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Nervous system

The system which coordinates the actions of the body in response to changes in the environment using electrical signals travelling through a system of nerves

Antagonist

Drugs that block receptors on or in a cell and prevent an unwanted response (in people) or may prevent a desirable response causing death (in pathogens).

Antibiotic

Medicine that acts against bacterial infections. Penicillin is an example of an antibiotic.

Prokaryotes

A group of single-celled organisms with few organelles and where the genetic material is not contained in a membrane-bound nucleus. They include bacteria and blue-green algae (cyanobacteria).

Agonist

Drugs that bind to receptors on or in a cell and stimulate a response.

Drug action and cells

Medicines often need to get inside cells to have their impact. They exert their effects in many different ways.

Drugs work at the level of the cells of the body. There are several key principles of drug action:

  • Most drugs act at specific receptors on the external or internal cell membranes of body cells
  • Drugs interfere with the physiological or biochemical processes of the body or in the pathogens which cause disease
  • Drugs often bind to a single type of receptor but this type of receptor may be present in many different types of cell.

Drugs may be taken into cells by diffusion through the membrane, facilitated diffusion, active transport or pinocytosis.

Many drugs act as agonists or antagonists. Agonists bind to receptors on or in a cell and stimulate a response. Antagonists block receptors on or in a cell and prevent an unwanted response (in people) or may prevent a desirable response causing death (in pathogens).

Medicines often affect cell membranes or get inside of cells to have an effect. Understanding some of the ways different drugs work is a useful way of clarifying transport and control mechanisms in cells.

Antibiotics

Bacteria are prokaryotes and there are many features of prokaryotic cells that are different from our eukaryotic cells. Antibiotics are drugs that target bacteria and cure bacterial diseases. They either kill the bacteria or stop them growing – but it is important that they do not destroy the human cells as well, so many of their actions affect bacterial cells only.

Animation showing how different antibiotics have their effect on bacterial cells in different ways

Drugs affecting the nervous system

Many drugs and poisons affect the nervous system in one way or another. They may increase or depress stimulation of particular nerve pathways, or block transmission of the impulse completely. They may bind to membrane receptors or interfere with enzyme action inside or outside of the cell as in the diagram below.

Animation showing some of the ways different drugs affect the nervous system at a cellular level.