Caffeine mainly works by opposing adenosine activity. Because adenosine promotes sleep, caffeine's inhibition of adenosine receptors reduces sleepiness and supports wakefulness; the passage also notes that caffeine may indirectly affect dopamine neurotransmission.

Caffeine's Mechanism of Action

Adenosine functions as a neurotransmitter that helps promote sleep.

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Neurotransmitters are chemical messengers that are released by the pre-synaptic cell into the synapse that changes electrical activity in the post-synaptic cell.
- Considered endogenous (produced inside the body) substances 
- Binds to receptors on the post-synaptic cell and either suppresses or enhances post-synaptic cell activity.

Neurotransmitters

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

- The substance exists in presynaptic cells
- The presynaptic cell contains the appropriate enzymes to create the substance
- The substance is released in large quantities when action potentials reach the presynaptic axon terminals
- Postsynaptic receptors that recognize the substance exist 
- The substance produces changes in postsynaptic cells
- Blocking release of the substance prevents the presynaptic cell from affecting the
postsynaptic cell

Neurotransmitter Criteria

- Amine Neurotransmitters
- Amino Acid Neurotransmitters
- Peptide Neurotransmitters
- Gas Neurotransmitters

Neurotransmitter Families

Neuronal receptors are specialized proteins located on a neuron's cell surface, typically on the dendrites, where neurotransmitters attach. The shape of each receptor is specific, allowing it to bind only with particular neurotransmitters, functioning like a lock that only a specific key can open.

Neuronal Receptors

Given the following scenario, explain how the described drug achieves its effect by altering the normal process of communication between nerve cells.

Analyzing a Drug's Effect on Neural Communication

Both hormones and neurotransmitters are chemical messengers that must bind to specific receptors to transmit their signals. However, they differ significantly in their mechanism, scope, and timing. Hormones are secreted into the bloodstream, leading to widespread effects that are slower to manifest but tend to be longer-lasting. In contrast, neurotransmitters are released in close proximity to their target cells, resulting in localized, rapid, and transient effects.

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