Introduction to Physiology

Introduction to Physiology

• Physiology is the study of the functions of living things, focusing specifically on how the human body works.

Levels of Organization of the Human Body

• The human body is organized in a hierarchy from cells to tissues, organs, organ systems, and finally, the organism.

• Cells are the basic structural and functional units of the body. They are microscopic in size and vary in shape and form.

• Tissues are groups of similar cells that perform a specific function.

• Organs are structures composed of different tissues working together for a specific function.

• Systems are groups of organs that work together to perform a larger function.

• Organisms are complete living beings, formed from the organization of cells, tissues, organs, and organ systems.

The Cell

• Cells are the smallest functional units of the body, composed of different structures.

• The cell membrane is a thin, flexible, and elastic structure. It separates the cell's contents from the surrounding environment, which is mostly extracellular fluid.

• The membrane is semi-permeable, controlling what substances enter and exit the cell.

Structure of the Cell

• The cell membrane, nucleus, and cytoplasm form the cell.

• Detailed structures within cell, like mitochondria, lysosomes, smooth and rough endoplasmic reticulum are also present.

The Cell Membrane

• Composed of three types of substances: proteins (55%), lipids (42% - phospholipids and cholesterol), and carbohydrates (3%).

• Has a phospholipid bilayer as its basic structure.

• Contains various proteins like channel proteins, carrier proteins, pumps, and receptors embedded in the bilayer, involved in cell function and transport.

Membrane Protein

• Membrane proteins are crucial for cell processes.
• Proteins are categorized into channels, carriers, pumps, receptors, and enzymes.
• Channel proteins allow the movement of small molecules across the membrane.
• Carrier proteins bind and transport specific molecules.
• Pumps move molecules against their concentration gradient, consuming energy.
• Receptors bind with signaling molecules to initiate cellular responses.
• Enzymes catalyze specific chemical reactions within or at the cell surface.

Membrane Transport

• Membrane transport is critical for the movement of substances across the cell membrane.
• Divided into passive (no energy required) and active (energy required) transport.

1- Passive Transport

• Simple diffusion: Movement of substances from high to low concentration. No energy or carrier needed. Examples include oxygen and carbon dioxide.

• Osmosis: Simple diffusion of water across a semi-permeable membrane. Water moves from high water concentration to low water concentration.

• Facilitated diffusion: Passive transport of substances through carrier proteins down a concentration gradient. This is used for large molecules that can't readily cross the membrane on their own, like glucose.

The Rate of Diffusion

• Rate of diffusion is affected by concentration gradient, surface area, temperature, solubility, molecular weight, and membrane thickness.

2- Active Transport

• Movement of substances against a concentration gradient, requiring energy (ATP).

• Primary active transport uses ATP directly to move substances. Examples include the sodium-potassium pump.

• Secondary active transport uses the electrochemical gradient created by primary active transport to move other substances. Absorption of glucose with sodium in the intestine is an example of secondary active transport.

3- Bulk Transport

• Movement of large molecules or groups of molecules into or out of a cell using endocytosis or exocytosis.

• Endocytosis: Uptake of materials from outside the cell into a vesicle.

• Exocytosis: Release of materials from inside the cell to the outside through a vesicle.

Homeostasis

• Is the maintenance of constant conditions in the internal environment of the body, critical for normal cell function.

• Different body systems work together to maintain homeostasis for factors like body temperature, water levels, and blood sugar.

Body Compartments

• The body is composed of proteins, fats, minerals, and water.
• Total Body Water (TBW): Approximately 60% of body weight in adult males, lower in women and obese individuals.
• Body Water is divided into intracellular fluid (inside cells) and extracellular fluid (outside cells).
• Extracellular fluid is further divided into intravascular fluid (in blood vessels) and interstitial fluid (surrounding cells).

Significance of Body Fluids

• Body fluids are crucial for various functions, including transport, reactions, and temperature regulation. .

Explore the fundamentals of physiology, focusing on the organization of the human body from cells to organisms. This quiz covers the basic structures and functions vital to understanding how living systems operate.