Pharmacognosy and pharmacodynamics are both related to the field of pharmacology, but they focus on different aspects:

1. Pharmacognosy: This is the study of natural sources of drugs, particularly plants and other natural materials. Pharmacognosy involves identifying, isolating, and studying the active components of these natural sources and understanding their chemical and biological properties. It’s essentially about discovering and utilizing the medicinal properties of natural substances.

2. Pharmacodynamics: This refers to the study of how drugs interact with the body at the molecular, cellular, and physiological levels. It involves understanding how drugs exert their effects, including their binding to receptors, activation of cellular pathways, and resultant physiological responses. Pharmacodynamics is about comprehending how drugs work within the body to produce therapeutic or adverse effects.

In summary, pharmacognosy focuses on natural sources of drugs and their properties, while pharmacodynamics delves into the mechanisms by which drugs interact with the body to produce their effects.