Lecture 2 Concepts in Physiology 3pp(1)

Key Concepts in Physiology

• Instructor: Dr. Ben Perry, PhD

• Sources: Includes concepts from Silverthorn text chapter 6 and Amerman.

Lecture Learning Outcomes

• Describe and discuss the following physiological concepts:

  • Cell to cell communication

  • Cell membrane

  • Structure and function

  • Homeostasis

  • Adaptation across the lifespan

  • Movement of substances

  • Integration

Importance of Physiology Concepts

• Understanding physiology provides guiding principles to connect various biological systems.

• Example: Pressure gradients explain blood movement in the cardiovascular system and gas exchange in the respiratory system.

Seven Key Physiological Concepts

1. Cell to cell communication

2. Cell membrane

3. Structure and function

4. Homeostasis

5. Adaptation across the lifespan

6. Movement of substances

7. Integration

• All concepts are equally important; no specific order of precedence.

1. Cell to Cell Communication

• Essential for coordinating organism functions; involves transmitting information between cells.

• Communication Methods:

  • Short-range (local) signals: gap junctions and contact-dependent signals (Cell Adhesion Molecules - CAMs).

  • Local signals: paracrine (affect nearby cells of different types) and autocrine (affect the same cell type).

Visuals

• Figure 6.1 shows forms of cell communication including local (paracrine/autocrine) and long-distance methods.

Long-Distance Communication

• Takes form through:

  • Hormones: Chemicals in the blood affecting other tissues.

  • Neurocrines: Chemical signals by neurons (e.g., neurotransmitters, neurohormones).

Cytokines

• Peptides from all nucleated cells in response to stimuli with roles in:

  • Local signaling (autocrine/paracrine) during development.

  • Long-distance signaling during stress/inflammation.

  • Different from hormones due to their production by all nucleated cells.

2. Cell Membrane

• Function: Regulates substance entry/exit and facilitates signaling.

• Composed of a phospholipid bilayer acting as a barrier to hydrophilic substances; requires receptors, transporters, or channels to allow movement.

• Substances trafficked include:

  • Ions, hormones, nutrients (e.g., glucose, amino acids).

Examples of Membrane Activities

1. Propagation of action potentials

2. Glucose release in response to insulin

Signal Pathways and the Membrane

Receptor Proteins

• Necessary for cells to respond to chemical signals.

• Signal Pathway Steps:

  1. The first messenger binds to the receptor.

  2. Activates the receptor.

  3. Triggers intracellular molecules.

  4. Modifies proteins or synthesizes new ones.

Visuals

• Figures 6.4 and 6.5 illustrate signal transduction processes.

3. Structure and Function

• Structure and function are inherently linked at microscopic and organ levels.

Organ Level Example: Heart Chambers

• Heart has four chambers; thicker walls in left ventricle facilitate systemic blood ejection.

Microscopic Level Example: Skeletal Muscle

• Structure of thick myosin filaments interacting with actin for muscle contraction.

• Sodium-potassium pump functionality tied to conformational changes driven by ATP.

4. Homeostasis

• Definition: Regulation of internal environment through feedback systems.

• Feedback Loops:

  • Negative Feedback: Reduces output as a function stabilizer.

  • Positive Feedback: Enhances output to amplify responses.

• Homeostasis doesn't mean constant set points but maintaining variables within survivable ranges.

Visuals

• Figures 1.13 and 1.14 depict negative and positive feedback loops.

5. Adaptation Across the Lifespan

• Organisms adapt to acute and chronic internal/external changes:

  • Examples include hypertrophy from resistance training, altitude adaptation, compensatory mechanisms in diseases.

Specific Examples:

• Hypertrophy: Results from repeated resistance training; muscles adapt by increasing size and strength.

• Cardiovascular Response to Altitude: Increased heart rate, respiratory rate, and eventual red blood cell production to counter low oxygen availability.

6. Movement of Substances

• Movement of ions, molecules, fluids, and gases is fundamental across biological levels.

Mechanisms Driving Movement:

1. Pressure Gradient: Movement from high to low pressure (e.g., blood from heart to capillaries).

2. Diffusion Gradient: Substances move from areas of high to low concentration (e.g., sodium ions during action potentials).

3. Osmotic Pressure: Water moves toward areas of high solute concentration; nephron is a prime example.

7. Integration

• Interactions between cells, tissues, organs, and systems are crucial for life.

• Physiological systems are often taught separately but operate in complex, interconnected ways.

Integration Levels

• Cellular Level: Example: Cardiac muscle cell interactions.

• Organ Systems Level: Interaction of the heart and lungs to supply oxygenated blood.