Module 3 pp. Pharmacology and Physiology Basics

Pharmacology

• Pharmacokinetics: Involves drug dose, absorption, distribution, metabolism, and excretion. It’s about how the body affects the drug.
• Pharmacodynamics: Focuses on drug action's effect at the target site, and how the drug affects the body.
• Effect Site Concentration: The concentration of a drug at the site where it exerts its effect.
• Plasma Concentration: The concentration of a drug in the blood plasma.

Physiology Review

• Cell Membrane: A phospholipid bilayer, mainly impermeable to water-soluble substances (like ions and glucose).
• Diffusion: Mechanism for oxygen and carbon dioxide movement across cell membranes.
• Sodium-Potassium ATPase (Pump): Moves 3 sodium ions out and 2 potassium ions into the cell.
• Ion Channels: Transport charged ions across cell membranes, enabling electrical signals (action potentials).
• Endoplasmic Reticulum: Synthesizes proteins, lipids, and metabolizes carbohydrates.
• Sarcoplasmic Reticulum: Stores and releases calcium ions in muscle tissue.

Action Potential

• Depolarization: A change in membrane potential, making it less negative (e.g., from -70mV to +30mV).
• Repolarization: Return of membrane potential to its resting state.
• Resting Membrane Potential: The stable electrical potential across the cell membrane when the cell is at rest (typically around -70mV).
• Threshold Potential: The membrane potential that must be reached for an action potential to be initiated (-55mV).
• Refractory Period: The time after an action potential when the membrane cannot be stimulated by a weaker signal to produce another one.
• Action Potential Speed: Varies depending on the type of cell (motor neuron, skeletal muscle, cardiac ventricle).
• Action Potential Propagation: Spreads along the membrane.

Neuronal Action Potential

• Resting Membrane Potential: Slightly polarized at -70 mV (inside of the cell is slightly more negative than outside), caused by differences in ion concentration across the membrane.
• Sodium (Na+) and Potassium (K+) Channels: Crucial in generating and propagating the action potential.
• Time Scales (Action Potential): Different time scales for different cell types
• Stimulus: Initiates the action potential.
• Threshold: -55mV: Triggers Na+ channels opening.
• Depolarization: Influx of Na+ (makes the membrane potential more positive).
• Repolarization: Efflux of K+ (membrane potential returns toward resting state).
• Hyperpolarization: Temporary steeper negativity below resting potential.
• Na+/K+ ATPase: Maintains ion gradients across the membrane.

Action Potential Anomalies

• Hypocalcemia: Prevents Na+ channels from closing during action potentials, leading to sustained depolarization. (Tetany is an example)
• Hypercalcemia: Decreases cell membrane permeability to Na+, reducing excitability.
• Hypokalemia: Increased negativity of resting membrane potential, less ability to reach threshold potential for action potential.
• Hyperkalemia: Influx of K+ decreases membrane excitability.
• Sodium Channel Blockade: Prevents reaching threshold for action potentials.

Synapse

• Synaptic Transmission: Transfer of signals between neurons across synaptic clefts.
• Neurotransmitters: Chemical messengers released from pre-synaptic neuron to bind to receptors on the post-synaptic neuron.
• Synaptic Vesicles: Contain neurotransmitters, stored in the presynaptic terminal and released into the cleft during stimulation.
• Postsynaptic Density: A protein-rich region on the postsynaptic membrane, important in maintaining synaptic homeostasis.
• Synaptic Cleft: Fluid-filled gap separating the pre-synaptic and post-synaptic neurons.

Synaptic Responsiveness

• Changes in pH and excitability: Alkalosis increases excitability; acidosis decreases excitability.
• Changes in PaO2 and excitability: Hypoxia decreases excitability.

Receptor Pharmacology

• Neurotransmitter Receptors: Receptor types are crucial in influencing physiological responses.
• Neurotransmitter Function: Crucial in influencing physiological responses.

Cell Membrane Lipid Bilayer

• Phospholipid Bilayer: The framework of cell membranes, composed of phospholipid molecules.
• Polar Heads: Hydrophilic (water-attracting) portions of phospholipids and external regions of cell membrane.
• Nonpolar Tails: Hydrophobic (water-repelling) portions of phospholipids.