane from a region of higher water concentration (lower solute concentration) to a region of lower water concentration (higher solute concentration). 

Explain the concept of concentration gradients and their role in driving diffusion and osmosis

Diffusion is the movement of particles dissolved (the solute) in the solution to even the distribution of that particle in the solution

Osmosis is the movement of water (the solvent) across a semi-permeable barrier to even the concentration of dissolved particles on either side of the barrier

A concentration gradient is the difference in concentration of a substance between two areas, which drives diffusion or osmosis.

refer to lecture slide 11-18

Predict the movement of solutes and solvents across semi-permeable membranes in various scenarios

In a semi-permeable membrane, solvents (like water) will move from an area of high solvent concentration (low solute concentration) to an area of low solvent concentration (high solute concentration) through osmosis, to equalize the concentration on both sides. [osmosis]

Solutes, on the other hand, will move down their concentration gradient, from high to low, if the membrane is permeable to them.[diffusion]

If the membrane is impermeable to a solute, it will not cross, but will still influence solvent movement via osmosis

Compare the physiological effects of administering different types of intravenous fluids

(e.g.,normal saline vs. dextrose).

Normal saline ( 1L 0.9% sodium chloride)

dextrose solution (1L 5% dextrose)

Normal saline ( 1L 0.9% sodium chloride) and

• NaCl cannot penetrate cellular membrane

• fluid volume increases by 1L (extracellular)

• Osmotic pressure falls, resists filtration

Dextrose solutions, particularly 5% dextrose, are often used for hypoglycemia

• dextrose is a sugar, can penetrate cellular membrane, absorbed rapidly and directly

• most of the water will enter cell, intravascular fluid osmolarity