lecture 3

Neuron Structure and Muscle Cells

• Neurons: Specialized cells that consist of axons and dendrites to interact with other cells.

• Muscle Cells:

  • The number of muscle cells remains constant from birth; they do not undergo mitosis.

  • Muscle cells can increase in size and strength (e.g., bodybuilders) but not in number.

Basic Structure of Cells

• Discussion on the basic structure of the cell membrane.

Cell Membrane

• Unit Membrane: Composed of two layers of phospholipids.

  • Phospholipids: Main component; there are three types of fats in the body: neutral fats, cholesterol, and phospholipids.

  • Each cell in the body has two layers of phospholipids with proteins interspersed.

Types of Proteins in Cell Membrane

1. Structural Proteins:

   • Provide strength to the membrane, similar to rebar in concrete.

2. Receptor Proteins:

   • Bind with specific hormones or chemicals (e.g., follicle stimulating hormone (FSH) binds to ovaries and testes).

   • Example: Prolactin assists lactation; testosterone works on muscle cells.

3. Transport Proteins:

   • Facilitate the entry and exit of substances across the cell membrane.

   • Insulin works by activating transport proteins to carry glucose into cells (active transport).

4. MHC Proteins (Major Histocompatibility Complex):

   • Determine individual uniqueness based on body’s DNA; crucial for organ transplantation compatibility.

Functions of Cell Membrane

• Shape: Surrounds and gives shape to the cell.

• Regulation: Controls what enters and exits the cell, primarily water.

Osmosis

• Definition: Movement of water through a semipermeable membrane from an area of lower solute concentration to higher solute concentration.

• Solute vs. Solvent:

  • Solute: Substance dissolved in a solution (e.g., salt).

  • Solvent: Substance that dissolves the solute (e.g., water).

Types of Solutions

1. Isotonic:

   • Equal concentrations of solute both inside and outside of the cell.

2. Hypotonic:

   • Lower concentration of solute outside the cell compared to inside.

   • Water enters the cell, potentially causing it to swell.

3. Hypertonic:

   • Higher concentration of solute outside the cell compared to inside.

   • Water leaves the cell, causing it to shrink (crenation).

Osmotic Shock

• Definition: Gain or loss of water by a cell.

  • Reversible Osmotic Shock: Cell can recover/regain normal state after water fluctuation.

  • Irreversible Osmotic Shock: Cell cannot regain normal state after water fluctuation.

Fluid and Electrolyte Balance in the Body

• Importance of fluid balance in various body processes, including blood pressure and temperature regulation.

• Water aids in a large number of cellular chemical reactions.

Applications in Medicine

• IV solutions must match body’s saline levels to prevent osmotic shock in patients (e.g., using saline instead of pure water).

• Hemolysis: Destruction of red blood cells when placed in hypotonic solutions.

• Understanding osmosis is crucial in medical settings for treating fluid imbalances.

Illustrative Examples to Reinforce Concepts

• using examples of temperature control:

  • Water’s high specific heat allows it to store and release heat without significant temperature change.

• Behavioral implications of osmosis in aquatic beings:

  • E.g., salmon adapting between fresh and saltwater environments.

Recap and Importance for Future Learning

• The topics discussed are foundational for understanding cellular processes, physiological functions, and medical applications.

• Prepare to recognize and apply these concepts in clinical and physiological contexts.