Histamine and Its Functions

These flashcards cover key concepts related to histamine, its receptors, and their physiological effects.

Histamine

An organic nitrogenous molecule synthesized from L-histidine, released during immune reactions and inflammation.

Mediator

A substance that facilitates communication and coordination between cells, often involved in biological responses.

Mast Cells

Immune cells that contain histamine and are involved in allergic reactions.

H1 Receptors

Histamine receptors involved in excitatory physiological responses such as smooth muscle contraction and increased vascular permeability.

H2 Receptors

Histamine receptors that primarily mediate gastric acid secretion from parietal cells.

H3 Receptors

Histamine receptors primarily found in the central nervous system, functioning as auto-receptors to regulate histamine release.

Triple Response

The classic reaction characterized by flush, flare, and wheal in response to histamine release.

Pruritis

The sensation of itching, often mediated by the action of histamine on sensory nerve endings.

H1 Antagonists

Drugs that block H1 receptors, used in the treatment of allergies, motion sickness, and insomnia.

H2 Antagonists

Drugs that inhibit H2 receptors, primarily used to reduce gastric acid secretion and treat peptic ulcers.

Sedative Effects

Effects of some H1 antagonists that cause drowsiness by blocking H1 receptors in the central nervous system.

CAMP

Cyclic adenosine monophosphate, a second messenger involved in signaling pathways, notably in gastric acid secretion.

ECL Cells

Enterochromaffin-like cells that release histamine in the stomach, stimulating gastric acid production.

Oedema

Swelling caused by excess fluid trapped in the body's tissues, often mediated by histamine's effects on vascular permeability.

Histamine Drugs

Medications that target histamine receptors, used primarily for allergies, gastric ulcers, and as anti-emetics.