Lab Background Reading

Cell Structure and Function

  • Cell Membrane

    • Enclosed by a phospholipid bilayer.

    • Phospholipids consist of:

      • Hydrophilic heads facing inside and outside of the cell (interacting with water).

      • Hydrophobic tails facing inward (away from water).

    • Membrane controls entry and exit of materials:

      • Inflow: glucose, amino acids.

      • Outflow: waste products (e.g., carbon dioxide).

    • Proteins embedded in the membrane act as doorways for specific substances.

      • Example proteins include:

        • Aquaporins for water.

        • Transport proteins for glucose and amino acids.

Tissues, Organs, and Organ Systems

  • Cells organized into:

    • Tissues: groups of similar cells serving a common function.

      • Example: Muscle tissue in the bladder.

    • Organs: body parts with two or more tissues working together.

      • Examples: Brain, heart, stomach, kidneys, bladder.

    • Organ Systems: multiple organs that cooperate for a major body function.

      • Example: Excretory system (kidneys, bladder, ureters).

Relationship Between Structure and Function

  • Structure relates to function in tissues, organs, organ systems.

  • Example: Human Excretory System.

Importance of Water Balance in the Body

  • Osmoregulation: control of water levels and mineral salts in blood.

    • Kidneys help regulate this balance.

    • Body cells require a stable internal environment regarding water and solute balance.

  • Osmosis: movement of water in relation to solute concentration.

    • Risks:

      • Cells shrivel if losing too much water.

      • Cells burst if gaining too much water.

  • Kidneys filter excess water and manage reabsorption.

Organs of Excretion in Humans

  • Skin: Excretes water, ions, urea via sweat.

  • Lungs: Exhale water vapor and excess carbon dioxide.

  • Kidneys: Primary focus of the excretory system.

    • Remove excess water, salts, and urea (a by-product of protein breakdown).

Kidney Function

  • Blood Filtering:

    • Blood enters kidneys via the renal artery.

    • High-pressure filtration removes small molecules (urea, water, ions, glucose).

    • Large molecules (proteins, cells) remain in blood.

  • Selective Reabsorption:

    • Useful materials reabsorbed (glucose, required water, ions).

    • Purified blood returns via renal vein.

  • Urinary Pathway: Urine travels from kidneys to bladder through ureters.

Urine Composition

  • Main Components: Water, urea, ions.

  • Role of Nephrons: Filtering units responsible for urine formation and maintaining water balance.

Process of Filtration in Nephrons

  • Stage 1 - Filtration: Blood filtered through capillaries in nephron at high pressure.

  • Stage 2 - Selective Reabsorption:

    • Body reabsorbs needed molecules while wasting unneeded ones.

    • Reabsorbs:

      • All glucose

      • Required water

      • Required ions

  • Stage 3 - Formation of Urine: Waste products (urea, excess water, ions) progress to bladder as urine.

Hormonal Regulation of Water Balance

  • ADH (Anti-Diuretic Hormone):

    • Release controlled via hypothalamus responses to blood water level.

    • In lower water levels: Increased ADH leads to more water reabsorption in kidneys.

    • In higher water levels: Decreased ADH results in less reabsorbed water and production of dilute urine.

Negative Feedback Mechanism

  • Constant adjustment of water levels through drinking, sweating, excreting.

  • Goal: Maintain stable blood plasma concentration.

Effects of Excessive Water Intake

  • Possible severe consequences including:

    • Death by Water Intoxication: Disruption of ion balance, especially sodium.

    • Case studies: Show the dangers of excessive water consumption impacting the kidney’s function.

  • Environmental Impact on Osmoregulation:

    • Road salt pollution affects freshwater organisms' osmoregulatory capability, impacting amphibians significantly.