L1 physiology

What is Physiology?

• The study of the functions and vital processes of living organisms.
• It explains the physical and chemical factors responsible for life's origin, development, and progression.
• Physiology helps understand the principles that underlie normal function to cure impairments.
• It distinguishes between process and function.

Cell Structure and Function

• The cell is the structural and functional unit of life.
• The cell membrane (plasma membrane) is a thin, elastic, and semipermeable barrier between the cell and its surroundings.
• The cell membrane consists of a lipid bilayer made up of phospholipids and cholesterol.
• The lipid bilayer has hydrophilic heads that are exposed to water outside (ECF) and inside (ICF) the cell, and hydrophobic tails that meet in the water-poor interior of the membrane.
• The genetic material (DNA) is the hereditary material of the cell.
• DNA appears as chromatin in non-dividing cells and condenses to form chromosomes in dividing cells.

Cell Organelles

• Mitochondria: The powerhouse of the cell, containing its own DNA (mDNA), RNA, and ribosomes. Produces ATP (high-energy compound).
• Endoplasmic Reticulum (ER):
  • Smooth ER: Detoxifies drugs and pesticides, absorbs, synthesizes, and transports fats, breaks down glycogen to form glucose.
  • Rough ER: Contains ribosomes for protein manufacture.
• Ribosomes: The protein factories of the cell, responsible for protein synthesis. Can be either free-floating or attached to the ER.
• Golgi Apparatus: Modifies, packages, stores, and transports materials out of the cell. Works with ribosomes and ER.
• Lysosomes: Membrane-bound organelles containing digestive enzymes to digest food particles inside or outside the cell.
• Cytoskeleton: Provides support for the cell, giving it shape and helping with organelle movement. Consists of small microfilaments and larger microtubules.

Transport Mechanisms

• Diffusion: Passive movement of substances from a higher concentration to a lower concentration.
  • Factors affecting diffusion: Lipid solubility, Concentration gradient, Surface area, Temperature.
  • Inversely related to membrane thickness and molecular weight.
• Facilitated diffusion: Passive movement of substances down their concentration gradient with the help of transport proteins. Regulated by hormones.
• Active Transport: Requires specific carrier proteins and energy (from ATP hydrolysis) to move substances against their concentration gradient.
  • Primary Active Transport: Directly uses ATP for transport. Examples: Na+-K+ pump, Ca2+ pump, H+ pump.
  • Secondary Active Transport: Uses the electrochemical gradient created by primary active transport to transport other substances. Example: Sodium-dependent glucose transport.
• Na+-K+ Pump: Maintains cell volume and creates an electrochemical gradient across the membrane. pumps three Na+ ions out of the cell and two K+ ions into the cell for every ATP molecule hydrolyzed.
• Endocytosis: Transport of large particles into the cell.
  • Pinocytosis (Cell Drinking): Engulfment of fluids and small particles.
  • Phagocytosis (Cell Eating): Engulfment of bacteria and dead tissue.
• Exocytosis: Transport of materials out of the cell by fusing vesicles with the cell membrane.
• Filtration: Passive movement of water through a porous membrane due to a pressure difference. Examples: formation of interstitial fluid and glomerular filtrate.
• Osmosis: Passive movement of water through a semipermeable membrane from a dilute solution to a concentrated solution.
  • Osmotic pressure: Pressure required to prevent water movement from a dilute solution to a concentrated solution.
  • Osmoles: Measure of osmotic activity.

Homeostasis

• Maintenance of a stable internal environment despite external changes.
• Regulated by feedback loops.
• Feedback loops: Cycles of events that monitor and adjust body conditions.
  • Receptor: Detects changes in the body.
  • Control Center: Determines the set point and receives input from the receptor.
  • Effectors: Cause the response determined by the control center.
• Negative Feedback Loops: Response counteracts the change, stabilizing the internal environment.
  • Most feedback loops in the body are negative feedback loops.
• Positive Feedback Loops: Response enhances the change, amplifying the initial stimulus. Examples: blood clotting, childbirth.

Human Physiology

• Studies the functions of the human body and its various parts.
• Integrates knowledge from different bodily systems like the nervous, endocrine, and respiratory systems.
• Focuses on maintaining homeostasis, the body's ability to regulate its internal environment despite external changes.
• Key processes include metabolism, growth, reproduction, and responding to stimuli.

Cell Physiology

• Examines the functions of individual cells and their internal structures (organelles).
• Key concepts include:
  • Membrane Potentials: The difference in electrical charge across cell membranes, crucial for nerve impulses.
  • Cellular Respiration: The process of converting glucose and oxygen into ATP (energy), involving glycolysis, the Krebs cycle, and oxidative phosphorylation.
  • Cell Signaling: Communication between cells through hormones, neurotransmitters, and receptors.

Physiological Systems

• Nervous System: Includes the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves throughout the body). It's responsible for coordinating, controlling, and responding to stimuli.
• Endocrine System: Composed of glands that release hormones into the bloodstream. Regulates long-term bodily processes such as growth and metabolism.
• Respiratory System: Responsible for gas exchange, taking in oxygen and releasing carbon dioxide between the body and the environment. This involves lungs, the trachea, and the diaphragm.
• Digestive System: Breaks down food into nutrients that can be absorbed by the body. Major parts include the mouth, stomach, intestines, liver, and pancreas.
• Excretory System: Eliminates waste and regulates water and electrolytes in the body. This system mainly involves the kidneys and urinary tract.
• Musculoskeletal System: Facilitates movement and provides support to the body. It's made up of bones, muscles, and connective tissues.
• Immune System: Defends the body against pathogens and diseases. This system includes the lymphatic system and various immune cells.

Cardiovascular Physiology

• Focuses on the heart, blood vessels, and the circulation of blood.
• Key functions:
  • Transporting nutrients, gases, hormones, and waste throughout the body.
  • Maintaining blood pressure and regulating body temperature.
  • The cardiac cycle consists of systole (heart contraction) and diastole (heart relaxation).
  • Blood flow is regulated by valves and autoregulatory mechanisms.

Structure of Plasma Membrane

• Composed of a phospholipid bilayer with proteins embedded within it.
• Functions:
  • Selective Permeability: Regulates what enters and exits the cell.
  • Cell Signaling: Receptors on proteins bind to signaling molecules, enabling communication.
• Key components:
  • Phospholipids: Hydrophilic heads face outwards, hydrophobic tails face inwards.
  • Proteins: Integral proteins span the membrane, while peripheral proteins remain on the surface.
  • Carbohydrates: These are attached to proteins or lipids and play a role in cell recognition.
• The Fluid Mosaic Model describes the dynamic nature and organization of membrane components.

This quiz explores the fundamentals of physiology and the intricate details of cell structure and function. It covers essential aspects such as the functions of living organisms, the role of the cell membrane, and the importance of DNA. Test your understanding of how these components contribute to life and its processes.