Chapter 42: Nervous System and Drugs

Learning Objectives

• Define the term drug and identify where drugs work within the nervous system.

• Define the following terms as they relate to drugs:

  • Receptor site: The location on a cell where a drug binds to exert its effect.

  • Receptor affinity: The strength of the binding between a drug and its receptor.

  • Agonist: A substance that activates a receptor to produce a biological response.

  • Antagonist: A substance that blocks or inhibits the action of an agonist at a receptor.

  • Length of effect: The duration that a drug's action lasts after administration.

  • Ability: The capacity of a drug to achieve its intended effect.

  • Effect: The outcome or change resulting from drug administration.

  • Action: The specific biochemical mechanism through which a drug produces its effect.

• Describe the difference between intracellular and extracellular drugs:

  • Intracellular drugs work within cells, specifically targeting cellular processes.

  • Extracellular drugs function outside of cells, typically affecting receptor sites on cell membranes.

• Distinguish between physical dependence, drug addiction, and tolerance:

  • Physical dependence: A physiological state where the body adapts to the presence of a drug, leading to withdrawal symptoms upon cessation.

  • Drug addiction: A chronic, relapsing disorder characterized by compulsive drug seeking, continued use despite harmful consequences, and long-lasting changes in the brain.

  • Tolerance: A condition where a person requires increased doses of a drug to achieve the same effect due to reduced sensitivity over time.

• Name the major sources of drugs:

  • Natural sources (plants, animals) and synthetic (chemicals produced in laboratories).

• Provide examples of drugs obtained from plants and their functions:

  • Digitalis: Used to strengthen heart contractions.

  • Atropine: Used to treat bradycardia (slow heart rate).

  • Morphine: Used for pain relief.

• Diagram and describe cocaine's mechanism of action:

  • Cocaine blocks dopamine reuptake in the brain, increasing its availability and resulting in heightened mood and euphoria.

• Discuss the effects of substances such as: Strychnine, Lead, Black Widow spider venom, and Curare on the nervous system and their mechanisms of action:

  • Strychnine: Acts as an antagonist, causing convulsions and muscle spasms by blocking inhibitory receptors.

  • Lead: Interferes with neurotransmitter release, often leading to neurotoxicity.

  • Black Widow spider venom: Triggers excessive release of neurotransmitters, leading to muscle spasms and pain.

  • Curare: Blocks acetylcholine receptors at the neuromuscular junction, resulting in paralysis.